JP2010041908A - Motor drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor drive that reduces the number of components. <P>SOLUTION: In a motor drive 10, a direct current voltage from a direct current power supply is applied to one electrode on a motor M, and the other electrode on the motor M is grounded via a switching transistor 22. The motor drive 10 drives the motor M by turning on/off the switching transistor 22 with a PWM signal, and controls its rotation speed. A common mode cancellation circuit 30 is provided that detects a voltage change in the switching transistor 22 to suppress a common mode current flowing through the motor M by subtracting the voltage depending on the detected voltage change from voltages of both poles Ma and Mb on the motor M. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a motor drive device that reduces common mode noise.

  Conventionally, a vehicle motor drive device including a noise current detection circuit and a noise cancellation circuit is known (see Patent Document 1).

  Such a motor drive device includes an inverter for converting a DC high voltage of a DC high voltage power supply into a three-phase AC voltage and applying the same to a three-phase motor, and a noise current detection interposed between the DC high voltage power supply and the inverter. A circuit and a noise cancellation circuit for causing a current corresponding to the noise current detected by the noise current detection circuit to flow from the ground side to the inverter.

According to this motor drive device, since the current corresponding to the noise current detected by the noise current detection circuit is returned from the ground side to the inverter by the noise cancellation circuit, the ground fault current is reduced accordingly. That is, the common mode noise current can be reduced.
JP 2006-333647 A

  However, since such a motor drive device is composed of an emitter follower circuit formed by connecting two transistors in series, the number of parts is large, which causes problems such as an increase in cost and an increase in the size of the device. there were.

  An object of the present invention is to provide a motor drive device capable of reducing the number of parts.

The present invention includes an inverter that converts a DC power supply voltage into a pulse voltage, and drives the motor by a pulse voltage output from the inverter.
Common mode cancellation means is provided for applying a voltage obtained by subtracting a voltage corresponding to a change in the pulse voltage from a voltage at each output terminal of the inverter to each electrode of the motor.

  According to this invention, the number of parts can be reduced, and the cost can be reduced and the apparatus can be downsized.

  Hereinafter, an embodiment which is an embodiment of a motor drive device according to the present invention will be described with reference to the drawings.

[First embodiment]
FIG. 1 shows a motor drive device 10 for a vehicle mounted on the vehicle. The motor drive device 10 includes an inverter 20 that converts the voltage of the DC power source E into a pulse voltage, and a common mode cancellation circuit (common mode cancellation means) 30 that suppresses a common mode current flowing through the motor M. The motor M is a motor for rotating a radiator fan, for example.

  The inverter 20 includes a signal generator 21 that outputs a pulse signal (PWM signal), a switching transistor 22 that is turned on for a period (pulse width) during which the pulse signal is output from the signal generator 21 and generates a pulse voltage, and the like. And have.

  The pulse width of the pulse signal output from the signal generator 21 can be arbitrarily changed by a control signal of a control device (not shown), and the pulse signal is input to the gate of the switching transistor 22.

  The source of the switching transistor 22 is grounded, and the drain of the switching transistor 22 is connected to the anode of the DC power source E via the diode D1. Further, the drain thereof is connected to one end of a secondary coil 32 described later via a PWM signal line (signal line) L1.

  The common mode cancel circuit 30 has a primary coil 31 having one end grounded via a capacitor C1 and the other end connected to the drain (signal line L1) of the switching transistor 22, and one end connected to the drain of the switching transistor 22 and the other end. Has a secondary coil 32 connected to the low-potential power line 11 of the motor M, one end connected to the anode of the DC power source E via the power line L2, and the other end connected to the high-potential power line 12 of the motor M. A secondary coil 33 is provided. The high potential power line 12 is connected to one electrode Ma of the motor M, and the low potential power line 11 is connected to the other electrode Mb of the motor M.

