Compressor diagnostic system

ES 2 346 752 T3

DESCRIPTION

Diagnostic system for compressor.

The present invention relates to a diagnostic system for a refrigeration or air conditioning system. More particularly, the present invention relates to a diagnostic system for a refrigeration or air conditioning system that uses various operating characteristics and compressor "trip" information to diagnose problems associated with the refrigeration or air conditioning system.

There is a class of machines in the art generally known as spiral machines that are used to move various types of fluid. These spiral machines can be configured as an expander, a displacement motor, a pump, a compressor, etc. and the characteristics of the present invention are applicable to any of these machines. However, for purposes of illustration, the disclosed embodiment is in the form of a hermetic refrigerant scroll compressor used within a refrigeration or air conditioning system.

Scroll compressors are becoming increasingly popular for use as compressors in both refrigeration and air conditioning applications primarily due to their highly efficient ability to operate. Generally, these machines incorporate a pair of interlocking spiral windings, one of which is orbited relative to the other to define one or more moving chambers that progressively decrease in size as they move from an external suction opening towards a central discharge opening. An electric motor is provided which functions to drive the orbital scroll member by means of a suitable drive shaft attached to the rotor of the motor. In a hermetic compressor, the bottom of the hermetic housing normally contains an oil pan for lubrication and cooling purposes. Although the diagnostic system of the present invention will be described in conjunction with a scroll compressor, it is to be understood that the diagnostic system of the present invention can also be used with other types of compressors.

Traditionally, when an air conditioning or refrigeration system does not perform as designed, a technician is called on site to troubleshoot the problem. The technician performs a series of checks that help isolate the problem with the system. One of the causes of the system problem could be the compressor used in the system. A faulty compressor exhibits some operating patterns that could be used to detect the fact that the compressor is faulty. Unfortunately, many other causes of system problems can be attributed to other system components, and these other causes can also affect the performance of the compressor and its operating pattern. It is possible to analyze system problems and operating patterns and determine that the compressor is faulty when, in fact, the problem lies elsewhere and the compressor is not the problem. This confusion of causes usually results in the replacement of a good compressor. This misdiagnosis is costly since the compressor is generally the most expensive component in the system. The problem is further compounded by the fact that the root cause of the system problem has not been solved and the problem reappears in time. Any tool that can help avoid misdiagnosing the system problem as described above would be helpful and inexpensive. The present invention discloses a device that increases the accuracy of problem diagnosis for an air conditioning or refrigeration system.

A large part of the compressors used in air conditioning and refrigeration systems have built-in protection devices called "internal line break protectors." These protectors are thermally sensitive devices that are wired in electrical series with the motor. Shields react thermally to the line current drawn by the motor and also other temperatures within the compressor including, but not limited to, the discharge gas temperature, the suction gas temperature, or the temperature of a particular component in the compressor. When one of these temperatures exceeds a designed threshold, the protector will open the electrical connection to the motor. This shuts down the motor that runs the compressor which in turn shuts down the compressor and prevents it from running in areas that would lead to its failure. After a period of time, when temperatures have dropped to safe levels, the protector automatically resets and the compressor runs again. The temperatures at which the protector is reacting are a result of the operation of the compressor and the entire refrigeration or air conditioning system. The operation of the compressor or the operation of the entire system can influence the temperatures detected by these protectors. The significant aspect of the protection system is that some categories of failures repeatedly trip the protector with very short compressor on time and other categories of failures trip the protector less frequently, thus providing relatively longer compressor on times. For example, a compressor with seized bearings would trip the protector in less than about twenty seconds or on time or less. On the other hand, a system that has a very low refrigerant charge will trip the protector after typically more than ninety minutes of on-time. An analysis of the trip frequency, trip reset times, and compressor on times will provide valuable clues in identifying the cause of system problems.

US5,454,229 discloses means for monitoring compressor failure conditions. However, no attempt is made to diagnose the problem.

The present invention provides and a device which is based on this principle and is defined in claim 1. The device of the preferred embodiment continuously records the status of the protector (open or closed) as a function of time and then analyzes this status information to determine a faulty situation. The device

ES 2 346 752 T3 goes further and isolates the failure of the compressor or the rest of the system. Once the fault has been isolated, the device will activate a visual indicator (light) and will also send an electrical signal to any intelligent device (controller, computer, etc.) informing about the situation. The technician, upon arriving on the scene, then has a clear indication that the problem is most likely with system components other than the compressor or most likely the problem is with the compressor. You can then focus your troubleshooting and further troubleshooting on the identified area. The device thus avoids the previously described situation of confusing diagnosis and the potential of mistakenly replacing a good compressor.

