JP2011223788A - Motor drive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor drive device that prevents the wiring of an electric motor from burning if a switching element of an inverter fails by a short-circuit.SOLUTION: The motor drive device comprises an AC motor 1, an inverter 2 with a fuse 26 for overcurrent protection, a DC power source 3 which supplies DC electric power to the inverter 2, and a controller 4 which supplies a driving signal to the inverter 2 to control the AC motor 1. The controller 4 includes a short-circuit detection unit 47 which specifies which of the switching elements of the inverter 2 fails by a short-circuit in accordance with the size and polarity of a load current in a state in which the inverter 2 is stopped if the inverter 2 gets out of order, and a fuses blowing control unit 48 which blows the fuse 26 by turning on a predetermined switching element in a predetermined timing in accordance with the detection result of the short-circuit detection unit 47.

Description

  The present invention relates to an electric motor drive device, and more particularly to an electric motor drive device capable of preventing winding burnout of an electric motor when a switching element of an inverter is short-circuited.

  In recent years, there have been increasing cases in which a synchronous motor using a permanent magnet as a field for a rotor is driven by an inverter. An electric motor with a field generates an induced voltage by rotating with an external force. When the field is an electromagnet type, no induced voltage is generated if the excitation is turned off. However, when the field magnet is a permanent magnet type, the excitation cannot be turned off and an induced voltage is generated. When the switching element of the inverter has a short circuit failure, even if an OFF signal is given to all the switching elements, if the motor rotates due to external force or its own inertia, the switching element and the free wheel diode that are short-circuited due to the induced voltage generated in the motor A short-circuit current flows through Since the induced voltage is generated in proportion to the speed of the motor, the higher the speed, the larger the short circuit current. If this short-circuit current is larger than the maximum allowable current of the motor windings, overheating will cause the motor windings to burn out.

  For this reason, when a short circuit failure of the switching element occurs, by performing a switching operation of the switching element that belongs to a normal circuit that does not include the switching element and that constitutes an arm different from the arm that the switching element constitutes, A technique for suppressing an increase in the passing current of a short-circuited circuit has been proposed (see, for example, Patent Document 1).

JP 2008-11683 A (Overall)

  The method disclosed in Patent Document 1 suppresses an increase in the passing current of a short-circuited circuit, and in some cases, attempts to continue the operation in this state. However, as described above, when a short circuit failure of the switching element occurs when the motor operating speed is high, the short circuit current becomes large, and it is possible to prevent the accident from spreading to other arms or the burning of the motor winding. There is a risk of disappearing. For this reason, it is conceivable to insert a fuse into the circuit and blow the fuse to protect it when a short circuit failure occurs in the switching element. In this case, depending on the operating conditions such as the rotation speed of the motor, the short circuit current May become relatively small, the fuse will not blow, and the motor windings may not be burned out.

  There is a method of using a switch such as a contactor instead of a fuse, but it has a large outer shape and is disadvantageous in terms of cost.

  The present invention has been made to solve the above-described problems, and provides an electric motor drive device that can surely blow a fuse when a short circuit failure of a switching element occurs and can prevent the winding of an electric motor from burning out. With the goal.

  In order to achieve the above object, an electric motor driving device of the present invention comprises an AC motor, an output side provided with a current detector and an overcurrent protection fuse, an inverter that drives the AC motor, and a DC power supply to the inverter. And a control device for supplying a drive signal to a switching element constituting the inverter and controlling the AC motor, and the control device stops the inverter when the inverter fails. In the state, according to the detection result of the short-circuit detection unit, a short-circuit detection unit that identifies which switching element among the switching elements according to the magnitude and polarity of the detection current of the current detector, and the detection result of the short-circuit detection unit, By turning on a predetermined switching element at a predetermined timing among the switching elements constituting the inverter, It is characterized by having a blown fuse control unit for controlling to blow the's.