  The primary coil 31 and the secondary coils 32 and 33 constitute a transformer T, and the turns ratio of the primary coil 31 and the secondary coils 32 and 33 is 2: 1: 1.

Further, C2 and C3 shown in FIG. 1 are stray capacitances between the winding of the motor M and the frame of the motor M.
[Operation]
Next, the operation of the motor drive device 10 configured as described above will be described.

  When a pulse signal is output from the signal generator 21, the switching transistor 22 is turned on, and from the anode of the DC power source E, the power line L 2, the secondary coil 33, the high potential power line 12, the motor M, the low potential power line 11, It flows through the secondary coil 32 and the switching transistor 22 to the cathode of the DC power supply E.

  That is, a pulse voltage is output from the inverter 20, and this pulse voltage is applied to the motor M to drive the motor M.

  A voltage corresponding to the change in the pulse voltage is generated in the primary coil 31 due to a change in the drain voltage of the switching transistor 22, that is, a change in the pulse voltage, and a voltage is generated at both ends of the secondary coils 32 and 33 by electromagnetic induction.

  Since the turn ratio of the primary coil 31 and the secondary coils 32 and 33 is 2: 1: 1, if the voltage generated in the primary coil 31 is V1, the voltage V2 (= V1 / 2) occurs.

If the voltages at one end of the secondary coils 32, 33 are Vp1, Vd1, the voltages Vp2, Vd2 at the other end of the secondary coils 32, 33 are
Vp2 = Vp1-V2
Vd2 = Vd1-V2
It becomes.

  Since the common mode voltage Vc is ½ of the change (Vp1) of the pulse voltage, the common mode voltage Vc can be made constant.

  That is, as shown in FIG. 1A, when Vp1 changes as shown by a solid line and Vd1 is constant, the common mode voltage Vc (= (Vp1 + Vd1) / 2) is shown by a chain line, but the secondary coil 32 33, the voltage V2 is generated as indicated by a broken line, so that the voltage Vp2 is indicated by a solid line in FIG. 1B. The voltage Vd2 is indicated by a broken line. Since the common mode voltage Vc is (Vp2 + Vd2) / 2, the common mode voltage Vc becomes constant as indicated by a chain line.

  Since the common mode voltage Vc becomes constant, the common mode noise currents Ic2 and Ic3 are prevented from flowing from the winding of the motor M via the stray capacitances C2 and C3.

  In this embodiment, the common mode voltage Vc is not detected, and the primary coil of the transformer T is branched from the signal line L1 which is a PWM signal line by utilizing the fact that the common mode voltage is ½ of the pulse voltage. 31 and the turn ratio of the transformer T is set to 2: 1: 1 so that a voltage corresponding to the common mode voltage is subtracted from the signal line L1 and the power supply line L2. For this reason, an element necessary for detecting the common mode voltage becomes unnecessary, and the number of components of the common mode cancel circuit 30 can be reduced. For this reason, the cost reduction and size reduction of the motor drive device 10 can be achieved.

  FIG. 2 shows the simulation result of the common mode noise current based on the circuit diagram shown in FIG. As can be seen from FIG. 2, the common mode noise current is as small as about 23.4 μA, and it is understood that the common mode noise current can be sufficiently suppressed by the common mode cancellation circuit 30.

FIG. 3 shows a conventional circuit diagram when only the common mode choke coils 41 and 42 for suppressing the common mode noise current are used. That is, the primary coil 31 and the capacitor C1 in FIG. 1 are omitted, and common mode choke coils 41 and 42 are provided. The simulation result of the common mode noise current in this case is shown in FIG. As can be seen from FIG. 4, in the case where the common mode choke coils 41 and 42 are provided, the common mode noise current is about 3.3 mA, which is a large current. That is, the conventional mode using only the common mode choke coils 41 and 42 cannot sufficiently suppress the common mode noise current.
[Second Embodiment]
FIG. 5 shows a motor driving apparatus 100 according to the second embodiment. The motor driving apparatus 100 includes an inverter 101 that alternately outputs a pulse voltage from two output terminals, and suppresses common mode noise current using two common mode cancel circuits 30 and 130.

