Compressor sensor module

0001The present disclosure relates to compressors, and more particularly, to a compressor with a sensor module.

0002The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

0003Compressors are used in a variety of industrial and residential applications to circulate refrigerant within a refrigeration, heat pump, HVAC, or chiller system (generically "refrigeration systems") to provide a desired heating or cooling effect. <patcit id="pcit0001" dnum="US20040016253A1"><text>U.S. Pub. No. 2004/0016253 A1</text></patcit> references a refrigeration system and a method of operating the same. Compressors may include an electric motor to provide torque to compress vapor refrigerant. The electric motor may be powered by an alternating current (AC) or direct current (DC) power supply. In the case of an AC power supply, single or poly-phase AC may be delivered to windings of the electric motor. For example, the compressor may include an electric motor configured to operate with three phase AC. The electric motor may include at least one set of windings corresponding to each of the three phases.

0004In each application, it is desirable for the compressor to provide consistent and efficient operation to ensure that the refrigeration system functions properly. Variations in the supply of electric power to the electric motor of the compressor may disrupt operation of the electric motor, the compressor, and the refrigeration system. Such variations may include, for example, excessive, or deficient, current or voltage conditions. In the case of a poly-phase AC power supply, such variations may include an unbalanced phase condition wherein the current or voltage of at least one phase of AC is excessively varied from the current or voltage of the other phases. Further, such variations may include a loss of phase condition wherein one phase of AC is interrupted while the remaining phases continue to be delivered. Excessive current or voltage conditions may cause the electric motor to overheat which may damage the electric motor or the compressor. Deficient current or voltage conditions, unbalanced phase conditions, and loss of phase conditions may disrupt operation of the electric motor, the compressor, or the refrigeration system and cause unnecessary damage.

0005The electric motor of a compressor may be equipped with a temperature or current sensor to detect overheating of the electric motor during electrical power disturbances. For example, a bi-metallic switch may trip and deactivate the electric motor when the electric motor is overheated or drawing excessive electrical current. Such a system, however, does not detect variations in the power supply that may not immediately or drastically increase the temperature of the electric motor. In addition, such systems may not detect a variation in electrical power until the condition has increased the temperature of the electric motor or the electric motor windings.

0006Further, such systems do not provide sufficient data to evaluate electrical efficiency of the electric motor overall. Variations in the supply of electric power may result in inefficient operation of the compressor, the electric motor, or the refrigeration system. Refrigeration systems generally require a significant amount of energy to operate, with energy requirements being a significant cost to retailers. As a result, it is in the best interest of retailers to closely monitor the supply of electric power to their refrigeration systems to maximize efficiency and reduce operational costs. <patcit id="pcit0002" dnum="US20060222507A1"><text>U.S. Pub. No. 2006/0222507 A1</text></patcit> references an example compressor protection and diagnostic system.

0007According to the present invention there is provided the system of claim 1 and the method of claim 9. Further aspects are set out in the dependent claims. There is described a sensor module for a compressor having an electric motor connected to a power supply. The sensor module may comprise a first input connected to a first voltage sensor that generates a voltage signal corresponding to a voltage of said power supply, a second input connected to a first current sensor that generates a current signal corresponding to a current of said power supply, and a processor connected to the first and second inputs that calculates a power factor of the compressor based on voltage measurements from the first input and current measurements from the second input. The processor may be disposed within an electrical enclosure of the compressor and the electrical enclosure may being configured to house electrical terminals for connecting the power supply to the electric motor.

0008The processor may be disposed within a tamper-resistant enclosure within the electrical enclosure.

0009The processor may calculate an active power and an apparent power of the compressor based on the voltage measurements from the first input and current measurements from the second input and may calculate the power factor according to a ratio of the active power to the apparent power.

0010The processor may determine a voltage waveform based on voltage measurements from the first input and a current waveform based on current measurements from the second input and may calculate the power factor according to an angular difference between the current waveform and the voltage waveform.

0011The processor may calculate a power consumption of the compressor based on the voltage measurements from the first input and the current measurements from the second input.

0012The processor may calculate an active power of the compressor based on the voltage measurements from the first input and the current measurements from the second input and calculates the power consumption by averaging the active power over a time period.

0013The sensor module may further comprise a communication port for communicating information from the sensor module to a control module for the compressor, a system controller for a system associated with the compressor, a portable computing device, and/or a network device.

0014The information communicated may include the power factor, a calculated active power, a calculated apparent power, and/or a calculated power consumption of the compressor.

0015The power supply may includes first, second, and third phases, with the voltage signal generated by the first voltage sensor corresponding to the first phase, and the current signal generated by the first current sensor corresponding to the first phase. Further, the sensor module may further comprise a third input connected to a second voltage sensor that generates a voltage signal corresponding to a voltage of the second phase. A fourth input connected to a third voltage sensor may generate a voltage signal corresponding to a voltage of the third phase. The processor may be connected to the third and fourth inputs and may calculate the power factor based on voltage measurements received from the third and fourth inputs.

0016The processor may estimate a current of the second phase and a current of the third phase and may calculate the power factor based on the estimated currents of the second and third phases.

0017The processor may calculate an active power and an apparent power of the compressor based on the voltage measurements from the first input, the current measurements from the second input, the voltage measurements from the third input, the voltage measurements from the fourth input and the estimated currents of the second and third phases and may calculate the power factor according to a ratio of the active power to the apparent power.

0018The sensor module may further comprise a fifth input connected to a second current sensor that generates a current signal corresponding to a current of the second phase. The processor may be connected to the fifth input and may calculate the power factor based on current measurements received from the fifth input.

0019The processor may estimate a current of the third phase and may calculate the power factor based on the estimated current of the third phase.

0020The processor may calculate an active power and an apparent power of the compressor based on the voltage measurements from the first input, the current measurements from the second input, the voltage measurements from the third input, the voltage measurements from the fourth input, the current measurements from the fifth input, and the estimated current of the third phase and calculates the power factor according to a ratio of the active power to the apparent power.

0021The sensor module may further comprise a fifth input connected to a second current sensor that generates a current signal corresponding to a current of the second phase and a sixth input connected to a third current sensor that generates a current signal corresponding to a current of the third phase. The processor may be connected to the fifth and sixth inputs and may calculate the power factor based on current measurements received from the fifth and sixth inputs.

0022The processor may calculate an active power and an apparent power of the compressor based on the voltage measurements from the first input, the current measurements from the second input, the voltage measurements from the third input, the voltage measurements from the fourth input, the current measurements from the fifth input, and the current measurements from the sixth input and calculates the power factor according to a ratio of the active power to the apparent power.

0023There is described a compressor having the sensor module.

0024There is also described a method for a sensor module with a processor disposed within an electrical enclosure of a compressor having an electric motor connected to a power supply. The electrical enclosure may be configured to house electrical terminals for connecting the power supply to the electric motor. The method may comprise receiving voltage measurements of the power supply from a first voltage sensor connected to the sensor module, receiving current measurements of the power supply from a first current sensor connected to the sensor module, calculating a power factor of the compressor based on the voltage measurements and the current measurements, and generating an output based on the power factor.

0025Calculating the power factor may comprise calculating an active power and an apparent power of the compressor based on the voltage measurements and the current measurements and calculating the power factor according to a ratio of the active power to the apparent power.

0026Calculating the power factor may comprise determining a voltage waveform based on the voltage measurements, determining a current waveform based on the current measurements, and calculating the power factor according to an angular difference between the current waveform and the voltage waveform.

0027The method may further comprise calculating a power consumption of the compressor based on the voltage measurements and the current measurements.

0028Calculating the power consumption may comprise calculating an active power of the compressor based on the voltage measurements and the current measurements and calculating the power consumption by averaging the active power over a time period.

0029Generating the output based on the power factor may comprise communicating the power factor to a control module, a system controller, a portable computing device, and/or a network device, connected to the sensor module.

0030Power supply may include first, second, and third phases, with the voltage measurements from the first voltage sensor corresponding to the first phase, and the current measurements from the first current sensor corresponding to the first phase. The method may further comprise receiving voltage measurements corresponding to the second phase of the power supply from a second voltage sensor connected to the sensor module, receiving voltage measurements corresponding to the third phase of the power supply from a third voltage sensor connected to the sensor module. The calculating the power factor may comprise calculating the power factor based on the voltage measurements corresponding to the second phase and the voltage measurements corresponding to the third phase.

0031The method may further comprise calculating a current estimate for the second phase and calculating a current estimate for the third phase. Calculating the power factor may comprise calculating the power factor based on the current estimates for the second and third phases.

0032Calculating the power factor may comprise calculating an active power and an apparent power of the compressor based on the voltage measurements for the first, second, and third phases, the current measurements for the first phase, and the current estimates for the second and third phases and calculating the power factor according to a ratio of the active power to the apparent power.

0033The method may further comprise receiving current measurements corresponding to the second phase of the power supply from a second current sensor connected to the sensor module. Calculating the power factor may comprise calculating the power factor based on the current measurements corresponding to the second phase.

0034The method may further comprise calculating a current estimate for the third phase. Calculating the power factor may comprise calculating the power factor based on the current estimate for the third phase.

0035Calculating the power factor may comprise calculating an active power and an apparent power of the compressor based on the voltage measurements for the first, second, and third phases, the current measurements for the first and second phases, and the current estimate for the third phase and calculating the power factor according to a ratio of the active power to the apparent power.

0036The method may further comprise receiving current measurements corresponding to the third phase of the power supply from a third current sensor connected to the sensor module. Calculating the power factor may comprise calculating the power factor based on the current measurements corresponding to the third phase.

0037Calculating the power factor may comprise calculating an active power and an apparent power of the compressor based on the voltage measurements for the first, second, and third phases, and the current measurements for the first, second, and third phases and calculating the power factor according to a ratio of the active power to the apparent power.