In addition to the status of the protector, additional information can be gathered by sensors that monitor other operating characteristics of the cooling system such as supply voltage and outside ambient temperature. This additional information can then be used to further diagnose problems associated with the refrigeration or air conditioning system.

More areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.

The present invention will be more fully understood from the detailed description and accompanying drawings, in which

Figure 1 is a vertical cross section of a hermetic scroll compressor incorporating the single compressor diagnostic system in accordance with the present invention;

Figure 2 is a schematic representation of the diagnostic system for a single-phase motor for the compressor according to the present invention;

Figure 3 is a schematic representation of a diagnostic system for a three-phase motor for the compressor according to another embodiment of the present invention;

Figure 4 is a flow chart of the diagnostic system for the single-phase motor for the compressor according to the present invention;

Figure 5 is a flow chart of the diagnostic system for the three-phase motor for the compressor according to the present invention;

Figure 6 is a flow chart that is followed when diagnosing a compressor system;

Figure 7 is a schematic view of a typical refrigeration system using the compressor and the diagnostic system in accordance with the present invention;

Figure 8 is a perspective view of a contactor integrated with the diagnostic system circuitry in accordance with another embodiment of the present invention;

Figure 9 is a schematic view illustrating the circuitry of the contactor illustrated in Figure 8;

Figure 10 is a schematic view of a compressor plug illustrating the circuitry of the diagnostic system in accordance with another embodiment of the present invention;

Figure 11 is a flow chart of a diagnostic system for the compressor in accordance with another embodiment of the present invention;

Figure 12 is a chart indicating possible system failures based on ignition time before trips;

Figure 13 is a graph showing electric current versus condenser temperature;

Figure 14 is a graph showing percent run time versus outside ambient temperature; and Figure 15 is a schematic illustration of a diagnostic system in accordance with the present invention.

The following description of the preferred embodiment (s) is merely exemplary in nature and is not intended in any way to limit the invention, its application, or uses.

Referring now to the drawings in which like reference numerals designate equal or corresponding parts throughout the various views, Figure 1 shows a scroll compressor incorporating the single compressor diagnostic system in accordance with the present invention and which is generally designated

ES 2 346 752 T3 by reference number 10. Although compressor 10 is being illustrated as a scroll compressor in conjunction with a refrigeration or air conditioning system, it is within the scope of the present invention to use, if desired, other types of compressors in the refrigeration or air conditioning system as well as having any of the compressor designs in conjunction with other types of systems.

Scroll compressor 10 comprises a generally cylindrical hermetic casing 12 having a cover 14 welded to the upper end thereof and a base 16 having a plurality of mounting legs (not shown) integrally formed with the scroll compressor at the lower end thereof. same. The cap 14 is provided with a refrigerant discharge fitting 18 which may have the usual discharge valve therein. A transversely extending gap 20 is attached to housing 12 by being welded around its periphery at the same point that cover 14 is welded to housing 12. A compressor mounting frame 22 is snapped within housing 12 and is supported by the end of the base 16. Base 16 is slightly smaller in diameter than housing 12 such that base 16 is received within housing 12 and is welded around its periphery as shown in Figure 1.

The fundamental elements of the compressor 10 that are attached to the frame 22 include a two-piece main bearing case assembly 24, a lower bearing case 26, and a motor stator 28. A drive shaft or crankshaft 30 having an eccentric crankshaft journal 32 at the upper end thereof is rotatably hinged on a bearing 34 secured within the main bearing case assembly 24 and a second bearing 36 secured within the bearing case. lower bearing 26. The crankshaft 30 has at the lower end thereof a relatively large diameter concentric bore 38 communicating with a radially outwardly positioned smaller diameter bore 40 extending upwardly from it to the top of the crankshaft 30. The lower portion of the interior of the housing 12 defines an oil pan 44 that is filled with lubricating oil to a level slightly above the lower end of a rotor, and the bore 38 acts as a pump to pump lubricating fluid through the crankshaft 30. and within bore 40 and ultimately to all the various portions of compressor 10 that require lubrication.

Crankshaft 30 is rotationally driven by an electric motor that includes stator 28, windings 46 passing through it, and a rotor 48 snapped within crankshaft 30. An upper counterweight 50 is secured to crankshaft 30 and a counterweight 52 is secured to rotor 48. A temperature protector 54, of the usual type, is provided in the vicinity of the motor windings 46. Temperature protector 54 will trip the motor if thermal protector 54 exceeds its normal temperature range. The temperature shield 54 can be heated by the motor windings 46, the suction gas inside a suction chamber 56 and / or the discharge gas inside a discharge chamber 58 that is released into the discharge chamber. aspiration 56. Both suction chamber 56 and discharge chamber 58 are defined by housing 12, lid 14, base 16, and gap 22 as shown in Figure 1.