  ADVANTAGE OF THE INVENTION According to this invention, when the short circuit failure of a switching element arises, the electric motor drive device which can blow a fuse reliably and can prevent the burning of the winding of an electric motor can be provided.

1 is a block diagram showing a basic configuration of an electric motor drive device according to Embodiment 1 of the present invention. The figure explaining the path | route through which a short circuit current flows, when the switching element of a three-phase inverter carries out a short circuit failure. The figure which shows the schematic waveform of the induced voltage and electric current of each phase when the switching element of a three-phase inverter has a short circuit failure. The figure which shows the relationship between the polarity of an electric current, and the switching element which the short circuit failure of the three-phase inverter. The figure explaining fuse fusing control when a switching element fails in a short circuit in Example 1. FIG. The figure which shows the schematic waveform of the induced voltage and electric current at the time of fuse blow control when the switching element of a three-phase inverter has a short circuit failure. The figure which shows the relationship between the switching element which short-circuited in Example 1, and the switching element which gives an ON signal by fuse blowing control. 5 is a flowchart for explaining control of the electric motor drive device according to the first embodiment. The block diagram which shows the basic composition of the electric motor drive device which concerns on Example 2 of this invention. The block diagram which shows the basic composition of the electric motor drive device which concerns on Example 3 of this invention. The figure explaining the path | route through which a short circuit current flows, when the switching element of a single phase inverter carries out a short circuit failure. The figure which shows the schematic waveform of the induced voltage and electric current of each phase when the switching element of a single phase inverter carries out a short circuit failure. The figure which shows the relationship between the polarity of an electric current, and the switching element by which the short circuit failure of the single phase inverter. The figure explaining fuse fusing control when a switching element fails in a short circuit in Example 3. The figure which shows the schematic waveform of the induced voltage at the time of fuse blowing control at the time of the short circuit failure of the switching element of a single phase inverter, and an electric current. The figure which shows the relationship between the switching element which short-circuited in Example 3, and the switching element which gives an ON signal by fuse blowing control. 9 is a flowchart for explaining control of an electric motor drive device according to a third embodiment.

  Embodiments of an electric motor driving device according to the present invention will be described below with reference to the drawings.

  Hereinafter, an electric motor drive device according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 8.

  FIG. 1 is a block diagram showing a basic configuration of an electric motor drive device according to Embodiment 1 of the present invention. The three-phase synchronous motor 1 is driven by the AC output of the three-phase inverter 2. The three-phase inverter 2 is supplied with power from the DC power source 3 and is controlled by the control device 4. A rotational position detector 5 is attached to the three-phase synchronous motor 1 for control purposes.

  The armature winding of the three-phase synchronous motor 1 includes three-phase windings of U phase, V phase, and W phase. The three-phase inverter 2 includes an input fuse 21 at an input, and smoothes a DC voltage by a smoothing capacitor 22. This DC voltage is formed by bridge-connecting switching elements 23U, 23V, 23W, 23X, 23Y and 23Z, and by connecting free-wheeling diodes 24U, 24V, 24W, 24X, 24Y and 24Z to each switching element in reverse parallel. Power is supplied to the inverter main circuit. The inverter main circuit generates an alternating voltage and drives the three-phase synchronous motor 1 through the current detector 25 and the fuse 26. Each phase of the fuse 26 is a fuse FU, FV and FW. The switching element is illustrated with an IGBT symbol, but may be another switching element such as a MOS-FET.

  Hereinafter, the internal configuration of the control device 4 will be described.

  The rotational position detector 5 detects the rotational position of the electric motor, converts it into a phase angle at the phase angle detector 41, and converts it into a speed at the speed detector 42. The speed control unit 43 performs speed control so that the speed of the motor matches the speed command given from the outside, and gives a current command to the current control unit 44. The current detector 45 calculates a V-phase current IV based on the U-phase current IU and the W-phase current IW detected by the current detector 25. The current control unit 42 performs current control so that the detected current matches the current command, and gives a switching operation command to the drive signal generating unit 46 so that the three-phase inverter 2 outputs a desired voltage. The drive signal generator 46 gives an ON signal or an OFF signal to the switching elements 23U, 23V, 23W, 23X, 23Y, and 23Z based on the given switching operation command. Note that the drive signal generator 46 normally stops all the switching elements by supplying an OFF signal while detecting a failure of the three-phase inverter 2.

