JP2013240192A - Motor drive and control method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To limit heating while suppressing increase in the circuit scale and cost.SOLUTION: The motor drive includes a polyphase motor 11, a rotational position detection unit 12 which detects the rotational position of the polyphase motor and outputs a rotational position signal corresponding to the rotational position, an inverter 14 which has a plurality of arms each including a switching element and supplies a DC voltage Vi, supplied from a DC source BAT, to the polyphase motor while converting into a motor drive current, and a control unit 15 which turns each switching element of the inverter on or off depending on the rotational position signal. The control unit calculates the phase currents Iu, Iv, Iw flowing to respective phases of the polyphase motor by using the arm currents flowing to the plurality of arms, calculates the output current being output from the DC source to the inverter by using the plurality of phase currents thus calculated, and controls the inverter so as to reduce the arm current when a value based on the output current thus calculated reaches a predetermined upper limit.

Description

  The present invention relates to a motor drive device for driving a multiphase motor and a control method for the motor drive device.

  In recent years, a boost converter has been mounted on a motor drive device that drives a multiphase motor using an inverter. The reason why the boost converter is mounted is to reduce the current flowing through the inverter and the multiphase motor by supplying the boosted voltage to the inverter, thereby reducing the size of the motor drive device.

  In a motor drive device that is required to reduce the size, it is difficult to improve heat dissipation. Therefore, the heat generation of the motor drive device has become a problem. In particular, when the motor needs to generate a strong torque, or when the rotation of the motor is forcibly stopped depending on the load conditions, a large current flows through the boost converter, inverter, and motor, so these heat generations are large. Become. When this heat generation is large, there is a risk of damage to the semiconductor elements and capacitors of the boost converter. Therefore, it is necessary to limit heat generation by limiting the output current value of the boost converter.

  In Patent Document 1, when the output current of the booster circuit obtained from the motor current detected by the phase current sensor and the duty of the pulse width modulation is larger than the upper limit value corresponding to the input voltage of the booster circuit, the output current A technique for reducing the above is disclosed.

Japanese Patent No. 4869771

  However, in the technique described in Patent Document 1, a dedicated phase current sensor is used to detect the motor current. Therefore, there is a problem that the circuit scale and cost increase.

  Therefore, an object of the present invention is to provide a motor drive device and a motor drive device control method capable of limiting heat generation while suppressing an increase in circuit scale and cost.

A motor drive device according to an aspect of the present invention is provided.
A multiphase motor,
A rotational position detector that detects a rotational position of the multiphase motor and outputs a rotational position signal corresponding to the rotational position;
An inverter having a plurality of arms including a switching element, converting a DC voltage supplied from a DC source into a motor driving current and supplying the motor to the multiphase motor;
A control unit that controls each switching element of the inverter to be turned on or off according to the rotational position signal, and
The controller is
Calculate the phase current flowing in each phase of the multiphase motor using the arm current flowing in the plurality of arms,
Using the calculated plurality of phase currents, calculating an output current output from the DC source to the inverter,
The inverter is controlled so that the arm current decreases when a value based on the calculated output current reaches a predetermined upper limit value.

In the motor driving device,
A booster that boosts a DC voltage supplied from the DC source and outputs a boosted voltage;
The controller is
Using the calculated plurality of phase currents, an output current output from the boosting unit to the inverter is calculated,
The inverter may be controlled so that the arm current decreases when a value based on the calculated output current reaches a predetermined upper limit value.

In the motor driving device,
The control unit may calculate a sum of the plurality of phase currents in which a negative phase current is replaced with zero, and use the sum as the output current.

In the motor driving device,
The controller is
Using the effective value of the output current as a value based on the output current,
A rotation state of the multiphase motor is determined according to the rotation position signal output from the rotation position detection unit, and when it is determined that the multiphase motor is rotating, the output current is set to a predetermined constant. When it is determined that the multiphase motor is stopped with the value divided by the effective value, the output current may be the effective value.

In the motor driving device,
The rotational position detector is composed of a resolver,
When the rotation angle information obtained from the rotation position signal output from the resolver is changing, the control unit determines that the multiphase motor is rotating, and when the rotation angle information is a constant value, It may be determined that the multiphase motor is stopped.

In the motor driving device,
The constant may be a square root of 2.