The upper surface of the two-piece main bearing box assembly 24 is provided with a flat thrust bearing surface on which is disposed an orbital spiral member 60 having the spiral blade or coil 62 extending upwardly from a plate. terminal 64. Projecting downward from the lower surface of end plate 64 of orbital scroll member 60 is a cylindrical hub 66 having a plain bearing therein and a drive sleeve 68 having an inner bore in which is rotatably disposed the crankshaft journal 32 is drivably arranged. Crankshaft journal 32 has a flat on a surface that drivably engages a flat surface formed in a portion of the inner bore of the drive bushing 68 to provide a radially conformal drive arrangement, as shown in the invention patent of US 4,877,382 of the assignee. Also provided is an Oldham gasket 70 positioned between the orbital scroll member 60 and two two-piece bearing box assemblies 24. Oldham gasket 70 is keyed to orbital scroll member 60 and non-orbital scroll member 72 to prevent rotational movement of orbital scroll member 60.

The non-orbital scroll member 72 is also provided with a coil 74 that extends downwardly from an end plate 76 that is positioned in mesh with the coil 62 of the orbital coil member 60. The non-orbital coil member 72 has a discharge conduit provided. centrally 78 communicating with an upwardly open gap 80 which, in turn, is in communication with discharge chamber 58. An annular gap 82 is also formed in the non-orbital scroll member 72 within which a floating seal assembly 84 is disposed.

Gaps 80 and 82 and floating seal assembly 84 cooperate to define axial pressure bypass chambers that receive pressurized fluid that is compressed by windings 62 and 74 to exert an axial biasing force on non-orbital scroll member 72 to thereby force the tips of the respective windings 62 and 74 into tight engagement with the opposite end surfaces of the end plates 76 and 64, respectively. The floating seal assembly is preferably of the type described in greater detail in assignee's US Patent 5,156,639. The non-orbital scroll member 72 is designed to be mounted for limited axial movement relative to the two-piece main bearing box assembly 24 in a suitable manner as disclosed in the aforementioned US patent 4,877,382. or the assignee's US patent 5,102,316.

Compressor 10 is powered by electricity that is provided to the electric motor within housing 12 through a molded electrical plug 90.

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Referring now to Figures 1-3, the present invention is directed to a single compressor diagnostic system 100. The diagnostic system 100 comprises one or more current sensing devices 102 and associated logic circuitry 104. The devices Current sensors 102 are mounted in a housing 106 mounted externally to housing 12. The logic circuitry 104 may be mounted in the housing 106 or it may be located in a convenient position relative to the compressor 10 as shown in hidden lines in Figure 2. Optionally, the sensing device and the circuitry may be integrated. inside a special contactor, a special wire harness, or inside a molded plug used for some compressor designs.

The current sensing devices 102 sense the current in the power cables feeding the compressor 10. Figure 2 illustrates two current sensing devices 102 in conjunction with a single phase motor. One of the current sensing devices 102 is associated with the main windings for the compressor motor and the other current sensing device 102 is associated with the auxiliary windings for the compressor motor. Figure 3 also illustrates two current sensing devices 102 in conjunction with a three phase motor. Each current sensing device 102 is associated with one of the phases of the three-phase power supply. Although Figure 3 illustrates two current sensing devices that sense current in two phases of the three-phase power supply, it is within the scope of the present invention to include a third current sensor 102 to detect current in the third phase of the power source. 3-phase power as shown in hidden lines in Figure 3, if desired. These current signals represent an indication of the status of protector 54 (open or closed). Although the current sensing devices 102 detect the state of the protector 54 using current in the power cables, it is also possible to detect the state of the protector 54 by detecting the presence or absence of voltage on the motor side of the protector 54. The inventors of This is considered by the present invention to be a less desirable but effective procedure in some cases because it requires a hermetic through-pin extending through the housing 12. The signals received from current sensing devices 102 are combined in logic circuitry 104 with the demand signal for compressor 10. The demand signal for compressor 10 is acquired by detecting the presence of supply voltage or with a controller system (not shown) supplying a discrete signal representing demand. The demand signal and the signal received by the logic circuitry 104 are processed by the logic circuitry 104 to obtain the information about the trip frequency of the protector 54 and the average on time and off time of the compressor. 10. The logic circuitry 104 analyzes the combination of current signals, the demand signal, and the obtained protector trip frequencies to determine if a fault condition exists. The logic circuitry also has the unique ability to identify a specific cause based on some faults. This information is provided to service personnel using a green LED 110 and a yellow LED 112. The green LED 110 is used to indicate that there is currently no fault condition and that the system is operating normally.

