Drive unit

Abstract

Further reduction of iron loss in the motor. [Solution] The drive device comprises an energy storage device, a motor having a three-phase open winding, a first inverter unit connected to the power line to which the energy storage device is connected and connected to one end of the three-phase open winding, a second inverter unit connected to the power line on the opposite side of the power line from the first inverter and connected to the other end of the three-phase open winding, and a changeover switch provided between the first and second inverter units for switching between an H drive, which drives the motor using the first and second inverter units, and a Y drive, which neutralizes the motor on the side of the motor closer to the second inverter unit and drives the motor using the first inverter unit. The first inverter unit has a three-level inverter.

Description

Technical Field

[0001] This disclosure relates to a drive device.

Background Art

[0002] Conventionally, a drive device has been proposed that includes a power storage device, a motor having a three-phase open winding, a first inverter unit connected to a power line to which the power storage device is connected and also connected to one end side of the three-phase open winding, a second inverter unit connected to the power line on the side opposite to the power storage device with respect to the first inverter and also connected to the other end side of the three-phase open winding, and a switching switch provided between the first and second inverters of the power line (see, for example, Patent Document 1). In such a drive device, Δ drive (H drive) in which the switching switch is in the on state and the motor is driven by the first and second inverter units, and Y drive in which the switching switch is in the off state, the other end side of the three-phase open winding is neutralized by the second inverter, and the motor is driven by the first inverter unit are switched and executed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above drive device, in the case of H drive, the maximum value of the applied voltage of each phase of the motor is approximately equal to the voltage of the power storage device, while in the case of Y drive, the maximum value of the applied voltage of each phase of the motor is approximately equal to 1 / 2 of the voltage of the power storage device. Therefore, in Y drive, although the iron loss of the motor can be reduced compared to H drive, further reduction of the iron loss of the motor is required.

[0005] The main object of the drive device of this disclosure is to further reduce the iron loss of the motor. [Means for solving the problem]

[0006] The drive device of this disclosure employs the following means to achieve the main objective described above.

[0007] [1] The drive device of the present disclosure is Energy storage device, A motor having a 3-phase open winding, The first inverter unit is connected to the power line to which the energy storage device is connected and is connected to one end of the three-phase open winding, A second inverter section is connected to the power line on the opposite side of the first inverter from the energy storage device and to the other end of the three-phase open winding, A changeover switch is provided between the first and second inverter sections for switching between an H drive, which drives the motor using the first and second inverter sections, and a Y drive, which neutralizes the motor on the side of the second inverter section and drives the motor using the first inverter section. A drive device equipped with, The first inverter section has a 3-level inverter. This is the gist of it.

[0008] In the drive device of this disclosure, the first inverter unit has a 3-level inverter. This allows for a 2-level H drive mode in which the first and second inverter units switch the potential of one end and the other end of the 3-phase open winding at 2 levels each in H drive mode, and a 2-level Y drive mode in which the first inverter unit switches the potential of one end of the 3-phase open winding at 2 levels each in Y drive mode, as well as a 3-level Y drive mode in which the first inverter unit switches the potential of one end of the 3-phase open winding at 3 levels each in Y drive mode. By implementing this 3-level Y drive mode, further reduction of iron loss in the motor can be achieved.

[0009] [2] The drive device of the present disclosure (the drive device described in [1] above) may further include a control device that performs, in order from the side with the smallest torque and rotational speed of the motor, a 3-level Y drive mode in which the first inverter unit switches the potential of one end of the three-phase open windings at 3 levels in the Y drive mode, a 2-level Y drive mode in which the first inverter unit switches the potential of one end of the three-phase open windings at 2 levels in the Y drive mode, and a 2-level H drive mode in which the first and second inverter units switch the potential of one end and the other end of the three-phase open windings at 2 levels in the H drive mode. This makes it possible to further reduce the iron loss of the motor in the low rotational speed and low torque region of the motor.

[0010] [3] In this case (the drive device described in [2] above), the first inverter unit has three phase upper and lower arms connected in series with respect to the positive and negative power lines of the power lines for each phase, and the connection points of each arm are connected to the one end of the corresponding open winding; first and second capacitors connected in series with respect to the positive and negative power lines; three phase intermediate potential lines connecting the connection points of the upper and lower arms of the three phases to the connection points of the first and second capacitors, respectively; and three phase intermediate potential switches provided on the three phase intermediate potential lines, wherein the intermediate potential switches may have lower power capacity and lower voltage resistance compared to the upper and lower arms. This makes it possible to reduce the cost of the intermediate potential switches.