  An electric motor with a field has a feature that an induced voltage is generated by rotating by an external force. When the field is an electromagnet type, no induced voltage is generated if the excitation is turned off. However, when the field magnet is a permanent magnet type, the excitation cannot be turned off and an induced voltage is generated. The three-phase synchronous motor 1 has a permanent magnet type field. If any switching element of the three-phase inverter 2 is short-circuited, if the three-phase synchronous motor 1 is rotated by an external force or its own inertia even if an OFF signal is given to all the switching elements, as described later, 3 A short-circuit current flows through the switching element and the return diode that are short-circuited due to the induced voltage generated in the phase-synchronous motor 1. Since the induced voltage is generated in proportion to the speed of the three-phase synchronous motor 1, the higher the speed, the larger the short-circuit current. If this short circuit current is larger than the maximum allowable current of the windings of the three-phase synchronous motor 1, overheating will cause the motor windings to burn out. The fuse 26 provided in each phase is for interrupting this short circuit current.

  FIG. 2 is a diagram illustrating a path through which a short-circuit current flows when the switching element 23U has a short-circuit failure. A short-circuit current as indicated by an arrow flows through the switching element 23U and the free-wheeling diodes 24V and 24W that are short-circuited due to the induced voltage generated in the three-phase synchronous motor 1. Since this short-circuit current is concentrated in the U phase, the U phase current IU is larger than the V phase current IV and the W phase current IW. At this time, if the U-phase current IU is sufficiently large, the U-phase portion FU of the fuse 26 is melted to cut off the short-circuit current.

  FIG. 3 is a diagram showing a schematic waveform of the induced voltage and current of each phase when the switching element 23U has a short circuit failure. An off signal is given to all the switching elements so that the three-phase synchronous motor 1 is rotating in the forward direction by an external force or the like. The phase order of the induced voltage is the order of U phase, V phase, and W phase. The phase angle is based on the phase voltage of the U-phase induced voltage. The direction in which the current flows into the three-phase synchronous motor 1 is positive. As illustrated, when the switching element 23U has a short circuit failure, the current IU is a positive current, and the currents IV and IW are negative currents.

  FIG. 4 is a diagram generally showing the relationship between the polarity of the current and the short-circuited switching element. When one of the switching elements is short-circuited, the current of each phase is either a positive current or a negative current. Therefore, the switching element that is short-circuited can be identified based on the polarity of the current of each phase. When two or more switching elements have a short circuit failure, the current includes both a positive current and a negative current. Therefore, it can be distinguished from a case where one switching element has a short circuit failure.

  The short-circuit detecting unit 47 performs switching in which a short-circuit failure has occurred based on the polarities of the currents IU, IV, and IW of each phase by the above-described method when a current exceeding a specified value flows when an OFF signal is applied to all switching elements. Identify the element.

  FIG. 5 is a diagram illustrating fuse blow control when the switching element 23U has a short circuit failure. When an ON signal is given to the switching elements 23Y and 23Z, a current flows from the DC power source 3 shown in FIG. 1 through the switching element 23U, the three-phase synchronous motor 1, the switching element 23Y, and the switching element 23Z that are short-circuited. At this time, since the V phase and the W phase of the three-phase synchronous motor 1 are connected in parallel, if the impedance of each phase is the same, the V-phase current IV and the W-phase current IW are the same, and the U-phase current IU Is twice that. This current makes it possible to blow the FU for the U phase of the fuse 26.

