Motor control device

Abstract

This motor control device controls a multi-phase AC motor provided with a multi-phase coil unit (70) having a plurality of multi-phase coil parts (71) each including coil parts (72) of different phases electrically connected to each other. The motor control device comprises: a current path unit (20) that forms a current path between a power supply device (11) and the multi-phase AC motor; and an AC conversion unit (50) that has a plurality of AC conversion parts (51) capable of converting a DC current of the power supply device into an AC current. The AC conversion unit is configured to be able to electrically separate one coil part from another coil part of the same phase by switching off one AC conversion switching element.

Description

Motor control device Cross-reference to related applications

[0001] This application is based on Japanese Patent Application No. 2024-201078 filed in Japan on November 18, 2024, and the contents of the base application are incorporated herein by reference in their entirety.

[0002] The disclosure in this specification relates to a motor control device.

[0003] Patent Document 1 discloses a drive device including a motor device and an inverter device. The description of the prior art document is incorporated herein by reference as an explanation of the technical elements in this specification.

[0004] Japanese Patent Application Laid-Open No. 2024-34954

[0005] In the configuration of the prior art document, in each of the U-phase, V-phase, and W-phase in the upper arm of the inverter device, a plurality of switching elements are connected in parallel. Similarly, in the lower arm, in each of the U-phase, V-phase, and W-phase, a plurality of switching elements are connected in parallel. In this configuration, when performing power conversion, it is necessary to control a plurality of switching elements connected in parallel simultaneously. For example, when flowing a current through the U-phase coil, it is necessary to turn on the three switching elements corresponding to the U-phase of the upper arm. Assume a case where only one of the three switching elements connected in parallel is in the on state. In this case, a current three times the current flowing in the on state of all three flows through one switching element. Even if the control timing of the switching element deviates slightly, a state where only one of the three switching elements is on will occur. Such an unintended large current is one of the causes of causing a failure in the switching element. From the above viewpoints or other viewpoints not mentioned, further improvement is required for the motor control device.

[0006] One object to be disclosed is to provide a motor control device capable of driving a motor stably.

[0007] The above objectives are achieved by combinations of features described in the independent claims. Subordinate claims further specify advantageous examples. The reference numerals in parentheses in the claims indicate correspondences with specific embodiments described later in the embodiments, and do not limit the disclosed technical scope. The objectives, features, and effects disclosed in this specification will become clearer with reference to the subsequent detailed description and the accompanying drawings.

[0008] One disclosure for achieving the above objective is a motor control device for controlling a multiphase AC motor having a multiphase coil unit having a plurality of multiphase coil sections in which coil sections of different phases are electrically connected to each other, comprising a current path section that forms a current path between a power supply and a multiphase AC motor, and an AC conversion unit having a plurality of AC conversion sections capable of converting the DC current of the power supply into AC current, wherein the AC conversion unit is configured to electrically isolate one coil section from other coil sections that are in the same phase by switching off one AC conversion switching element.

[0009] The disclosed motor control device includes an AC conversion unit configured to separate one coil section from another coil section in the same phase to an electrically independent state by switching off one AC conversion switching element, thereby separating them from a state where they are electrically connected in parallel. Therefore, compared to configurations where multiple AC conversion switching elements must be switched off to electrically separate coil sections in the same phase, or configurations where coil sections in the same phase cannot be electrically separated at all, this device allows for quicker electrical separation of coil sections in the same phase. Consequently, in situations where a malfunction occurs in a switching element or coil section and it is necessary to electrically separate coil sections in the same phase, the coil sections can be quickly separated to an electrically independent state. Thus, a motor control device capable of stably driving a motor can be provided.

[0010] This is a diagram showing the configuration of the drive system. This is a diagram showing the configuration of the three-phase coil unit. This is a configuration diagram showing the circuit configuration of the drive system. This is a configuration diagram showing the circuit configuration of the DC step-down section. This is a timing chart for explaining step-down control. This is a configuration showing the circuit configuration of the AC conversion section and the three-phase coil section. This is a timing chart for explaining AC conversion control. This is a diagram showing the configuration of the drive system in the second embodiment.

[0011] Multiple embodiments will be described with reference to the drawings. In multiple embodiments, functionally and / or structurally corresponding and / or related parts may be given the same reference numeral, or reference numerals that differ by hundreds or more digits. For corresponding and / or related parts, refer to the description of other embodiments.

[0012] <First Embodiment> In Figure 1, the drive system 100 includes a power supply unit 11, a current path unit 20, a DC step-down unit 30, an AC conversion unit 50, and a three-phase AC motor 80. In this figure, the DC step-down unit 31 is shown as CNV, the AC conversion unit 51 as INV, and the three-phase coil unit 71 as MOT.