  FIG. 6 shows a result of simulating the common mode noise current of the motor driving apparatus 100. The common mode noise current is as small as about 8 μA, and the common mode noise current is reduced by the common mode cancellation circuits 30 and 130. It turns out that it can fully suppress.

On the other hand, in FIG. 7, the common mode noise current is suppressed only by the common mode choke coils 41 and 42 without using the common mode cancellation circuits 30 and 130 of FIG. The simulation result of the common mode noise current in this case is shown in FIG. As can be seen from FIG. 8, the common mode noise current is about 3.3 mA, and the common mode choke coils 41 and 42 alone cannot sufficiently suppress the common mode noise current.
[Third embodiment]
FIG. 9 shows a motor driving apparatus 200 according to the third embodiment. The motor driving device 200 drives a three-phase motor 201 and includes an inverter 202 and three common mode cancel circuits 210, 220, and 230.

  The inverter 202 repeatedly outputs a pulse voltage in order from the three output terminals U, V, and W.

  The common mode cancel circuit 210 is connected to the primary coil 211 having one end grounded via the capacitor C1 and the other end connected to the output terminal W of the inverter 202, and one end connected to the output terminals U, V, and W of the inverter 202. And three secondary coils 212, 213, and 214. The turns ratio of the primary coil 211 and the secondary coils 212, 213, and 214 is 3: 1: 1: 1. The transformer T1 is configured by the primary coil 211 and the secondary coils 212, 213, and 214. ing.

  The common mode cancel circuit 220 has a primary coil 221 having one end grounded via a capacitor C 1 and the other end connected to the output terminal V of the inverter 202, and secondary coils 212, 213 and 214 of the common mode cancel circuit 210. Three secondary coils 222, 223, and 224 respectively connected to the other end of each. The turns ratio of the primary coil 221 and the secondary coils 222, 223, and 224 is 3: 1: 1: 1. The transformer T2 is configured by the primary coil 221 and the secondary coils 222, 223, and 224. ing.

  The common mode cancel circuit 230 includes a primary coil 231 having one end grounded via the capacitor C1 and the other end connected to the output terminal U of the inverter 202, and one end of the secondary coils 222, 223, and 224 of the common mode cancel circuit 220. Three secondary coils 232, 233, and 234 connected to the other end of each. The other ends of the secondary coils 232, 233, and 234 are connected to the respective electrodes of the three-phase motor 201. Further, the turns ratio of the primary coil 231 and the secondary coils 232, 233, and 234 is 3: 1: 1: 1, and the transformer T3 is configured by the primary coil 231 and the secondary coils 232, 233, and 234. ing.

Here, in the case of the three-phase motor 201, the common mode voltage Vc1 is set such that the voltage of each electrode of the three-phase motor 201 is Vmu, Vmv, Vmw.
Vc1 = (Vmu + Vmv + Vmw) / 3.

  Further, since the turns ratio of the primary coil and the secondary coil of each transformer T1 to T3 is 3: 1: 1: 1, when the voltage generated in the primary coil 211 of the transformer T1 is Vw, The voltage generated in the coils 212 to 214 is Vw / 3. Similarly, when the voltages generated in the primary coils 221 and 231 of the transformers T2 and T3 are Vv and Vu, the voltages generated in the secondary coils 222 to 224 and 232 to 234 are Vv / 3 and Vu / 3.

When the output voltages of the output terminals U, V, and W of the inverter 202 are Eu, Ev, and Ew,
The voltages Vmu, Vmv, Vmw applied to each electrode of the three-phase motor 201 are
Vmu = Eu− (Vw + Vv + Vu) / 3
Vmv = Ev− (Vw + Vv + Vu) / 3
Vmw = Ew− (Vw + Vv + Vu) / 3
It becomes.

