JP2017225236A - Motor drive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor drive device in which an overcurrent protection function prevents an overvoltage protection function from being damaged by winding short-circuit control in the case of failure detection of an inverter.SOLUTION: A motor drive device comprises: first protection means for performing overcurrent protection by detecting an output current of an inverter INV exceeding an overcurrent threshold by output overcurrent detection means 16to 16; and second protection means for performing overvoltage protection by short-circuiting motor winding by turning on switching elements of upper arms or lower arms of all phases in the case of a failure of the inverter INV. The motor drive device further comprises: short-circuit control means 15 which outputs an arm selection command and a short-circuit control command for short-circuiting the motor winding in the case of failure detection; and threshold change means 161 which changes a normal-time threshold to a short-circuit-control-time threshold greater than the normal-time threshold just after short-circuit control is started. The output overcurrent detection means 16to 16compare the normal-time threshold or the short-circuit-control-time threshold with the output current as the overcurrent detection threshold.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a technique for protecting an inverter for driving an electric motor from overvoltage and overcurrent.

FIG. 6 is a configuration diagram of an inverter for an electric machine described in Patent Document 1, and shows an inverter mounted on, for example, a hybrid vehicle.
In FIG. 6, 1A is an electric machine including an electric motor, 2 is a three-phase inverter that drives the electric machine 1A, 3 is an output stage unit provided corresponding to each of the three-phase phases, 4 is a control unit, and 5 is a power supply. A unit, 6 is an energy supply network including a storage element, 7 is a main switch, and 8 is an energy storage device such as a battery.

FIG. 7 shows the configuration of the output stage unit 3 for one phase.
In FIG. 7, 3a is a phase power supply unit, 3b is an emergency operation power supply unit connected to the energy supply network 6, 3c is an emergency operation control unit, and 3d is a comparison that compares the output voltage of the phase power supply unit 3a with a threshold A. A unit 3e is a comparison unit that compares the output voltage of the emergency operation power supply unit 3b with the threshold B, 3f is an output stage drive control unit, and 3g is a normal control signal and an emergency control signal C from the control unit 4. A changeover switch 3h for selecting either by the output of the comparison unit 3e, a drive unit for generating a drive command in accordance with a control signal from the changeover switch 3g, and 3i for performing DC / AC conversion by turning on / off by the drive command The output stage is composed of a plurality of semiconductor switching elements, and AC power is supplied from the output stage 3i to the electric machine 1A shown in FIG.

  In this prior art, when a failure occurs in the control unit 4, the power supply unit 5, etc., the changeover switch 3g is switched to the emergency control signal C side by the output of the comparison unit 3e, and the power supplied from the emergency operation power supply unit 3b is supplied. The unit 3h controls the output stage 3i of each phase so as to short-circuit the motor winding in the electric machine 1A by turning on the switching elements of the upper arm or the lower arm of all phases. For this reason, it is possible to protect the inverter 2 by preventing the energy supply network 6 (storage element) from being overvoltage due to the induced voltage of the electric motor.

Here, FIG. 8 is a main circuit configuration diagram of an inverter provided with the above-described output stage 3i for three phases, and shows, for example, a drive device for driving the permanent magnet synchronous motor 1. FIG.
In FIG. 8, E is a direct current power supply, C is a smoothing _capacitor, Ry _p, Ry _{n relay, Q u, Q v, Q} w, Q x, Q y, Q z is a semiconductor switching element such as an _{IGBT, F} u, _{F v, F w, F x} , F y, F z is the abnormality detection circuit connected to the sense emitter of the switching element _Q u to Q _z.

In the circuit of Figure 8, by any of the abnormality detection circuit F _u to F _z, the control circuit and a power supply circuit, when detecting an abnormality such as a switching element, power supply from the DC power source E by opening the relay Ry _p or Ry _n To stop. Then, upon detecting the opening of the relay Ry _p or Ry _n, the switching element _Q u of the upper arm of all _phases, Q v, _{Q w} or lower arm switching element _{Q x,} Q y, turns on the _{Q z} motor 1 Are prevented from being excessively increased by the induced voltage of the electric motor 1.