[0013] The drive system 100 can be used, for example, in an electrically powered aircraft to provide the driving force to rotate the aircraft's propellers. However, the drive system 100 may also be mounted on something other than the aircraft to provide driving force. In particular, manned aircraft need to maintain power as much as possible, and a motor control device 60 capable of stably driving the motor is required.

[0014] The current path section 20, the DC step-down unit 30, and the AC conversion unit 50 constitute the motor control device 60. The motor control device 60 is a device for driving and controlling a three-phase AC motor 80 by converting the power output from the power supply unit 11. However, the motor control device 60 may also be used to drive and control a multi-phase AC motor by converting the AC current to a multi-phase other than three-phase.

[0015] The power supply unit 11 is a DC power supply that outputs a DC voltage. The drive system 100 is equipped with two power supply units 11. The current path section 20 forms a current path that electrically connects the power supply unit 11 and the three-phase AC motor 80. The current path section 20 is equipped with a current path that electrically connects the power supply unit 11 and the DC step-down unit 30. The current path section 20 is equipped with a current path that electrically connects the DC step-down unit 30 and the AC conversion unit 50. The current path section 20 is equipped with a current path that electrically connects the AC conversion unit 50 and the three-phase AC motor 80.

[0016] The DC step-down unit 30 is a device that transforms and reduces the voltage output from the power supply unit 11, i.e., steps down the voltage. The DC step-down unit 30 steps down the voltage so that the voltage and current in the AC conversion switching element 53 (described later) are below the rated voltage and below the rated current. At this time, the DC step-down unit 30 has the role of increasing or decreasing the output current according to the output required by the three-phase AC motor 80 (described later). The DC step-down unit 30 is equipped with eight DC step-down sections 31. The DC step-down unit 30 provides an example of a DC transformer unit. The DC step-down section 31 provides an example of a DC transformer unit.

[0017] The AC conversion unit 50 is a device that converts the DC current stepped down by the DC step-down unit 30 into AC current. In the case of a three-phase motor, the AC conversion unit 50 converts the DC current into three phases of AC current: U-phase, V-phase, and W-phase, with their electrical angles shifted by 120 degrees from each other. The AC conversion unit 50 is equipped with eight AC conversion units 51.

[0018] The three-phase AC motor 80 is a motor driven using three phases of alternating current: U-phase, V-phase, and W-phase, with electrical angles shifted by 120 degrees from each other. The three-phase AC motor 80 includes a three-phase coil unit 70, which has eight three-phase coil sections 71. However, a multi-phase AC motor other than a three-phase motor may be used instead of the three-phase AC motor 80. The three-phase AC motor 80 provides an example of a multi-phase AC motor. The three-phase coil unit 70 provides an example of a multi-phase coil unit. The three-phase coil section 71 provides an example of a multi-phase coil section. The multi-phase coil unit has multiple multi-phase coil sections.

[0019] In Figure 2, the three-phase coil unit 70 has a stator composed of 48 coil elements 75 arranged in a ring. Each coil element 75 is an element formed by winding a wire around a stator core. The three-phase coil unit 70 can be said to be a motor with 24 slots, considering two adjacent reactor elements as one slot. Although not shown in the figure, the rotor of this three-phase motor has 40 magnetic poles, and the so-called slot / pole combination of the motor is 12 slots / 10 poles. Therefore, the three-phase coil unit 70 can more easily secure a larger torque and reduce torque pulsation compared to motors with a slot / pole combination other than 12 slots / 10 poles.

[0020] Adjacent coil elements 75 form a coil section 72. However, even if two coil elements 75 are adjacent to each other, they cannot be connected in parallel if they are in different phases. Here, "in phase" means that the electrical phases are the same, and "different phases" means that the electrical phases are different. Adjacent U-phase coil elements 75 form a U-phase coil section 72U. Adjacent V-phase coil elements 75 form a V-phase coil section 72V. Adjacent W-phase coil elements 75 form a W-phase coil section 72W. The coil elements 75 that make up each coil section 72 have different electrical phases but are connected in series, so they can form an in-phase coil section 72.

[0021] Six adjacent coil elements 75 constitute a single three-phase coil section 71. More specifically, the three-phase coil section 71 is formed by combining one U-phase coil section 72U, one V-phase coil section 72V, and one W-phase coil section 72W. In the three-phase coil section 71, the W-phase coil section 72W is located between the U-phase coil section 72U and the V-phase coil section 72V.