0038There is also described a computer-readable medium having computer executable instructions for performing the method.

0039There is also described another sensor module for a compressor having an electric motor connected to a power supply. The sensor module may comprise a first input connected to a first voltage sensor that generates a voltage signal corresponding to a voltage of the power supply, a second input connected to a first current sensor that generates a current signal corresponding to a current of the power supply, and a processor connected to the first and second inputs that monitors the first and second inputs. The processor may detect an unexpected variation of electric power from the power supply and/or a mechanical malfunction based on voltage measurements from the first input and current measurements from the second input. The processor may be disposed within an electrical enclosure of the compressor, the electrical enclosure being configured to house electrical terminals for connecting the power supply to the electric motor.

0040The processor may be disposed within a tamper-resistant enclosure within the electrical enclosure.

0041The sensor module may further comprise a communication port for communicating a notification corresponding to the expected variation and/or the mechanical malfunction to a control module for the compressor, a system controller for a system associated with the compressor, a portable computing device, and/or a network device.

0042The processor may detect the unexpected variation of electric power including a no-power condition.

0043The processor may compare the voltage measurements from the first input with a predetermined voltage threshold and may determine that the no-power condition exists when the voltage measurements remain less than the predetermined voltage threshold for a predetermined time period.

0044The sensor module may detect the unexpected variation of electric power including a low-voltage condition.

0045The processor may determine a normal operating voltage of the compressor and may determine that the low-voltage condition exists when the voltage measurements from the first input are less than a predetermined percentage of the normal operating voltage.

0046The processor may determine the normal operating voltage based on historical data of the compressor.

0047The processor may determine the normal operating voltage based on an inputted normal operating voltage.

0048The sensor module may detect the unexpected variation of electric power including a current-overload condition.

0049The processor may determine a current maximum threshold, may compare the current measurements from the second input with the current maximum threshold, and may determine that the current-overload condition exists based on the comparison

0050The power supply may include first, second, and third phases, with the voltage signal generated by the first voltage sensor corresponding to the first phase, and with the current signal generated by the first current sensor corresponding to the first phase. The sensor module may further comprise a third input connected to a second voltage sensor that generates a voltage signal corresponding to a voltage of the second phase and a fourth input connected to a third voltage sensor that generates a voltage signal corresponding to a voltage of the third phase. The processor may be connected to the third and fourth inputs and may detect the unexpected variation of electric power from the power supply based on voltage measurements received from the third and fourth inputs.

0051The unexpected variation of electric power may include a phase-loss condition.

0052The processor may compare voltage measurements received from the first, third, and fourth inputs and may determine that the phase-loss condition exists when voltage measurements from the first input are less than a predetermined percentage of an average of voltage measurements from the third and fourth inputs.

0053The unexpected variation of electric power may include a voltage-imbalance condition.

0054The processor may calculate an average of voltage measurements received from the first, third, and fourth inputs and may determine that the voltage-imbalance condition based on the greatest of a difference between voltage measurements from the first input and the average, a difference between voltage measurements from the third input and the average, and a difference between voltage measurements from the fourth input and the average.

0055The sensor module may further comprise a fifth input connected to a second current sensor that generates a current signal corresponding to a current of the second phase. The processor may be connected to the fifth input and may detect the unexpected variation of electric power from the power supply based on current measurements received from the fifth input.

0056The unexpected variation of electric power may include a current-delay condition.

0057The processor may determine that the current-delay condition exists when a current measurement from the second input is greater than a predetermined current threshold and a current measurement from the fifth input is not greater than the predetermined current threshold within a predetermined time period.

0058The sensor module may detect the mechanical malfunction including a welded-contactor condition.

0059The processor may receive run-state data corresponding to a current run-state of the compressor, may compare the voltage measurements from the first input with a voltage threshold, and may determine that the welded-contactor condition exists based on the current run-state and the comparison.

0060The sensor module may detect the mechanical malfunction including a locked-rotor condition.

0061The processor may compare the current measurements from the second input with a current threshold and may determine that the locked-rotor condition exists when the current measurements are greater than the current threshold.

0062The processor may generate a buffer of the current measurements from the second input, may determine a greatest current value from the buffer, may compare the current measurements with the greatest current value from the buffer, and may determine that the locked-rotor condition exists when the current measurements are greater than a predetermined percentage of the greatest current value.

0063The sensor module may detect the mechanical malfunction including a protection-trip condition.

0064The processor may compare the voltage measurements with a voltage threshold and the current measurements with a current threshold and may determine that the protection-trip condition exists when the voltage measurements are greater than the voltage threshold and the current measurements are less than the current threshold.

0065There is also described another method for a sensor module with a processor disposed within an electrical enclosure of a compressor having an electric motor connected to a power supply. The electrical enclosure may be configured to house electrical terminals for connecting the power supply to the electric motor. The method may comprise receiving voltage measurements of the power supply from a first voltage sensor connected to the sensor module, receiving current measurements of the power supply from a first current sensor connected to the sensor module, detecting an unexpected variation of electric power from the power supply and/or a mechanical malfunction of the compressor based on the voltage measurements and the current measurements, and generating an output based on the detecting.

0066Generating the output based on the detecting may comprise communicating a result of the detecting to a control module, a system controller, a portable computing device, and/or a network device, connected to the sensor module.

0067The detecting may include detecting the unexpected variation of electric power including a no-power condition.

0068Detecting the no-power condition may comprise comparing the voltage measurements with a predetermined voltage threshold, and determining that the no-power condition exists when the voltage measurements remain less than the predetermined voltage threshold for a predetermined time period.

0069The detecting may include detecting the unexpected variation of electric power including a low-voltage condition.

0070Detecting the low-voltage condition may comprise determining a normal operating voltage of the compressor, and determining that the low-voltage condition exists when the voltage measurements are less than a predetermined percentage of the normal operating voltage.

0071Determining the normal operating voltage may comprise determining the normal operating voltage based on historical data of the compressor.

0072Determining the normal operating voltage may comprise determining the normal operating voltage based on an inputted normal operating voltage.

0073The detecting may include detecting the unexpected variation of electric power including a current-overload condition.

0074Detecting the current-overload condition may comprise determining a current maximum threshold, comparing the current measurements with the current maximum threshold, and determining that the current-overload condition exists based on the comparison.

0075The power supply may include first, second, and third phases, with the voltage measurements from the first voltage sensor corresponding to the first phase, and with the current measurements from the first current sensor corresponding to the first phase. The method may further comprise receiving voltage measurements corresponding to the second phase of the power supply from a second voltage sensor connected to the sensor module, and receiving voltage measurements corresponding to the third phase of the power supply from a third voltage sensor connected to the sensor module. Detecting the unexpected variation of electric power from the power supply may be based on the voltage measurements corresponding to the first, second, and third phases and the current measurements.

0076Detecting the unexpected variation of electric power may include detecting a phase-loss condition.

0077Detecting the phase-loss condition may comprise comparing voltage measurements corresponding to the first, second, and third phases, and determining that the phase-loss condition exists when voltage measurements corresponding to the first phase are less than a predetermined percentage of an average of voltage measurements corresponding to the second and third phases.

0078Detecting the unexpected variation of electric power may include detecting a voltage-imbalance condition.

0079Detecting the voltage-imbalance condition may comprise calculating an average of the voltage measurements corresponding to the first, second, and third phases and determining that the voltage-imbalance condition exists based on the greatest of a difference between voltage measurements corresponding to the first phase and the average, a difference between voltage measurements corresponding to the second phase and the average, and a difference between voltage measurements corresponding to the third phase and the average.

0080The method may further comprise receiving current measurements corresponding to the second phase of the power supply from a second current sensor connected to the sensor module. The detecting the unexpected variation of electric power from the power supply may include detecting the unexpected variation of electric power based on the current measurements corresponding to the first and second phases.

0081Detecting the unexpected variation of electric power may include detecting a current-delay condition.

0082Detecting the current-delay condition may comprise comparing the current measurements corresponding with the first phase and the current measurements corresponding with the second phase with a predetermined current threshold and determining that the current-delay condition exists when the current measurements corresponding to the first phase are greater than the predetermined current threshold and the current measurements corresponding with the second phase are not greater than the predetermined current threshold within a predetermined time period.

0083The detecting may include detecting the mechanical malfunction including a welded-contactor condition.

0084The method may further comprise receiving run-state data corresponding to a current run-state of the compressor, comparing the voltage measurements with a voltage threshold, and determining that the welded-contactor condition exists based on the current run-state and the comparison.

0085The detecting may include detecting the mechanical malfunction of the compressor including a locked-rotor condition.

0086The detecting the locked-rotor condition may comprise comparing the current measurements with a current threshold and determining that the locked-rotor condition exists when the current measurements are greater than the current threshold.

0087Detecting the locked-rotor condition may comprise generating a buffer of the current measurements, determining a greatest current value from the buffer, comparing the current measurements with the current value from the buffer, and determining that the locked-rotor condition exists when the current measurements are greater than a predetermined percentage of the greatest current value.

0088The detecting may include detecting the mechanical malfunction including a protection-trip condition.

0089The detecting the protection-trip condition may comprise comparing the voltage measurements with a voltage threshold, comparing the current measurements with a current threshold, and determining that the protection-trip condition exists when the voltage measurements are greater than the voltage threshold and the current measurements are less than the current threshold.

0090Further areas of applicability will become apparent from the description provided herein.