JP2013-183522A (paragraphs [0019] to [0026], FIG. 1 etc.)

In the inverter for electric machines described in Patent Document 1 and the circuit of FIG. 8, the induced voltage and transient reactance of the motor over a certain period determined by the transient time constant of the motor during short-circuit control of the motor winding accompanying the occurrence of the inverter failure. A large current flows depending on the current.
FIG. 9 is a waveform diagram showing temporal changes in the output currents i _u , i _v , i _w of each phase of the inverter and the voltage of the smoothing capacitor C, where t ₀ is the time when the relay is opened due to failure detection, t ₁ is, for example, the time when the switching elements Q _u , Q _v , Q _w of the upper arms of all phases are turned on to start the short-circuit control of the motor windings.
According to FIG. 9, the output currents i _u , i _v , i _w become large over a period Δt after time t ₁ and then converge as a permanent short-circuit current. In particular, as is apparent from the portion P surrounded by the broken line, the output current becomes extremely large immediately after the start of the short-circuit control.

On the other hand, this type of inverter usually has an overcurrent protection function that detects that the output current has become excessive and turns off all switching elements (so-called all gate off). Therefore, as shown in FIG. 9, exceeds a predetermined overcurrent threshold becomes excessive output current at time t ₁ after, will be all the gate-off operation short circuit control is executed is canceled, as a result The function of protecting the inverter from overvoltage may not work.

  Accordingly, the problem to be solved by the present invention is that an overcurrent protection function for an inverter and an overvoltage protection function for preventing overvoltage application to a DC circuit by short-circuiting the motor winding when the inverter fails are overdriven. It is an object of the present invention to provide an electric motor drive device that does not impair an overvoltage protection function by short-circuit control by adjusting the magnitude of a current threshold, its effective period, and the like.

In order to solve the above problems, the invention according to claim 1 is an electric motor drive device for driving an electric motor by an inverter,
A first protection means for detecting that the output current of the inverter has exceeded an overcurrent threshold by an output overcurrent detection means and performing an overcurrent protection operation of the inverter; In the electric motor drive device comprising: a second protection means for performing an overvoltage protection operation of the inverter by turning on the semiconductor switching element of the lower arm and short-circuiting the winding of the electric motor;
Short-circuit control means for outputting an arm selection command and a short-circuit control command for short-circuiting the winding of the electric motor when detecting a failure of the inverter;
Immediately after the short-circuit control command is output, threshold value changing means for changing the normal-time threshold value as the over-current threshold value to a short-circuit control time threshold value greater than the over-current threshold value,
The output overcurrent detection means includes
According to the presence or absence of the short-circuit control command, the short-circuit control threshold value or the normal-time threshold value is compared with the output current of the inverter.

  According to a second aspect of the present invention, in the electric motor drive device according to the first aspect, the threshold value changing means sets the normal time threshold value to the short circuit control time threshold value for a certain period immediately after the short circuit control command is output. The threshold value is changed and restored to the normal threshold value after the lapse of the predetermined period.

The invention according to claim 3 is an electric motor drive device for driving an electric motor by an inverter,
A first protection means for detecting that the output current of the inverter has exceeded an overcurrent threshold by an output overcurrent detection means and performing an overcurrent protection operation of the inverter; In the electric motor drive device comprising: a second protection means for performing an overvoltage protection operation of the inverter by turning on the semiconductor switching element of the lower arm and short-circuiting the winding of the electric motor;
Short-circuit control means for outputting an arm selection command and a short-circuit control command for short-circuiting the winding of the electric motor when detecting a failure of the inverter;
Means for disabling the operation of the first protection means for a certain period while the second protection means is operating according to the short-circuit control command;
It is equipped with.

  According to a fourth aspect of the invention, there is provided the electric motor drive device according to the first or second aspect, further comprising means for outputting a protective operation abnormality signal when an output current of the inverter exceeds the short-circuit control threshold value. It is.

  According to a fifth aspect of the present invention, in the electric motor drive device according to any one of the first to fourth aspects, a means for outputting a protective operation abnormality signal when a DC voltage of the inverter exceeds an overvoltage threshold is provided. It is a thing.

