Motor drive device

A motor is driven while suppressing drive torque ripple generated by the motor, when any of the phases is opened during the driving of the motor. A motor drive device controls the driving of a motor in which the armature windings of respective phases are independently provided. The motor drive device is equipped with: an inverter circuit for converting the DC power supplied through DC bus lines to three-phase AC powers and respectively outputting the three-phase AC powers to the armature windings of the respective phases; and a controller for controlling the inverter circuit. When any of the phases is opened in the AC powers output from the inverter circuit, the controller adjusts the difference between the phases of the respective currents flowing through the armature windings of normal phases so that the AC powers of the other normal phases except the opened phase are compensated each other.

TECHNICAL FIELD

The present invention relates to a motor drive device.

BACKGROUND ART

Conventionally, devices, which perform drive control of an independent winding multi-phase motor (for example, a six-line three-phase motor) capable of controlling current of an armature winding of each phase provided in a motor stator independently from each other, have been known. When such a motor is used, it is possible to solve a lack in voltage without using a booster circuit and to acquire higher output of the motor. In addition, it is possible to increase capacity and to increase a maximum rotational velocity.

A technique has been proposed in which a pseudo-square wave current, obtained by superimposing a harmonic component on a winding of each phase, is caused to flow in an independent winding multi-phase motor as described above so as to enable drive of a motor to continue even when a current or a voltage is abnormal in a winding of any phase (PTL1).

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

In the technique described in PTL1, the drive of the motor may continue when the abnormality is caused in a winding of any phase, but it is difficult to control pulsation of a drive torque generated by the motor.

The present invention has been made in order to solve the problems of the related art described above. A main object thereof is to provide a motor drive device to control drive of an independent winding multi-phase motor that is capable of continuing the drive of the motor while suppressing pulsation of a drive torque generated by the motor when any phase becomes an open phase during the drive of the motor.

Solution to Problem

A motor drive device according to the present invention is configured to control drive of a multi-phase motor in which armature windings of respective phases are provided to be independent from each other, and is provided with: an inverter circuit, which converts a DC power supplied via a DC bus line into a multi-phase AC power and outputs the converted power to each of the armature windings of the respective phases; and a controller configured to control the inverter circuit, in which when any open phase occurs in the AC power, the controller adjusts a phase difference of each current flowing in the armature windings of normal phases such that the respective AC powers of the normal phases other than the open phase offset each other.

Advantageous Effects of Invention

According to the present invention, it is possible to provide the motor drive device to control the drive of the independent winding multi-phase motor that is capable of continuing the drive of the motor while suppressing the pulsation of the drive torque generated by the motor when any phase becomes the open phase during the drive of the motor.

DESCRIPTION OF EMBODIMENTS

First Embodiment

FIG. 1is a diagram illustrating a configuration of a motor drive device200according to a first embodiment of the present invention. The motor drive device200is connected to a motor100, which is used in a hybrid electric vehicle (HEV), an electric vehicle (EV) or the like, and controls drive of the motor100. The motor drive device200includes a DC power supply201, a smoothing capacitor202, a controller203, and an inverter circuit210.

The motor100is a six-line three-phase AC motor of an independent winding type which includes three-phase armature windings102a,102band102cwhich respond to a U-phase, a V-phase and a W-phase, respectively. These armature windings102ato102care provided to be independent from each other. The motor drive device200can drive the motor100by independently controlling each current flowing in the armature windings102ato102c. A magnetic pole position detector110, which detects a magnetic pole position θ of the motor100, is attached to an output shaft105of the motor100. A detection result of the magnetic pole position θ obtained by the magnetic pole position detector110is output to the controller203.

The DC power supply201supplies a DC power to the inverter circuit210via DC bus lines201aand201b. It is possible to use a secondary battery such as a lithium ion battery, or the like for the DC power supply201.

The smoothing capacitor202is configured to control a variation in DC voltage caused depending on an operation of the inverter circuit210, and is connected between the DC bus line201aand the DC bus line201bto be parallel with the inverter circuit210.

The controller203outputs drive signals Gu, Gv and Gw, respectively, to bridge circuits210a,210band210cof the respective phases included in the inverter circuit210. The controller203can control the inverter circuit210by operating the bridge circuits210a,210band210caccording to the drive signals Gu, Gv and Gw.