0091The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. <ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">Figure 1</figref> is a schematic view of a refrigeration system;</li><li><figref idref="f0001">Figure 2</figref> is a schematic view of a compressor with a sensor module and a control module;</li><li><figref idref="f0002">Figure 3</figref> is a schematic view of a compressor with a sensor module and a control module;</li><li><figref idref="f0002">Figure 4</figref> is a schematic view of a compressor with a sensor module and a control module;</li><li><figref idref="f0003">Figure 5</figref> is a perspective view of a compressor with a sensor module and a control module;</li><li><figref idref="f0003">Figure 6</figref> is a top view of a compressor with a sensor module and a control module;</li><li><figref idref="f0004">Figure 7</figref> is a schematic view of an electrical enclosure of a compressor including a sensor module;</li><li><figref idref="f0004">Figure 8</figref> is a schematic view of an electrical enclosure of a compressor including a sensor module;</li><li><figref idref="f0005">Figure 9</figref> is a schematic view of an electrical enclosure of a compressor including a sensor module;</li><li><figref idref="f0005">Figure 10</figref> is a schematic view of an electrical enclosure of a compressor including a sensor module;</li><li><figref idref="f0006">Figure 11</figref> is a schematic view of an electrical enclosure of a compressor including a sensor module;</li><li><figref idref="f0006">Figure 12</figref> is a schematic view of an electrical enclosure of a compressor including a sensor module;</li><li><figref idref="f0007">Figure 13</figref> is a flow chart illustrating an operating algorithm of a sensor module in accordance with the present teachings;</li><li><figref idref="f0007">Figure 14</figref> is a flow chart illustrating a diagnostic algorithm of a sensor module in accordance with the present teachings;</li><li><figref idref="f0008">Figure 15</figref> is a flow chart illustrating a diagnostic algorithm of a sensor module in accordance with the present teachings;</li><li><figref idref="f0008">Figure 16</figref> is a flow chart illustrating a diagnostic algorithm of a sensor module in accordance with the present teachings;</li><li><figref idref="f0009">Figure 17</figref> is a flow chart illustrating a diagnostic algorithm of a sensor module in accordance with the present teachings;</li><li><figref idref="f0009">Figure 18</figref> is a flow chart illustrating a diagnostic algorithm of a sensor module in accordance with the present teachings;</li><li><figref idref="f0010">Figure 19</figref> is a flow chart illustrating a diagnostic algorithm of a sensor module in accordance with the present teachings;</li><li><figref idref="f0010">Figure 20</figref> is a flow chart illustrating a diagnostic algorithm of a sensor module in accordance with the present teachings;</li><li><figref idref="f0011">Figure 21</figref> is a flow chart illustrating a diagnostic algorithm of a sensor module in accordance with the present teachings;</li><li><figref idref="f0011">Figure 22</figref> is a flow chart illustrating a diagnostic algorithm of a sensor module in accordance with the present teachings; and</li><li><figref idref="f0012">Figure 23</figref> is a flow chart illustrating a diagnostic algorithm of a sensor module in accordance with the present teachings.</li></ul>

0092The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

0093As used herein, the terms module, control module, and controller refer to one or more of the following: an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, or other suitable components that provide the described functionality. Further, as used herein, computer-readable medium refers to any medium capable of storing data for a computer. Computer-readable medium may include, but is not limited to, memory, RAM, ROM, PROM, EPROM, EEPROM, flash memory, punch cards, dip switches, CD-ROM, floppy disk, magnetic tape, other magnetic medium, optical medium, or any other device or medium capable of storing data for a computer.

0094With reference to <figref idref="f0001">Figure 1</figref>, an exemplary refrigeration system 10 may include a plurality of compressors 12 piped together with a common suction manifold 14 and a discharge header 16. Compressor 12 may be a reciprocating compressor, a scroll type compressor, or another type of compressor. Compressor 12 may include a crank case. Compressors 12 may be equipped with electric motors to compress refrigerant vapor that is delivered to a condenser 18 where the refrigerant vapor is liquefied at high pressure, thereby rejecting heat to the outside air. The liquid refrigerant exiting the condenser 18 is delivered to an evaporator 20. As hot air moves across the evaporator, the liquid turns into gas, thereby removing heat from the air and cooling a refrigerated space. This low pressure gas is delivered to the compressors 12 and again compressed to a high pressure gas to start the refrigeration cycle again. While a refrigeration system 10 with two compressors 12, a condenser 18, and an evaporator 20 is shown in <figref idref="f0001">Figure 1</figref>, a refrigeration system 10 may be configured with any number of compressors 12, condensers 18, evaporators 20, or other refrigeration system components.

0095Each compressor 12 may be equipped with a control module (CM) 30 and a sensor module (SM) 32. As described herein, SM 32 may be affixed to compressor 12 and may monitor electric power delivered to compressor 12 with one or more voltage sensors and one or more current sensors. Based on electrical power measurements, such as electric current (I) and voltage (V), SM 32 may determine apparent power, actual power, power consumption, and power factor calculations for the electric motor of compressor 12. SM 32 may communicate the electric power measurements and calculations to CM 30. SM 32 may also alert CM 30 of variations in the power supply, or of mechanical failures, based on the measurements and calculations. For example, SM 32 may alert CM 30 of an excessive current or voltage condition, a deficient current or voltage condition, a current or voltage imbalance condition, or a loss of phase or current delay condition (if poly-phase electric power is used). Based on the monitoring of the electric power supply and based on the communication with CM 30, SM 32 may detect and alert CM 30 to a welded contactor condition, or a locked rotor condition.

0096CM 30 may control operation of compressor 12 based on data received from SM 32, based on other compressor and refrigeration system data received from other compressor or refrigeration system sensors, and based on communication with a system controller 34. CM 30 may be a protection and control system of the type disclosed in <patcit id="pcit0003" dnum="US20050235660A"><text>U.S. Patent Publication No. 2005/0235660</text></patcit>. Other suitable protection and control systems may be used.

0097In addition to the data received by CM 30 from SM 32, CM 30 may receive compressor and refrigeration system data including discharge pressure, discharge temperature, suction pressure, suction temperature, and other compressor related data from pressure and temperature sensors connected to or, embedded within, compressor 12. In addition, oil level and oil pressure data may be received by SM 32 and communicated to CM 30 and/or received by CM 30 directly. In this way, CM 30 may monitor the various operating parameters of compressor 12 and control operation of compressor 12 based on protection and control algorithms and based on communication with system controller 34. For example, CM 30 may activate and deactivate the compressor 12 according to a set-point, such as a suction pressure, suction temperature, discharge pressure, or discharge temperature set-point. In the case of a discharge pressure set-point, CM 30 may activate compressor 12 when the discharge pressure, as determined by a discharge pressure sensor, falls below the discharge pressure set-point. CM 30 may deactivate compressor 12 when the discharge pressure rises above the discharge pressure set-point.

0098Further, CM 30 may activate or deactivate compressor 12 based on data and/or alerts received from SM 32. For example, CM 30 may deactivate compressor 12 when alerted of an excessive current or voltage condition, a deficient current or voltage condition, a current or voltage imbalance condition, or a loss of phase or current delay condition (if poly-phase electric power is used). Further, CM 30 may activate compressor 12 when alerted of a welded contactor condition or deactivate compressor 12 when alerted of a locked rotor condition. CM 30 may communicate operating data of compressor 12, including electric power data received from SM 32, to system controller 34.

0099In this way, SM 32 may be specific to compressor 12 and may be located within an electrical enclosure 72 of compressor 12 for housing electrical connections to compressor 12 (shown in <figref idref="f0003 f0004 f0005 f0006">Figures 5-12</figref>) at the time of manufacture of compressor 12. CM 30 may be installed on compressor 12 after manufacture and at the time compressor 12 is installed at a particular location in a particular refrigeration system, for example. Different control modules may be manufactured by different manufacturers. However, each CM 30 may be designed and configured to communicate with SM 32. In other words, SM 32 for a particular compressor 12 may provide data and signals that can be communicated to any control module appropriately configured to communicate with SM 32. Further, manufacturers of different control modules may configure a control module to receive data and signals from SM 32 without knowledge of the algorithms and computations employed by SM 32 to provide the data and signals.

0100System controller 34 may be used and configured to control the overall operation of the refrigeration system 10. System controller 34 is preferably an Einstein Area Controller offered by CPC, Inc. of Atlanta, Georgia, or any other type of programmable controller that may be programmed to operate refrigeration system 10 and communicate with CM 30. System controller 34 may monitor refrigeration system operating conditions, such as condenser temperatures and pressures, and evaporator temperatures and pressures, as well as environmental conditions, such as ambient temperature, to determine refrigeration system load and demand. System controller 34 may communicate with CM 30 to adjust set-points based on operating conditions to maximize efficiency of refrigeration system 10. System controller 34 may evaluate efficiency based on electric power measurements and calculations made by SM 32 and communicated to system controller 34 from CM 30.

0101With reference to <figref idref="f0001">Figure 2</figref>, three phase AC electric power 50 may be delivered to compressor 12 to operate an electric motor. SM 32 and CM 30 may receive low voltage power from one of the phases of electric power 50 delivered to compressor 12. For example, a transformer 49 may convert electric power 51 from one of the phases to a lower voltage for delivery to SM 32 and CM 30. In this way, SM 32 and CM 30 may operate on single phase AC electric power at a lower voltage than electric power 50 delivered to compressor 12. For example, electric power delivered to SM 32 and CM 30 may be 24V AC. When low voltage power, for example 24 V AC, is used to power CM 30 and SM 32, lower voltage rated components, such as lower voltage wiring connections, may be used.

0102SM 32 may be connected to three voltage sensors 54, 56, 58, for sensing voltage of each phase of electric power 50 delivered to compressor 12. In addition, SM 32 may be connected to a current sensor 60 for sensing electric current of one of the phases of electric power 50 delivered to compressor 12. Current sensor 60 may be a current transformer or current shunt resistor.