  According to a sixth aspect of the present invention, in the electric motor drive device according to the first, second, or fourth aspect, the short-circuit control time threshold is set to at least the short-circuit control start time by the second protection means. It is set based on the terminal voltage and transient reactance of the electric motor.

  According to a seventh aspect of the present invention, in the electric motor drive device according to the second or fourth aspect, the effective period of the short-circuit control threshold value changed by the threshold value changing means is based on at least a short-circuit transient time constant of the electric motor. Is set.

  According to an eighth aspect of the present invention, in the electric motor drive device according to the third aspect, the fixed period for invalidating the operation of the first protection means is set based on at least the short-circuit transient time constant of the electric motor. is there.

  The invention according to claim 9 is the electric motor drive device according to claim 4 or 5, wherein the arm to which all-phase semiconductor switching elements to be turned on by the second protection means based on the protection operation abnormality signal belongs. Is to switch.

  According to the present invention, when the motor winding is short-circuit controlled at the time of failure of the inverter, the short-circuit control by the operation of the switching element of the inverter is performed by adjusting the magnitude of the over-current threshold or masking the over-current threshold. It is possible to prevent the overvoltage from being applied to the DC circuit of the inverter and to reliably perform the overvoltage protection.

It is a circuit block diagram which shows embodiment of this invention. It is a wave form diagram which shows the output current of the inverter in Example 1 of this invention, and the voltage of a smoothing capacitor. It is a wave form diagram which shows the output current of the inverter in Example 2 of this invention, and the voltage of a smoothing capacitor. It is a wave form diagram which shows the output current of the inverter in Example 3 of this invention, and the voltage of a smoothing capacitor. It is a circuit block diagram which shows other embodiment of this invention. 1 is a configuration diagram of an electric machine inverter described in Patent Document 1. FIG. It is a block diagram of the output stage unit in FIG. FIG. 3 is a main circuit configuration diagram of an inverter including an output stage (for three phases) in Patent Document 1. FIG. 9 is an operation waveform diagram during short-circuit control for the main circuit of FIG. 8.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of a drive device according to the present embodiment. This drive device is for driving the electric motor 1 such as a permanent magnet synchronous motor by, for example, a three-phase inverter (voltage source inverter) INV.

In the main circuit of the inverter INV, is between both electrodes of the DC power source E, a smoothing capacitor C is connected via the relay _Ry p, _{Ry n.} Semiconductor switching elements Q _u , Q _v , Q _w , Q _x , Q _y , Q _z such as IGBTs are connected to both ends of the smoothing capacitor C by a three-phase bridge, and the motor 1 is connected to the AC output terminal. Yes. 2 _u , 2 _v , 2 _w are current detectors that detect output currents i _u , i _v , i _w of each phase of the inverter INV.

Relay _Ry p, at both ends of Ry _n connected relay state detector ₃ p, _{3 n,} respectively, the relay _Ry p, relay opening signal from Ry _n relay state detector upon opening of the _{3 p, 3 n F p,} F _n is output. Here, the relay Ry _p, Ry _n is the failure of the abnormality and the control device of the power supply voltage, is opened when the failure of the switching element Q _u to Q _z occurs, it stops the power supply from the DC power source E.

On the other hand, a control device that generates drive signals (gate signals) for the switching elements Q _{u to} Q _z includes an electric motor control means 11, a PWM (pulse width modulation) generation means 12, a drive signal control means 13, a failure detection means 14, and a short circuit. control means 15, and has an output overcurrent detector _{16 u, 16 v, 16 w} corresponding to each phase.
Hereinafter, the function of each means described above will be described.

First, the motor control means 11 generates a control command for driving the motor 1 at a predetermined speed and torque. The PWM generator 12 generates a PWM signal using the control command and the carrier signal.
The drive signal control means 13 generates and outputs a drive signal for turning on / off the switching elements Q _u , Q _v , Q _w , Q _x , Q _y , Q _z based on the PWM signal and each command described later. .

