Method for operating an electronically commutated motor, and motor for carrying out one such method

Translation of description of equivalent WO 03034581 A2

A method of operating an electronically commutated motor, and motor for carrying out such a method

Electronically commutated motors are used for many drive tasks, eg in vacuum cleaners, Gerätelüftem, medical equipment, recording devices for video, etc. At such motors are placed many demands under which a low price is paramount. This means that such a motor for each drive object has to be well utilized, without being overloaded thereby.

This is usually achieved by a current limitation, that is, the motor current is limited so that it can not exceed a predetermined upper limit value. The performance of such a motor is then but, needless limited during start-up, where a particularly high engine power is required. Also, some such engines could be operated at high speeds with higher performance, because their cooling is then better and such a motor could absorb and release a higher power. Also, such an engine could often temporarily make a higher power at peak load, because he has a "thermal reserve", ie the short-term occurrence of an overload, the motor is overheated immediately. There are special circuits to which an engine is "modeled" by an electronic or mechanical model, but such solutions for low-cost applications too expensive.

It is therefore an object of the invention to provide a novel method of operating an electronically commutated motor, and a new electronically commutated motor for carrying out such a method.

According to a first aspect of the invention, this object is to solved by the subject matter of claim 1. In the event such a motor, a load peak, so that the motor current exceeds its predetermined limit, this limit is increased for a predetermined time by a timer, provided that the motor rotates. In this way, the available power of the engine is temporarily increased with a peak load. However, it is preferably avoided that this increase also occurs when the motor is blocked, because in this case, should the motor current as low as possible to avoid overheating banks and the resulting fire. - Preferred developments of such a process are the subject of the claims 2 and 3. A motor for implementing this method is the subject of claim 10.

Another solution of the problem is the subject of claim 4. In that at least one current pulse is generated and the voltage divider is fed to the to the voltage divider current flowing increases the duration of this current pulse, and thereby the upper limit of the current increases. This allows better utilization of the motor, especially when speed-dependent current pulses are generated, which increase with increasing speed, the upper limit of the current. This is because an engine speed increases is usually cooled better and therefore can deliver more power. This is especially true for external rotor motors. - A motor for carrying out such a method is the subject of claim 11.

Another solution of the problem is the subject of claim 7. The capacitor is connected in parallel which a partial resistor of the voltage divider is discharged before starting the motor. Immediately after turning it acts therefore like a short circuit for this part of resistance and therefore increases at the start of the upper limit temporarily, namely until this capacitor has recharged. In this way, the starting torque can be increased in such a motor, without this having a permanent overloading of the motor. - A motor for carrying out such a method is the subject of patent claim 12.

Another solution of the problem is the subject of claim 8. In such a motor, the output signals of the rotor position sensors have a relatively low frequency, which is proportional to the speed of the motor. The invention makes it possible to increase this frequency, in such a way that a signal is available from the zero speed, where the increased frequency is zero are available, whose frequency is increased at a three-phase motor, for example, a factor of 3, which allows for example a more accurate indication of speed, a more accurate speed control, more accurate detection of the rotational position of the rotor, and a more precise adjustment of the upper limit of the motor current at the current speed. In many cases, can be dispensed with expensive encoder.

A preferred embodiment of the invention according to claim 8 is the subject of claim 9.

The invention is, according to claim 13, with particular advantage for electronically commutated external rotor motors.

Further details and advantageous refinements of the invention will become apparent from the hereinafter described and illustrated in the drawing, in no way to limit the invention to be understood embodiment, and from the dependent claims. It shows:

FIG. 1 is an overview diagram to illustrate the invention,

Fig. 2 shows an example of a full bridge circuit for a three-phase motor,

Fig. 3 shows a circuit for generating a signal 50 with speed-dependent frequency, the frequency three times as high as the frequency of the Hall signals of the engine, from where the signal is derived 50,

Fig. 4 is a diagram for explaining the operation of Fig. 3,

Fig. 5 is an overview diagram showing several preferred components and their interactions,

Fig. 6 is a circuit diagram showing further details of the arrangement of FIG. 5, Fig. 7 is a schematic diagram showing the change of the upper limit Isoii for the motor current is dependent on various operating parameters on a sample,

Fig. 8 is graphs showing the increase in the upper limit of the current speed increases to the specified embodiment; the lower curve Iw shows the speed-dependent increase this limit, and the upper curve Iwmax shows the speed-dependent increase in the upper limit, the additional increase is superimposed by activating an arrangement yet, indicated in Fig. 5 and 6 with 260,

Fig. 9 is a diagram for explaining the operation of the PWM generator 56 of FIGS. 5 and 6,

FIG. 10 is a view analogous to FIG. 9, showing the processes in a temporary increase in the ceiling of the current,

Fig. 11 is a circuit diagram showing a variant of the arrangement of FIG. 5 or 6, and

Fig. 12 is a diagram for explaining the operation of Fig. 11.