In the motor driving device,
The controller is
Integrate the calculated effective value of the output current with time to calculate the integrated value,
As the value based on the output current, the integrated value may be used instead of the effective value of the output current.

A control method of a motor drive device according to an aspect of the present invention includes:
Supplied from a DC source with a multi-phase motor, a rotational position detector that detects the rotational position of the multi-phase motor and outputs a rotational position signal corresponding to the rotational position, and a plurality of arms including switching elements An inverter that converts the DC voltage that has been converted into a motor drive current and supplies the same to the multiphase motor, and a control unit that controls each switching element of the inverter to be turned on or off according to the rotational position signal. A method for controlling a drive device, comprising:
By the control unit,
Calculate the phase current flowing in each phase of the multiphase motor using the arm current flowing in the plurality of arms,
Using the calculated plurality of phase currents, calculating an output current output from the DC source to the inverter,
The inverter is controlled so that the arm current decreases when a value based on the calculated output current reaches a predetermined upper limit value.

  According to the present invention, the phase current flowing in each phase of the multiphase motor is calculated using the arm current flowing in the plurality of arms, and the output current output from the DC source is calculated using the calculated plurality of phase currents. The inverter is controlled so that the arm current decreases when a value based on the calculated output current reaches an upper limit value. Thus, since the output current is calculated based on the arm current that can be detected without using the phase current sensor, heat generation can be limited while suppressing an increase in circuit scale and cost.

1 is a block diagram illustrating a schematic configuration of a motor drive device according to Embodiment 1. FIG. 3 is a flowchart illustrating an operation of the motor drive device according to the first embodiment. It is a wave form diagram which shows the phase current and output current of the motor drive device which concern on Example 1. FIG. It is a figure explaining the limiting operation | movement of the output current of the motor drive device which concerns on Example 1. FIG.

  Embodiments according to the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram illustrating a schematic configuration of the motor drive device according to the first embodiment. As shown in FIG. 1, the motor drive device includes a motor (multiphase motor) 11, a resolver (rotational position detection unit) 12, a boost converter (boost unit) 13, an inverter 14, and a control unit 15. Prepare.

  The motor 11 is, for example, a three-phase DC brushless motor.

  The resolver 12 detects the rotational position of the motor 11 based on the excitation signal supplied from the control unit 15, and outputs a rotational position signal corresponding to the rotational position to the control unit 15.

  Boost converter 13 boosts DC power supply voltage Vi (for example, 12V) supplied from battery (DC source) BAT, and outputs DC boosted voltage Vo (for example, 24V). Boost converter 13 includes an input capacitor Cin, an inductor L, two switching elements Q1 and Q2 which are N-type MOS transistors, and an output capacitor Cout.

  The input capacitor Cin has one end connected to the positive terminal of the battery BAT and the other end connected to the negative terminal of the battery BAT and is grounded. One end of the inductor L is connected to the positive terminal of the battery BAT.

  The switching element Q1 has one end (drain) connected to the other end of the inductor L and the other end (source) grounded. The switching element Q2 has one end (source) connected to the other end of the inductor L, and outputs the boosted voltage Vo from the other end (drain).

  One end of the output capacitor Cout is connected to the other end of the switching element Q2, and the other end is grounded. That is, the voltage between one end and the other end of the output capacitor Cout is the boost voltage Vo.

  Output current Io is output from boost converter 13 to inverter 14. The polarity of the output current Io is positive in the direction flowing from the boost converter 13 to the inverter 14. The output current Io is substantially equal to the current output from the positive terminal of the battery BAT.

  The inverter 14 converts the boosted voltage Vo supplied from the boost converter 13 into a motor drive current and supplies it to the motor 11. The motor drive current includes a phase current Iu flowing in the U phase of the motor 11, a phase current Iv flowing in the V phase, and a phase current Iw flowing in the W phase. Regarding the polarities of the phase currents Iu, Iv, and Iw, the direction from the inverter 14 to the motor 11 is positive.

  The inverter 14 has a three-phase bridge circuit configuration, and includes six switching elements Q3 to Q8 that are N-type MOS transistors, and three resistors Ru, Rv, and Rw for arm current detection.

  The boosting voltage Vo is supplied to one end (drain) of the switching element Q3. The switching element Q4 has one end (drain) connected to the other end (source) of the switching element Q3. The resistor Ru has one end connected to the other end (source) of the switching element Q4 and the other end grounded. The switching elements Q3 and Q4 constitute a U-phase arm Au.