0103When a single current sensor 60 is used, electric current for the other phases may be estimated based on voltage measurements and based on the current measurement from current sensor 60. Because the load for each winding of the electric motor may be substantially the same as the load for each of the other windings, because the voltage for each phase is known from measurement, and because the current for one phase is known from measurement, current in the remaining phases may be estimated.

0104Additional current sensors may also be used and connected to SM 32. With reference to <figref idref="f0002">Figure 3</figref>, two current sensors 57, 60 may be used to sense electric current for two phases of electric power 50. When two current sensors 57, 60 are used, electric current for the remaining phase may be estimated based on voltage measurements and based on the current measurements from current sensors 57, 60. With reference to <figref idref="f0002">Figure 4</figref>, three current sensors 55, 57, 60 may be used to sense electric current for all three phases of electric power 50.

0105In the case of a dual winding three phase electric motor, six electrical power terminals may be used, with one terminal for each winding resulting in two terminals for each of the three phases of electric power 50. In such case, a voltage sensor may be included for each of the six terminals, with each of the six voltage sensors being in communication with SM 32. In addition, a current sensor may be included for one or more of the six electrical connections.

0106With reference to <figref idref="f0003">Figures 5 and 6</figref>, CM 30 and SM 32 may be mounted on or within compressor 12. CM 30 may include a display 70 for graphically displaying alerts or messages. As discussed above, SM 32 may be located within electrical enclosure 72 of compressor 12 for housing electrical connections to compressor 12.

0107Compressor 12 may include a suction nozzle 74, a discharge nozzle 76, and an electric motor disposed within an electric motor housing 78.

0108Electric power 50 may be received by electrical enclosure 72. CM 30 may be connected to SM 32 through a housing 80. In this way, CM 30 and SM 32 may be located at different locations on or within compressor 12, and may communicate via a communication connection routed on, within, or through compressor 12, such as a communication connection routed through housing 80.

0109With reference to <figref idref="f0004 f0005 f0006">Figures 7 through 12</figref>, SM 32 may be located within electrical enclosure 72. In <figref idref="f0004 f0005 f0006">Figures 7 through 12</figref>, a schematic view of electrical enclosure 72 and SM 32 is shown. SM 32 may include a processor 100 with RAM 102 and ROM 104 disposed on a printed circuit board (PCB)106. Electrical enclosure 72 may be an enclosure for housing electrical terminals 108 connected to an electric motor of compressor 12. Electrical terminals 108 may connect electric power 50 to the electric motor of compressor 12.

0110Electrical enclosure 72 may include a transformer 49 for converting electric power 50 to a lower voltage for use by SM 32 and CM 30. For example, electric power 51 may be converted by transformer 49 and delivered to SM 32. SM 32 may receive low voltage electric power from transformer 49 through a power input 110 of PCB 106. Electric power may also be routed through electrical enclosure 72 to CM 30 via electrical connection 52.

0111Voltage sensors 54, 56, 58 may be located proximate each of electrical terminals 108. Processor 100 may be connected to voltage sensors 54, 56, 58 and may periodically receive or sample voltage measurements. Likewise, current sensor 60 may be located proximate one of electrical power leads 116. Processor 100 may be connected to current sensor 60 and may periodically receive or sample current measurements. Electrical voltage and current measurements from voltage sensors 54, 56, 58 and from current sensor 60 may be suitably scaled for the processor 100.

0112PCB 106 may include a communication port 118 to allow communication between processor 100 of SM 32 and CM 30. A communication link between SM 32 and CM 30 may include an optical isolator 119 to electrically separate the communication link between SM 32 and CM 30 while allowing communication. Optical isolator 119 may be located within electrical enclosure 72. Although optical isolator 119 is independently shown, optical isolator 119 may also be located on PCB 106. At least one additional communication port 120 may also be provided for communication between SM 32 and other devices. A handheld or portable device may directly access and communicate with SM 32 via communication port 120. For example, communication port 120 may allow for in-circuit programming of SM 32 a device connected to communication port 120. Additionally, communication port 120 may be connected to a network device for communication with SM 32 across a network.

0113Communication with SM 32 may be made via any suitable communication protocol, such as I2C, serial peripheral interface (SPI), RS232, RS485, universal serial bus (USB), or any other suitable communication protocol.

0114Processor 100 may access compressor configuration and operating data stored in an embedded ROM 124 disposed in a tamper resistant housing 140 within electrical enclosure 72. Embedded ROM 124 may be a compressor memory system disclosed in assignee's commonly-owned <patcit id="pcit0004" dnum="US40502106" dnum-type="L"><text>U.S. Patent Application No. 11/405,021, filed April 14, 2006</text></patcit>, <patcit id="pcit0005" dnum="US47486506" dnum-type="L"><text>U.S. Patent Application No. 11/474,865, filed June 26, 2006</text></patcit>, <patcit id="pcit0006" dnum="US47482106" dnum-type="L"><text>U.S. Patent Application No. 11/474,821, filed June 26, 2006</text></patcit>, <patcit id="pcit0007" dnum="US47479806" dnum-type="L"><text>U.S. Patent Application No. 11/474,798, filed June 26, 2006</text></patcit>, or <patcit id="pcit0008" dnum="US67478105" dnum-type="L"><text>U.S. Patent Application No. 60/674,781, filed April 26, 2005</text></patcit>. In addition, other suitable memory systems may be used.

0115Embedded ROM 124 may store configuration and operating data for compressor 12. When configuration data for compressor 12 is modified, the modified data may likewise be stored in embedded ROM 124. Configuration data for compressor 12 may be communicated to CM 30 or system controller 34. When compressor and/or SM 32 are replaced, the default configuration data for the new compressor 12 may be communicated to CM 30 and/or system controller 34 upon startup. In addition, configuration data may be downloaded remotely. For example, configuration data in embedded ROM 124 may include operating and diagnostic software that may be upgraded via a network connection. In this way, operating and diagnostic software may be upgraded efficiently over the network connection, for example, via the internet.

0116Relays 126, 127 may be connected to processor 100. Relay 126 may control activation or deactivation of compressor 12. When SM 32 determines that an undesirable operating condition exists, SM 32 may simply deactivate compressor 12 via relay 126. Alternatively, SM 32 may notify CM 30 of the condition so that CM 30 may deactivate the compressor 12. Relay 127 may be connected to a compressor related component. For example, relay 127 may be connected to a crank case heater. SM 32 may activate or deactivate the crank case heater as necessary, based on operating conditions or instructions from CM 30 or system controller 34. While two relays 126, 127 are shown, SM 32 may, alternatively, be configured to operate one relay, or more than two relays.

0117Processor 100 and PCB 106 may be mounted within a housing enclosure 130. Housing enclosure 130 may be attached to or embedded within electrical enclosure 72. Electrical enclosure 72 provides an enclosure for housing electrical terminals 108 and transformer 49. Housing enclosure 130 may be tamper-resistant such that a user of compressor 12 may be unable to inadvertently or accidentally access processor 100 and PCB 106. In this way, SM 32 may remain with compressor 12, regardless of whether compressor 12 is moved to a different location, returned to the manufacturer for repair, or used with a different CM 30.

0118LED's 131, 132 may be located on, or connected to, PCB 106 and controlled by processor 100. LED's 131, 132 may indicate status of SM 32 or an operating condition of compressor 12. LED's 131, 132 may be located on housing enclosure 130 or viewable through housing enclosure 130. For example, LED 131 may be red and LED 132 may be green. SM 32 may light green LED 132 to indicate normal operation. SM 32 may light red LED 131 to indicate a predetermined operating condition. SM 32 may also flash the LED's 131, 132 to indicate other predetermined operating conditions.

0119In <figref idref="f0004">Figure 7</figref>, one current sensor 60 is shown. Additional current sensors may also be used and connected to SM 32. With reference to <figref idref="f0004">Figure 8</figref>, two current sensors 57, 60 may be used to sense electric current for two phases of electric power 50. When two current sensors 57, 60 are used, electric current for the remaining phase may be estimated based on voltage measurements and based on the current measurements from current sensors 57, 60. With reference to <figref idref="f0005">Figure 9</figref>, three current sensors 55, 57, 60 may be used to sense electric current for all three phases of electric power 50.

0120With reference to <figref idref="f0005 f0006">Figures 10 to 12</figref>, in the case of a dual winding three phase electric motor, electrical enclosure 72 may include additional electrical terminals 109 for additional windings. In such case, six electrical terminals 108, 109 may be located within electrical enclosure 72. Three electrical terminals 108 may be connected to the three phases of electric power 50 for a first set of windings of the electric motor of compressor 12. Three additional electrical terminals 109 may also connected to the three phases of electric power 50 for a second set of windings of the electric motor of compressor 12.

0121Voltage sensors 61, 62, 63 may be located proximate each of electrical terminals 109. Processor 100 may be connected to voltage sensors 61, 62, 63 and may periodically receive or sample voltage measurements. With reference to <figref idref="f0005">Figure 10</figref>, processor 100 may periodically receive or sample current measurements from a current sensor 64 for sensing electrical current flowing to one of the additional electrical terminals 109. Additional current sensors may also be used. With reference to <figref idref="f0006">Figure 11</figref>, four current sensors 57, 60, 64, 65 may be connected to processor 100. Two current sensors 57, 60 may be associated with electrical terminals 108 and two current sensors 64, 65 may be associated with electrical terminals 109. With reference to <figref idref="f0006">Figure 12</figref>, six current sensors 55, 57, 60, 64, 65, 66 may be connected to processor 100. Three current sensors 55, 57, 60 may be associated with electrical terminals 108 and three current sensors 64, 65, 66 may be associated with electrical terminals 109. With six current sensors 55, 57, 60, 64, 65, 66, processor 100 may receive current measurements for each winding of a dual winding three phase electric motor associated with compressor 12.