[0011] [4] In the drive device of the present disclosure (the drive device described in any one of [1] to [3] above), the changeover switch may be provided between the first and second inverter sections of the power line.

[0012] [5] In the drive device of the present disclosure (the drive device described in any one of [1] to [3] above), the changeover switch may be provided between the three-phase open winding and the second inverter section. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic diagram of the drive device according to the embodiment of the disclosure. [Figure 2] This is a schematic diagram of the drive unit. [Figure 3] This is an explanatory diagram showing an example of the 2-level H drive mode. [Figure 4] This is an explanatory diagram showing an example of the 2-level Y drive mode. [Figure 5] This is an explanatory diagram showing an example of an execution mode map. [Figure 6] This is a schematic diagram of the drive mechanism of a modified example. [Modes for carrying out the invention]

[0014] Embodiments for implementing this disclosure will be described with reference to the drawings. Figure 1 is a schematic diagram showing a drive unit 10 according to an embodiment of this disclosure. Figure 2 is a schematic configuration diagram showing the general configuration of the drive unit 10. As shown in Figures 1 and 2, the drive unit 10 of the embodiment includes a battery 12 as an energy storage device, a motor 18, a first inverter unit 22, a second inverter unit 28, a changeover switch 30, and an electronic control unit (hereinafter referred to as "ECU") 50 as a control device. The drive unit 10 is mounted on electric vehicles, hybrid vehicles, fuel cell vehicles, etc.

[0015] The battery 12 is configured as, for example, a lithium-ion secondary battery or a nickel-metal hydride secondary battery and is connected to the power line 20 (positive electrode line 20p and negative electrode line 20n). The motor 18 is configured as a three-phase AC motor and comprises a rotor with permanent magnets embedded in the rotor core and a stator with three-phase (U-phase, V-phase, W-phase) coils (open windings) wound around the stator core. The rotor is connected to a drive shaft which is linked to the drive wheel via a differential gear.

[0016] The first inverter section 22 is connected to the power line 20. The first inverter section 22 includes a T-type three-level inverter. Specifically, it includes six transistors T11 to T16, six diodes D11 to D16 connected in parallel to the six transistors T11 to T16 respectively, two capacitors 23, 24, three-phase (U-phase, V-phase, W-phase) intermediate potential lines 25u, 25v, 25w, and three-phase intermediate potential switches 26u, 26v, 26w.

[0017] For the transistors T11 to T16, for example, MOSFETs, IGBTs, etc. are used respectively. The transistors T11 to T16 are arranged in pairs of two so that they become the source side and the sink side with respect to the positive electrode side line 20p and the negative electrode side line 20n. The connection points of the transistors T11, T14, the connection points of the transistors T12, T15, and the connection points of the transistors T13, T16 are respectively connected to one end side of the U-phase, V-phase, and W-phase coils of the motor 18. Hereinafter, the transistors T11 to T13 may be referred to as the "first upper arm", and the transistors T14 to T16 may be referred to as the "first lower arm".

[0018] The capacitors 23, 24 are connected in series with each other in this order with respect to the positive electrode side line 20p and the negative electrode side line 20n. The capacitors 23, 24 are of the same specification as each other. The three-phase intermediate potential lines 25u, 25v, 25w connect the connection points of the transistors T11, 14, the connection points of the transistors T12, T15, the connection points of the transistors T13, T16, and the connection points of the capacitors 23, 24 respectively. The three-phase intermediate potential switches 26u, 26v, 26w are respectively provided on the three-phase intermediate potential lines 25u, 25v, 25w. For the three-phase intermediate potential switches 26u, 26v, 26w, for example, semiconductor switches, specifically, wide-bandgap semiconductor switches using gallium nitride (GaN), silicon carbide (SiC), etc. are used. The intermediate potential switch 26u may be configured, for example, by using two sets of a transistor and a diode connected in parallel to the transistor and connecting them in series so that the diodes face each other in opposite directions. The same applies to the intermediate potential switches 26v, 26w.