The inverter circuit210includes the full-bridge type bridge circuit210a,210band210cwhich respond to the U-phase, the V-phase, and the W-phase, respectively. Each of the bridge circuits210a,210band210cincludes four IGBTs221functioning as switching elements of respective upper and lower arms, and four diodes222provided to be parallel with the respective IGBTs221. Each of the IGBTs221performs a switching operation according to the drive signals Gu, Gv and Gw from the controller203in the bridge circuits210a,210band210c. Accordingly, the DC power supplied from the DC power supply201is converted into a three-phase AC power, and the converted power is output to the armature windings102a,102band102cof the respective phases of the motor100via AC output lines120of the respective phases from the bridge circuits210a,210band210c.

An AC sensor130, which is configured to detect each current flowing in the armature windings102a,102band102cof the motor100, is provided to each of the AC output lines120of the respective phases. Current values iu, ivand iwof the respective phases each phase, detected by the AC sensor130, are output to the controller203. The controller203performs a predetermined current control operation based on the current values iu, ivand iwof the respective phases input from the AC sensor130, and the magnetic pole position θ input from the magnetic pole position detector110, and outputs the drive signals Gu, Gv and Gw of the respective phases based on a result of the operation.

FIG. 2is a diagram illustrating an arrangement example of the armature windings102a,102band102cin the motor100. As illustrated inFIG. 2, the armature windings102a,102band102care arranged in a stator of the motor100to be mechanically shifted each by 120° such that each phase difference of waveforms of the induced voltages of the respective phases becomes 120° based on an electrical angle. Incidentally, the armature windings102a,102band102care provided to be independent from each other in the motor100as described above, which is different from a structure of Y-connection or A-connection in general three-phase equilibrium motors of the related art.

FIG. 3is a diagram illustrating an example of a structure of the motor100. As illustrated inFIG. 3, for example, the motor100is a surface magnet motor which is configured of a stator core101to which a plurality of armature windings102are attached and a rotor core103which is fixed to the output shaft105and has a surface to which a plurality of permanent magnets104are pasted. Incidentally, each of the armature windings102corresponds to any of the armature windings102a,102band102cinFIG. 2.

FIG. 4is a diagram illustrating each aspect of changes of an interlinkage magnetic flux, an induced voltage, and an inductance in the motor100having the structure illustrated inFIG. 3. When an interlinkage magnetic flux, an induced voltage, and a self-inductance of the U-phase are set to ψu, euand Lu, respectively, and a mutual inductance between the U-phase and the V-phase is set to Muv, these are changed as illustrated inFIG. 4, for example, depending on the electrical angle of the motor100. That is, the interlinkage magnetic flux ψuand the induced voltage euare periodically changed having an electrical angle of 360° as a single period. On the other hand, the self-inductance Luand the mutual inductance Muvare constant regardless of the electrical angle in the structure ofFIG. 3. Incidentally, the same description is also applied regarding the V-phase and the W-phase.

FIG. 5is a diagram illustrating another example of the structure of the motor100. As illustrated inFIG. 5, for example, the motor100is an embedded magnet motor which is configured of the stator core101to which the plurality of armature windings102are attached, similar toFIG. 3, and the rotor core103which is fixed to the output shaft105and has the plurality of permanent magnets104are embedded therein.

FIG. 6is a diagram illustrating each aspect of changes of an interlinkage magnetic flux, an induced voltage, and an inductance in the motor100having the structure illustrated inFIG. 5. When the interlinkage magnetic flux, the induced voltage, and the self-inductance of the U-phase are set to ψu, euand Lu, respectively, and the mutual inductance between the U-phase and the V-phase is set to Muv, these are changed as illustrated inFIG. 6, for example, depending on the electrical angle of the motor100. That is, the interlinkage magnetic flux ψuand the induced voltage euare periodically changed having an electrical angle of 360° as a single period. On the other hand, the self-inductance Luand the mutual inductance Muvare periodically changes having an electrical angle of 360° as two periods (that is, having an electrical angle of 180° as a single period) in the structure ofFIG. 5. Incidentally, the same description is also applied regarding the V-phase and the W-phase.