In the following description, identical or equivalent parts are denoted by the same numerals and are usually described only once.

FIG. 1 shows an overview diagram showing an electronic commutated motor (ECM) 10, as an example of an engine with three strands 12, 14, 16 in a delta connection to the terminals 18, 20, 22, and a permanent magnet rotor 24. The latter is an example depicted with four poles. It controls three Hall generators 26, 28, 30, which have angular spacings of 120 ° el and operating three signals H1, H2, H3 produce, as shown in FIG 4A -.. 4C are each phase-shifted by 120 ° to each other. These signals are used for measuring the speed and controlling the currents through the phases 12, 14, 16. Preferably, the ECM 10 an external rotor motor.

The signals H1, H2, H3 of a signal processing 36 are fed, which is shown in Fig. 3 and their output signals via a schematically illustrated connection 38 to an output stage 40 can be supplied, which is shown in Fig. 2 and a control logic for controlling the currents contains in the strands 12, 14, 16th The terminals 18, 20, 22 are connected to the output stage 40th The latter is connected to an operating voltage + UB, z. B. to +24 V, +48 V, +60 V, or the like., And it is connected via a current sensing resistor 42 to ground 44. Via the resistor 42, the total current of the motor 10, which is full so the actual current value (actual value) referred flows.

On 42 resistance arises in operation, a voltage drop, and this is a device supplied to 46, which list the current limited and serves as a dynamic engine protection. At this device can be set for the motor 10 via a potentiometer 48 a desired speed (rated speed) nSoll.

The device 46 is a signal 50 supplied via a line 52, which has three times the frequency of the signals H1, H2, H3, and is produced in the signal processing 36th

Via a signal connection 54, an output signal from the device 46, a PWM controller 56 is supplied from the signal which depends on the

Compound 54, a PWM signal 60 provides. This has a frequency f z. B.

25 kHz corresponding to a period T = 0.04 ms. This signal has a 60

PWM duty ratio of PWM = t / T ... (1), which lies between 0 and 100%, depending on the magnitude of the signal at the input 54th

The signal 60 is fed via a connection 62 of the output stage 40th The device 46 has preferred to limit the usual in such motors basic function, to control the speed to a desired value, z. B. to 10,000 rev / min, and this list the motor current to a predetermined value of 10,000 according to FIG. 8 U / min z. B. is about 4.2A.

At the start of the device 46 to the power momentarily, z. B. for 0.5 s, limit to a higher value, as shown in FIG. 7 or 12 z. B. 7 A.

If temporarily high loads occur, the device 46 is to this load increases by field to a higher current of 5.5A allowing z. B. during one second, even at the start, being between these higher currents (5.5 A) always sections should lie with "normal" current of 3.5 A, which sections z. B. 4 s take.

And finally to the motor is blocked at 10, ie in the speed 0, the current to a low value can be lowered, for. Example, to 1.3 A, so that the motor 10 is not overheated at a standstill.

In addition to FIG. 8 with an external rotor motor 10 the permissible current Isoii (Iw in Fig. 8) increases with the speed n, because particularly an external rotor motor with increasing speed is better cooled and therefore a higher power "tolerates" when high speed runs.

Naturally need at a specific motor 10 not all of these features to be implemented, but they can also be used only partially, and the figures are only examples to facilitate understanding.

Fig. 2 shows the essential elements of the power unit 40. This contains a full bridge circuit with three upper transistors 70, 72, 74, which are formed as P-channel MOSFETs, and three low-side transistors 76, 78, 80, which, as N-channel MOSFETs are formed. For each of these transistors is a freewheeling diode 70 ', 72', 74 ', 76', 78 ', 80' connected in anti-parallel. In the upper transistors 70, 72, 74, the source S is connected via a line 82 with + UB. In the lower transistors 76, 78, 80, the source S is connected to a manifold 84 which is connected via the sensing resistor 42 to ground 44, so that the full motor current flows through the resistor 42nd

The drain terminals D of the transistors 70 and 76 are connected with the winding terminal 18 of the motor 10, the D-terminals of the transistors 72 and 78 with the winding terminal 20 and the D-terminals of the transistors 74 and 80 to the terminal 22. If z . B. the transistor 70 and the transistor 78 are conductive, a current flows from left to right through the strand 12 and a smaller current through the series connection of the strands 16 and 14. the amount of these flows will depend very much on what stresses in these strands are induced by the rotating rotor 24 (Fig. 1).