Yellow LED 112 is used to indicate the presence of a fault. When the yellow LED 112 is on, the green LED 110 is off. Thus, the yellow LED 112 is used to visually communicate that there is a fault, as well as indicate the type of fault that is present. This communication is accomplished by turning the yellow LED 112 on and then off for a specific duration and sequence to indicate both that there is a fault and to identify what fault it is: for example, turn on the 112 light for one second and turn it off for nineteen seconds and repeat. this sequence every twenty seconds will create the effect of a blinking light that blinks on once every twenty seconds. This sequence corresponds to a fault type that is coded as a Type 1 fault. If the 112 light blinks on twice for one second during the twenty second window, it is an indication that a fault is present which is coded as Type 1. 2. This sequence continues to indicate a type 3, a type 4, and so on, with the type of fault being indicated by the number of flashes of the 112 light. This pattern of flashing light 112 for a specific number of times is used to visually communicate to the technician the various types of faults detected by logic circuitry 104. Although the present invention uses flashing light 112 to transmit fault codes It is within the scope of the present invention to use a plurality of lights to increase the effectiveness of the transmission of a large number of fault codes, if desired. In addition, other methods of providing the default code may also be employed, including providing a coded voltage output that may be interfaced with other electronic devices.

In addition to visually communicating the specific fault code using light 112, logic circuitry 104 also outputs a coded sequence of electrical pulses to other intelligent controllers that may exist in the system. These coded pulses represent the type of fault that has been detected by the diagnostic system 100. The types of faults that can be detected by logic circuitry 104 include, but are not limited to:

1. The protector has “tripped”.

2. The auxiliary winding of a single phase motor has no power or is open or has a faulty run capacitor.

3. The main winding of a single phase motor has no power or the winding is open.

Four. The main circuit breaker has contacts that have been soldered closed.

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5. One of the phases in a three-phase circuit is missing.

6. The phase sequence in a three-phase circuit is reversed.

7. The supply voltage is too low.

8. The rotor inside the compressor has seized.

9. The protector is tripping due to problems with the cooling circuit on the high pressure side of the system.

10. The protector is tripping due to cooling circuit problems on the lower pressure side of the system.

eleven. The motor windings are open or the internal line break protector is faulty.

12. The supply voltage to the compressor is low.

As a variation with respect to the above, as shown in Figure 3, the diagnostic system 100 can send only the status of the protector 54 to an intelligent device 116. In this option, the parameters of firing frequencies, ignition times and Shutdown times with the diagnostic information can be generated on the smart device 116. Smart device 116 can be a compressor controller associated with compressor 10, it can be a system controller that monitors a plurality of compressors 10, it can be a remotely located device, or it can be any other device that is selected to monitor the system. diagnostic 100 of one or more compressors.

Figure 4 depicts a flow chart for the diagnostic system 100 in conjunction with a single phase compressor. The demand signal is provided to logic circuitry 104 from a device or contactor 120 (Figures 2 and 3) along with the current signal from sensing devices 102. When the system is initially powered up, an initialization procedure is performed at 122 and, if successful, the system, as shown by arrow 124, goes into a normal shutdown condition as shown at 126. When in In normal shutdown condition 126, if a demand signal is provided to the system, the system shifts as shown by arrow 128 to a normal running condition shown at 130. Once the demand has been met, the system returns to the normal shutdown condition 126 as shown by arrow 132.

While in the normal shutdown condition 126, if current is detected in the main winding or current in the auxiliary winding and there has been no demand signal, the system shifts as shown by arrow 134 to a shorted contactor condition 136 While the shorted contactor condition 136 is indicated, if demand is indicated, the system shifts as shown by arrow 138 to normal run condition 130. The normal running condition 130 continues until the demand has been satisfied where the system travels as shown by arrow 132 back to the normal off condition 126 which can travel back to the shorted contactor condition 136 depending on whether whether or not current is detected in the main or auxiliary windings.