A voltage equation of the motor100, which employs the permanent magnet illustrated inFIG. 3 or 5, is expressed by the following Formula (1).

In the above-described Formula (1), vu, vv, Vw, iu, iv, and iwrepresent each voltage and current of the U-phase, the V-phase, and the W-phase, R represents a winding resistance for one phase, and P represents a differential operator. In addition, the induced voltages eu, evand ewof the respective phases, the self-inductances Lu, Lvand Lwof the respective phases, the mutual inductances Muv, Mvwand Mwuamong the respective phases in Formula (1) are represented by the following Formulae (2), (3) and (4), respectively.

In Formula (2), ωerepresents an electrical angular velocity of the motor100, and ψmrepresents a winding interlinkage magnetic flux of the permanent magnet104. In addition, la represents a leakage inductance for one phase in Formula (3), and Laand Lasrepresent an average value component and an amplitude component, respectively, of an effective inductance for one phase in Formulae (3) and (4).

Incidentally, Las=0 in Formulae (3) and (4) in the case of the surface magnet motor as illustrated inFIG. 3. On the other hand, Las≠0 in Formulae (3) and (4) in the case of the embedded magnet motor as illustrated inFIG. 5.

A shaft torque T to be output from the motor100to the output shaft105is expressed by the following Formula (5). In Formula (5), POUTrepresents mechanical energy (shaft output) output from the motor100to the output shaft105, and ωmrepresents a rotation angular velocity (shaft rotational velocity) of the output shaft105. That is, the shaft torque T is a value obtained by dividing the shaft output POUTby the shaft rotational velocity ωm. Thus, when the shaft rotational velocity ωmand the motor the shaft output POUTare constant values, the shaft torque T also becomes a constant value. Incidentally, calculation is performed by setting the number of pole pairs of the motor100to1, and ωe=ωmin Formula (5) in order to simplify the calculation, and relation of ωm=ωe/Ppis established in practice when the number of pole pairs of the motor100is set to Pp.

The shaft output POUTof the motor100in the above-described Formula (5) is expressed by the following Formula (6).
[Formula 6]
POUT=Pu+Pv+Pw=eu·iu+ev·iv+ew·iw(6)

Incidentally, the shaft output POUTexpressed by Formula (6) is equal to a value that is obtained by subtracting each loss such as a copper loss and an iron loss from an input power PINof the motor100. The input power PINof the motor100is sought as a value obtained by adding respective products between the instantaneous voltages vu, vvand vwand the instantaneous currents iu, ivand iwof the respective phases as illustrated in the following Formula (7).
[Formula 7]
PIN=vu·iu+vv·iv+vw·iw(7)

Powers Pu, Pvand Pw, determined based on the respective products between the induced voltages eu, evand ewand the instantaneous currents iu, ivand iwof the respective phases, in the input power PINare mainly converted into the shaft output POUTin the surface magnet motor or the embedded magnet motor having a relatively small salient pole ratio as illustrated in Formula (6)

As apparent from Formula (5), the shaft output POUTis a constant value when the motor100rotates at the constant shaft rotational velocity ωm, the shaft torque T becomes constant. As apparent from Formula (6), a sum of the powers Pu, Pvand Pwof the input power PIN, determined by the respective products between the induced voltages eu, evand ewand the instantaneous currents iu, ivand iwof the respective phases as described above, needs to be constant in order to set the shaft output POUTof the motor100to be constant.

FIG. 7is a diagram illustrating each waveform example of the induced voltage, the current, and the power of each phase in the motor100in a normal state. As described above, each phase difference of the induced voltages eu, evand ewof the respective phases caused in the armature windings102a,102band102cis 120°. In the normal state, the motor drive device200determines an operation timing of the IGBT221in each of the bridge circuits210a,210band210csuch that the currents iu, ivand iwof the respective phases flowing in the armature windings102a,102band102chave the phase differences by 120° from each other as illustrated inFIG. 7. As a result, the powers Pu, Pvand Pwof the respective phases, obtained based on the product between the induced voltage and the current, pulsate at a frequency, which is twice of each frequency of the induced voltage and the current, and have each phase difference of 60° as illustrated inFIG. 7. Meanwhile, the input power PINwhich is the sum of the powers Pu, Pvand Pwof the three phases becomes constant as illustrated inFIG. 7. Therefore, it is understood that a torque pulsation is not generated in principle as long as the induced voltage and the current sine waves.