0122Processor 100 may sample current and voltage measurements from the various sensors periodically over each cycle of AC power to determine multiple instantaneous current and voltage measurements. For example, processor 100 may sample current and voltage measurements twenty times per cycle or approximately once every millisecond in the case of alternating current with a frequency of sixty mega-hertz. From these actual current and voltage measurements, processor 100 may calculate additional power related data such as true and apparent power, power consumption over time, and power factor.

0123Based on actual current and voltage measurements, processor 100 may determine a root mean square (RMS) value for voltage and current for each phase of electric power 50. Processor 100 may calculate an RMS voltage value by squaring each of the sampled voltage measurements, averaging the squared measurements, and calculating the square root of the average. Likewise, processor 100 may calculate an RMS current value by squaring each of the sampled current measurements, averaging the squared measurements, and calculating the square root of the average.

0124From RMS voltage and RMS current calculations, processor 100 may calculate apparent power (S) according to the following equation: <maths id="math0001" num="(1)"><math display="block"><mi>S</mi><mo>=</mo><msub><mi>V</mi><mi mathvariant="italic">RMS</mi></msub><mo>×</mo><msub><mi>I</mi><mi mathvariant="italic">RMS</mi></msub><mo>,</mo></math><img file="EP3133286B1_D0001.tif" /></maths> where V_RMS is the calculated RMS of voltage over at least one cycle of AC and where I_RMS is the calculated RMS of current over at least one cycle of AC. Apparent power may be calculated in units of Volt-Amps (VA) or kilo-Volt-Amps (kVA)

0125Processor 100 may calculate apparent power for each phase of electric power 50. When current sensors 55, 57, 60, 64, 65, 66 are available for all three phases of electric power 50, actual current measurements may be used to calculate apparent power. When current sensors are not available for all three phases, current for a missing phase may be estimated by interpolation from known current and voltage measurements.

0126Processor 100 may calculate total apparent power (S_Total) for an electric motor of compressor 12 based on apparent power calculations for each of the phases, according to the following equation: <maths id="math0002" num="(2)"><math display="block"><msub><mi>S</mi><mi mathvariant="italic">Total</mi></msub><mo>=</mo><msub><mi>V</mi><mrow><mi mathvariant="italic">RMS</mi><mfenced><mn>1</mn></mfenced></mrow></msub><mo>×</mo><msub><mi>I</mi><mrow><mi mathvariant="italic">RMS</mi><mfenced><mn>1</mn></mfenced></mrow></msub><mo>+</mo><msub><mi>V</mi><mrow><mi mathvariant="italic">RMS</mi><mfenced><mn>2</mn></mfenced></mrow></msub><mo>×</mo><msub><mi>I</mi><mrow><mi mathvariant="italic">RMS</mi><mfenced><mn>2</mn></mfenced></mrow></msub><mo>+</mo><msub><mi>V</mi><mrow><mi mathvariant="italic">RMS</mi><mfenced><mn>3</mn></mfenced></mrow></msub><mo>×</mo><msub><mi>I</mi><mrow><mi mathvariant="italic">RMS</mi><mfenced><mn>3</mn></mfenced></mrow></msub><mo>,</mo></math><img file="EP3133286B1_D0002.tif" /></maths> where V_RMS(1), V_RMS(2), and V_RMS(3) are the calculated RMS voltage over a cycle of AC for the first, second, and third phase of AC, respectively, and where I_RMS(1), I_RMS(2), and I_RMS(3) are the calculated RMS current a cycle of AC for the first, second, and third phase of AC, respectively. Apparent power is calculated in units of Volt-Amps (VA) or kilo-Volt-Amps (kVA)

0127Active power (P), in units of watts (W) or kilo-watts (kW) may be calculated as an integral of the product of instantaneous currents and voltages over a cycle of AC, according to the following equation: <maths id="math0003" num="(3)"><math display="block"><mi>P</mi><mo>=</mo><mfrac><mn>1</mn><mi>T</mi></mfrac><mstyle displaystyle="true"><mrow><msubsup><mo>∫</mo><mn>0</mn><mi>T</mi></msubsup><mrow><mfenced separators=""><mi>v</mi><mfenced><mi>t</mi></mfenced><mi>i</mi><mfenced><mi>t</mi></mfenced></mfenced><mi mathvariant="italic">dt</mi><mo>,</mo></mrow></mrow></mstyle></math><img file="EP3133286B1_D0003.tif" /></maths> where v(t) is instantaneous voltage at time t, in units of volts; where i(t) is instantaneous current at time t, in units of amps; and where T is the period.

0128Based on the actual instantaneous electrical current and voltage measurements sampled over a cycle of the AC power, processor 100 may calculate (P) as the sum of the products of instantaneous voltage and current samples for each sample interval (e.g., one millisecond), over one cycle of AC. Thus, P may be calculated by processor 100 according to the following equation: <maths id="math0004" num="(4)"><math display="block"><mi>P</mi><mo>≅</mo><mfrac><mn>1</mn><mi>T</mi></mfrac><mstyle displaystyle="true"><munderover><mo>∑</mo><mrow><mi>k</mi><mo>=</mo><mn>1</mn></mrow><mrow><mi>k</mi><mo>=</mo><mfrac><mi>T</mi><mrow><mi mathvariant="normal">Δ</mi><mo>⁢</mo><mi>t</mi></mrow></mfrac></mrow></munderover><mrow><mi>v</mi><mfenced><mi>k</mi></mfenced><mi>i</mi><mfenced><mi>k</mi></mfenced><mi mathvariant="normal">Δ</mi><mo>⁢</mo><mi>t</mi><mo>,</mo></mrow></mstyle></math><img file="EP3133286B1_D0004.tif" /></maths> where v(k) is the instantaneous voltage measurement for the kth sample; i(k) is the instantaneous current measurement for the kth sample; T is the period; and Δt is the sampling interval (e.g., 1 millisecond).

0129P may be calculated for each phase of electric power. Processor 100 may calculate a total active power (P_Total) by adding the active power for each phase, according to the following equation: <maths id="math0005" num="(5)"><math display="block"><msub><mi>P</mi><mi mathvariant="italic">Total</mi></msub><mo>=</mo><msub><mi>P</mi><mfenced><mn>1</mn></mfenced></msub><mo>+</mo><msub><mi>P</mi><mfenced><mn>2</mn></mfenced></msub><mo>+</mo><msub><mi>P</mi><mfenced><mn>3</mn></mfenced></msub><mo>,</mo></math><img file="EP3133286B1_D0005.tif" /></maths> Where P₍₁₎, P₍₂₎, and P₍₃₎ are the active power for the first, second, and third phase of AC, respectively.

0130Based on the active power calculations, processor 100 may calculate energy consumption by calculating an average of active power over time. Energy consumption may be calculated by processor 100 in units of watt-hours (WH) or kilo-watt-hours (kWH).

0131Further, based on the active power calculation and the apparent power calculation, processor 100 may calculate the power factor (PF) according to the following equation: <maths id="math0006" num="(6)"><math display="block"><mi mathvariant="italic">PF</mi><mo>=</mo><mfrac><mi>P</mi><mi>S</mi></mfrac><mo>,</mo></math><img file="EP3133286B1_D0006.tif" /></maths> where P is active power in units of watts (W) or kilo-watts (kW); and where S is apparent power in units of volt-amps (VA) or kilo-volt-amps (kVA). Generally, PF is the ratio of the power consumed to the power drawn. Processor 100 may calculate PF for each phase of electric power. Processor 100 may also calculate a total PF as a ratio of total actual power to total apparent power, according to the following equation: <maths id="math0007" num="(7)"><math display="block"><msub><mi mathvariant="italic">PF</mi><mi mathvariant="italic">Total</mi></msub><mo>=</mo><mfrac><msub><mi>P</mi><mi mathvariant="italic">Total</mi></msub><msub><mi>S</mi><mi mathvariant="italic">Total</mi></msub></mfrac><mo>,</mo></math><img file="EP3133286B1_D0007.tif" /></maths> where P_total and S_Total are calculated according to formulas 2 and 5 above.

0132Alternatively, processor 100 may calculate power factor by comparing the zero crossings of the voltage and current waveforms. The processor may use the angular difference between the zero crossings as an estimate of PF. Processor 100 may monitor voltage and current measurements to determine voltage and current waveforms for electric power 50. Based on the measurements, processor may determine where each waveform crosses the zero axis. By comparing the two zero crossings, processor 100 may determine an angular difference between the voltage waveform and the current waveform. The current waveform may lag the voltage waveform, and the angular difference may be used by processor 100 as an estimate of PF.

0133PF may be used as an indication of the efficiency of the electric motor or the compressor. Increased lag between the current waveform and the voltage waveform results in a lower power factor. A power factor near one, i.e., a unity power factor, is more desirable than a lower power factor. An electric motor with a lower power factor may require more energy to operate, thereby resulting in increased power consumption.

0134SM 32 may provide continually updated power factor calculations, as well as RMS voltage, RMS current, active power, apparent power, and energy consumption calculations, based on continually sampled instantaneous electrical current and voltage measurements, to CM 30 and/or system controller 34. CM 30 and system controller 34 may utilize the electrical electric power measurements and calculations communicated from SM 32 to control and evaluate efficiency of compressor 12 or refrigeration system 10.

0135Further, electrical measurements and calculations, including PF, may be accessed by a user through system controller 34 or CM 30. Additionally, electrical measurements and calculations may be accessed through direct communication with SM 32 via communication port 120. Electrical measurements and calculations may be stored and periodically updated in embedded ROM 124.