While operating in the normal running condition 130, one of three paths can be followed other than returning to the normal shutdown condition 126. First, if the system detects demand and current from the main winding but does not detect current from the auxiliary winding, the system travels as shown by arrow 140 to an open auxiliary circuit condition 142. From here, the system moves to a tripped protector 144 condition as shown by arrow 146 when neither a main winding current nor an auxiliary winding current is sensed. Second, if the system detects demand and auxiliary winding current but does not detect main winding current, the system travels as shown by arrow 148 to a main open circuit condition 150. From here, the system shifts to the tripped protector 144 condition as shown by arrow 152 when a main winding current is not detected, not an auxiliary winding current. Third, if the system detects demand and does not detect auxiliary winding current or main winding current, the system shifts as shown by arrow 154 to protector tripped condition 144.

While operating in the tripped guard 144 condition, one of four paths can be followed. First, if main winding current or auxiliary winding current is sensed and the demand is satisfied, the system shifts as shown by arrow 160 to normal running condition 130. Second, with the guard tripped, and the system's on-time moving window average has been less than twelve seconds, the system travels as shown by arrow 162 to a multiple low gear condition. From the multiple downshift condition, the system returns to the tripped guard 144 condition as shown by arrow 166. Third, with the guard tripped, and the system's on-time moving window average has been greater than fifteen minutes, the system travels as shown by arrow 168 to a multi-high gear condition 170. The system returns to protector tripped condition 144 as shown by arrow 172. Fourth, with the protector tripped, if the tripped time exceeds four hours, the system travels as shown by arrow 174 to a loss of power or faulty protector 176 condition.

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If, while the system is in the loss of power or faulty protector condition 176 and current is detected from the main or auxiliary winding, the system returns to the tripped protector 144 condition as shown by arrow 178.

As the system travels to the various positions shown in Figure 4, the flashing of light 112 is dictated by the detected fault condition. In the preferred embodiment, if a protector tripped condition is detected at 154 because demand is present but current is missing, light 112 blinks once. If compressor 10 is stuck or there is a low supply voltage problem as indicated by arrow 162 because the average on time for the last five shots was less than twelve seconds, the light 112 blinks twice. If the motor windings are open, the protector is faulty, or the contactor is faulty as indicated by arrow 174 because the shutdown time is greater than four hours, the light 112 blinks three times. If the auxiliary windings are open or there is a faulty run capacitor as indicated by arrow 140, light 112 blinks four times. If the main winding is open as indicated by arrow 148, light 112 blinks five times. If the contactor is welded as indicated by arrow 134 because current is sensed but there is no demand, light 112 blinks six times. Lastly, if there are repeated shots of the protector due to other system problems as indicated by arrow 168 because the average on time for the last five shots was less than fifteen minutes, the 112 light blinks seven times.

Figure 5 depicts a flow chart for the diagnostic system 100 in conjunction with a three-phase compressor. The demand signal is provided to logic circuitry 104 from contactor 120 (Figures 2 and 3) along with current signal from sensing devices 102. When the system is initially powered up, an initialization procedure is performed at 122 and, if successful, the system, as shown by arrow 124, goes into a normal shutdown condition as shown at 126. When in In normal shutdown condition 126, if a demand signal is provided to the system, the system shifts as shown by arrow 128 to a normal running condition shown at 130. Once the demand has been met, the system returns to the normal shutdown condition 126 as shown by arrow 132.

While in the normal shutdown condition 126, if current is detected in one of the three phases or current is detected in a second of the three phases and there has been no demand signal, the system moves as shown by arrow 234 to a shorted contactor condition 136. While the shorted contactor condition 136 is indicated, if demand is indicated, the system moves as shown by arrow 238 to normal run condition 130. The normal running condition 130 continues until the demand has been satisfied where the system travels as shown by arrow 132 back to the normal off condition 126 which can travel back to the shorted contactor condition 136 depending on whether whether or not current is detected in the main or auxiliary windings.

While operating in the normal running condition 130, one of three ways can be followed other than returning to the normal shutdown condition 126. First, if the system detects demand and eleven milliseconds is less than the zero crossing time difference between the first and second phases of the 3-phase power supply or this time difference is less than fourteen milliseconds, the system shifts as shown by arrow 240 to an inverted phase sequence condition 242. From here, the system moves to a tripped protector 144 condition as shown by arrow 246 when a first phase current or second phase current is not detected. Second, if the system detects demand and sixteen milliseconds is less than the zero crossing time difference between the first and second phases or this time difference is less than twenty-one milliseconds, the system scrolls as shown by the arrow 248 to a 250 phase fault condition. From here, the system shifts to the tripped protector 144 condition as shown by arrow 252 when neither a first phase current nor a second phase current is sensed. Third, if the system detects demand and does not detect first phase current or second phase current, the system travels as shown by arrow 254 to the tripped protector condition 144.