Incidentally, it is assumed that the induced voltage waveform and the current waveform are the ideal sine waves in the above description, but in practice, the induced voltage waveform or the current waveform includes some harmonic waves and is not the ideal sine wave. However, the motor drive device200can operate the motor100mostly without any problem even in this case by controlling the motor100while dealing the induced voltage waveform or the current waveform as the sine wave.

As described above, it is possible to cause the motor100to rotate while generating a constant torque by creating a state in which three phase currents are equilibrated also in the independent winding motor100which is capable of independently controlling each current flowing in the armature windings102a,102band102cof the respective phases. This principle is established for an independent winding multi-phase motor other than the three-phase motor. That is, when the number of phases of the motor is set to n, it is possible to cause the respective phase currents to be equilibrated by shifting each phase of the respective phase currents by 360/n°, and to cause the motor to rotate with a constant torque.

The motor drive device200in the normal state can control the torque of the motor100and rotationally drive the motor100the motor100by energizing the entire phase of the motor100. However, it is difficult to suitably control the torque of the motor100using the same control method at the normal state when any phase is lost and is incapable of being energized as an abnormality occurs in the operation of the IGBT221in any of the bridge circuits210a,210band210cor an abnormality such as disconnection occurs in the AC output line120or a wiring inside the motor100in any phase, for example. That is, when any phase is lost in the AC power to be output from the inverter circuit210to each of the armature windings102a,102band102cof the motor100, a significant torque pulsation is caused in the motor100if the current control is performed by shifting each phase of the currents iu, ivand iwof the respective phases by 120° in the same manner as in the normal state.

A description will be given in detail regarding an example of torque pulsation in the above-described open-phase state with reference toFIG. 8.FIG. 8is a diagram illustrating each waveform example of the induced voltage, the current, and the power of each phase in the motor100in a case in which phase adjustment of current is not performed when the W-phase is lost. In this case, each phase difference between the U-phase current iuand the V-phase current ivis still 120° as illustrated inFIG. 8, which is similar to that in the normal state. However, the current iwand the power Pwof the W-phase become zero since the W-phase is in the open-phase state. Thus, the input power PIN, which is the sum of the powers Pu, Pvand Pw(where Pw=0) of the three phases, is not constant as illustrated inFIG. 8, and pulsates at a frequency, which is twice of that of the induced voltage, along with each pulsation of the U-phase power Puand the V-phase power Pv.

As described above, when any phase is lost and incapable of being energized, the significant pulsation occurs in an output torque of the motor if the motor control is performed using the same control method at the normal state. Thus, it is necessary to stop the rotation of the motor when any phase is lost in the AC power, which is output to the motor, in a conventional motor drive device.

Meanwhile, the motor drive device200according to the present invention adjusts the phase difference of the current flowing in the armature winding of the normal phase such that the respective AC powers of the other normal phases, except for the open phase, offset each other by the controller203in a case in which any phase is lost in the AC power output to the motor100. Accordingly, it is possible to reduce the pulsation of the output torque in the motor100and to continue the rotation of the motor100.

FIG. 9is a diagram illustrating each waveform example of the induced voltage, the current, and the power of each phase in the motor100in a case in which phase adjustment of current is performed when the W-phase is lost. When the W-phase is lost, the motor drive device200shifts a phase of the V-phase current ivin a direction of decreasing 60° from the normal state (to the left in the drawing) to adjust each phase difference of the V-phase current ivand the U-phase current iuto be 60° as illustrated inFIG. 9. To be specific, the phase of the V-phase current ivto be output is adjusted in the current control operation performed by the controller203, and the controller203outputs the drive signal Gv to the V-phase bridge circuit210bin accordance with the adjusted phase. Accordingly, a mountain portion of the U-phase power Puand a valley portion of the V-phase power Pv, and a valley portion of the U-phase power Puand a mountain portion of the V-phase power Pvare set to overlap each other and offset each other as illustrated inFIG. 9. As a result, it is possible to make the input power PIN, which is the sum of the powers Pu, Pvand Pwof the three phases, constant as illustrated inFIG. 9even when the W-phase is lost. Thus, it is possible to continue the rotation of the motor100while suppressing the torque pulsation.