  Since the common mode voltage Vc1 is 1/3 of the change in the pulse voltage output from the inverter 202, the turns ratio of the primary coil and the secondary coil of each transformer T1 to T3 is 3: 1. By being 1: 1, the common mode voltage Vc1 can be canceled by the transformers T1 to T3.

  For example, when an output pulse of voltage 3Va is output from the output terminal W of the inverter 202, the voltage 3Va is generated in the secondary coil 211, and the voltage Va is generated in the secondary coils 212 to 124. At this time, since output pulses are not output from the output terminals U and V of the inverter 202, no voltage is generated in the primary coils 221 and 231 and the secondary coils 222 to 224 and 232 to 234 of the transformers T2 and T3. Become.

  On the other hand, when the voltage Va is generated in the secondary coils 212 to 124 of the transformer T1, each electrode of the three-phase motor 201 corresponding to the output terminals U, V, W of the inverter 202 has 0-Va, 0-Va. , 3Va−Va = 2Va is applied, and the common mode voltage Vc1 (= (− Va−Va + 2Va) / 3) becomes zero.

  In this embodiment, the motor driving device 200 of the three-phase motor 201 has been described. In the case of an N-phase motor, the common mode voltage Vcn is Vcn = Vcn = V1, V2,. (V1 + V2... Vn) / N, and the ratio of the primary winding to the secondary winding of the transformer may be N: 1: 1.

By the way, the other ends of the primary coils 221 and 231 of the transformers T2 and T3 are connected to the output terminals U and V of the inverter 202. For example, the other end of the primary coil 221 is connected to the secondary coil 213 of the transformer T1. This is because the voltage affected by the secondary coil 213 of the transformer T1 affects the secondary coils 222 to 224 of the transformer T2 by the primary coil 221 when connected between the secondary coil 223 of the transformer T2. .
[Fourth embodiment]
FIG. 10 shows a motor driving device 300 of the fourth embodiment. This motor drive device 300 is provided with a switch element (switching means) 301 between the other end of the primary coil 31 of the common mode cancel circuit 30 and the signal line L1.

  The switch element 301 is turned on when the duty ratio of the pulse voltage output from the inverter 20 is greater than or equal to a predetermined value, and turned off when the duty ratio is smaller than the predetermined value.

  That is, a control device (not shown) applies a predetermined voltage to the gate of the switch element 301 when the signal generator 21 outputs a pulse signal for outputting a pulse voltage with a duty ratio equal to or higher than a predetermined value from the inverter 20. When the switch element 301 is turned on and a pulse signal for outputting a pulse voltage having a duty ratio smaller than a predetermined value is output from the signal generator 21, the switch element 301 is turned off.

  When the common mode cancellation circuit 30 is not operated, as shown in FIG. 11, the common mode noise current increases in proportion to the duty ratio of the pulse voltage. However, the common mode noise current is within an allowable range. If there is, it is not necessary to operate the common mode cancel circuit 30, so that the switch element 301 is turned off when the duty ratio of the pulse voltage is smaller than a predetermined value.

  FIG. 12 shows a graph of the common mode noise current when the switch element 301 is turned on when the duty ratio is larger than 30%, for example, when the common mode noise current exceeds the allowable range. is there.

  FIG. 13 shows the common mode cancel circuit when the switch element 301 is turned on, that is, when the common mode cancel circuit 30 is operated, and the duty ratio of the pulse voltage output from the inverter 20 is 30%. 3 is a graph showing a loss due to 30.

  FIG. 14 shows the common mode cancel circuit 30 when the switch element 301 is off, that is, when the common mode cancel circuit 30 is not operated, and when the duty ratio of the pulse voltage output from the inverter 20 is 30%. It is the graph which showed the loss by.

  As can be seen from the graph shown in FIG. 14, the loss when the common mode cancel circuit 30 is not operated is approximately zero watts.