  FIG. 6 is a diagram showing schematic waveforms of induced voltage and current during fuse blow control when the switching element 23U has a short circuit failure. As shown in the figure, when an ON signal is given to the switching elements 23Y and 23Z by the fuse blowing control, the U-phase current rapidly increases, the U-phase FU of the fuse 26 is blown, and the short-circuit current is cut off. The timing to give the ON signal to the switching element by the fuse blow control is the current of the phase including the shorted switching element, that is, the short circuit current due to the induced voltage, so that the current flowing through the fuse is increased as much as possible for faster and more reliable fuse blow. It is preferable that the phase has a peak. When the switching element 23U is short-circuited, the U-phase current IU due to the short-circuit current due to the induced voltage peaks at a phase angle of about −90 °. Therefore, an ON signal is given to the switching elements 23Y and 23Z at the timing of the phase angle of −90 °. Note that the phase angle shown in the present embodiment assumes that the current delay due to the impedance of the motor winding is sufficiently small. Since the phase at which the current peaks due to the induced voltage differs depending on the impedance of the winding of the motor, it may be adjusted each time.

  In the description of the fuse blow control described above, the method of giving the on signal to both the healthy switching elements 23Y and 23Z has been described. However, if a method of giving the on signal at a timing according to the current peak due to the induced voltage is used. Since the short-circuited phase fuse 26 can be blown, a method of giving an ON signal to any one of the healthy switching elements 23Y and 23Z may be used.

  FIG. 7 is a diagram showing a relationship between a short-circuited switching element and a switching element that gives an ON signal by fuse fusing control. An ON signal is given to a switching element that belongs to a short-circuited switching element and a healthy arm that does not include the short-circuited switching element, and that has a polarity opposite to that of the short-circuited switching element. It is not always necessary to give an ON signal to the shorted switching element. The timing at which the ON signal is given to the switching element is a timing at which the phase current including the short-circuited switching element, that is, the short-circuit current due to the induced voltage peaks. The timing at which the short-circuit current due to the induced voltage reaches its peak differs depending on the rotation direction of the short-circuit faulty switching element and the motor, so that an ON signal is given according to the polarity of the speed of the short-circuit faulty switching element and motor as shown in the figure. As a result, the fuse of the phase including the shorted switching element can be blown.

  The fuse blowing control unit 48 is based on the short-circuited switching element detected by the short-circuit detection unit 47, the phase angle that is the output of the phase angle detector 41, and the polarity of the motor speed that is the output of the speed detection unit 42. An ON signal is given to a predetermined switching element at a predetermined timing by the method described above.

  The phase angle that gives the ON signal in FIG. 7 corresponds to the timing at which the induced voltage of the short-circuited phase is minimized when the positive arm has a short circuit failure, and when the negative arm has a short circuit failure, It can be seen that this corresponds to the timing at which the induced voltage of the short-circuited phase becomes maximum.

  FIG. 8 is a flowchart for explaining the control of the electric motor drive device according to this embodiment. First, it is determined whether or not the three-phase inverter has detected a failure (S01). If a failure is being detected, the operation of the three-phase inverter is stopped (S02). It is determined whether the current is greater than or equal to a predetermined value in the stopped three-phase inverter (S03). When the current is greater than or equal to a predetermined value, it is determined whether the currents IU, IV, and IW of each phase are positive currents or negative currents (S04). If the currents are both positive and negative, the system is stopped (S07) and the process ends. . In the case of a positive current or a negative current, a switching element having a short circuit failure is specified based on the polarities of the currents IU, IV, and IW of each phase (S05). Then, fuse fusing control is performed based on the identified switching element (S06), and the process ends. If the current is less than the predetermined value in step S03, the fuse is already blown or the induced voltage is small because the speed is low.