The failure detection means 14 detects that a failure has occurred in the inverter INV based on the relay open signals F _p and F _n and outputs a failure detection signal F to the short-circuit control means 15.
The short-circuit control means 15 responds to the failure detection signal F to the upper-arm selection command S _p for short-circuiting the upper-arm switching elements Q _u , Q _v , and Q _w for all phases, or the lower-arm switching elements for all phases. _{Q x,} Q y, and sends one of the lower arm selection command _{S n} shorting _{Q z} to the drive signal control means 13. At the same time, short circuit control unit 15, depending on the arm shorting by the selection instruction S _p or S _n, it generates a short-circuit control command S _s to the effect of starting the short-circuit control with respect to the upper arm or the lower arm of each phase of the output The current is sent to the overcurrent detection means 16 _u , 16 _v , 16 _w .

Since the configurations of the output overcurrent detection means 16 _u , 16 _v , and 16 _w are the same for all of the U, V, and W phases, the U-phase output overcurrent detection means 16 _u will be described here.
The output overcurrent detection means 16 _u includes a threshold change means 161 to which the short-circuit control command S _s is input, a variable power supply 162 whose direct current voltage, that is, an overcurrent threshold is changed by the output, and a positive overcurrent by the variable power supply 162. Polarity reversing means 163 for reversing the polarity of the threshold to obtain a negative overcurrent threshold, and a positive overcurrent threshold from the variable power source 162 is applied to the positive input terminal, and a voltage corresponding to the U-phase output current _iu is input negatively. A negative overcurrent threshold output from the first comparison means 164 applied to the terminal and the polarity inversion means 163 is applied to the negative input terminal, and a voltage corresponding to the U-phase output current _iu is applied to the positive input terminal. Second comparing means 165. The logical sum of the output signals of the first and second comparison means 164 and 165 is sent to the drive signal control means 13 as a U-phase cutoff command S _uoff .

In the other V-phase and W-phase output overcurrent detection means 16 _v and 16 _w , the input signals to the first and second comparison means 164 and 165 become V-phase and W-phase output currents i _v and i _w , respectively. Only the corresponding voltage is changed, and the configuration and function are the same as those of the U-phase output overcurrent detection means 16 _u . These V-phase, W-phase output overcurrent detector ₁₆ v, 16 V-phase cutoff command _{S voff} generated by _w, also W-phase disconnection command _{S woff,} is sent to the drive signal control means 13.
Incidentally, U-phase interruption command _{S uoff,} V-phase interruption command _{S voff,} W-phase disconnection instruction _{S woff,} for example when it is "Low" level, which turns off the switching elements of the arm or the lower arm on the corresponding phase And

The drive signal control means 13 generates drive signals for the switching elements Q _{u to} Q _{z in} accordance with the PWM signal from the PWM generation means 12 at normal times when no failure has occurred in the inverter INV. Then, when the output current of the inverter INV in normal time exceeds the over-current threshold, the output overcurrent detector _{16 u,} 16 v, 16 cutoff command _S Uoff output from _w, S _voff, according _{S woff} total the switching element Q _u to Q _z of the upper and lower arms of the phase are turned off, when a failure in the inverter INV is generated, all phases of one arm selected by the upper arm selection command S _p or lower arm selection instruction S _n The switching element is turned on to perform short circuit control of the motor winding.

In the above configuration, the output overcurrent detection means 16 _u , 16 _v , 16 _w and the drive signal control means 13 mainly constitute the first protection means in the claims, and include the failure detection means 14, the short-circuit control means 15, and the drive. Similarly, the signal control means 13 constitutes a second protection means.

Next, the operation of the output overcurrent detection means 16 _u , 16 _v , 16 _w will be described in detail as Example 1 to Example 3 with reference to FIGS.

FIG. 2 is a waveform diagram showing the output current of the inverter INV and the voltage of the smoothing capacitor C in the first embodiment.
As described above, by opening the relay at time t ₀ with the fault detection of the inverter INV, at time t ₁ immediately after, for example, the upper arm selection instruction S switching elements of _p upper arm of all phases on the basis of Q _u, Q _v , _Qw are turned on to start short circuit control of the motor windings, the output currents i _u , i _v , i _w of the inverter INV become excessive as shown in the upper part of FIG.