Incidentally, the reduction of torque pulsation through the current phase adjustment in the open-phase state as described above can be applied to an independent winding multi-phase motor other than the three-phase motor. That is, when the number of phases of the motor serving as a control target is set to n and the number of open phases is set to m, the motor drive device according to the present invention enables the respective AC powers of the normal phases to offset each other by adjusting each current of the normal phases such that a phase difference Dp(°) between the respective AC powers of the normal phases satisfy the following Formula (8) when any phase is lost. As a result, it is possible to continue the rotation of the motor by suppressing the pulsation of the output torque of the motor.
Dp=360/2(n−m)  (8),

where n and m are positive integers, and n≥m+2.

Each phase difference Di (°) of the currents flowing in the armature windings of the normal phases may be adjusted to satisfy the following Formula (9) in order to satisfy the above-described Formula (8). Accordingly, it is possible to cause the respective AC powers of the normal phases to offset each other when the open phase is caused in any phase, and to suppress the pulsation of the output torque of the motor.
Di=360/(n−m)−360/n(9)

Incidentally, Dp=90° and Di=60° when n=3 and m=1 in the above-described Formulae (8) and (9), which matches each of the relation between the U-phase power Puand the V-phase power Pvand the relation between the U-phase current iuand the V-phase current ivillustrated inFIG. 9.

The motor drive device needs to be provided with an inverter circuit, which includes n bridge circuits in response to the number n of phases of the motor serving as the control target, and a controller which outputs the drive signal to each bridge circuit of the inverter circuit in order to realize the above-described current control. Meanwhile, the motor driven by the motor drive device needs to include n independent windings, which can be controlled to be independent from each other, and the current flowing in each independent winding is controlled by the motor drive device. When the present invention is applied in the combination of the motor drive device and the motor described above, it is possible to adjust each phase difference of the current flowing in the armature windings of the normal phases such that the respective AC powers of the other normal phases, except for the open phase, offset each other in a case in which any phase is lost. As a result, it is possible to continue the rotation of the motor by suppressing the pulsation of the output torque of the motor and generating a rotating magnetic field that smoothly rotates in the armature winding of the motor.

Next, a description will be given in more details regarding the operation of the motor drive device200during the current phase adjustment in the open-phase state described above.

It is considered a case in which a current does not flow in the W-phase armature winding102cand an open phase occurs in the W-phase AC power as an operation abnormality is generated in the IGBT221or the diode222inside the W-phase bridge circuit210c, for example, in the motor drive device200or disconnection is caused in the wiring inside the motor100or the AC output line120. In this case, the motor drive device200can perform the current control using the remaining armature windings102aand102bof the two normal phases. However, the significant pulsation occurs in the input power PINwhich is the sum of the U-phase instantaneous power Puand the V-phase instantaneous power Pv, as described with reference toFIG. 8, when the motor100is driven by outputting the respective phase currents with each phase difference of 120 degrees even in the open-phase state similarly to the state in which the normal three phases are equilibrated. As a result, a significant torque pulsation occurs in the motor100.

Thus, the motor drive device200adjusts phases of the instantaneous powers Puand Pvof the two normal phases, as described above, using the characteristic that it is possible to independently control each current flowing the armature windings102a,102band102cof the respective phases of the motor100to cause the mountain and valley portions thereof to be offset by each other. At this time, the motor drive device200seeks each phase of induced voltages of the respective phases based on the magnetic pole position information output from the magnetic pole position detector110, attached to the output shaft105of the motor100and performs the current control operation with respect to the induced voltage in order to individually control each current phase of the respective phases using the controller203. Accordingly, the phase difference between the instantaneous powers Puand Pvis adjusted, and the torque pulsation of the motor100is reduced.