  As described above, according to the first embodiment of the present invention, the switching element having the short-circuit fault is quickly identified, and the switching element having the short-circuit fault and the gate of the switching element belonging to the other arm having the opposite polarity to the switching element having the short-circuit fault are provided. By supplying an ON signal and supplying as much current as possible to the fuse from the DC power supply side, the phase fuse including the shorted switching element can be surely blown. Thereby, even if the electric motor rotates due to an external force, a short-circuit current does not flow, so that the motor windings can be prevented from being burned out due to overheating.

  FIG. 9 is a block diagram showing a basic configuration of an electric motor drive device according to Embodiment 2 of the present invention. In the second embodiment, the same parts as those in the block diagram of the first embodiment shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted. The second embodiment is different from the first embodiment in that the three-phase synchronous motor 1 is a multiple synchronous motor 1A and two sets of three-phase windings are provided. This is a point in which an AC voltage is applied from the three-phase inverter 2A controlled by 4A.

  Such a motor drive device for a multiple synchronous motor has a feature that even if one of the three-phase inverters fails, the motor can be driven only by the remaining healthy three-phase inverters. In the present embodiment, the double multiplex synchronous motor is driven by two inverters, but the same configuration can be achieved even when there are three or more.

The three-phase inverter 2A has basically the same configuration as the three-phase inverter 2, and converts the direct current fed from the direct current power source 3 into alternating current and feeds power to the second set of three-phase windings of the multiple synchronous motor 1A. The control device 4A has basically the same configuration as that of the control device 4, but as shown in FIG. 9, a synchronization command is given from the control device 4, for example, the load sharing of the three-phase inverter 2 and the three-phase inverter 2A is Master-slave control can be performed so as to be the same. However, in this case, if the master-side three-phase inverter 2 fails, it becomes difficult to control the slave-side three-phase inverter 2A.
It is preferable to control the control device 4A at the same level as the control device 4 so that even if any one of the three-phase inverters fails, the operation can be continued on the other side.

  Also in the second embodiment, when one of the switching elements of the three-phase inverter 2 is short-circuited, if the phase fuse including the shorted switching element is not blown, the short-circuited switching element is quickly identified, Short-circuited switching element and switching circuit short-circuited by applying an ON signal to the gate of the switching element belonging to the other arm having the opposite polarity to that of the short-circuit-failed switching element, and flowing as much current as possible from the DC power supply 3 to the fuse. Fuse the phase fuse that contains the element. As a result, the short-circuit current does not flow in the windings of the short-circuited three-phase inverter and the motor, and the drive of the multiple synchronous motor 1A can be continued with only a sound three-phase inverter.

  Hereinafter, an electric motor driving apparatus according to Embodiment 3 of the present invention will be described with reference to FIGS. 10 to 17.

  FIG. 10 is a block diagram showing a basic configuration of an electric motor drive device according to Embodiment 3 of the present invention. In the third embodiment, the same parts as those in the block diagram of the first embodiment shown in FIG. The third embodiment differs from the first embodiment in that the three-phase synchronous motor 1 is replaced with a multi-phase synchronous motor 1B in which each winding is independent, and the three-phase inverter 2 is replaced with a single-phase inverter 2B. The first phase winding of 1B is fed and controlled by the control device 4B, and the second to fifth phase windings of the multiphase synchronous motor 1B are respectively connected by single-phase inverters 2C to 2F. The control is performed by the control devices 4C to 4F, respectively, so that the single-phase inverters 2C to 2F are controlled.

  Such a multi-phase synchronous motor drive device has a feature that even if one of the single-phase inverters fails, the motor can be driven only by the remaining healthy single-phase inverter. In the present embodiment, the five-phase multiphase synchronous motor 1B is driven by the five single-phase inverters 2B to 2F, but a multiphase synchronous motor having another number of phases can be similarly configured.

  The single-phase inverter 2B has a configuration in which the three-phase inverter 2 is changed to a single phase, and the inverter circuit has a single-phase bridge configuration of switching elements 23U, 23V, 23X, and 23Y. Although the switching element is illustrated as an IGBT, other switching elements such as a MOS-FET may be used. The current detector 25 detects the phase current IU, and the fuse 26 is configured only for the U phase. The single-phase inverters 2C, 2D, 2E, and 2F have the same configuration as the single-phase inverter 2B.