The individual transistors 70 to 80 are turned on AND gates. For example applies according to FIG. 4 between 0 ° el. And 60 ° el. H1 = 1, H2 = 1, H3 = 0, or abbreviated HS = 110th

In this case, the transistors 72 to 80 is controlled as follows:

Transistors 70, 74, 76, 78 = 0

Transistors 72, 80 = 1

This is done by the AND gates shown in Fig. 2. In the

Combination H1 and H3 = 1 = 0, the transistor 80 is turned on, and at the

Combination H2 = 1 and H3 = 0 the transistor 72 is turned on. The other

Transistors remain blocked.

Also applies between 60 ° el. And 120 ° el. HS = 101.

In this case, the transistors are turned on 70 and 78, and the remaining

Transistors 72, 74, 76 and 80 are locked. In this way, the switching state of the full bridge circuit 70 to 80 is. Indexed respectively by 60 ° el, so that the winding phases 12, 14, 16 generate in a known manner a rotating electromagnetic field, as is usual in such motors practice.

When transistor 70 is connected to this end, the gate G via a resistor 88 to the line 82 and via a resistor 90 to the collector of an NPN transistor 92, whose emitter is connected to ground and a base of which via a resistor 94 to the output aND gate 96 is connected, at its a usgang a positive signal outputs (and thus the transistors 92 and 70 conductive makes) when at the input 98 of the aND gate 96 a signal H1 = 1 and at the input 100 a signal H2 / = 1 (corresponding to H2 = 0) is located.

In the same manner, the transistor 72 is conducting 102 controlled by an AND gate, if = present on the latter 102 the values ​​H2 1 and H3 = 0th

And the transistor 74 is conductively controlled by an AND gate 104 when = present in this, the signals H3 and H1 = 1 0th '

The lower transistor 76 is 106 then conductively controlled by an AND gate with three inputs, if H2 = 1, H1 = 0 and (on line 62), the PWM signal 60 = 1, that is, the PWM signal 60 turns to those lower transistor 76, 78 or 80 on and off, which is made conducting just by combining the signals H1, H2, H3.

To control the transistor 78 serves an AND gate 108, which from H2 = 0, H3 = 1 and PWM signal 60 = 1 is activated, and for controlling the transistor 80 serves an AND gate 110, that of H3 = 0, H1 = 1 and PWM signal 60 = 1 is activated.

The commutation according to FIG. 2 is just an example to better understand the Invention.

Fig. 3 shows the circuit 36 ​​to form the signal 50 with three times the frequency of the signals H1, H2, H3. It is especially advantageous to this circuit is that it is reduced effectively to speed 0, and that by the tripling of the rate means better measurement of the speed of the motor 10 and an optimal adjustment of the current limitation to the instantaneous rotational speed of said engine is possible.

As shown in FIG. 3, the current inputs of the three Hall generators 26, 28, 30 are connected in series. The upper current input of the Hall generator 26 is connected through a resistor 120 to a line 122 (eg., +5 V), and the lower current terminal of the lower Hall generator 30 is connected through a resistor 124 to ground 44. The resistors 120, 124 are preferably approximately the same size.

The Hall generator 26 is associated with a comparator 126, to whose two inputs 128 (+) and 130 (-), the two outputs of the Hall generator are connected 26th The output 132 of the comparator 126 is connected via a pull-up resistor 134 to the positive lead 122, via a resistor 136 to the input 128 and via a resistor 138 to the negative input 140 of a Vergleichskomparators 142nd

As shown in FIG. 3, the Hall generator 28 has a comparator 126 ', and the Hall generator 30 has a comparator 126 ". The circuit is respectively the same, and therefore the same reference numerals are used, ie, for. Example, 128, 128' and 128" and these parts will not be described again.

The positive input 144 of Vergleichskomparators 142 is connected via a resistor 146 to lead 122 and via a resistor 148 to ground 44th

The output 150 of the comparator 142 is connected via a resistor 152, a Hysteresis causes connected to the input 140 via a resistor 154 to lead 122 and via a resistor 156, a node 158 and a resistor 160 to ground 44th

To node 158, the base of an npn transistor 162 is connected, an emitter connected to ground 44 and whose collector is connected to an output 164, at which a pulse sequence can be removed with a frequency which nist of the instantaneous speed of the motor 10 is proporzional ,

Preferred values ​​of 3 k = k ohms. M = MOhm comparators 126, 126 ', 126 ", 142. 4 x 2901 LM resistors 120, 124, 200 Ohm resistors 136, 136', 136". 220K resistors 134, 134 ', 134 ", 154,. 3.3 k resistors 138, 138', 138", 146, 148, 156. 33 k resistance 152nd 1M resistance 160th 10 k

Operation of Fig. 3

The two resistors 146, 148, which are the same size, set the input 144 of the comparator 142 to about +2.5 V.