The above-described current control operation is performed using current value information, output from the AC sensors130of the respective phases attached between the motor drive device200and the motor100, and the magnetic pole position information output from the magnetic pole position detector110attached to the output shaft105of the motor100. The controller203outputs the drive signals Gu, Gv and Gw to the IGBTs221included in the respective bridge circuits210a,210band210cof the inverter circuit210according to a result of the current control operation. It is possible to individually adjust the induced voltages of the respective phases as the bridge circuits210a,210band210cof the respective phases performs the switching operation according to the drive signals Gu, Gv and Gw.

Next, a description will be given regarding the rotating magnetic field generating inside the motor100in the case of performing the current phase adjustment in the open-phase state.FIG. 10is a diagram illustrating each waveform of a U-phase current iuand a V-phase current ivafter phase adjustment when the W-phase is lost.FIG. 11is a diagram illustrating a magnetomotive force vector inside the motor100corresponding to each electrical angle of A to G illustrated inFIG. 10.

The current phase adjustment is performed such that the phase of the V-phase current ivis shifted by 60° with respect to the U-phase current iuwhen the W-phase is lost as illustrated inFIG. 10, and then, the rotating magnetic field caused by the magnetomotive force vector illustrated inFIG. 11is generated inside the motor100. At this time, the U-phase armature winding102aand the V-phase armature winding102bgenerate each magnetomotive force alternating depending on a change of current in a direction perpendicular to each armature winding.

When the electrical angle is 0° illustrated by A ofFIG. 10, the U-phase current iuis zero, and only the V-phase current ivflows. At this time, a U-phase magnetomotive force Fubecomes zero, and only a V-phase magnetomotive force Fvis generated inside the motor100as illustrated in A ofFIG. 11. Therefore, a combined magnetomotive force Fuvgenerated by the U-phase armature winding102aand the V-phase armature winding102bis the same as the V-phase magnetomotive force Fv.

Next, when the electrical angle is 30° illustrated by B ofFIG. 10, the current flows to both sides of the U-phase and the V-phase. At this time, the combined magnetomotive force Fuvgenerated inside the motor100becomes a vector sum of the U-phase magnetomotive force Fuand the V-phase magnetomotive force Fvas illustrated by B ofFIG. 11. In this manner, when a current value is changed by the electrical angle of 30° from A to B in the current waveform ofFIG. 10, the magnetomotive force inside the motor100changes from A to B ofFIG. 11. When A and B ofFIG. 11are compared, it is understood that each magnitude of the U-phase magnetomotive force Fuand the V-phase magnetomotive force Fvchanges while the combined magnetomotive force Fuvthereof rotates by 30° in a counter-clockwise manner with the same magnitude.

Similarly, magnetomotive forces of the motor100are illustrated by C to G ofFIG. 11corresponding to current values, shifted each by 30°, illustrated by C to G inFIG. 10. FromFIG. 11, it is understood that the combined magnetomotive force Fuvof the U-phase and the V-phase rotates in a counter-clockwise manner with a constant magnitude along with a change in the U-phase current iuand the V-phase current ivas illustrated inFIG. 10. That is, it is understood that the rotating magnetic field with a constant magnitude is generated inside the motor100.

Incidentally,FIG. 11does not illustrate magnetomotive force vectors generated at each electrical angle in a range of 210° to 360° illustrated by H to M ofFIG. 10. However, each value of the U-phase current iuand the V-phase current ivis the same that is obtained by inverting a sign of each value at each electrical angle illustrated by B to G ofFIG. 10. Therefore, it is understood that the combined magnetomotive force Fuvof the U-phase and the V-phase also rotates in a counter-clockwise manner with the same magnitude at these electrical angles similarly to the above description.

Although the description has been given inFIG. 11by exemplifying a bipolar motor in which the electrical angle and a mechanical angle matches each other, it is possible to generate a magnetic field rotating in an armature winding along with a change in current value in the same manner even in a multipolar motor in which an electrical angle and a mechanical angle are different from each other.

As described above, the motor drive device200performs the current phase adjustment using the two remaining normal phases and drives the motor100when any phase is lost due to the operation abnormality in any of the bridge circuits210a,210band210cof the inverter circuit210or the disconnection in the wiring inside the motor100or the AC output line120. As a result, it is possible to drive the motor100without causing the significant torque pulsation by generating the rotating magnetic field that smoothly rotates inside the motor100.