As described above, when the common mode noise current is within the allowable range, the loss generated in the common mode cancellation circuit 30 can be suppressed by not operating the common mode cancellation circuit 30.
[Fifth embodiment]
FIG. 15 shows a motor driving device 400 of the fifth embodiment. In the motor driving device 400, a filter circuit (high frequency noise suppression circuit) 401 for removing high frequency noise is connected between a low potential power line 11 and a high potential power line 12.

  The filter circuit 401 is composed of a series circuit of a capacitor C4 and a resistor R4.

  The graph shown in FIG. 16 shows the high frequency noise of the motor driving device 400, the graph G1 is a graph of the high frequency noise when the common mode cancellation circuit 30 is not provided, and the graph G2 is the common mode cancellation circuit 30. (Graphs G1 and G2 are high-frequency noise voltages generated between the low-potential power line 11 and the high-potential power line 12).

  As can be seen from the graphs G1 and G2, when the common mode cancel circuit 30 is provided, high frequency noise around 30 MHz is generated.

  The graph shown in FIG. 17 shows the high frequency noise generated from the motor driving device 400, the graph G3 is a graph of the high frequency noise when the filter circuit 401 is not provided, and the graph G4 is provided with the filter circuit 401. It is a graph of the high frequency noise in the case of.

  From these graphs G3 and G4, it can be seen that high frequency noise around 30 MHz is suppressed when the filter circuit 401 is provided.

  A graph G7 shown in FIG. 18 shows a common mode noise current when the common mode cancellation circuit 30 is not provided, and a graph G8 shows a common mode noise current of the motor driving device 400 when the common mode cancellation circuit 30 is provided.

  It can be seen from the graphs G7 and G8 that the common mode noise current can be suppressed even if the filter circuit 401 is provided.

  FIG. 19 shows another example of the motor driving apparatus 500 according to the fifth embodiment. The motor driving device 500 is obtained by connecting a filter circuit (high frequency noise suppression circuit) 401 to the low potential power supply line 11.

  The graph shown in FIG. 20 shows the high frequency noise generated in the motor driving device 500, the graph G5 is a graph of the high frequency noise when the filter circuit 401 is not provided, and the graph G6 is provided with the filter circuit 401. It is a graph of the high frequency noise in the case of.

  From these graphs G5 and G6, it can be seen that high frequency noise around 30 MHz is suppressed when the filter circuit 401 is provided.

  The graph shown in FIG. 21 shows voltage waveforms applied to the motor M. The graphs Ga1 and Ga2 are voltage waveforms when the filter circuit 401 is not provided, and the graphs Gb1 and Gb2 are provided with the filter circuit 401. It is a voltage waveform in the case of.

  From the graphs Ga1, Ga2, Gb1, and Gb2, it can be seen that the graphs Gb1 and Gb2 have low high-frequency noise. That is, it can be seen that high-frequency noise can be suppressed by providing the filter circuit 401.

  FIG. 19A shows another example of a motor driving apparatus 600. This motor drive device 600 is provided with a high-pass filter circuit (high-frequency noise suppression circuit) 402 between the other end of the primary coil 31 of the common mode cancel circuit 30 and the signal line L1. The high pass filter circuit 402 includes a capacitor C5 and a resistor R5.

  A graph G11 shown in FIG. 25 shows a voltage applied to the motor M when the high-pass filter circuit 402 is not provided, and a graph G12 shows a voltage applied to the motor M when the high-pass filter circuit 402 is provided. Indicates.

  As can be seen from the graphs G11 and G12, the high-pass filter circuit 402 is provided to suppress high frequency noise.

  A graph G13 shown in FIG. 26 shows a waveform of a pulse (PWM) voltage applied to the motor M when the high-pass filter circuit 402 is provided, and a graph G14 shows when the pulse voltage is output from the inverter 20. The voltage of the high pass filter circuit 402 is shown.