In the range 0 ... 60 ° el., According to FIG. 4 H1 = 1, H2 = 1, H3 = 0. Therefore, the output of the comparator 126 "to ground, and the outputs of comparators 126, 126 is' ​​do not lie on mass, so that via the resistors 134, 138 and 134 ', 138', a current flows from the line 122 to point 140 and from there through resistor 138 "flows to ground 44th This results in Fig. 4D at point 140, a potential of about two thirds of the voltage U = 5 V, and the Vergleichskomparator 142 receives at its output 150 a high signal, which is denoted in Fig. 4E 1. In the area of ​​60 ... 120 ° el. In accordance with FIG. 4 H1 = 1, H2 = 0, H3 = 0, ie, the outputs of comparators 126 ', 126' are connected to ground, and the output of the comparator 126 has a high impedance. now a current flows from the line 122 through the resistors 134 138 flowing to the point 140 and from there through resistor 138 'to ground, as well as through resistor 138' to ground. This results in Fig. 4D at point 140, a potential of about one third of the voltage U = 5 V, and consequently the Vergleichskomparator 142 receives at its output 150 a low signal, indicated in Fig. 4E. 0

In this manner, each potential jumps to 60 ° el. At the output 150, either from 0 to 1 or from 1 to 0, and to get there the signal 50 whose frequency is three times higher than the frequency of the signals H1, etc. This signal is also at the output 164 is available, for. example, for monitoring the speed of the motor 10. such monitoring is required by many clients.

Fig. 5 is an illustrative view for explaining the principles of the invention. The voltage at the measuring resistor 42 is the negative input 210 of a comparator 204 fed through a resistor 207 and a smoothing capacitor 208, the output of which is designated by the 216th The positive input 212 of comparator 204 is connected to a node 214, the potential of the upper limit of the current in the motor 10, so the available power determined. If this upper limit is exceeded, the duty ratio of pulses 60 is automatically reduced, which are generated by a PWM generator 56th

The node 214 is connected through a resistor 240 to ground 44, via a resistor 238 to a node 232, and through a resistor 300 to the switch 286 of a timer 260 which is connected via a capacitor 262 to the output 216 of the comparator 204th

Node 232 is connected via a resistor 234 and a connected to this parallel capacitor 236 to the line 122nd He is also on a resistor 230 connected to the collector of a PNP transistor 226 whose emitter is connected to line 122 and to the base of which a speed-dependent signal f (n) is supplied.

The output 216 is connected via a resistor 202 (having the value R2) to the input of the PWM generator 56, which via a resistor 196 (with the value of R1), a speed designating signal "n" signal is supplied, usually by a speed controller or a manual speed adjustment. The resistance value of R1 is much greater than R2. The following are typical values ​​are given, from which a preferred ratio of R1 to R2 results.

The PWM generator 56 delivers at an output 190 of the PWM signal 60, via line 62 (see. Figs. 1 and 2) of the commutation controller 40 is supplied.

Operation of Fig. 5

As long as the potential U210 at the input 210 of the comparator 204 is lower than the potential U212 to the input 212, the output of comparator 204 216 is highly resistive and has no effect on the modules 56 connected thereto and 260. This is the case as long as the motor current list is smaller than an upper limit, which is determined by the potential of the point U212 214th

This potential is in turn determined by the ratio of resistors 234, 238, 240, and by a speed-dependent current 248 flowing through the transistor 226 and resistor 230 to node 232, whereby the potential is smoothed at the point 232 by the capacitor 236th The potential U212 at node 214, and thus list the upper limit of the current, ie increase with increasing speed.

If the current list is too large, comparator 204 flips and its output 216 is connected to ground 44th The occurring potential change at Output 216 is transmitted to the timer 260 via the capacitor 262 and switches, for example, during one second, the switch 286, so that the resistor 300 to the resistors 234, 238 is connected in parallel and increased the potential U212 of the point 214 during this second is such that the output 216 of the comparator 204 becomes high impedance once again and list the current may rise further. After this second switch opens 286, and the potential U212 at node 214 falls again, whereby the current list again is limited to a lower value. Here, if the output is 216 connected to ground, a current flows from input 194 through resistor 202 and the comparator 204 to ground 44, whereby the potential of the input 194 is abruptly reduced flows. This also the duty cycle pwm (equation 1) of the PWM signal 60 is immediately reduced to the motor current list to reduce and keep it below the desired upper limit. The frequency of the signal 60 remains unchanged, which is an important advantage.