According to the first embodiment of the present invention described above, the following operational effects are achieved.

(1) The motor drive device200is configured to control the drive of the motor100in which the armature windings102a,102band102cof the respective phases are provided to be independent from each other, and is provided with the inverter circuit210, which converts the DC power supplied via the DC bus lines201aand201binto the three-phase AC power and outputs the converted power to each of the armature windings102a,102band102cof the respective phases, and the controller203configured to control the inverter circuit210. Meanwhile, the controller203adjusts the phase difference of the current flowing in the armature winding of the normal phase such that the respective AC powers of the other normal phases, except for the open phase, offset each other in a case in which any phase is lost in the AC power output from the inverter circuit210in the motor drive device200. Accordingly, it is possible to control the drive of the motor100while suppressing the pulsation of the drive torque generated by the motor100when any phase becomes the open phase during the drive of the motor100.

(2) When any phase is lost in the AC power output from the inverter circuit210, the controller203adjusts the phase difference of the current flowing in the armature winding of the normal phase such that the respective AC powers of the normal phases offset each other as the phase difference Dp(°) of each AC power of the normal phase satisfies Formula (8) described above assuming that the number of phases of the motor100is n and the number of open phases is m. Accordingly, it is possible to suppress the pulsation of the drive torque in the open-phase state and to continue the drive of the motor not only in the three-phase motor such as the motor100but also in various the independent winding multi-phase motors other than the three-phase motor.

(3) The controller203performs adjustment such that each phase difference Di (°) of the currents flowing in the armature windings of the normal phases satisfies the above-described Formula (9). Accordingly, it is possible to suitably adjust each phase difference of the currents flowing in the armature windings of the normal phases regardless of the number of phases of the motor and to reliably offset the respective AC powers of the normal phases.

Second Embodiment

A second embodiment of the present invention will be described hereinafter. In present embodiment, a description will be given regarding an example in which an AC power of any open phase is cut off when the open phase occurs in the AC power output from the inverter circuit210of the motor drive device200to the motor100.

Incidentally, a configuration of the motor drive device200and a configuration of the motor100according to the present embodiment are the same as the configurations ofFIG. 1that has been described in the first embodiment. Therefore, a description will be given in the present embodiment with reference to the configuration illustrated in the configuration diagram ofFIG. 1.

FIG. 12is a diagram illustrating an aspect in which an off failure occurs in the W-phase bridge circuit210cof the inverter circuit210in the motor drive device200. For example, as illustrated inFIG. 12, it is assumed a case in which a failure in which one of the IGBTs221is constantly in an OFF state without any change occurs in the W-phase bridge circuit210c. In this case, the bridge circuit210cperforms the same operation as that in a full-wave rectifier circuit.

If an off failure occurs as illustrated inFIG. 12, a voltage |Vw|, which is obtained by rectifying a W-phase induced voltage is lower than a DC voltage Vdc supplied from the DC power supply201as illustrated inFIG. 13when the rotational velocity of the motor100is relatively low. Thus, the current flowing from the motor100to the motor drive device200is not generated.

However, when the rotational velocity of the motor100is a certain value or higher, the voltage |Vw|, which is obtained by rectifying the W-phase induced voltage sometimes becomes higher than the DC voltage Vdc supplied from the DC power supply201as illustrated inFIG. 14.FIG. 15is a diagram illustrating a current path in the W-phase bridge circuit210cduring the off failure. As illustrated inFIG. 15, a current flows from the motor100to the motor drive device200passing through the respective diodes222included in the W-phase bridge circuit210cby the induced voltage generating in the W-phase armature winding102cin the motor100during the off failure. This current causes a brake torque or torque pulsation in the motor100. Therefore, it is necessary to disconnect the W-phase bridge circuit210chaving the failure from the motor100to prevent the flow of the current as illustrated inFIG. 15.