While operating in the tripped guard 144 condition, one of four paths can be followed. First, if first phase current or second phase current is detected and the demand is satisfied, the system shifts as shown by arrow 260 to normal running condition 130. Second, with the guard tripped, and the system's on-time moving window average has been less than twelve seconds, the system travels as shown by arrow 162 to a multi-low gear condition 164. From multiple downshift condition, the system returns to the tripped guard 144 condition as shown by arrow 166. Third, with the guard tripped, and the system's on-time moving window average has been greater than fifteen minutes, the system travels as shown by arrow 168 to a multi-high gear condition 170. The system returns to protector tripped condition 144 as shown by arrow 172. Fourth, with the protector tripped, if the tripped time exceeds four hours, the system travels as shown by arrow 174 to a loss of power or faulty protector 176 condition. Yes, while the system is in the condition. loss of power or faulty protector 176 and first phase current or second phase current is detected, the system returns to the tripped protector 144 condition as shown by arrow 278.

As the system travels to the various positions shown in Figure 5, the flashing of the light 112 is dictated by the fault condition detected. In the preferred embodiment, if a protector tripped condition is detected at 254 because demand is present but current is missing, light 112 blinks once. If compressor 10

ES 2 346 752 T3 is stuck or there is a low supply voltage problem as indicated by arrow 162 because the average on time for the last five shots was less than twelve seconds, the light 112 blinks twice. If the motor windings are open, the protector is faulty, or the contactor is faulty as indicated by arrow 174 because the shutdown time is greater than four hours, the light 112 blinks three times. If the contactor is welded as indicated by arrow 234 because current is sensed but there is no demand, light 112 blinks four times. If there are repeated shots of the protector due to other system problems as indicated by arrow 168 because the average on time for the last five shots was less than fifteen minutes, the 112 light blinks five times. If the power supply phases are reversed as indicated by arrow 240 because the zero crossing time difference is between eleven and fourteen milliseconds, the light 112 blinks six times. Finally, if a phase is missing from the 3-phase power supply as indicated by arrow 248 because the zero crossing time difference is between sixteen and twenty-one milliseconds, the light 112 blinks seven times.

Although the prior art has been described as monitoring moving window averages for compressor 10, it is within the scope of the present invention for logic circuitry 104 to use real time or instantaneous conditions for compressor 10. For example, By considering arrows 162 or 168, instead of considering the moving window average, logic circuitry 104 could consider the previous run time for compressor 10.

Figure 6 represents a flow chart that is followed when diagnosing a system problem. At step 300, the technician determines if there is a problem by checking the LEDs at step 302. If the green LED 110 is illuminated, the indication at 304 is that the compressor 10 is operating normally and the problem is with other components. If the yellow LED 112 is flashing, the technician counts the number of flashes as 306. Based on the number of flashes of the light 112, the determination of the type of failure is made at 308. The failure is corrected and the system is recovered and started at 310. The system returns to step 300 which will again indicate any failure with the compressor 10.

Therefore, the diagnostic system 100 provides the technician arriving on the scene with a clear indication of where the problem with the system is most likely to be present. The technician can then direct his attention to the most likely cause of the problem and possibly avoid replacing a known good compressor.

Figure 7 illustrates a typical refrigeration system 320. Refrigeration system 320 includes compressor 10 in communication with a condenser 322 that is in communication with an expansion device 324 that is in communication with an evaporator 326 that is in communication with the compressor 10. Refrigerant piping 328 connects the various components as shown in Figure 7.

Referring now to Figure 8, there is illustrated a contactor 120 incorporating the diagnostic system 100 in the form of current sensors 102, logic circuitry 104, green LED light 110, and yellow light 112. Contactor 120 is designed to receive information from various system controls such as a system thermostat 350 (Figures 2 and 3), a group of system safety devices 352 (Figures 2 and 3), and / or other sensors incorporated within the system. system and based on three inputs provide power to the compressor 10.

Contactor 120 includes a set of power input connectors 354, a set of power output connectors 356, a set of contactor 358 coil connectors, light 110, and light 112. The internal schematic for contactor 120 is shown. shown in Figure 9. A power supply 360 receives power from connectors 354, converts input power as needed, and then supplies the required power to input circuitry 362, processing circuitry 364, and output circuitry 366, which collectively form the logic circuitry 104.