Thus raising the potential at the point 232, and thus also at the point 214 is as large as possible, the resistance 234 is preferably substantially greater than the sum of the resistors 238 and 240 selected. The voltage drop at the current sensing resistor 42 is kept as small as possible. Thus, the potential value of U212 is at point 214 for the upper current limit Isoii small, and through the parallel circuit of the resistor 300, a doubling of the current upper limit Isoii be trouble, if desired.

At the start of the capacitor is discharged 236 and then acts like a short circuit of the resistor 234, so that when you start the potential is raised U212 of node 214 until the capacitor 236 has charged. As a result, the starting current of the motor 10 for a short time greatly increased to ensure reliable starting, as shown in Fig. 7 at 252. Prolonged increase is with the variant according to FIGS. 11 and 12 possible.

An important aspect of the present invention, therefore, the voltage divider 234, 238, 240, which, dependent of engine parameters, various signals from the outside Type are supplied in order to utilize the available power of the motor 10 optimally or limit. Naturally, the various external influences described on this voltage divider just examples of the many possibilities is what provides this principle.

Fig. 6 shows details of a preferred embodiment of FIG. 5. The same or equivalent parts as in Fig. 5, the same reference numerals as there. The PWM generator 56 includes a triangular wave generator with a comparator 170 whose positive input lead 122 (+5 V), is connected via a resistor 176 to the output 178, and via a resistor 180 to ground 44 172 via a resistor 174th The output 178 is connected via a resistor 181 to lead 122 and via a resistor 182 to negative input 184, which is also connected to the negative input of a comparator 186 and a capacitor 188 to ground 44th At the output 190 of the comparator 186, the PWM signal 60 is generated. The output 190 is connected via a pull-up resistor 192 to the line 122nd

The comparator 170 and its various switching elements generates a triangular voltage U184 (see. Fig. 9) with, for. Example, 25 kHz at the input 184, and this is supplied to the comparator 186th

The positive input 194 is - u as potential - is supplied via the resistor 196 as the output signal of a speed controller 200, which is indicated only schematically, and via the resistor 202, the input 194 is connected to the output of the comparator 204, which is part of an arrangement for current limiting is.

is via the resistor 207 and the filter capacitor 208, the motor current list specific voltage at the measuring resistor 42 to the negative input 210 of the comparator 204 is supplied, as already described in FIG. 5 shows. Its positive input 212 is applied to the node 214, and the local potential U212 determines the current Isoii, wherein the current limiting device is activated: If the potential at node 214 is high, the current is to a high value limited, and it is low, at a low value.

Namely, list the current is so high that the potential U210 the input 210 becomes higher than the potential U212 of the input 212, so comparator 204 flips and its output 216 is at ground potential, so that the entrance 194 a current through the resistor 202 flows to ground, whereby the potential U194 at the input 194 of the comparator 186 abruptly decreases, hence the pulse duty factor pwm of pulses 60 is small, and thereby list the current is reduced, since the transistors 76, 78, 80 off with this duty and are turned on, as described in FIG. 2.

Fig. 9 shows the triangle voltage U, which is supplied from the comparator 170, which serves as a triangle generator. This triangular voltage is compared in comparator 186 with the potential U194 at the input 194 of that comparator.

When the motor current list at the time is tio higher than the predetermined value Isoii, comparator 204 flips, its output 216 is LOW, and through resistor 202, a current flows to ground 44 so that the potential U194 at the time tio a jump 195 by makes below.

Thereby, as shown in Fig. 9B, the pulses of the PWM signal 60 from the time tio shorter, and consequently, the motor current list so long, until it is smaller again than Isoii. If this is the case, the comparator 204 flips back to its other state in which its output 216 is high impedance, and via the resistor 202, current no longer flows.

A negative potential change at the output 216 causes a switching of a transistor 264 and a temporary increase of the current limit Isoii, as shown in Fig. 7 at 304, and in this case, the length of the pulses 60 momentarily again.

The controller only on the pulse duty factor pwm of pulses 60 using a fixed frequency of the PWM signal 60 is very advantageous, since, for example continuously at 20 kHz can be used or higher. This frequency is beyond the audible range of man, and the engine 10 is thereby silent.