  FIG. 19B shows another example of a motor driving device 700. In the motor driving device 700, a band-pass filter circuit (high-frequency noise suppression circuit) 403 is provided between the other end of the primary coil 31 of the common mode cancel circuit 30 and the signal line L1. The band pass filter circuit 403 includes a coil H6, a capacitor C6, a resistor R6, and the like.

  A graph G15 shown in FIG. 27 shows a voltage applied to the motor M when the bandpass filter circuit 403 is not provided, and a graph G16 is applied to the motor M when the bandpass filter circuit 403 is provided. Voltage.

  As can be seen from the graphs G15 and G16, high-frequency noise is suppressed by providing the band-pass filter circuit 403.

A graph G17 shown in FIG. 28 shows a waveform of a pulse (PWM) voltage applied to the motor M when the bandpass filter circuit 403 is provided, and a graph G18 shows when the pulse voltage is output from the inverter 20. The voltage of the band pass filter circuit 403 is shown.
[Sixth embodiment]
FIG. 22 shows a motor driving device 600 of the sixth embodiment. In the motor driving device 600, one end of the capacitor C1 of the common mode cancel circuit 40 is connected to the source of the switching transistor 22 and to the cathode of the DC power source E.

  FIG. 23 shows a graph G9 of a common mode noise current flowing between the DC power source (battery) E and the inverter 20. As can be seen from the graph G9, the common mode noise current is as small as about -20 to 20 [mA].

  Incidentally, when one end of the capacitor C1 is not connected to the source or the like of the switching transistor 22, that is, when one end of the capacitor C1 is grounded, as shown in the graph G10 of FIG. The mode noise current is about −80 to 100 [mA], and it can be seen that the common mode noise current is greatly reduced.

  In any of the above-described embodiments, the motor driving devices 10, 100, 130, and 200 to 800 of the motor M that rotates the radiator fan have been described. However, the present invention is not limited to this, and for example, a blower motor for blowing an air conditioner. It may be.

  Further, although the common mode cancellation circuits 30, 210, 220, and 230 are composed of transformers, they may be other than transformers as long as they operate in the same manner.

  Of course, the motor driving devices of the fourth to sixth embodiments can be applied to a three-phase motor or an N-phase motor having three or more phases.

It is the circuit diagram which showed the structure of the motor drive device based on this invention. It is explanatory drawing which showed the voltage of the principal part of the circuit shown in FIG. It is explanatory drawing which showed the voltage which arises at the other end of the secondary coil of FIG. It is the graph which simulated the common mode noise current of the circuit shown in FIG. This shows a circuit in which the primary coil 31 and the capacitor C1 shown in FIG. 1 are omitted. It is the graph which simulated the common mode noise current of the circuit of FIG. It is the circuit diagram which showed the structure of the motor drive device of 2nd Example. The graph which simulated the common mode noise current of the motor drive device of 2nd Example is shown. FIG. 6 is a circuit diagram in which the common mode cancellation circuit of FIG. 5 is omitted. It is the graph which simulated the common mode noise current of the circuit of FIG. It is a circuit diagram of the motor drive device of 3rd Example. It is a circuit diagram of the motor drive device of 4th Example. 6 is a graph showing a relationship between a common mode noise current and a duty ratio of a pulse voltage. It is the graph which showed the relationship between the common mode noise current of 4th Example, and the duty ratio of a pulse voltage. It is the graph which showed the loss of the common mode cancellation circuit when operating the common mode cancellation circuit. It is the graph which showed the loss of the common mode cancellation circuit when not operating the common mode cancellation circuit. It is a circuit diagram of the motor drive device of 5th Example. It is the graph which showed the high frequency noise which generate | occur | produces from the motor drive apparatus with and without a common mode cancellation circuit. It is the graph which showed the high frequency noise which generate | occur | produces from the motor drive apparatus with and without providing a filter circuit. It is the graph which showed the common mode noise current when not providing a common mode cancellation circuit, and the common mode noise current when providing a common mode cancellation circuit. It is a circuit diagram of the motor drive device of the other example of 5th Example. It is a circuit diagram of the motor drive device of another example of 5th Example. It is the graph which showed the high frequency noise to generate. It is. It is a circuit diagram of the motor drive device of another example of 5th Example. It is the graph which showed the high frequency noise which generate | occur | produces in the motor drive device with and without a filter circuit. It is the graph which showed the high frequency noise voltage of the common mode cancellation circuit with and without a filter circuit. It is a circuit diagram of the motor drive device of 6th Example. It is the graph which showed the common mode noise current which flows between the DC power supply of 6th Example, and an inverter. It is the graph which showed the common mode noise current which flows between a direct-current power supply and an inverter at the time of grounding one end of a capacitor. It is the graph which showed the high frequency noise which generate | occur | produces in the motor drive device of another example of 5th Example. It is the graph which showed the pulse voltage applied to the motor of the motor drive device of another example of the 5th example, and the voltage of a high pass filter. The circuit diagram of the motor drive device of the other another example of 5th Example is shown. It is the graph which showed the pulse voltage applied to the motor of the motor drive device of another example of the 5th example, and the voltage of a band pass filter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Motor drive device 22 Switching transistor 30 Common mode cancellation circuit 31 Primary coil 32 Secondary coil 33 Secondary coil T Transformer M Motor Ma, Mb Electrode