The input circuitry 362 receives the input from the current sensors 102 and the demand signal to diagnose the health of the compressor 10. The information received by the input circuitry 362 is directed to the processing circuitry 364. which analyzes the information provided and then provides information to the output circuitry 366 to operate the compressor 10 and / or activate the LEDs 110 and 112. Incorporation of logic circuitry 104 within contactor 120 simplifies the system due to the fact that both line power and demand signal are already provided to contactor 120. The function and operation of diagnostic system 100 incorporated within contactor 120 is the same as described above for housing 106.

Referring now to Figure 10, molded plug 90 is illustrated incorporating diagnostic system 100 in the form of current sensors 102, logic circuitry 104, light 110, and light 112. In some applications, the incorporation of the Diagnostic system 100 within molded plug 90 offers some distinct advantages. When the diagnostic system 100 is incorporated within the molded plug 90, power is provided through connectors 354 and must also be provided to the diagnostic system from input power or it may be provided separately through connector 370. In addition, the power supply Demand signal must also be provided to socket 90 and this can be done through connectors 372. The function and operation of the diagnostic system 100 incorporated within the molded plug 90 is the same as previously described for the housing 106. Communication from the plug 90 is accomplished through the connection 374.

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Figures 4 and 5 illustrate flow charts for the diagnostic system 100. While operating in the tripped guard 144 condition, different paths are followed depending on the moving window average of the ignition time or the ignition time of the previous cycle. These various paths help determine what type of fault is present.

This concept can be extended by making additional assumptions based on the compressor on time between overload trips. The duration of the compressor on time before overload tripping can be extended to be useful in diagnosis if the fault is likely located on the high side (condenser) or low side (evaporator) of the refrigeration or air conditioning system . This added information would help the technician to speed up his search for the fault. Figure 11 illustrates the flow chart for a diagnostic system 100. Although Figure 11 illustrates a diagnostic system for a single-phase motor, the diagnostic system illustrated in Figure 11 and described below can be used with a three-phase motor, if desired. .

Using this procedure, there are four fundamental system faults, as shown in Figure 12, which can be identified based on the on time and / or the off time. First, a "locked rotor" condition (LR trip) typically results from a mechanical compressor stall or an electrical start problem from an outside source. This results in the shortest firing time usually after twenty seconds or less. This is illustrated in Figure 11 by arrow 162 'leading to a locked rotor condition 164: from the locked rotor condition 164, the system returns to the tripped guard 144 condition as shown by arrow 166'. Second, a "short cycle" condition is typically due to automatic turning on and off of the high side or low side safety pressure switches. Both the on time and the off time during the short cycle are typically on the order of two minutes or less. This is illustrated in Figure 11 by arrow 162 "leading to a short cycle run condition 164". From the short cycle run condition 164 ", the system returns to the tripped guard 144 condition as shown by arrow 166". Third, a normal overload trip condition (protector trip) is the one that is expected to occur most often imposing a maximum load condition on the compressor due to system failures such as a blocked or failed condenser fan. The ignition time between shots can be anywhere from four to ninety minutes, depending on the severity of the failures. This is illustrated in Figure 11 by arrow 168 'leading to a normal overload trip condition 170'. From the normal overload trip condition 170 ', the system returns to the tripped protector condition 144 as shown by arrow 172'. As shown in Figure 12, normal overload tripping can be broken down into two separate areas of temperature if capacitor 322 (Tc) is known. Fourth, a "high run time" fault condition results in very long run times typically greater than ninety minutes. A fifty percent normal run time thermostat that is cyclically repeated based on a frequency of three cycles per hour would produce a ten minute on time. Therefore, running for more than ninety minutes is typically a failure. This is illustrated in Figure 11 by arrow 174 'leading to loss of head failure 176'. From the loss of load failure 176 ', the system returns to the tripped protector 144 condition as shown by arrow 178'. The diagnostic system 100 'can replace the diagnostic system 100 shown in Figures 4 and 5 or the diagnostic system 101' can operate simultaneously with these other two diagnostic systems.

Additional information can be obtained using additional sensors. By adding key sensors, the diagnostic systems described above can be expanded to a higher capacity that can clearly distinguish between a compressor failure and a system failure under any set of conditions.