  Although illustration of the internal configuration of the control device 4B is omitted, the internal configuration is basically the same as that of the control device 4 shown in FIG. However, in this case, the gate pulse generated by the drive signal generator is equivalent to four switching elements.

  The control devices 4C to 4F have basically the same configuration as that of the control device 4B. However, as shown in FIG. 10, the control device 4B is given a synchronization command, and for example, the single-phase inverter 2B and other single-phase inverters Master-slave control can be performed so that the load sharing is the same. However, in this case, if the master-side single-phase inverter 2B fails, it becomes difficult to control the slave-side single-phase inverters 2C to 2F. Therefore, the control of the control devices 4C to 4F is set to the same level as that of the control device 4B. Even if the phase inverter breaks down, it is preferable that the operation can be continued with the remaining healthy single-phase inverter.

  FIG. 11 is a diagram illustrating a path through which a short-circuit current flows when the switching element 23U of the single-phase inverter 2B has a short-circuit failure. Only a single-phase inverter that has a short-circuit failure is illustrated, and other healthy single-phase inverters are not illustrated. A short-circuit current flows through the switching element 23U and the free-wheeling diode 24V that are short-circuited due to the induced voltage generated in the multiphase synchronous motor 1B. If the phase current IU is sufficiently large, the fuse 26 is blown to cut off the short-circuit current.

  FIG. 12 is a diagram showing schematic waveforms of induced voltage and current when the switching element 23U of the single-phase inverter 2B has a short circuit failure. An off signal is given to all the switching elements so that the motor is rotating in the forward direction by an external force or the like. The phase angle is based on the phase voltage of the induced voltage. When the switching element 23U has a short circuit failure, the current IU becomes a positive current.

  FIG. 13 is a diagram showing the relationship between the polarity of the current and the switching element in which a short circuit has occurred. When one short-circuit failure occurs in the switching element, the phase current is either a positive current or a negative current, and the short-circuited switching element can be identified based on the polarity of the phase current. Here, the short-circuit faulty switching element shown in FIG. 13 is specified as one of the two switching elements. However, as will be described later, the operation of the fuse blow control unit 48 is the same in any case, so this detection is performed. There is no problem with the method. Further, when two or more switching elements are short-circuited, the current includes both a positive current and a negative current. Therefore, it can be distinguished from a case where one switching element is short-circuited.

  Also in the third embodiment, as in the first embodiment, the short-circuit detection unit 47 detects the phase current IU by the above-described method when a current exceeding a specified value flows in a state where an OFF signal is applied to all the switching elements. A switching element having a short circuit failure is identified based on the polarity.

  FIG. 14 is a diagram for explaining the fuse blowing control when the switching element 23U has a short circuit failure. When an ON signal is given to the switching element 23Y, a current flows from the DC power supply 3 of FIG. 1 via the switching element 23U that has a short circuit failure, the first phase winding of the multiphase synchronous motor 1B, and the switching element 23Y. The fuse 26 is blown by this current.

  FIG. 15 is a diagram showing a schematic waveform of induced voltage and current during fuse blowing control when the switching element 23U has a short circuit failure. When an ON signal is given to the switching element 23Y by the fuse blow control, the phase current increases rapidly, and the fuse 26 is blown to cut off the short-circuit current. The timing at which the ON signal is given to the switching element by the fuse blowing control is preferably set to a phase in which the short-circuit current due to the induced voltage peaks so as to increase the current flowing through the fuse as much as possible for faster and more reliable fuse blowing. When the switching element 23U is short-circuited, the phase current IU due to the short-circuit current due to the induced voltage has a peak near the phase angle of −90 °. Therefore, an ON signal is given to the switching element 23Y at the timing of the phase angle −90 °. The phase angle shown in the present embodiment assumes that the current delay due to the impedance of the motor winding is sufficiently small. Since the phase at which the current peaks due to the induced voltage differs depending on the impedance of the winding of the motor, it may be adjusted each time.