[0019] The second inverter section 28 is connected to the power line 20 on the side opposite to the battery 12 with respect to the first inverter section 22. The second inverter section 28 includes a two-level inverter, specifically, six transistors T21 to T26, six diodes D21 to D26 respectively connected in parallel to the six transistors T21 to T26, and a capacitor 29.

[0020] For the transistors T21 to T26, for example, MOSFETs, IGBTs, etc. are used respectively. The transistors T21 to T26 are arranged in pairs of two so as to be on the source side and the sink side with respect to the positive electrode side line 20p and the negative electrode side line 20n. The connection points of the transistors T21, T24, the connection points of the transistors T22, T25, and the connection points of the transistors T23, T26 are respectively connected to the other ends of the U-phase, V-phase, and W-phase coils of the motor 18. Hereinafter, the transistors T21 to T23 may be referred to as the "second upper arm", and the transistors T24 to T26 may be referred to as the "second lower arm". The capacitor 29 is connected to the positive electrode side line 20p and the negative electrode side line 20n.

[0021] The switching switch 30 includes a positive electrode side switch 30p and a negative electrode side switch 30n. The positive electrode side switch 30p is provided between the first and second inverter sections 22, 28 of the positive electrode side line 20p. The negative electrode side switch 30n is provided between the first and second inverter sections 22, 28 of the negative electrode side line 20n. For the positive electrode side switch 30p and the negative electrode side switch 30n, for example, semiconductor switches, etc. are used respectively. The positive electrode side switch 30p may be configured, for example, by using two sets of a transistor and a diode connected in parallel thereto and connected in series so that the diodes are in opposite directions to each other. The same applies to the negative electrode side switch 30n.

[0022] The ECU50 is a microcomputer equipped with a CPU, ROM, RAM, flash memory, input / output ports, and communication ports, as well as various drive circuits and various logic ICs. Signals from various sensors are input to the ECU50. For example, the ECU50 receives the voltage Vb of battery 12 from voltage sensor 12v, the current Ib of battery 12 from current sensor 12i, and the temperature Tb of battery 12 from temperature sensor 12t. The ECU50 also receives the rotational position θm of the rotor of motor 18 from rotational position sensor 18a, and the phase currents Iu, Iv, and Iw of each phase of motor 18 from current sensors 18u, 18v, and 18w. The ECU50 also receives the voltage Vc1 of capacitor 23 from voltage sensor 23v, the voltage Vc2 of capacitor 24 from voltage sensor 24v, and the voltage Vc3 of capacitor 29 from voltage sensor 29v. The ECU 50 also receives the following inputs: an on / off signal from the power switch 60, the shift position SP which is the operating position of the shift lever 61 from the shift position sensor 62, the accelerator opening Acc which is the amount the accelerator pedal 63 is pressed from the accelerator pedal position sensor 64, the brake pedal position BP which is the amount the brake pedal 65 is pressed from the brake pedal position sensor 66, and the vehicle speed V from the vehicle speed sensor 67.

[0023] The ECU 50 outputs various control signals. For example, the ECU 50 outputs control signals to the first inverter section 22 (transistors T11 to T16 and the three-phase intermediate potential switches 26u, 26v, 26w), control signals to the second inverter section 28 (transistors T21 to T26), and control signals to the changeover switch 30 (positive side switch 30p and negative side switch 30n). The ECU 50 calculates the state of charge (SOC) of the battery 12 based on the integrated value of the current Ib of the battery 12, and calculates the electrical angle θe and rotational speed Nm of the motor 18 based on the rotational position θm of the rotor of the motor 18.

[0024] In the drive unit 10 of this embodiment, the ECU 50 first sets the required torque Td* required for driving based on the accelerator opening Acc and vehicle speed V, and sets the torque command Tm* for the motor 18 to drive with the set required torque Td*. Subsequently, based on the torque command Tm* and rotational speed Nm of the motor 18, it sets an execution mode from the 2-level H drive mode, 2-level Y drive mode, and 3-level Y drive mode, and executes the set execution mode. The 2-level H drive mode, 2-level Y drive mode, and 3-level Y drive mode will be described below, followed by a description of how to set the execution mode. Here, H drive means driving the motor 18 with the first and second inverter units 22 and 28, and Y drive means neutralizing the motor 18 on the side of the second inverter unit 28 and driving the motor 18 with the first inverter unit 22.