0136In this way, electrical calculations and measurements, such as RMS voltage, RMS current, active power, apparent power, power factor, and energy calculations may be accurately and efficiently made at the compressor 12 and communicated to other modules or controllers or to a user of the compressor 12 or refrigeration system 10 for purposes of evaluating electrical power usage.

0137In addition to communicating electrical calculations and measurements to other modules, controllers, or users, SM 32 may use the electrical calculations and measurements diagnostically to detect certain variations in operating conditions. SM 32 may alert CM 30 to certain operating conditions based on the electrical calculations and measurements.

0138Referring now to <figref idref="f0007">Figure 13</figref>, a flow chart illustrating an operating algorithm 1300 for SM 32 is shown. In step 1301, SM 32 may initialize. Initialization may include resetting counters, timers, or flags, checking and initializing RAM 102, initializing ports, including communication ports 118, 120, enabling communication with other devices, including CM 30, checking ROM 104, checking embedded ROM 124, and any other necessary initialization functions. SM 32 may load operating instructions from ROM 104 for execution by processor 100.

0139In step 1302, SM 32 may receive actual electrical measurements from connected voltage and current sensors. SM 32 may receive a plurality of instantaneous voltage and current measurements over the course of a cycle of the AC electrical power. SM 32 may buffer the voltage and current measurements in RAM 102 for a predetermined time period.

0140In step 1304, SM 32 may calculate RMS voltage and RMS current based on the instantaneous voltage and current measurements. Based on the RMS voltage and RMS current calculations, SM 32 may calculate apparent power in step 1304. Based on the instantaneous voltage and current measurements, SM 32 may also calculate active power. Based on the apparent power calculation and the active power calculation, SM 32 may calculate the power factor. SM 32 may also calculate the power factor from the instantaneous voltage and current measurements by examining an angular difference between the zero crossings of the electrical current waveform and the voltage waveform.

0141In step 1306, SM 32 may receive run state data from CM 30. The run state data may include data indicating whether an electric motor of compressor 12 is currently in an activated or deactivated state. The run state data may also include timing data indicating a period of time that the electric motor has been in the current state. If the electric motor is a dual winding three phase electric motor, the run state data may also including data indicating whether one or both of the windings are activated.

0142In step 1308, based on the electrical measurements and calculations, and based on the data received from CM 30, SM 32 may perform and/or monitor diagnostic algorithms as described in more detail below. Some diagnostic algorithms may be executed once per each iteration of operating algorithm 1300. Some diagnostic algorithms may be executed concurrently with, and monitored by, operating algorithm 1300.

0143In step 1310, SM 32 may communicate the results of the electrical measurements and calculations to CM 30. SM 32 may also communicate the results of any diagnostic algorithms to CM 30. As described below, SM 32 may set operating flags corresponding to operating conditions according to diagnostic algorithms. SM 32 may communicate any operating flags to CM 30 in step 1310.

0144In step 1312, SM 32 may receive and respond to communications from CM 30. For example, CM 30 may request particular data from SM 32. CM 30 may also request certain data from embedded ROM 124. CM 30 may update SM 32 with operating parameters or thresholds for use in diagnostic algorithms. CM 30 may direct SM 32 to activate or deactivate any compressor related devices, such as a crank case heater, controlled by SM 32 via relay 127.

0145After responding to communications from CM 30 in step 1312, SM 32 may loop back to step 1302 and continue operation.

0146Referring now to <figref idref="f0007">Figure 14</figref>, a flow chart illustrating an algorithm 1400 for SM 32 to detect a no-power condition is shown. The algorithm 1400 may be one of the diagnostic algorithms performed/monitored by SM 32, as described with reference to step 1308 of <figref idref="f0007">Figure 13</figref> above. Prior to execution of the algorithm 1400, a no-power flag may have been reset by SM 32.

0147In step 1401, SM 32 may determine whether the current run state is set to run, based on run state data received from CM 30, as described with reference to step 1306 of <figref idref="f0007">Figure 13</figref> above. When the run state is not set to run, compressor 12 is not activated, and SM 32 may end execution of the algorithm in step 1402.

0148When the run state is set to run, SM 32 may proceed to step 1404 and check voltage measurements. When three phase power is used, SM 32 may check each of three voltage measurements, V₁, V₂, and V₃. SM 32 may determine whether V₁, V₂, and V₃ are less than a minimum voltage threshold, V_min-14. In step 1404, when V₁, V₂, and V₃ are greater than or equal to V_min-14, SM 32 may determine that compressor 12 has sufficient power, and end execution of algorithm 1400 in step 1402.

0149In step 1404, when SM 32 determines that V₁, V₂, and V₃ are less than V_min-14, SM 32 may proceed to step 1406. In step 1406, SM 32 may determine whether the time since the compressor 12 was activated is greater than a time threshold, Tm_Thr-14. For example, Tm_Thr-14 may be set to two seconds. In this way, SM 32 may allow for any bounce of any contactor coil relays. In step 1406, when the time since compressor activation is not greater than Tm_Thr-14, SM 32 may return to step 1401.

0150In step 1406, when the time since compressor activation is greater than TM_Thr-14, SM 32 may proceed to step 1408. In step 1408, SM 32 may set a no-power flag. By setting the no-power flag, SM 32 may indicate that compressor 12 does not have sufficient electrical power to operate. The no-power flag may be communicated to, or detected by, CM 30 and/or system controller 34. CM 30 and/or system controller 34 may adjust compressor and refrigeration system operation accordingly.

0151Referring now to <figref idref="f0008">Figure 15</figref>, a flow chart illustrating an algorithm 1500 for SM 32 to detect a welded contactor condition is shown. The algorithm 1500 may be one of the diagnostic algorithms performed / monitored by SM 32, as described with reference to step 1308 of <figref idref="f0007">Figure 13</figref> above. Prior to execution of the algorithm 1500, a welded-contactor flag may have been reset by SM 32. A welded contactor may cause compressor 12 to continue to operate, even though SM 32 or CM 30 may have attempted to open a contactor to deactivate the compressor.

0152In step 1501, SM 32 may determine whether the current run state is set to run, based on run state data previously received from CM 30, as described with reference to step 1306 of <figref idref="f0007">Figure 13</figref> above. When the run state is set to run, the compressor 12 is activated, and SM 32 may end execution of the algorithm in step 1502.

0153When the run state is not set to run, SM 32 may proceed to step 1504 and check voltage measurements. When three phase power is used, SM 32 may check each of three voltage measurements, V₁, V₂, and V₃. SM 32 may determine whether voltages V₁, V₂, or V₃ are greater than a maximum voltage threshold, V_max-15. In step 1504, when V₁, V₂, or V₃ are not greater than or equal to V_max-15, SM 32 may determine that a welded contactor condition does not exist, and end execution of the algorithm in step 1502.

0154When V₁, V₂, or V₃ are greater than V_max-15, SM 32 may proceed to step 1506. In step 1506, SM 32 may determine whether the time since compressor 12 was deactivated is greater than a time threshold, Tm_Thr-15. For example, Tm_Thr-15 may be set to two seconds. By waiting for the Tm_Thr-15, SM 32 may allow for any bounce of any contactor coil relays. In step 1506, when the time since compressor deactivation is not greater than Tm_Thr-15, SM 32 may return to step 1501.

0155In step 1506, when the time since compressor deactivation is greater than TM_Thr-15, SM 32 may proceed to step 1508. In step 1508, SM 32 may set a welded-contactor flag. By setting the welded-contactor flag, SM 32 may indicate that compressor 12 may have at least one welded contactor. In such case, power may be delivered to compressor 12, due to the welded contactor, despite the attempt of CM 30 or SM 32 to deactivate compressor 12. The welded-contactor flag may be communicated to, or detected by, CM 30 and/or system controller 34. CM 30 and/or system controller 34 may adjust compressor and refrigeration system operation accordingly. Specifically, CM 30 may activate compressor 12 while it is in the welded-contactor state to avoid a voltage imbalance condition and prevent damage or overheating of compressor 12. Further, CM 30 or system controller 34 may notify a user that compressor 12 is being operated in a welded-contactor state.

0156Referring now to <figref idref="f0008">Figure 16</figref>, a flow chart illustrating an algorithm 1600 for SM 32 to detect a locked rotor condition is shown. Algorithm 1600 may be one of the diagnostic algorithms performed / monitored by SM 32, as described with reference to step 1308 of <figref idref="f0007">Figure 13</figref> above. In a locked rotor condition, a rotor of the electric motor may be seized. Normally, when an electric motor is activated, electric current of the motor (I) increases for an initial period during startup, and then decreases as the motor reaches operating speed. If, however, the rotor is seized, I will not decrease after the initial period. Prior to execution of the algorithm 1600, a locked-rotor flag may have been reset by SM 32.

0157In step 1601, SM 32 may buffer electrical current measurements for a predetermined buffer period. For example, SM 32 may buffer electrical current measurements for 200 ms.

0158In step 1602, SM 32 may determine whether I is greater than a minimum electric current threshold (I_min-16). When I is not greater than I_min-16, SM 32 may loop back to step 1601 and continue to buffer I. In step 1602, when SM 32 determines that I is greater than I_min-16, SM 32 may proceed to step 1604.

0159In step 1604, SM 32 may determine the greatest I value currently in the buffer (I_grtst-16). In step 1606, SM 32 may determine whether I_grtst is greater than an electric current threshold (I_max-16). SM 32 may then wait in steps 1608 and 1610 for a time threshold (TM_Thr-16) to expire. For example, TM_Thr-16 may be set to two seconds. In this way, SM 32 allows I to settle to a normal operating current if the electric motor does not have a locked rotor.

0160When I_grtst-16 is greater than I_max-16 in step 1606, then in step 1612, SM 32 may use I_max-16 as the current threshold. In step 1612, when I is greater than I_max-16, SM 32 may determine that a locked rotor condition exists and may proceed to step 1614 to set the locked-rotor flag. In step 1612, when I is not greater than I_max-16, SM 32 may end execution of the algorithm in step 1616.