FIG. 16is a diagram illustrating a current path when an on failure occurs in the W-phase bridge circuit210cof the inverter circuit210in the motor drive device200. For example, as illustrated inFIG. 16, it is assumed a case in which a failure in which one of the IGBTs221is constantly in the ON state without any change occurs in the W-phase bridge circuit210c. In this case, the IGBT221is turned into a short-circuit state, and thus, a current circulating inside the W-phase bridge circuit210cflows as illustrated inFIG. 16by the induced voltage generated in the W-phase armature winding102cin the motor100. This current also causes the brake torque or the torque pulsation in the motor100, which is similar toFIG. 15. Therefore, it is necessary to disconnect the W-phase bridge circuit210chaving the failure from the motor100to prevent the flow of the current as illustrated inFIG. 16.

Thus, a switch, which is configured to cut off power of a portion corresponding to an open phase when the open phase occurs in the AC power output from the inverter circuit210, is provided inside the motor drive device200in the present embodiment. Accordingly, the current as described above is prevented from flowing even when any of the bridge circuits210a,210band210chas a failure in the inverter circuit210. Details thereof will be described hereinafter.

FIG. 17is a diagram illustrating an example in which a power cut-off switch213is provided in each of the bridge circuits210a,210band210cof the respective phase. When the above-described abnormality occurs in the motor drive device200or the motor100and any phase is lost in the AC power output from the inverter circuit210, the motor drive device200turns the four switches213, which are connected to a bridge circuit corresponding to the open phase among the bridge circuits210a,210band210cof the respective phases, into an open state according to an instruction of the controller203inFIG. 1or other devices. Accordingly, the bridge circuit of a portion of the inverter circuit210corresponding to the open phase is disconnected from the DC bus lines201aand201bto cut off the AC power from the corresponding bridge circuit to the motor100. As a result, it is possible to prevent an adverse impact from occurring in the drive of the motor100due to the current flowing in the circuit of the open-phase portion.

FIG. 18is a diagram illustrating an example in which a power cut-off switch214is provided in each of the AC output lines120of the respective phases. When the above-described abnormality occurs in the motor drive device200or the motor100and any phase is lost in the AC power output from the inverter circuit210, the motor drive device200turns the switch214, which is provided in the middle of the AC output line corresponding to the open phase among the AC output lines120of the respective phases, into an open state according to an instruction of the controller203inFIG. 1or other devices. Accordingly, the armature winding corresponding to the open phase among the armature windings102a,102band102cof the respective phases is disconnected from the inverter circuit210to cut off the AC power from the inverter circuit210to the corresponding armature winding. As a result, it is possible to prevent the current from flowing to the circuit of the open-phase portion and to avoid the occurrence of the adverse impact in the drive of the motor100.

According to the second embodiment of the present invention described above, the motor drive device200is further provided with the switch213, which is configured to disconnect the portion of the inverter circuit210corresponding to the open phase from the DC bus lines201aand201b, or the switch214which is configured to disconnect the armature winding corresponding to the open phase among the armature windings102a,102band102cof the respective phases from the inverter circuit. Accordingly, when an open-phase occurs in the AC power output from the inverter circuit210, it is possible to cut off the AC power of the open phase. Therefore, it is possible to prevent an adverse impact from occurring in the drive of the motor100due to the current flowing in the circuit of the open-phase portion.

Incidentally, the description has been given in the respective embodiments described above with by exemplifying the independent winding three-phase motor100capable of independently controlling each current flowing in the armature windings102a,102band102cof the respective phases, but the present invention can be applied to multi-phase motors other than the three-phase motor. That is, it is possible to adjust each phase difference of the current flowing in the armature winding of the normal phase such that the respective AC powers of the normal phases offset each other when any phase is lost in the AC power to be output from the inverter circuit to the motor by applying the present invention in any motor drive device that controls drive of an independent winding multi-phase motor that can independently control each current flowing in the armature windings of the respective phases. Accordingly, it is possible to reduce the pulsation of the output torque of the motor even in the open-phase state, and to generate the rotating magnetic field that smoothly rotates in the armature winding of the motor. As a result, it is possible to continue the drive of the motor.

In addition, the above respective embodiments and various modified examples have been described only as examples, and the present invention is not limited thereto as long as the characteristics of the invention are not compromised. The present invention is not limited to the above-described embodiments, and various modifications can be made within a range not departing from a gist of the present invention.

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