  The boosting voltage Vo is supplied to one end (drain) of the switching element Q5. The switching element Q6 has one end (drain) connected to the other end (source) of the switching element Q5. The resistor Rv has one end connected to the other end (source) of the switching element Q6 and the other end grounded. Switching elements Q5 and Q6 constitute a V-phase arm Av.

  The switching element Q7 is supplied with a boosted voltage Vo at one end (drain). The switching element Q8 has one end (drain) connected to the other end (source) of the switching element Q7. The resistor Rw has one end connected to the other end (source) of the switching element Q8 and the other end grounded. Switching elements Q7, Q8 constitute a W-phase arm Aw.

  Phase current Iu is output from the connection point of switching elements Q3 and Q4, phase current Iv is output from the connection point of switching elements Q5 and Q6, and phase current Iw is output from the connection point of switching elements Q7 and Q8.

  The voltage between both ends of each resistor Ru, Rv, Rw is a voltage representing the arm currents Iu_s, Iv_s, Iw_s.

  The control unit 15 is composed of, for example, a microcomputer and controls the resolver 12, the boost converter 13, and the inverter 14.

  The boost voltage Vo is supplied from the boost converter 13. The control unit 15 supplies the boost converter drive signal to the control terminals (gates) of the switching elements Q1 and Q2 so that the boosted voltage Vo becomes a predetermined constant value (for example, 24 V), and each switching element PWM control is performed to turn on and off Q1 and Q2.

  The control unit 15 is supplied with a current target value from the outside, is supplied with a rotational position signal from the resolver 12, and is supplied with voltages representing arm currents Iu_s, Iv_s, and Iw_s from the inverter 14. The control unit 15 includes an AD converter (not shown). The AD converter samples a voltage representing the arm currents Iu_s, Iv_s, and Iw_s, and uses the arm currents Iu_s, Iv_s, and Iw_s obtained thereby. Then, the inverter 14 is controlled. The sampling period is equal to the switching period of the inverter 14, for example. Specifically, the control unit 15 sends the inverter drive signal to the control terminals (gates) of the switching elements Q3 to Q8 according to the rotation position signal so that the current based on the arm currents Iu_s, Iv_s, and Iw_s becomes the current target value. ) And PWM control is performed to turn on or off each of the switching elements Q3 to Q8.

  The above control of the boost converter 13 and the inverter 14 by the control unit 15 is a known control. By such control, the rotation of the motor 11 can be controlled according to the current target value.

  This motor drive device is configured to monitor a value based on the output current Io of the boost converter 13 by the control unit 15 while driving and controlling the motor 11, and to limit the output current Io according to the monitoring result. Has been. Hereinafter, the operation of limiting the output current Io will be described in detail with reference to FIGS.

  FIG. 2 is a flowchart illustrating the operation of the motor drive device according to the first embodiment. A series of processing from step S1 to step S9 in FIG. 2 is performed at each sampling timing.

  First, as described above, the control unit 15 controls the boost converter 13 and obtains the arm currents Iu_s, Iv_s, and Iw_s flowing through the three arms Au, Av, and Aw by sampling, and the inverter based on the arm currents 14 is controlled (step S1).

  Next, the control unit 15 calculates phase currents Iu, Iv, Iw flowing in the respective phases of the motor 11 using the arm currents Iu_s, Iv_s, Iw_s obtained in step S1 (step S2). Since the method for calculating the phase currents Iu, Iv, and Iw is a known method, the description thereof is omitted here.

  Next, the control unit 15 calculates the output current Io output from the boost converter 13 to the inverter 14 using the calculated three phase currents Iu, Iv, and Iw. Specifically, the control unit 15 replaces the negative phase current among the phase currents Iu, Iv, and Iw with zero (step S3). Then, the sum of the three phase currents Iu, Iv, Iw obtained by replacing the negative phase current with zero is calculated, and the sum is set as the output current Io (step S4). That is, Io = Iu + Iv + Iw (formula (1)).

  The reason for substituting the negative phase current with zero in this way is that if the sum of the three phase currents Iu, Iv, Iw is calculated as it is, it becomes zero.