0161In step 1606, when I_grtst-16 is not greater than I_max-16, SM 32 may use a predetermined percentage (X%) of I_grtst-16 as the current threshold in step 1618. In step 1618, when I_mtr-16 is greater than X% of I_grtst-16, SM 32 may determine that a locked rotor condition exists and may set the locked-rotor flag in step 1614. SM 32 may end execution of the algorithm in step 1616. The locked-rotor flag may be communicated to, or detected by, CM 30 and/or system controller 34. CM 30 and/or system controller 34 may adjust compressor and refrigeration system operation accordingly.

0162If a locked-rotor condition is detected a predetermined number of consecutive times, SM 32 may set a locked rotor lockout flag. SM 32 may cease operation of the compressor until the lockout flag is cleared by a user. For example, SM 32 may set the locked rotor lockout flag when it detects ten consecutive locked rotor conditions.

0163Referring now to <figref idref="f0009">Figure 17</figref>, a flow chart illustrating an algorithm 1700 for SM 32 to detect a motor protection trip is shown. Algorithm 1700 may be one of the diagnostic algorithms performed / monitored by SM 32, as described with reference to step 1308 of <figref idref="f0007">Figure 13</figref> above. Compressor 12 may be configured with internal line breaks. The internal line breaks may trip, or deactivate, compressor 12 when electric current is excessive or when compressor 12 is overheating. In such case, SM 32 may detect that an internal line break has occurred and notify CM 30. Prior to execution of the algorithm 1700, a protection-trip flag may have been reset by SM 32.

0164In step 1701, SM 32 determines whether any voltage, V₁, V₂, or V₃ is greater than a voltage minimum threshold (V_min-17). When V₁, V₂, or V₃ is not greater than V_min-17, SM 32 may end execution of algorithm 1700 in step 1702. When V₁, V₂, or V₃ is greater than V_min-17, SM 32 may proceed to step 1704. In step 1704, SM 32 may determine whether I is less than a current minimum I_min-17. When I is not less than I_min-17, SM 32 may end execution of algorithm 1700 in step 1702. When I is less than I_min-17, SM 32 may proceed to step 1706 and set a protection-trip flag. In this way, when voltage is present, but electric current is not present, SM 32 may determine that an internal line break condition has occurred. The protection-trip flag may be communicated to, or detected by, CM 30 and/or system controller 34. CM 30 and/or system controller 34 may adjust compressor 12 and refrigeration system 10 operation accordingly.

0165Referring now to <figref idref="f0009">Figure 18</figref>, a flow chart illustrating an algorithm 1800 for SM 32 to detect a low voltage condition is shown. Algorithm 1800 may be one of the diagnostic algorithms performed / monitored by SM 32, as described with reference to step 1308 of <figref idref="f0007">Figure 13</figref> above. Prior to execution of the algorithm 1800, a low-voltage flag may have been reset by SM 32.

0166In step 1801, SM 32 may determine the normal operating voltage of compressor (V_nml). SM 32 may determine V_nml based on historical data of previous compressor operating voltages. For example, V_nml may be calculated by averaging the voltage over the first five electrical cycles of power during the first normal run. V_nml may alternatively be predetermined and stored in ROM 104, 124, or calculated based on an average voltage over the operating life of the compressor.

0167In step 1802, SM 32 may monitor V_{1,2, and 3} for a predetermined time period TM_thr-18. For example, TM_Thr-18 may be set to two seconds. The time threshold may or may not be the same as the time threshold used in other diagnostic algorithms. In step 1804, SM 32 may determine whether V_{1, 2, and 3} are less than a predetermined percentage (X%) of V_nml for more than TM_thr-18. For example, the predetermined percentage may be 75 percent. In step 1804, when V_{1, 2, and 3} are not less than X% of V_nml for more than TM_thr-18, SM 32 loops back to step 1802. In step 1804, when V_{1, 2, and 3} are less than X% of V_nml for more than TM_thr-18, SM 32 may proceed to step 1806.

0168In step 1806, SM 32 may determine whether the run state is set to run. When the run state is not set to run in step 1806, SM 32 ends execution of algorithm 1800 in step 1808. When the run state is set to run, SM 32 may determine that a low-voltage condition exists and may set a low-voltage flag in step 1810. The low-voltage flag may be communicated to, or detected by, CM 30 and/or system controller 34. CM 30 and/or system controller 34 may adjust compressor 12 and refrigeration system 10 operation accordingly.

0169Referring now to <figref idref="f0010">Figure 19</figref>, a flow chart illustrating an algorithm 1900 for SM 32 to detect a phase loss condition for compressor 12, when three phase electric power 50 is used. Algorithm 1900 may be one of the diagnostic algorithms performed / monitored by SM 32, as described with reference to step 1308 of <figref idref="f0007">Figure 13</figref> above. SM 32 may compare each voltage, V₁, V₂, and V₃, to determine whether any particular voltage is lower than a predetermined percentage of the average of the other two voltages. Prior to execution of the algorithm 1900, a phase-loss flag may have been reset by SM 32

0170In step 1901, SM 32 may monitor V₁, V₂, and V₃. In step 1902, SM 32 may determine whether V₁ is less than a predetermined percentage, X%, of the average of V₂ and V₃, for a time (Tm) greater than a time threshold, TM_Thr-19. When V₁ is less than X% of the average of V₂ and V₃, SM 32 may set the phase-loss flag in step 1904 and end execution of algorithm 1900 in step 1906. When V₁ is not less than X% of the average of V₂ and V₃, SM 32 may proceed to step 1908.

0171In step 1908, SM 32 may determine whether V₂ is less than X% of the average of V₁ and V₃, for Tm greater than TM_Thr-19. When V₂ is less than X%, of the average of V₁ and V₃, SM 32 may set the phase-loss flag in step 1904 and end execution of algorithm 1900 in step 1906. When V₂ is not less than X% of the average of V₁ and V₃, SM may proceed to step 1910.

0172In step 1910, SM 32 may determine whether V₃ is less than X% of the average of V₁ and V₂, for Tm greater than TM_Thr-19. When V₃ is less than X%, of the average of V₁ and V₂, SM 32 may set the phase-loss flag in step 1904 and end execution of algorithm 1900 in step 1906. When V₃ is not less than X% of the average of V₁ and V₂, SM 32 may loop back to step 1901. In this way, algorithm 1900 may operate concurrently with algorithm 1300. The phase-loss flag may be communicated to, or detected by, CM 30 and/or system controller 34. CM 30 and/or system controller 34 may adjust compressor 12 and refrigeration system 10 operation accordingly.

0173If a phase-loss condition is detected a predetermined number of consecutive times, SM 32 may set a phase-loss lockout flag. SM 32 may cease operation of the compressor until the lockout flag is cleared by a user. For example, SM 32 may set the phase-loss lockout flag when it detects ten consecutive phase-loss conditions.

0174Referring now to <figref idref="f0010">Figure 20</figref>, a flow chart illustrating an algorithm 2000 for SM 32 to detect a voltage imbalance condition for compressor 12, when three phase electric power 50 is used. Algorithm 2000 may be one of the diagnostic algorithms performed / monitored by SM 32, as described with reference to step 1308 of <figref idref="f0007">Figure 13</figref> above. SM 32 may determine whether the difference between any of voltages V₁, V₂, or V₃ is greater than a predetermined percentage of the average of V₁, V₂, and V₃. When the difference between any of voltages V₁, V₂, or V₃ is greater than a predetermined percentage of the average of V₁, V₂, and V₃, SM 32 may determine that a voltage imbalance condition exists. Prior to execution of the algorithm 2000, a voltage-imbalance flag may have been reset by SM 32

0175In step 2001, SM 32 may monitor V₁, V₂, and V₃. In step 2002, SM 32 may calculate the average (V_avg) of V₁, V₂, and V₃. In step 2004, SM 32 may calculate the percentage of voltage imbalance (%V_imb) by determining the maximum of the absolute value of the difference between each of V₁ and V_avg, V₂ and V_avg, and V₃ and V_avg. The maximum difference is then multiplied by V_avg/100.

0176In step 2006, SM 32 determines whether the run state is set to run. In step 2006, when the run state is not set to run, SM 32 may end execution of algorithm 2000 in step 2008. In step 2006, when the run state is set to run, SM 32 may proceed to step 2010.

0177In step 2010, SM 32 may determine whether %V_imb is greater than a voltage imbalance threshold (%V_Thr-20). When %V_imb is not greater than %V_Thr-20, SM 32 loops back to step 2001. In this way, algorithm 2000 may execute concurrently with operating algorithm 1300. When %V_imb is greater than %V_Thr-20, a voltage imbalance condition exists, and SM 32 may set the voltage-imbalance flag in step 2012. SM 32 may end execution of algorithm 2000 in step 2008. The voltage-imbalance flag may be communicated to, or detected by, CM 30 and/or system controller 34. CM 30 and/or system controller 34 may adjust compressor 12 and refrigeration system 10 operation accordingly.

0178Referring now to <figref idref="f0011">Figure 21</figref>, a flow chart illustrating an algorithm 2100 for SM 32 to detect a current overload condition is shown. Algorithm 2100 may be one of the diagnostic algorithms performed / monitored by SM 32, as described with reference to step 1308 of <figref idref="f0007">Figure 13</figref> above. Prior to execution of the algorithm 2100, a current-overload flag may have been reset by SM 32

0179In step 2101, SM 32 may determine the maximum continuous current (MCC) for the electric motor of compressor 12. MCC may be predetermined and set during the manufacture of compressor 12. MCC may be stored in ROM 104 and/or embedded ROM 124. In addition, MCC may be user configurable. MCC may vary based on the type of refrigerant used. Thus, a user of compressor 12 may modify the default MCC value to conform to actual refrigeration system conditions.