For speed-dependent increase in the potential at node 214 (see. FIG. 8) is an arrangement 220 via the series circuit of a capacitor 222 and a resistor 224, the pulses 50 are fed (with triple frequency) of the base of a PNP transistor 226, which a resistor 228 is connected to the line 122 as well as the emitter of transistor 226. the collector of this transistor 226 is connected through a resistor 230 to a node 232 through a resistor 234 and a parallel thereto capacitor 236 to the line 122 (+ 5 V) is connected. Similarly, the node 232 is connected through a resistor 238 to the node 214, and the latter is connected via a resistor 240 to ground 44th

The resistors 234 (430 k), 238 (100 k) and 240 (8.2 k) form a voltage divider, and the steady-state, when are no external influences on the voltage divider, mass 44 has a potential of 0 V, the node 214 of 0.076 V, the node 232 from V 1 and the line 122 of +5 V.

The potential U212 at node 214 determines the current limit, the motor current list is limited, z. B. FIG. 8 in continuous operation at 10,000 rev / min to about 4.2 A. This potential U212 is the plus terminal 212 of the comparator 204 is supplied, and when it is low, the comparator 204 already turned on at a low current list order and reduces the potential U194 at the input 194 of the comparator 186, whereby the duty cycle pwm (equation 1) of the pulses 60 list already at a low motor current is reduced.

Increase the current limit function of the speed

Due to the arrangement 220 (FIG. 6) 50 (Fig. 4E), a current pulse is generated 248 at a constant pulse width for each pulse. For the constant pulse duration of the current pulses 248, a particularly advantageous solution results from the connection of the base of the transistor 226 to the capacitor 222, the resistor 224 and the resistor 228. The pulse duration is derived from the product of the value of the capacitance of the capacitor 222 and the sum of the values ​​of the resistors 224 and 228, so C222 * (R224 + R228). The current pulses 248 are supplied to the node 232, so that an additional current 248 flows through the resistors 238, 240 and increases the potential of the point 214th This additional current 248 but does not flow when the engine 10 is blocked, and in this manner results in a low motor current the motor is blocked.

Since with increasing speed per unit time more pulses are generated 50 and 248, this additional current through the resistors 238, 240 with increasing speed, so that the upper current limit increases with increasing speed.

Thus, the potential at node 232, and thus also at point 214 is thereby greatly increased as possible, the resistance 234 is preferably much greater than the sum of the resistors 238 and 240 selected.

Dynamic current increase in load surges

An ECM 10 is designed so that it has a power reserve, ie when it only briefly increased power is demanded, this has no bearing on its temperature. If the same increased power but constantly demanded of the motor 10, that would cause it to overheat and destruction.

Therefore, one can use very preferably at load surges dynamic current increase. To this end 6 is the part 260 of Fig., The function of which in Fig. 5 has been already explained.

The output 216 of the comparator 204 is connected through a capacitor 262 to the base of a PNP transistor 264, which in turn is connected through a resistor 266 to the line 122nd The collector of transistor 264 is connected to ground 44th Its emitter is connected via a resistor 268 to the line 122 through a resistor 270 to a node 272, and directly to the negative input of a comparator 274 276th Node 272 is connected via a resistor 278 to the Positive input 280 of the comparator 276 and through a resistor 282 connected to ground 44th

The output 284 of the comparator 276 is connected to the base of an NPN transistor 286, also through a resistor 288 to the line 122 and through a capacitor 290 to a node 292, which in turn through a resistor 294 to the positive input 280, and via the series circuit is a resistor 296 and a diode 298 to ground 44 is connected.

The collector of transistor 286 is connected to line 122, its emitter via resistor 300 to the node 214th

When transistor 286 is conductive, the resistor 300 (180 k) for series connection of the resistors 234 and 238 is connected in parallel, whereby the potential U212 at node 214 jumps to a higher value and the current limit according to FIG. 7, for example of 3, 5 is raised to 5.5 A.

When the motor current list is too high, comparator 204 flips to low, and this potential change is transferred to the base of the PNP transistor 264 via the capacitor 262 and makes it conductive, so that it bridges the resistors 270, 282 and the comparator 276 switch, is connected as a monostable multivibrator. Transistor 264 suppresses the positive pulses which occur during differentiation by the capacitor 262, so that only the negative pulses can cause a switch-over of the comparator 276th

The output 284 of the comparator 276 is at rest on low. If the one-shot triggered, the output 284 is as long as high, as is determined by the elements 290, 296, 298, and tilts then back to low.

As long as the output 284 is high, transistor 286 is turned on, and through him, and the resistor 300 flows an additional current to node 214, as already described. In this case, the transistor 286 acts as an ideal switch, ie, the resistor 300 is decoupled from node 214 when the transistor blocks 286th

The time during which the output 284 is high is, here for about 1 second, and them closes each at a time of 4 seconds, in which the output is 284 low, so you 7 short sections 304 has according to FIG. higher current that are lower power separated by long sections 306th This prevents overloading of the motor 10, but allows adaptation to brief load surges, as may occur in some engines.