At this time, the short-circuit control command S _s from the short-circuit control means 15 is input to the threshold value changing means 161 of the output overcurrent detection means 16 _u , 16 _v and 16 _w in FIG. As a result, the threshold value changing means 161 for each phase operates the variable power source 162 to set the normal overcurrent threshold value (normal side threshold value) TH ₀ ⁺ in the normal state to a positive overcurrent threshold value (positive side) larger than that. Side short-circuit control threshold value) TH ₁ ⁺ and, via polarity reversing means 163, the normal negative side overcurrent threshold value (negative normal time threshold value) TH ₀ ^{− is changed} to a TH ₁ ⁺ polarity inversion signal. To the negative-side overcurrent threshold TH ₁ ⁻ (threshold at the time of negative-side short-circuit control).

Here, by setting the magnitudes of the short-circuit control thresholds TH ₁ ⁺ and TH ₁ ⁻ on the positive side and the negative side to a value larger than the maximum value of the short-circuit current indicated by the portion P surrounded by a broken line in FIG. output overcurrent detection unit _{16 u,} 16 v, 16 logical sum of the output of the comparator means 164 and 165 _w, in other words each phase shutoff _{S uoff, S voff, S woff} is "High" level.
Therefore, the switching elements Q _{u to} Q _z are not forcibly turned off. For example, the short-circuit control in a state where the switching elements Q _u , Q _v , and Q _w of the upper arms of all phases are turned on is maintained as it is. It will be. Incidentally, as shown, over-voltage threshold will be increased slightly to voltage period time t ₀ ~t ₁ of the smoothing capacitor C, a time t ₁ after that gradually decreases, which is set to the DC circuit of the inverter INV There is no fear of exceeding.

Note that the maximum value of the short-circuit current considered for determining the magnitudes of the positive and negative short-circuit control thresholds TH ₁ ⁺ and TH ₁ ⁻ is the speed (angular speed) of the motor 1 immediately before the short circuit, in other words, the motor 1. It is known that it is determined by the terminal voltage (induced voltage), the transient current and the transient time constant, and the transient current and the transient time constant are determined by the initial transient reactance, transient reactance, etc. of the motor 1 (for example, Sadahiro Kaga, Masaru Suzuki) Materials, "Synchronous machine", p.99-p.105, Tokyo Denki University Press, December 20, 1967, published first edition, or "Electrical Equipment Engineering II (The Institute of Electrical Engineers of Japan)", p.59. -P.63, The Institute of Electrical Engineers of Japan, February 20, 1978, 21st edition issued). Although the magnitude of the short-circuit current that flows depends on the type of short-circuit (three-phase short-circuit, line-to-line short-circuit, one-phase / neutral point short-circuit), the short-circuit control in this embodiment is considered to be due to a three-phase short-circuit. good.

Accordingly, the maximum value of the short circuit current of the electric motor 1 can be calculated based on the speed detection value (speed estimation value or speed command value) of the electric motor 1, the transient reactance, and the like. A value larger than the calculated maximum value of the short-circuit current may be set to the positive side and negative side short-circuit control thresholds TH ₁ ⁺ and TH ₁ ⁻ .
An excessively short circuit current temporarily flows through the switching element that is turned on by the short circuit control. Needless to say, each switching element is selected to have an overcurrent resistance against the short circuit current.

  As described above, according to the first embodiment, the short-circuit control is performed without any trouble by changing the normal threshold for overcurrent protection to the short-circuit control threshold when the inverter INV fails. Appropriate overvoltage protection can be performed by preventing the voltage of the smoothing capacitor C from rising.

Next, FIG. 3 is a waveform diagram showing the output current of the inverter INV and the voltage of the smoothing capacitor C in the second embodiment.
In the second embodiment, due to the operations of the threshold changing unit 161, the variable power source 162, and the polarity inverting unit 163, the positive side and negative side normal thresholds TH ₀ ⁺ , TH ₀ ⁻ after time t ₁ are the same as in the first embodiment. Is changed to the positive side and negative side short-circuit control thresholds TH ₁ ⁺ and TH ₁ ⁻ respectively, and the normal thresholds TH ₀ ⁺ and TH ₀ ⁻ are restored after _a period Δta when the short-circuit current is excessive. I do.
The above period Delta] t _a in order to time the short-circuit current is sufficiently attenuated, for example, about three times the time of the short circuit during the transient time constant of the motor 1, to have a timer function to the threshold changing unit 161 periods the Δt _a may be set.