[0025] First, the 2-level H drive mode will be explained. Figure 3 is an explanatory diagram showing an example of the 2-level H drive mode. As shown in the figure, in the 2-level H drive mode, the positive side switch 30p and the negative side switch 30n are turned ON. As a result, the voltage Vb of the battery 12 is applied to the second inverter unit 28. In addition, the 3-phase intermediate potential switches 26u, 26v, and 26w of the first and second inverter units 22 and 28 are turned OFF, and the transistors T11~T16 and T21~T16 are switched and driven. In this way, the potential of one end and the other end of the coil of each phase of the motor 18 are switched at two levels (the potential of the positive side line 20p and the potential of the negative side line 20n). In Figure 3, this is labeled as "2-level drive".

[0026] Next, the 2-level Y drive mode will be explained. Figure 4 is an explanatory diagram showing an example of the 2-level Y drive mode. As shown in the figure, in the 2-level Y drive mode, the positive-side switch 30p and the negative-side switch 30n are set to the OFF state. As a result, the voltage Vb of the battery 12 is not applied to the second inverter unit 28. In addition, for the second inverter unit 28, the 3-phase second upper arm (transistors T21 to T23) is set to the ON state and the 3-phase second lower arm (transistors T24 to T26) is set to the OFF state. In this way, the second inverter unit 28 side is neutralized from the motor 18 side. Alternatively, the 3-phase second upper arm may be set to the OFF state and the 3-phase second lower arm may be set to the ON state. Furthermore, for the first inverter unit 22, the 3-phase intermediate potential switches 26u, 26v, and 26w are set to the OFF state and transistors T11 to T16 are switched on. In this way, the potential at one end of each phase coil of the motor 18 is switched at two levels (the potential of the positive electrode line 20p and the potential of the negative electrode line 20n).

[0027] Next, the 3-level Y drive mode will be explained. The 3-level Y drive mode differs from the 2-level Y drive mode, in that the 3-phase intermediate potential switches 26u, 26v, and 26w and transistors T11 to T16 are switched and driven by the first inverter unit 22, in that the 3-level Y drive mode switches and drives the 3-phase intermediate potential switches 26u, 26v, and 26w and transistors T11 to T16. Through this operation of the first inverter unit 22, the potential on one end of each phase coil of the motor 18 is switched at three levels (potential of the positive side line 20p, potential of the connection point of capacitors 23 and 24, and potential of the negative side line 20n).

[0028] As can be seen from Figure 3, in H drive (2-level H drive mode), the maximum applied voltage to each phase of the motor 18 is approximately equal to the battery voltage Vb. On the other hand, as can be seen from Figure 4, in Y drive (2-level Y drive mode or 3-level Y drive mode), the maximum applied voltage to each phase of the motor 18 is approximately equal to half the battery voltage Vb. Therefore, in H drive, the applied voltage to the motor 18 can be increased compared to Y drive. In other words, in Y drive, the applied voltage to the motor 18 is lower compared to H drive. This reduces the iron loss of the motor 18. Also, in Y drive (2-level Y drive mode or 3-level Y drive mode), one of the 3 phases of the second upper arm and the second lower arm of the second inverter unit 28 is turned ON and the other is turned OFF. This reduces the switching loss of the second inverter unit 28 compared to H drive (2-level H drive mode) where the second inverter unit 28 is switched on. Furthermore, in 3-level Y drive mode, the voltage at one end of each phase coil of the motor 18 is switched at three levels. This reduces the ripple current of the motor 18 and further reduces the iron loss of the motor 18 compared to 2-level H drive mode and 2-level Y drive mode, where the voltage at one end of each phase coil of the motor 18 is switched at two levels.

[0029] Next, the method for setting the execution mode will be explained. In this embodiment, the execution mode is set from a 2-level H drive mode, a 2-level Y drive mode, and a 3-level Y drive mode based on the torque command Tm* and rotational speed Nm of the motor 18 and the execution mode map. Figure 5 is an explanatory diagram showing an example of an execution mode map. The execution mode map is predetermined by experiments, analyses, etc., as the relationship between the torque command Tm* and rotational speed Nm of the motor 18 and the execution mode. As shown in the figure, the execution modes are determined in the order of 3-level Y drive mode, 2-level Y drive mode, and 2-level H drive mode, starting from the side where the torque command Tm* and rotational speed Nm are smallest. By setting the 3-level Y drive mode to the lowest rotational speed and low torque region among the 3-level Y drive mode, 2-level Y drive mode, and 2-level H drive mode, the ripple current of the motor 18 can be reduced in the low rotational speed and low torque region, and the iron loss of the motor 18 can be further reduced. Furthermore, the power capacity and voltage rating of the three-phase intermediate potential switches 26u, 26v, and 26w, which are switched and driven only in the 3-level Y drive mode, can be designed to be relatively low. Specifically, the power capacity and voltage rating of the three-phase intermediate potential switches 26u, 26v, and 26w can be designed to be lower than those of the transistors T11 to T16, which are switched and driven in all modes. As a result, the cost of the three-phase intermediate potential switches 26u, 26v, and 26w can be reduced.