  FIG. 3 is a waveform diagram showing the phase currents Iu, Iv, Iw and the output current Io of the motor driving apparatus according to the first embodiment. 3A shows the phase currents Iu, Iv, Iw when the motor 11 is rotating, FIG. 3B shows the output current Io obtained by the equation (1), and FIG. Indicates an output current Io obtained by holding the output current Io in FIG. As shown in FIG. 3B, the output current Io obtained by the equation (1) is calculated based on the arm currents Iu_s, Iv_s, and Iw_s obtained by sampling, and thus has a discrete waveform. ing.

  As can be seen from FIGS. 3A to 3C and equation (1), the peak value of the output current Io is equal to the peak value of the phase currents Iu, Iv, and Iw of each phase.

  When the process of step S4 in FIG. 2 is completed, the control unit 15 determines whether or not the motor 11 is rotating (that is, the rotation state of the motor 11) in accordance with the rotational position signal output from the resolver (step 11). S5).

  When the motor 11 is rotating, a resolver 12 outputs a rotation position signal including rotation angle information (sin waveform and cos waveform) having a frequency equal to or higher than a certain value. Therefore, the control unit 15 determines that the motor 11 is rotating when the rotation angle information obtained from the rotation position signal has changed. When it is determined that the motor 11 is rotating (step S5; Yes), the value obtained by dividing the output current Io obtained in step S4 by the square root of 2 that is a predetermined constant is set as the effective value of the output current Io. (Step S6), the process proceeds to Step S8. The effective value of the output current Io obtained in step S6 is an approximate value. The constant may be an approximate value of the square root of 2. In this case, the phase currents Iu, Iv, and Iw are alternating currents as shown in FIG.

  On the other hand, when the rotation of the motor 11 is stopped by the load of the motor 11, a rotational position signal including substantially zero rotation angle information is output from the resolver 12. Therefore, when the rotation angle information is a constant value, the control unit 15 determines that the motor 11 is stopped (Step S5; No), and uses the output current Io as the effective value of the output current Io as it is (Step S7). The process proceeds to step S8. In this case, the phase currents Iu, Iv, Iw are substantially constant DC currents, and any of the phase currents Iu, Iv, Iw can be larger than when the motor 11 is rotating.

  Next, the control unit 15 integrates the calculated effective value of the output current Io with time to calculate an integrated value (step S8).

  Next, the control unit 15 determines whether or not the calculated integral value (a value based on the output current Io) has reached a predetermined upper limit value (step S9). When the integral value does not reach the upper limit value (step S9; No), the process returns to the process of step S1, and the process of the next sampling timing is performed.

  On the other hand, when the integral value reaches the upper limit value (step S9; Yes), the inverter 14 is controlled so that the arm currents Iu_s, Iv_s, and Iw_s decrease (step S10), and the process ends. That is, in step S10, the control unit 15 forcibly decreases the arm currents Iu_s, Iv_s, and Iw_s regardless of the current target value supplied from the outside. Thereby, heat generation of switching elements Q1, Q2, output capacitor Cout, etc. of boost converter 13 can be limited.

  FIG. 4 is a diagram illustrating the operation of limiting the output current Io of the motor drive device according to the first embodiment. The vertical axis in FIG. 4 indicates the effective value of the output current Io, and the horizontal axis indicates time.

  As shown in FIG. 4, for example, when the effective value of the output current Io continuously reaches the point a after the time W has passed with the value A, the effective value of the output current Io decreases to the limit value D. The control unit 15 controls the inverter 14 to decrease the arm currents Iu_s, Iv_s, and Iw_s. Similarly, when the effective value of the output current Io continuously reaches the point b after the time X (> time W) with the value B (<value A) passed, or the effective value of the output current Io continues. Thus, control is performed so that the effective value of the output current Io decreases to the limit value D even when the point C is reached after the time Y (> time X) has passed with the value C (<value B). On the other hand, as a case where the effective value of the output current Io does not change, for example, the rotation of the motor 11 may be forcibly stopped.

  The area of the rectangle 0AaW, the area of the rectangle 0BbX, the area of the rectangle 0CcY, and the upper limit value in step S9 in FIG. 2 are equal. Since this area, that is, the upper limit value has a correlation with the heat generation amount, the upper limit value may be set according to the allowable heat generation amount.