According to the second embodiment, the period Delta] t in _a, performs an overvoltage protection by suppressing the voltage rise of the smoothing capacitor C similarly by short-circuit control in Example 1, also, after the lapse of the period Delta] t _a is normal threshold TH Overcurrent protection using ₀ ⁺ and TH ₀ ⁻ can be performed.

Further, in the first embodiment or the second embodiment, when the output current of the inverter INV exceeds the thresholds TH ₁ ⁺ and TH ₁ ⁻ at the time of the short-circuit control, the protection operation indicating that the normal overcurrent protection operation cannot be used. An abnormal signal may be output.
When such a situation occurs, for example, there is a possibility that the on / off control of the switching element of one arm may be disabled, and in that case, using the above-described protection operation abnormality signal, Short-circuit control may be performed by turning on the switching elements of all phases of the arm. On other words, the protection operation abnormality signal when it detects a failure of the switching elements of one arm, the short circuit control unit 15 in FIG. 1 switches the an arm selection command S _p or S _n, the switching elements of all the phases of the other arm Thus, short circuit control can be performed.

FIG. 4 is a waveform diagram showing the output current of the inverter INV and the voltage of the smoothing capacitor C in the third embodiment.
In the third embodiment, the threshold value changing unit 161 maintains the normal side threshold values TH ₀ ⁺ and TH ₀ ⁻ on the positive side and the negative side after time t ₁ (fixing the threshold value without operating the threshold value changing function). output overcurrent detection unit _{16 u, 16 v, 16 w} is an invalid overcurrent detection function (overcurrent protection function) is masked for a period Delta] t _b from time _{t 1} to time _{t 2.} Specifically, it is to stop the operation of the comparison means 164 and 165 for a period Delta] t _b.

The mask period Δt _b includes at least a portion P surrounded by a broken line in FIG. 4 and is a period in which an excessive short circuit current may exceed the positive overcurrent threshold TH ₀ ⁺ or the negative overcurrent threshold TH ₀ ^−. It is. This mask period Delta] t _b also can be set on the basis of the short-circuit transition time constant of the motor 1 may be equal to the period Delta] t _a in Example 3.

As shown in FIG. 4, the upper arm selection instruction S _p or lower arm selection command S _n, the time t ₀ before is off, the time t ₁ thereafter turned on. Further, each phase of the shutoff _{S uoff, S voff, S woff} is over its longitudinal comprise mask period Delta] t _b, in the off ( "High" level).
According to the third embodiment, since the overcurrent threshold can be fixed, the configuration of the output overcurrent detection means 16 _u , 16 _v , 16 _w can be simplified.

Next, FIG. 5 is a configuration diagram of a driving apparatus according to another embodiment of the present invention.
In this embodiment, an overvoltage detection / protection function of the DC circuit of the inverter INV is added to the configuration of FIG.
In FIG. 5, a voltage detector 17 is connected to both ends of the smoothing capacitor C of the main circuit. The DC voltage detection value V _{dc obtained} by the voltage detector 17 is input to the overvoltage detection means 18, and the output signal is input to the short-circuit control means 15. Further, the output overcurrent detector _{16 u,} 16 v, 16 shut off all phases command output from _{w S uoff, S voff, S} woff are input to the AND gate 19, the input and the output signal is the short-circuit control unit 15 Has been.

Here, the overvoltage detection means 18 has a function of outputting an overvoltage detection signal when the DC voltage detection value V _dc exceeds the overvoltage threshold shown in FIGS. 2 to 4. This corresponds to a means for outputting a protection operation abnormality signal). The AND gate 19 corresponds to means for outputting a protection operation abnormality signal (protection operation abnormality signal related to overcurrent) according to claim 4 by detecting all gates OFF of the inverter INV.

In this embodiment, the arm selection command _Sp or _Sn is switched via the short-circuit control means 15 in the event that the voltage of the smoothing capacitor C does not decrease even if short-circuit control is performed when a failure of the inverter INV is detected. An operation for performing the control again is possible. Further, when all the gates are turned off, an operation for stopping the short-circuit control using the output signal of the AND gate 19 can be performed.