[0030] In the drive unit 10 of the embodiment described above, the first inverter unit 22 is equipped with a T-type 3-level inverter. This allows for the execution of a 3-level Y drive mode in addition to the 2-level Y drive mode and the 2-level H drive mode. By executing the 3-level Y drive mode, the iron loss of the motor 18 can be further reduced.

[0031] Furthermore, in the drive device of this embodiment, the 3-level Y drive mode, 2-level Y drive mode, and 2-level H drive mode are executed in order from the lowest torque command Tm* and rotational speed Nm of the motor 18. This makes it possible to further reduce the iron loss of the motor 18 in the low rotational speed and low torque region. Moreover, the power capacity and withstand voltage of the 3-phase intermediate potential switches 26u, 26v, and 26w, which are switched and driven only in the 3-level Y drive mode, can be designed to be lower than the power capacity and withstand voltage of the transistors T11 to T16, which are switched and driven in all modes. As a result, the cost of the 3-phase intermediate potential switches 26u, 26v, and 26w can be reduced.

[0032] In the above-described embodiment, the 3-level Y drive mode, 2-level Y drive mode, and 2-level H drive mode are executed in order from the smallest torque command Tm* and rotational speed Nm of the motor 18, but the system is not limited to this. For example, the 2-level Y drive mode, 3-level Y drive mode, and 2-level H drive mode may be executed in order from the smallest torque command Tm* and rotational speed Nm of the motor 18. Alternatively, the 3-level Y drive mode and 2-level H drive mode may be executed in order from the smallest torque command Tm* and rotational speed Nm of the motor 18. Furthermore, the output torque Tm may be used instead of the torque command Tm* of the motor 18. The output torque Tm can be estimated, for example, by performing a coordinate transformation (3-phase to 2-phase transformation) on the phase currents Iu, Iv, Iw of each phase to the d-axis and q-axis currents Id, Iq using the electrical angle θe.

[0033] In the embodiment described above, the power capacity and voltage rating of the three-phase intermediate potential switches 26u, 26v, and 26w were designed to be lower than those of the transistors T11 to T16, but this is not limited to this. For example, the power capacity and voltage rating of the three-phase intermediate potential switches 26u, 26v, and 26w may be designed to be approximately the same as those of the transistors T11 to T16.

[0034] In the embodiment described above, the first inverter unit 22 is provided with a T-type 3-level inverter, but any 3-level inverter will suffice; for example, a neutral point clamp type 3-level inverter may be provided.

[0035] In the embodiment described above, the changeover switch 30 is provided with a positive-side switch 30p and a negative-side switch 30n, but instead, it may be provided with only one of the positive-side switch 30p and the negative-side switch 30n.

[0036] In the embodiment described above, the drive unit 10 is equipped with a changeover switch 30 (positive-side switch 30p and negative-side switch 30n). However, instead, as shown in the modified drive unit 110 in Figure 6, a changeover switch 134 may be provided between the motor 18 and the second inverter unit 28. The changeover switch 134 has multiple switches and is configured to switch between a neutralized state in which the motor 18 is neutralized on the side of the second inverter unit 28 and a non-neutralized state in which the motor 18 is not neutralized on the side of the second inverter unit 28. The changeover switch 134 is controlled by the ECU 50. In this case, for Y drive, the motor 18 is driven by the first inverter unit 22 with the changeover switch 134 in the neutralized state, and for H drive, the motor 18 is driven by the first and second inverter units 22 and 28 with the changeover switch 134 in the non-neutralized state.