Claims (10)

In a motor drive device that includes an inverter that converts a DC power supply voltage into a pulse voltage, and that drives the motor with the pulse voltage output from the inverter,
A motor driving apparatus comprising: a common mode canceling unit that applies a voltage obtained by subtracting a voltage corresponding to a change in the pulse voltage from a voltage of each output terminal of the inverter to each electrode of the motor. When the motor is a single phase, the common mode canceling means includes at least one transformer interposed between the inverter and the motor,
The transformer has one end grounded and the other end connected to one output terminal of the inverter to detect a voltage change at the output terminal, and between the output terminals of the inverter and both electrodes of the motor. The motor drive device according to claim 1, comprising two secondary coils provided respectively.   The motor drive device according to claim 2, wherein a turn ratio between the primary winding of the transformer and the two secondary windings is 2: 1. When the motor is N-phase, the common mode canceling means includes N transformers interposed between the inverter and the motor,
Each transformer is connected to an output terminal of the inverter, one end of which is grounded and the other end of which corresponds to the primary coil that detects a voltage change of the output terminal, and between each output terminal of the inverter and each electrode of the motor. The motor drive device according to claim 1, further comprising N secondary coils provided.   5. The motor drive device according to claim 4, wherein a turn ratio of a primary coil and the N secondary coils of each transformer is N: 1.   There is provided switching means for stopping the operation of the common mode canceling means when the common mode noise current of the motor driving device is equal to or less than a predetermined value and for operating the common mode canceling means when the common mode noise current is larger than a predetermined value. The motor drive device according to claim 1, wherein the motor drive device is a motor drive device.   7. The motor driving apparatus according to claim 1, further comprising a high frequency noise suppression circuit that suppresses high frequency noise generated by the common mode canceling unit.   The high-frequency noise suppression circuit is a filter circuit including a capacitor and a resistor, and the filter circuit is connected to at least one of the high-potential power line and the low-potential power line of the motor, or the high-potential power line and the low-potential power line are low. The motor driving device according to claim 7, wherein the motor driving device is connected between potential power supply lines. A high-frequency noise suppression circuit is provided between the primary coil according to any one of claims 2 to 5 and one output terminal of the inverter,
The high-frequency noise suppression circuit is a high-pass filter circuit having a capacitor and a resistor, or a band-pass filter having a coil, a capacitor, and a resistor.   5. A motor drive device, wherein one end of the primary coil according to claim 2 is connected to an input terminal on the negative side of the inverter.

Images