Specifically, for a given voltage and type of power source, the operating current for compressor 10 is primarily a prescribed function of its discharge pressure and suction pressure as represented by typical published performance tables or equations. . Typically, for most scroll compressors, the compressor current varies primarily with discharge pressure and is quite insensitive to suction pressure. When a mechanical failure occurs within scroll compressors, their drawn current will increase significantly at the same discharge pressure. Therefore, by sensing the current with current sensing devices 102 and sensing the discharge pressure using a sensor 330 as shown in Figure 7, most faults can be detected within the compressor 10. For a given power source, a change in voltage can affect its current. However, these voltage changes are usually intermittent and not permanent, whereas a fault is typically permanent and irreversible. This difference can be distinguished by sensing current with current sensing devices 102 and sensing discharge pressure with sensor 330 over several repetitive cycles.

Typically, discharge pressure sensor 330 is a fairly expensive component, especially for implementation in a residential system. A low cost alternative is to use a temperature sensing CR thermistor 332 as shown in Figure 7 mounted at the midpoint of condenser 322 on one of the U-tube or return elbows. This temperature sensing is quite well known as it is used with demand type defrost control for residential heat pumps. Figure 13 illustrates a typical relationship between compressor current and condensing temperature. A generic equation or table for this relationship can be pre-programmed into diagnostic systems 100 or 100 '. Then by measuring two or three coordinate points during the initial 24 hours of operation after the first clean installation; The curve can then be obtained and calibrated to the system for use as a reference without failure.

ES 2 346 752 T3

In addition to current sensing devices 102, pressure sensor 330, or temperature sensor 332, an outdoor ambient temperature sensor 334 can be added as shown in Figures 2 and 3. The addition of sensor 334 is primarily for fault detection. using the data from sensors 102 and 330 or 332 with the data from sensor 334. As both the 332 temperature sensor and 334 temperature sensor are typically used with demand-type defrost controls on residential heat pumps, this concept is quite attractive because technicians are already familiar with these sensors and the added cost is just marginal.

The combination of condensing temperature and condenser delta T (condensing temperature minus ambient temperature) now provides a more powerful diagnostic capability of system faults as illustrated below including heat pumps in heating mode because the delta T becomes the evaporation temperature minus the ambient temperature. In the table below in cooling mode, delta T represents delta T of the condenser and in heating mode, delta T represents delta T of the evaporator.

<td></td><td>Cooling mode</td><td>Heating mode</td>

<td>Outdoor fan blocked / faulty or overload (high side)</td><td>High Delta T overload trip Tcond high High current</td><td>Low Delta T</td>

<td>Impeller fan interior blocked / damaged or loss of load (low side)</td><td>Low Delta T Low Delta T Time of long run</td><td>Overload trip Low Delta T Time of long run</td>

<td>Defrost start</td><td> —</td><td>Delta T high</td>

<td>Compressor fault</td><td>Current versus Tcond</td><td></td>

<td>Loss of capacity</td><td>% of operating time</td><td>% of operating time</td>

Finally, it is now possible to diagnose the loss of capacity with the addition of the outdoor ambient sensor 334 using the percentage of the operating time as shown in Figure 14. Now it is also possible to predict the energy use of the compressor because it is know the current, voltage and operating time. Energy use can be monitored and reported over time.

Generally speaking, the implementation of an electronic diagnostic tool is illustrated in Figure 15 with the current sensing devices 102, the condenser temperature sensor 332, and the outdoor ambient temperature sensor 334. As these sensors provide continuous system monitoring and not individual switches, it is now possible to integrate safety protection capability into this control and eliminate the need for high and low pressure safety switches.

Additional diagnostic capabilities can be achieved by sensing the voltage in the power cables feeding the compressor 10. As shown in Figures 2 and 3, they illustrate voltage sensors 402 incorporated for this purpose. Compressors with internal line breaks such as temperature sensor 54 will "trip" if the supply voltage to compressor 10 falls below a specified value. This value is typically ten percent below the rated voltage. Under this reduced voltage condition, the motor current will increase to a level that would generate enough heat to "trip" the protector 54. Therefore, if the voltage is known when the protector 54 trips, this low voltage condition can be marked as a specific fault. The service technician can then concentrate on finding the cause of the low voltage condition. The tension

ES 2 346 752 T3 can be detected by various methods. It can be detected directly at the compression terminals as shown with sensors 402 or at other points in the electrical circuit feeding the compressor 10. It can also be detected indirectly by monitoring the system control voltage using a sensor 404 as shown in Figures 2 and 3. The control voltage is typically a low voltage circuit (24 VAC) and is obtained using a step-down transformer (not shown). This control voltage would also change in direct proportion to the change in line voltage. Therefore, monitoring the control voltage could provide an idea of ​​the line voltage.

The description of the invention is merely exemplary in nature and, therefore, variations not departing from the appended claims are intended to be within the scope of the invention.