  Further, the limit value D may be set so that there is no problem even if the effective value of the output current Io continues to be the limit value D.

  By such control, the effective value of the output current Io is not a constant value as in the example of FIG. 4, for example, when it changes between the value A and the value C (for example, the rotation of the motor 11 is uneven). The output current Io can be similarly limited according to the integral value.

  Note that the controller 15 does not calculate an integral value when the effective value of the output current Io is equal to or less than the limit value D in step S8. As a result, when the effective value of the output current Io is continuously equal to or less than the limit value D, the processing of step S1 to step S9 is repeated, and control according to the current target value is performed.

  After step S10 of FIG. 2, for example, the control unit 15 monitors the temperature of the boost converter 13 using a temperature sensor (not shown), and performs control to decrease the arm currents Iu_s, Iv_s, and Iw_s after the temperature decreases. Then, the control may be returned to step S1 again to start the control according to the current target value. Even when such a temperature sensor is available, the control based on the output current Io described above is necessary. This is because the change in temperature is slower than the change in the output current Io, and therefore it is not appropriate to use only control that reduces the arm currents Iu_s, Iv_s, Iw_s when the temperature reaches a predetermined temperature. It is.

  As described above, according to the present embodiment, the phase currents Iu, Iv, Iw flowing in the respective phases of the motor 11 are calculated using the arm currents Iu_s, Iv_s, Iw_s flowing in the three arms Au, Av, Aw. The output current Io output from the boost converter 13 is calculated using the calculated phase currents Iu, Iv, and Iw. Then, when the value based on the calculated output current Io reaches the upper limit value, the inverter 14 is controlled so that the arm currents Iu_s, Iv_s, and Iw_s decrease. Thus, since the output current Io is calculated based on the arm currents Iu_s, Iv_s, and Iw_s that can be detected without using the phase current sensor, heat generation can be limited while suppressing an increase in circuit scale and cost. Thereby, it is possible to prevent the switching elements Q1, Q2 and the output capacitor Cout of the boost converter 13 from being damaged.

  Further, according to the present embodiment, when the rotation state of the motor 11 is determined according to the rotation position signal and it is determined that the motor 11 is rotating, a value obtained by dividing the output current Io by the square root of 2 is an effective value. When it is determined that the motor 11 is stopped, the output current Io is set to the effective value as it is. Thereby, an effective value corresponding to the actual output current Io can be obtained according to the rotation state of the motor 11. Since the effective value of the output current Io has a correlation with the heat generation amount, the heat generation can be more accurately limited according to the rotation state of the motor 11.

  Furthermore, according to the present embodiment, the output current Io is limited when the integral value of the effective value of the output current Io reaches the upper limit value, so that the effective value of the output current Io changes with time. However, the heat generation can be limited to a relatively constant level by the uniform processing.

  As an application example of the motor driving device described above, for example, an electric power steering device for an automobile can be cited.

(Modification)
As mentioned above, although the Example of this invention was explained in full detail, a concrete structure is not limited to the said Example, A various deformation | transformation can be implemented in the range which does not deviate from the summary of this invention.
For example, the boost converter 13 may not be provided, and the inverter 14 may convert the power supply voltage Vin supplied from the battery BAT into a motor drive current and supply it to the motor 11. And the control part 15 may calculate the output current Io output from the battery BAT using the phase currents Iu, Iv, and Iw calculated similarly to the said Example. Even if comprised in this way, like the said Example, after suppressing the increase in a circuit scale and cost, the heat_generation | fever of the inverter 14 or the motor 11 can be restrict | limited.

  The functions of the control unit 15 of the above-described embodiment may be limited to perform simpler processing. For example, in the flowchart of FIG. 2, step S8 may be omitted, and in step S9, the effective value of the output current Io may be used as a value based on the output current Io instead of the integral value. As a result, it is not possible to accurately limit heat generation based on the integral value, but the other effects described above can be obtained while reducing the processing of the control unit 15.

  Further, steps S5 to S8 may be omitted, and in step S9, the output current Io representing an instantaneous value may be used as it is as a value based on the output current Io. This makes it impossible to control the heat generation according to the rotation state of the motor 11, but the effect of reducing the processing of the control unit 15 and limiting the heat generation while suppressing an increase in circuit scale and cost is obtained. It is done.