[0037] The correspondence between the main elements of the embodiment and the main elements of the invention described in the section on the main elements of the embodiment and the means for solving the problem will be explained. In the embodiment, the battery 12 corresponds to the "energy storage device", the motor 18 corresponds to the "motor", the first inverter unit 22 corresponds to the "first inverter unit", the second inverter unit 28 corresponds to the "second inverter unit", and the changeover switch 30 corresponds to the "changeover switch". Also, the capacitors 23 and 24 correspond to the "first and second capacitors", the transistors T11 to T13 and T14 to T16 correspond to the "upper and lower arms of the three phases", the three-phase intermediate potential lines 25u, 25v, and 25w correspond to the "three-phase intermediate potential lines", and the three-phase intermediate potential switches 26u, 26v, and 26w correspond to the "three-phase intermediate potential switches".

[0038] Furthermore, the correspondence between the main elements of the embodiment and the main elements of the invention described in the section on means for solving the problem is merely an example to specifically explain the form in which the embodiment implements the invention described in the section on means for solving the problem, and does not limit the elements of the invention described in the section on means for solving the problem. In other words, the interpretation of the invention described in the section on means for solving the problem should be based on the description in that section, and the embodiment is merely one specific example of the invention described in the section on means for solving the problem.

[0039] The above describes the forms for implementing this disclosure using embodiments, but this disclosure is not limited in any way to these embodiments, and can of course be implemented in various forms without departing from the gist of this disclosure. [Industrial applicability]

[0040] This disclosure can be used in industries such as the manufacturing of drive systems. [Explanation of symbols]

[0041] 10,110 Drive unit, 12 Battery, 12i,18u,18v,18w Current sensor, 12t Temperature sensor, 12v,23v,24v,29v Voltage sensor, 18 Motor, 18a Rotation position sensor, 20 Power line, 20n Negative side line, 20p Positive side line, 22 First inverter section, 23,24,29 Capacitors, 25u,25v,25w Intermediate potential line, 26u,26v,26w Intermediate potential switch, 28 Second inverter section, 30,130 Changeover switch, 30n Negative side switch, 30p Positive side switch, 50 ECU, 60 Power switch, 61 Shift lever, 62 Shift position sensor, 63 Accelerator pedal, 64 Accelerator pedal position sensor, 65 Brake pedal, 66 Brake pedal position sensor, 67 Vehicle speed sensor, D11~D16, D21~D26 diodes, T11~T16, T21~T26 transistors.

Claims

1. Energy storage device, A motor having a three-phase open winding, The first inverter unit is connected to the power line to which the energy storage device is connected and is connected to one end of the three-phase open winding, A second inverter section is connected to the power line on the opposite side of the first inverter from the energy storage device and is connected to the other end of the three-phase open winding, A changeover switch is provided between the first and second inverter sections for switching between H drive, which drives the motor using the first and second inverter sections, and Y drive, which neutralizes the motor on the side of the second inverter section and drives the motor using the first inverter section. A drive device equipped with, The first inverter unit has a three-level inverter. Drive unit.

2. A drive device according to claim 1, A control device that, in order from the side with the smallest torque and rotational speed of the motor, executes: a 3-level Y drive mode in which the first inverter unit switches the potential of one end of the three-phase open windings at three levels in the Y drive mode; a 2-level Y drive mode in which the first inverter unit switches the potential of one end of the three-phase open windings at two levels in the Y drive mode; and a 2-level H drive mode in which the first and second inverter units switch the potential of one end and the other end of the three-phase open windings at two levels in the H drive mode. A drive system further equipped with the following.

3. The drive device according to claim 2, The first inverter unit comprises three phase upper and lower arms connected in series with respect to the positive and negative power lines of the power lines for each phase, with their connection points connected to one end of the corresponding open winding; first and second capacitors connected in series with respect to the positive and negative power lines; three phase intermediate potential lines connecting the connection points of the upper and lower arms of the three phases to the connection points of the first and second capacitors, respectively; and three phase intermediate potential switches provided on the three phase intermediate potential lines. The intermediate potential switch has lower power capacity and lower voltage resistance compared to the upper arm and the lower arm. Drive unit.

4. A drive device according to any one of claims 1 to 3, The aforementioned changeover switch is provided between the first and second inverter sections of the power line. Drive unit.

5. A drive device according to any one of claims 1 to 3, The aforementioned changeover switch is provided between the three-phase open winding and the second inverter section. Drive unit.

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