  FIG. 16 is a diagram showing a relationship between a short-circuited switching element and a switching element that gives an ON signal by fuse fusing control. An ON signal is given to a switching element that belongs to a short-circuited switching element and a healthy arm that does not include the short-circuited switching element, and that has a polarity opposite to the short-circuited switching element. For example, when the short-circuiting detection unit 47 specifies the short-circuited switching element as the switching element 23U or 23Y, the fuse blow control unit 48 gives an ON signal to both the switching elements 23U and 23Y. Further, the timing for giving the ON signal to the switching element is the timing at which the short-circuit current due to the induced voltage peaks. Since the timing at which the short-circuit current due to the induced voltage reaches a peak differs depending on the switching direction of the short-circuit faulty switching element and the motor, an ON signal is given according to the polarity of the speed of the short-circuit faulty switching element and motor. This blows the fuse.

  The fuse blowing control unit 48 is based on the short-circuited switching element specified by the short-circuit detection unit 47, the phase angle that is the output of the phase angle detection unit 41, and the polarity of the motor speed that is the output of the speed detection unit 42. In this way, an ON signal is given to a predetermined switching element at a predetermined timing.

  The short circuit detection and the fuse blow control described above are individually performed in the control devices 4B, 4C, 4D, 4E, and 4F.

  FIG. 17 is a flowchart for explaining the control of the electric motor drive device according to this embodiment. It is determined whether or not a failure has been detected in the single-phase inverter (S01). If a failure is being detected, the operation of the single-phase inverter is stopped (S02). It is determined whether or not the current is greater than or equal to a predetermined value in the stopped single-phase inverter (S03). If the current is equal to or greater than the predetermined value, it is determined whether the phase current IU is a positive current or a negative current (S04). If the current is a positive / negative bidirectional current, the system is stopped (S07) and the process is terminated. In the case of a positive current or a negative current, the short-circuited switching element is specified based on the polarity of the phase current IU (S05). The fuse blow control is performed based on the identified switching element (S06), and the process ends.

  As described above, according to the third embodiment, the switching element having the short-circuit failure is quickly identified, and the ON signal is given to the gate of the switching element of the other arm with the reverse polarity to the switching element having the short-circuit failure and the switching element having the short-circuit failure. By flowing as much current as possible from the DC power supply 3 to the fuse 26, the phase fuse including the shorted switching element can be surely blown. Thereby, even if the electric motor rotates due to an external force, a short-circuit current does not flow, so that the motor windings can be prevented from being burned out due to overheating. In addition, a short-circuit current does not flow through the single-phase inverter and the motor winding that are short-circuited, and it is possible to continue driving the motor with only a healthy single-phase inverter.

  In the description of the first to third embodiments, the target AC motor is described as a synchronous motor. However, the present invention is not limited to this, and the induction motor in which the residual induced voltage decreases with time. AC motors such as can also be included.

  In the description of the first to third embodiments, the fuse blowing control based on the phase detected by the rotational position detector has been described. However, the present invention is not limited to this, and the fuse blowing control is applied to the switching element. There is no limitation on the means for determining the timing for applying the ON signal. Therefore, the current of each phase may be detected, and the timing at which the phase current flowing through the switching element in which the short circuit has failed may be estimated. The optimum timing here is the timing at which the short-circuit current is maximized, but even if the timing is slightly shifted, the change in the magnitude of the short-circuit current is small, so that it may be in the vicinity of the optimum timing.