  Moreover, although the motor 11 demonstrated the example which is a three-phase DC brushless motor, other than a three-phase may be sufficient. Moreover, switching elements Q1-Q8 may be comprised from IGBT etc.

  The constant for obtaining the effective value is not limited to the square root of 2, and may be changed according to the waveform of the output current Io. That is, another value that can approximate the effective value of the output current Io may be used.

  At least a part of the functions of the control unit 15 of the motor driving apparatus described in the above-described embodiments may be realized by hardware or software. When implemented by software, a program for realizing at least a part of the functions of the control unit 15 may be stored in a recording medium such as a flexible disk or a CD-ROM, and read and executed by a computer. The recording medium is not limited to a removable medium such as a magnetic disk or an optical disk, but may be a fixed recording medium such as a hard disk device or a memory.

  Further, a program for realizing at least a part of the functions of the control unit 15 may be distributed via a communication line (including wireless communication) such as the Internet. Further, the program may be distributed in a state where the program is encrypted, modulated or compressed, and stored in a recording medium via a wired line such as the Internet or a wireless line.

11 Motor (Multi-phase motor)
12 Resolver (Rotation position detector)
13 Step-up converter (step-up part)
14 Inverter 15 Control unit Cin Input capacitor L Inductors Q1 to Q8 Switching element (N-type MOS transistor)
Cout output capacitor Ru, Rv, Rw resistance BAT battery

Claims (8)

A multiphase motor,
A rotational position detector that detects a rotational position of the multiphase motor and outputs a rotational position signal corresponding to the rotational position;
An inverter having a plurality of arms including a switching element, converting a DC voltage supplied from a DC source into a motor driving current and supplying the motor to the multiphase motor;
A control unit that controls each switching element of the inverter to be turned on or off according to the rotational position signal, and
The controller is
Calculate the phase current flowing in each phase of the multiphase motor using the arm current flowing in the plurality of arms,
Using the calculated plurality of phase currents, calculating an output current output from the DC source to the inverter,
The motor drive device, wherein the inverter is controlled so that the arm current decreases when a value based on the calculated output current reaches a predetermined upper limit value. A booster that boosts a DC voltage supplied from the DC source and outputs a boosted voltage;
The controller is
Using the calculated plurality of phase currents, an output current output from the boosting unit to the inverter is calculated,
The motor drive device according to claim 1, wherein when the value based on the calculated output current reaches a predetermined upper limit value, the inverter is controlled so that the arm current decreases. The motor according to claim 1, wherein the control unit calculates a sum of the plurality of phase currents in which a negative phase current is replaced with zero, and uses the sum as the output current. Drive device. The controller is
Using the effective value of the output current as a value based on the output current,
A rotation state of the multiphase motor is determined according to the rotation position signal output from the rotation position detection unit, and when it is determined that the multiphase motor is rotating, the output current is set to a predetermined constant. 4. The output current is set to the effective value when it is determined that the multi-phase motor is stopped with the value divided by the effective value as the effective value. 5. Motor drive device. The rotational position detector is composed of a resolver,
When the rotation angle information obtained from the rotation position signal output from the resolver is changing, the control unit determines that the multiphase motor is rotating, and when the rotation angle information is a constant value, The motor drive device according to claim 4, wherein the multiphase motor is determined to be stopped.   The motor driving apparatus according to claim 4, wherein the constant is a square root of 2. 6. The controller is
Integrate the calculated effective value of the output current with time to calculate the integrated value,
The motor drive device according to any one of claims 4 to 6, wherein the integral value is used instead of an effective value of the output current as a value based on the output current. Supplied from a DC source with a multi-phase motor, a rotational position detector that detects the rotational position of the multi-phase motor and outputs a rotational position signal corresponding to the rotational position, and a plurality of arms including switching elements An inverter that converts the DC voltage that has been converted into a motor drive current and supplies the same to the multiphase motor, and a control unit that controls each switching element of the inverter to be turned on or off according to the rotational position signal. A method for controlling a drive device, comprising:
By the control unit,
Calculate the phase current flowing in each phase of the multiphase motor using the arm current flowing in the plurality of arms,
Using the calculated plurality of phase currents, calculating an output current output from the DC source to the inverter,
A method for controlling a motor drive device, comprising: controlling the inverter so that the arm current decreases when a value based on the calculated output current reaches a predetermined upper limit value.

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