When the rotor 24 of the motor 10 is blocked, the current limiting device is always active, ie the comparator 204 is permanently tilted so that across the capacitor 262 no pulses are transmitted and the circuit 260 is not activated.

When the rotor 24 is blocked, no pulses 50 are generated more, so that no more current pulses 248 are generated. The current then decreases in accordance with the section 308 of FIG. 7, and is bounded at a standstill at a low value 310, so that overheating of the ECM 10 is avoided in the blocked state.

Fig. 10 shows the Fig. 5 and 6 is a schematic representation of the motor current list, represented by the potential U210 at the input 210 of the comparator 204, and the upper current limit Isoii represented by the potential U212 at the input 212 of the comparator 204, and the potential U216 at the output 216 of the comparator 204, when exceeding the upper current limit Isoii.

At the time t2o upper current limit is exceeded Isoii. Characterized the comparator switches 204 to LOW, and the one-shot circuit 260 is activated. See description of FIG. 5, so that the upper current limit Isoii is the determined by the one-shot circuit 260 time period Ti, for example 1 second, increased , This is the time t21, the potential U216 again high.

At the time t22, the motor current is list to normal levels returned since as no longer present the brief extra load or fault. After the time period Ti, the mono-flop circuit 260 is disabled and the upper current limit Isoii returns to the original value. Until time T.24 are no further current overruns. At the time t24, the upper current limit is exceeded Isoii again, and the output 214 is switched to LOW. Since the one-shot circuit 260 allows the end of the increase in the current limit during a time period T2, for example 4 seconds, no further increase in order to protect the motor from overheating, it has no effect until the time the 126th The motor current list can not continue to rise. Between t24 and t26, the potential changes U216 as shown continuously between high and low, since the current limit is effective here on the current value of Isoii.

At the time t26, the motor current falls list in this example, again under the current ceiling Isoii, and the output 216 goes to HIGH again.

At the time t28, the upper current limit is exceeded Isoii again. Since the period T2 is not expired, the upper current limit is not increased. This is done again until the time t30 at which the period of time T2 has elapsed. T30 from the upper current limit Isoii is increased again during the time period Ti. Thus, the motor current may rise for a short list again to a higher value, as in A shown.

At the time t32, the motor current drops list back to the normal range, and therefore the potential U216 is again constantly high. At the time t34 ends the period Ti, and the current limit is lowered again to the normal value

The operation of the arrangement according to FIG. 5 and 6 is in part that the potential U212 is modified at node 214, which defines the upper current limit, subject to certain operating conditions, so that it is either higher or lower and consequently the motor current, is automatically limited depending on operating parameters of the engine, to different values ​​to optimally utilize the capacity of the ECM 10th

Fig. 8 shows an example of the raising of the upper current limit at an engine which is designed for a rotational speed of approximately 10,000 U / min. When the motor is blocked (speed n = 0), the motor current is limited to a value of about 1.4A. The upper current limit Iw = f (n) increases at 10.000 U / min to about 4.2 Å. In the upper region, the curve is flatter and reaches a plateau, and this flat portion is defined by selection of the electrical components 222, 224, 228, 230 in the vicinity of the rated speed of the motor.

Fig. 8 also shows the curve Iwmax which corresponds to the increased current limit, which results from the activation of the monoflop 260th At 10,000 U / min is thereby increased, for example, the upper current limit of about 4.2 to about 4.8 A, and accordingly the torque decreases to M, which is shown in Fig. 8 on the left scale and which is proportional to the actual motor current is. As an external rotor motor at 10,000 rpm / min is well cooled by the generated air turbulence, it can at this speed pay a much higher heat loss than at a standstill, and therefore, at 10,000 rev / min, the permissible motor current to be substantially higher than in the motor is blocked. In this way it is possible, with a motor of a predetermined size to achieve higher speeds and thus higher performance.

In the invention, it is also possible, with stalled engine the engine power temporarily switch out and at regular intervals to try a new approach.

The capacitor 236 at node 232 causes a smoothing of the potential at this point and so provides a stable set point at comparator 204th

The arrangement 220 is therefore particularly low in external rotor motors, but can of course be used for all engines in which the cooling speed increases is better.