  The present invention is a drive device for driving a motor for a vehicle, a motor for an industrial machine or the like by an inverter, and various motor drive devices having an overcurrent protection function of the inverter and an overvoltage protection function due to a short circuit of the winding of the motor. Can be used as

INV: Inverter E: DC power source C: smoothing capacitor _Ry p, Ry _n: Relay _F p, _{F n:} relay opening signal _{Q u, Q v, Q w} , Q x, Q y, Q z: semiconductor switching element 1: Electric motors 2 _u , 2 _v , 2 _w : current detectors 3 _p , 3 _n : relay state detector 11: electric motor control means 12: PWM generation means 13: drive signal control means 14: failure detection means 15: short-circuit control means 16 _{u 1} , 16 _v , 16 _w : Output overcurrent detection means 161: Threshold change means 162: Variable power supply 163: Polarity inversion means 164 and 165: Comparison means 17: Voltage detector 18: Overvoltage detection means 19: AND gate

Claims (9)

An electric motor drive device for driving an electric motor by an inverter,
A first protection means for detecting that the output current of the inverter has exceeded an overcurrent threshold by an output overcurrent detection means and performing an overcurrent protection operation of the inverter; In the electric motor drive device comprising: a second protection means for performing an overvoltage protection operation of the inverter by turning on the semiconductor switching element of the lower arm and short-circuiting the winding of the electric motor;
Short-circuit control means for outputting an arm selection command and a short-circuit control command for short-circuiting the winding of the electric motor when detecting a failure of the inverter;
Immediately after the short-circuit control command is output, threshold value changing means for changing the normal-time threshold value as the over-current threshold value to a short-circuit control time threshold value greater than the over-current threshold value,
The output overcurrent detection means includes
The electric motor drive device, wherein the short-circuit control threshold value or the normal-time threshold value is compared with an output current of the inverter according to the presence or absence of the short-circuit control command. In the electric motor drive device according to claim 1,
The threshold value changing means changes the normal time threshold value to the short circuit control time threshold value for a certain period immediately after the short circuit control command is output, and returns to the normal time threshold value after the elapse of the certain time period. An electric motor drive device. An electric motor drive device for driving an electric motor by an inverter,
A first protection means for detecting that the output current of the inverter has exceeded an overcurrent threshold by an output overcurrent detection means and performing an overcurrent protection operation of the inverter; In the electric motor drive device comprising: a second protection means for performing an overvoltage protection operation of the inverter by turning on the semiconductor switching element of the lower arm and short-circuiting the winding of the electric motor;
Short-circuit control means for outputting an arm selection command and a short-circuit control command for short-circuiting the winding of the electric motor when detecting a failure of the inverter;
Means for disabling the operation of the first protection means for a certain period while the second protection means is operating according to the short-circuit control command;
An electric motor drive device comprising: In the electric motor drive device according to claim 1 or 2,
An electric motor drive device comprising means for outputting a protective operation abnormality signal when an output current of the inverter exceeds the short-circuit control threshold value. In the electric motor drive device according to any one of claims 1 to 4,
An electric motor drive device comprising means for outputting a protective operation abnormality signal when a DC voltage of the inverter exceeds an overvoltage threshold. In the electric motor drive device according to claim 1, claim 2 or claim 4,
The electric motor drive device characterized in that the short-circuit control threshold is set based on at least a terminal voltage and a transient reactance of the electric motor at the start of the short-circuit control by the second protection means. In the electric motor drive device according to claim 2 or 4,
An electric motor drive apparatus characterized in that an effective period of a short-circuit control threshold value changed by the threshold value changing means is set based on at least a short-circuit transient time constant of the electric motor. In the electric motor drive device according to claim 3,
An electric motor driving apparatus characterized in that a fixed period for invalidating the operation of the first protection means is set based on at least a short-circuit transient time constant of the electric motor. In the electric motor drive device according to claim 4 or 5,
An electric motor driving apparatus that switches an arm to which all-phase semiconductor switching elements that are turned on by the second protection means belong based on the protection operation abnormality signal.

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