0180In step 2102, SM 32 may determine whether the run state is set to run. When the run state is not set to run, SM 32 ends execution of algorithm 2100 in step 2104. In step 2102, when the run state is set to run, SM 32 may proceed to step 2106. In step 2106, when run state has not been set to run for a time period greater than a first time threshold (TM_Thr1-21), SM 32 loops back to step 2102. In step 2106, when run state has been set to run for a time period greater than TM_Thr1-21, SM 32 may proceed to step 2108.

0181In step 2108, SM 32 monitors I. In step 2110, SM 32 may determine whether I is greater than MCC multiplied by 1.1. In other words, SM 32 may determine whether I is greater than 110% of MCC for a time greater than a second time threshold (TM_Thr2-21). When SM 32 determines that I is not greater than 110% of MCC for a time greater than TM_Thr2-21, SM 32 may loop back to step 2102. In this way, algorithm 2100 may execute concurrently with operating algorithm 1300. When SM 32 determines that I is greater than 110% of MCC for a time greater than TM_Thr2-21, SM 32 may determine that a current-overload condition exists and may set the current-overload flag in step 2112. SM 32 may end execution of the algorithm 2100 in step 2104. The current-overload flag may be communicated to, or detected by, CM 30 and/or system controller 34. CM 30 and/or system controller 34 may adjust compressor and refrigeration system operation accordingly.

0182Referring now to <figref idref="f0011">Figure 22</figref>, a flow chart illustrating an algorithm 2200 for SM 32 to detect a current delay condition, in a two current sensor system, to detect a lag between two electrical currents I₁ and I₂. Algorithm 2200 may be one of the diagnostic algorithms performed / monitored by SM 32, as described with reference to step 1308 of <figref idref="f0007">Figure 13</figref> above. Prior to execution of the algorithm, a current-delay flag may have been reset by SM 32.

0183When SM 32 detects current greater than a current threshold (I_min-22) from one of the two current sensors, SM 32 may determine whether current indicated by the other current sensor becomes greater than I_min-22 within a time period threshold (TM_Thr-22). In step 2201, SM 32 may determine whether I₁ is greater than a current threshold I_min-22. When I₁ is greater than I_min-22, SM 32 may proceed to step 2203 and start a time counter (Tm). SM 32 may proceed to step 2205 to determine whether I₂ is greater than I_min-22. In step 2205, when I₂ is greater than I_min-22, SM 32 may determine that a current-delay condition does not exist, and end execution of the algorithm in step 2210. In step 2205, when I₂ is not greater than I_min-22, SM 32 may proceed to step 2207 and determine whether Tm is greater than Tm_Thr-22. In step 2207, when TM is not greater than TM_Thr-22, SM 32 may loop back to step 2205 to compare I₂ with I_min-22. In step 2207, when Tm is greater than Tm_Thr-22, the time period has expired and a current-delay condition exists. SM 32 may proceed to step 2209 to set a current-delay flag. SM 32 may end execution of the algorithm 2200 in step 2210. The current-delay flag may be communicated to, or detected by, CM 30 and/or system controller 34. CM 30 and/or system controller 34 may adjust compressor and refrigeration system operation accordingly.

0184When I₁ is not greater than I_min-22, SM 32 may proceed to step 2202 and determine whether I₂ is greater than I_min-22. When I₂ is not greater than I_min-22, SM 32 loops back to step 2201. When I₂ is greater than I_min-22, SM 32 may proceed to step 2204 to start time Tm counter. SM 32 may proceed to step 2206 to determine whether I₁ is greater than I_min-22. In step 2206, when I₁ is greater than I_min-22, SM 32 may determine that a current-delay condition does not exist, and end execution of the algorithm in step 2210. In step 2206, when I₁ is not greater than I_min-22, SM 32 may proceed to step 2208 and determine whether Tm is greater than Tm_Thr-22. In step 2208, when TM is not greater than TM_Thr-22, SM 32 may loop back to step 2206 to compare I₁ with I_min-22. In step 2208, when Tm is greater than Tm_Thr-22, the time period has expired and a current-delay condition exists. SM 32 may proceed to step 2209 to set the current-delay flag. SM 32 may end execution of the algorithm 2200 in step 2210. As noted above, the current-delay flag may be communicated to, or detected by, CM 30 and/or system controller 34, which may adjust compressor and refrigeration system operation accordingly.

0185Referring now to <figref idref="f0012">Figure 23</figref>, a flow chart illustrating an algorithm 2300 for SM 32 to detect a current delay condition is shown, in a three current sensor system, to detect a lag between three electrical currents I₁, I₂, and I₃. Algorithm 2300 may be one of the diagnostic algorithms performed / monitored by SM 32, as described with reference to step 1308 of <figref idref="f0007">Figure 13</figref> above. Prior to execution of the algorithm, a current-delay flag may have been reset by SM 32.

0186When SM 32 detects current greater than a current threshold (I_min-22) from one of the three current sensors, SM 32 may determine whether current indicated by the other current sensors becomes greater than I_min-22 within a predetermined time period (TM_Thr-22). In step 2301, SM 32 may determine whether I₁ is greater than a current threshold I_min-22. When I₁ is greater than I_min-22, SM 32 may proceed to step 2302 and start a time counter (Tm). SM 32 may proceed to step 2303 to determine whether I₂ and b are greater than I_min-22. In step 2303, when I₂ and I₃ are greater than I_min-22, SM 32 may determine that a current-delay condition does not exist, and end execution of the algorithm in step 2304. In step 2303, when I₂ and I₃ are not greater than I_min-22, SM 32 may proceed to step 2305 and determine whether Tm is greater than Tm_Thr-22. In step 2305, when TM is not greater than TM_Thr-22, SM 32 may loop back to step 2303 to compare I₂ and I₃ with I_min-22. In step 2305, when Tm is greater than Tm_Thr-22, the time period has expired and a current-delay condition exists. SM 32 may proceed to step 2306 to set a current-delay flag. SM 32 may end execution of the algorithm 2300 in step 2304. The current-delay flag may be communicated to, or detected by, CM 30 and/or system controller 34. CM 30 and/or system controller 34 may adjust compressor and refrigeration system operation accordingly.

0187In step 2301, when I₁ is not greater than I_min-22, SM 32 may proceed to step 2307 and determine whether I₂ is greater than I_min-22. When I₂ is greater than I_min-22, SM 32 may proceed to step 2308 to start Tm counter. SM 32 may proceed to step 2309 to determine whether I₁ and I₃ are greater than I_min-22. In step 2309, when I₁ and I₃ are greater than I_min-22, SM 32 may determine that a current-delay condition does not exist, and end execution of the algorithm in step 2304. In step 2309, when I₁ and I₃ are not greater than I_min-22, SM 32 may proceed to step 2310 and determine whether Tm is greater than TM_Thr-22. In step 2310, when TM is not greater than TM_Thr-22, SM 32 may loop back to step 2309 to compare I₁ and I₃ with I_min-22. In step 2310, when Tm is greater than TM_Thr-22, the time period has expired and a current-delay condition exists. SM 32 may proceed to step 2306 to set the current-delay flag. SM 32 may end execution of the algorithm 2300 in step 2304. As noted above, the current-delay flag may be communicated to, or detected by, CM 30 and/or system controller 34, which may adjust compressor and refrigeration system operation accordingly.

0188In step 2307, when I₂ is not greater than I_min-22, SM 32 may proceed to step 2311 and determine whether I₃ is greater than I_min-22. When I₃ is not greater than I_min-22, SM 32 may loop back to step 2301. When I₃ is greater than I_min-22, SM 32 may proceed to step 2312 to start Tm counter. SM 32 may proceed to step 2313 to determine whether I₁ and I₂ are greater than I_min-22. In step 2313, when I₁ and I₂ are greater than I_min-22, SM 32 may determine that a current-delay condition does not exist, and end execution of the algorithm in step 2304. In step 2313, when I₁ and I₂ are not greater than I_min-22, SM 32 may proceed to step 2314 and determine whether Tm is greater than TM_Thr-22. In step 2314, when TM is not greater than TM_Thr-22, SM 32 may loop back to step 2313 to compare I₁ and I₂ with I_min-22. In step 2314, when Tm is greater than TM_Thr-22, the time period has expired and a current-delay condition exists. SM 32 may proceed to step 2306 to set the current-delay flag. SM 32 may end execution of the algorithm 2300 in step 2304. As noted above, the current-delay flag may be communicated to, or detected by, CM 30 and/or system controller 34, which may adjust compressor and refrigeration system operation accordingly.

0189With respect to each of the diagnostic algorithms described above with reference to <figref idref="f0007 f0008 f0009 f0010 f0011 f0012">Figures 14 to 23</figref>, SM 32 may selectively execute the diagnostic algorithms as needed and as data for the diagnostic algorithms is available. When a communication link is not available, or when data from a connected sensor is not available, due to malfunction or otherwise, SM 32 may disable those portions of the diagnostic algorithms that require the missing communication link or data. In this way, SM 32 may execute those portions of the diagnostic algorithms that are executable, based on the data and communication link(s) available to SM 32.

0190In this way, SM 32 may monitor electrical current and voltage measurements, make data calculations based on the electrical current and voltage measurements, and execute diagnostic algorithms based on the measurements and based on the calculations. SM 32 may communicate the measurements, the calculations, and the results of the diagnostic algorithms to CM 30 or system controller 34. SM 32 may thereby be able to provide efficient and accurate electrical power measurements and calculations to be utilized by other modules and by users to evaluate operating conditions, power consumption, and efficiency.