Current increase when switching

The capacitor 236 (1, 5 uF) also has the function that it is unloaded at power and then momentarily acts like a short circuit for the resistance 234th Thus, the potential at node 232 is raised briefly to +5 V, and the potential at node 214 rises to 0.38 V, so that the current list to a high value is limited. This FIG. 7 at 252, where the current limit drops after switching within 0.5 seconds from 7 A to 5.5 A, so that the motor 10 can start with a very high torque but rapidly reduced. For the period of time T, the start pulse START applies approximately: tSTART = C236 * R234 * (R238 + R24θ) / (R234 + R238 + R24θ) ... (2)

Preferred values ​​of the components in Fig. 6

Voltage on line 122: +5 V, regulated. Motor with 10,000 U / min rated speed, k = kOhm, M = MOhm capacitor 222 3.3 nF

Resistor 224, 228 51 k

Transistors 226, 264 BC857

Transistor 286 BC847

Comparators 170, 186, 204, 276 4 x LM2901

Resistor 230 11k

Resistance 234 430 k

Resistors 180, 238 100k

Resistance 240 8.2 k

Resistance 42 0.082 Ohm

Resistance 206 1K

Capacitor 208 nF 1

Resistance 196 33 k

Resistors 181, 192, 202, 288 10k

Capacitor 188 220 pF

Resistance 182 75 k

Resistance 176 33 k

Resistance 174 62 k

Capacitor 262 nF 33

Resistance 266 22 k

Resistance 268 45 k

Resistance 3 270 k

Resistance 282 2 k Resistors 278, 294th 1M capacitor 290th 1 / F resistance 296th 620 k diode 298, respectively. 1 N4148 capacitor 236th 1, 5 uF resistance 300th 180 k

Fig. 11 shows a preferred variant, as that of the circuit 36 ​​(Fig. 3) at its output 150 formed speed-dependent signal 50 (Fig. 4E) is the node 232 sent to a circuit shown in FIG. 5 or Fig. 6. This variant differs by the two components 231, 233 of FIG. 6. The other components are largely identical to FIG. 6 and will therefore not be described again. The base of the pnp transistor 226 is connected in FIG. 11 via the series circuit of a resistor 231 and a capacitor 233 with ground 44.

At the start of the (previously discharged) capacitor is charged via the resistors 233 228 and 231st The during this charging across the resistor 228 voltage drop makes transistor 226 conductive temporarily connects through the resistor 230 in parallel with resistor 234, so that the potential is greatly increased at the point 232 during this time. The period Tstart233 this increase is due to approximately

Tstart233 = (R228 + R231) * C233 ... (3)

Subsequently, via the resistor 230 to node 232 pulses 248 (FIG. 6) is supplied with speed-dependent frequency to increase as the speed increases the upper current limit, as in FIGS. 5 and 6 described and illustrated in Fig. 8. While Tstart233 has the value Isoii (which is defined by the potential at node 214) an increase in the form of a plateau 239 (Fig. 12) which is superimposed on the increase by the capacitor 236, and over a longer start increasing the current limit is Isoii reachable. This enables the acceleration of larger inert masses, and the increased power allows a large dynamic starting torque. At the same time the engine at a stall is protected because the transistor 226 off and the motor current list is limited to a small value (see FIG. FIG. 7).

Preferred values ​​of the components in Fig. 11

Operating voltage +5 V; k = kOhm

Capacitor 222 ... 1 nF

Resistance 224 ... 200 k

Transistor 226 ... BC857

Capacitor 233 ... 1, 5 / F

Resistors 228, 231, 234 ... 430 k

The invention thus relates to a method for operating an ECM 10, which is provided with a current limiting arrangement. This acts on a PWM controller, which emits in operation PWM pulses with a controllable duty cycle PWM and a substantially constant frequency at a predetermined upper limit Isoii of the motor current is exceeded, the current limiting arrangement causes a change of the duty cycle PWM at the PWM by the controller 56 output pulses 60 to reduce the motor current. If during rotation of ECM the motor current reaches a predetermined upper limit Isoii exceeds this limit 304 (Fig. 7) is increased during a predetermined time period, and thereby the maximum available engine power is temporarily increased with a load peak, usually in the range of several seconds. Locked rotor 24 of the limit value is not increased but is lowered further. - Preferably, the upper limit value Iw is also increased depending on the rotational speed n of the engine up to a plateau, as shown in Fig. 8. - The above measures may be used singly or in any combination.

The invention allows in a very simple manner, 10 better than before to take advantage of the performance of an ECM, without the need for a special (thermal) replica of the motor would be required. The determination of the upper current limit Isoii (in Fig. 8: Iw) in the speed range of the engine is variable within wide limits. Naturally, many variations and modifications are also otherwise possible in the present invention.