1 three-phase synchronous motor 1A multiple synchronous motor 1B multi-phase synchronous motor 2, 2A three-phase inverter 2B, 2C, 2D, 2E, 2F single-phase inverter 3 DC power supply 4, 4A, 4B, 4C, 4D, 4E, 4F 5 rotational position detector 21 input fuse 22 smoothing capacitor 23U, 23V, 23W, 23X, 23Y, 23Z switching element 24U, 24V, 24W, 24X, 24Y, 24Z freewheeling diode 25 current detector 26, FU fuse 41 phase angle detector 42 Speed detector 43 Speed controller 44 Current controller 45 Current detector 46 Drive signal generator 47 Short-circuit detector 48 Fuse blow controller

Claims (8)

AC motor,
An inverter on the output side, provided with a current detector and a fuse for overcurrent protection, and driving the AC motor;
A DC power supply for supplying DC power to the inverter;
A control device for giving a drive signal to the switching elements constituting the inverter and controlling the AC motor;
The controller is
A short-circuit detecting unit that identifies which switching element among the switching elements has a short-circuit failure according to the magnitude and polarity of the detection current of the current detector in a state where the inverter is stopped when the inverter fails ,
A fuse blow control unit for controlling the fuse to blow by turning on a predetermined switching element at a predetermined timing among the switching elements constituting the inverter according to a detection result of the short circuit detection unit. An electric motor drive device. The AC motor is a three-phase AC motor, and the inverter is a three-phase inverter composed of three positive and negative three arms.
The fuse blow control unit is:
2. The electric motor drive device according to claim 1, wherein one or both of a switching element detected by the short-circuit detecting unit and a switching element belonging to another arm having a reverse polarity are turned on. The fuse blow control unit is:
3. The electric motor according to claim 2, wherein one or both of the switching element belonging to another arm having the opposite polarity to the switching element detected by the short-circuit detecting unit and the switching element having the short-circuit fault are turned on. Drive device. The three-phase AC motor is a multiple AC motor having a plurality of primary windings;
The three-phase inverter comprises a plurality of three-phase inverters that drive each of the plurality of primary windings via fuses,
Each control device that controls each of the plurality of three-phase inverters,
A short-circuit detection unit that identifies which switching element among the switching elements has a short-circuit failure according to the magnitude and polarity of the output current of the three-phase inverter;
A fuse blow control unit for controlling the fuse to blow by turning on a predetermined healthy switching element among the switching elements constituting the three-phase inverter according to the detection result of the short circuit detection unit. The electric motor drive device according to claim 2 or 3, wherein The AC motor is a multiphase AC motor having a plurality of primary windings;
The inverter comprises a plurality of single-phase inverters that drive each of the plurality of primary windings via a fuse,
Each control device that controls each of the plurality of single-phase inverters,
A short-circuit detection unit that identifies which switching element among the switching elements has a short-circuit failure according to the magnitude and polarity of the output current of the single-phase inverter;
According to the detection result of the short-circuit detection unit, by switching on a switching element that has a short circuit failure among switching elements that constitute the single-phase inverter, and a switching element that belongs to another arm having a reverse polarity to the switching element that has a short circuit failure The electric motor drive device according to claim 1, further comprising a fuse blow control unit that controls the fuse to blow. Rotation position detection means for detecting the rotation position of the AC motor, and speed detection means for detecting the motor speed from the rotation position,
The fuse blow control unit is:
The predetermined timing is determined so that the current flowing through the short-circuited switching element is substantially maximized by the rotational direction obtained from the motor speed and the phase angle obtained from the rotational position. The electric motor drive device according to any one of claims 1 to 5. The fuse blow control unit is:
When the short-circuited switching element is the positive arm, the induced voltage of the short-circuited phase is substantially minimized, so that when the short-circuited switching element is the negative arm, the induced voltage of the short-circuited phase is substantially maximum. The motor driving apparatus according to claim 6, wherein the predetermined timing is determined as follows. The fuse blow control unit is:
The predetermined timing is determined so that a current flowing through the switching element having a short circuit failure is substantially maximized by a detected current. Electric motor drive device.

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