[0022] The three-phase coil unit 70 comprises eight three-phase coil sections 71, from the first three-phase coil section 71A to the eighth three-phase coil section 71H. In the three-phase coil unit 70, the first three-phase coil section 71A is adjacent to the eighth three-phase coil section 71H and the second three-phase coil section 71B. The third three-phase coil section 71C is adjacent to the second three-phase coil section 71B and the fourth three-phase coil section 71D. The fifth three-phase coil section 71E is adjacent to the fourth three-phase coil section 71D and the sixth three-phase coil section 71F. The seventh three-phase coil section 71G is adjacent to the sixth three-phase coil section 71F and the eighth three-phase coil section 71H.

[0023] In Figure 1, the drive system 100 comprises eight electrical systems 15. Each of the eight electrical systems 15 includes one DC step-down unit 31, one AC converter unit 51, and one three-phase coil unit 71. The drive system 100 drives one three-phase AC motor 80 by controlling each of the eight electrical systems 15.

[0024] The first electrical system 15A is configured by electrically connecting the first DC step-down unit 31A, the first AC converter 51A, and the first three-phase coil unit 71A. The second electrical system 15B is configured by electrically connecting the second DC step-down unit 31B, the second AC converter 51B, and the second three-phase coil unit 71B. The third electrical system 15C is configured by electrically connecting the third DC step-down unit 31C, the third AC converter 51C, and the third three-phase coil unit 71C. The fourth electrical system 15D is configured by electrically connecting the fourth DC step-down unit 31D, the fourth AC converter 51D, and the fourth three-phase coil unit 71D. The four electrical systems 15 from the first electrical system 15A to the fourth electrical system 15D receive power from the same power supply unit 11.

[0025] The fifth electrical system 15E is configured by electrically connecting the fifth DC step-down unit 31E, the fifth AC converter unit 51E, and the fifth three-phase coil unit 71E. The sixth electrical system 15F is configured by electrically connecting the sixth DC step-down unit 31F, the sixth AC converter unit 51F, and the sixth three-phase coil unit 71F. The seventh electrical system 15G is configured by electrically connecting the seventh DC step-down unit 31G, the seventh AC converter unit 51G, and the seventh three-phase coil unit 71G. The eighth electrical system 15H is configured by electrically connecting the eighth DC step-down unit 31H, the eighth AC converter unit 51H, and the eighth three-phase coil unit 71H. The four electrical systems 15 from the fifth electrical system 15E to the eighth electrical system 15H receive power from the same power supply unit 11.

[0026] The four electrical systems 15 from the first electrical system 15A to the fourth electrical system 15D and the four electrical systems 15 from the fifth electrical system 15E to the eighth electrical system 15H are electrically isolated. For example, the first electrical system 15A and the fifth electrical system 15E are electrically isolated and are not electrically connected to each other.

[0027] Multiple power supply units 11 use the same power source. In other words, the multiple power supply units 11 output the same magnitude of DC voltage to each other. Furthermore, the control contents of the DC step-down unit 31 and the AC conversion unit 51 are matched for each electrical system 15. As a result, even though the electrical systems 15 are electrically isolated, it is possible to control them so that the output of the three-phase coil unit 71 matches.

[0028] The current path section 20 includes a DC branching section 23 that branches the current path to different electrical systems 15. The DC branching section 23 is provided in the electrical path between the power supply unit 11 and the DC step-down unit 30. The DC branching section 23 is provided in both the high-voltage current path and the low-voltage current path.

[0029] The DC branching section 23 includes a first DC branching section 23A that branches the current path to the first electrical system 15A and the other electrical systems 15. The DC branching section 23 includes a second DC branching section 23B that branches the current path to the second electrical system 15B and the other electrical systems 15. The DC branching section 23 includes a third DC branching section 23C that branches the current path to the third electrical system 15C and the other electrical systems 15. The four electrical systems 15, from the first electrical system 15A to the fourth electrical system 15D, are branched by the three DC branching sections 23 and are electrically connected to each other.

[0030] The DC branching section 23 includes a fifth DC branching section 23E that branches the current path to the fifth electrical system 15E and the other electrical systems 15. The DC branching section 23 includes a sixth DC branching section 23F that branches the current path to the sixth electrical system 15F and the other electrical systems 15. The DC branching section 23 includes a seventh DC branching section 23G that branches the current path to the seventh electrical system 15G and the other electrical systems 15. The four electrical systems 15 from the fifth electrical system 15E to the eighth electrical system 15H are branched by the three DC branching sections 23 and are electrically connected to each other.

[0031] The drive system 100 comprises a DC section housing 41 and an AC section housing 91. The DC section housing 41 houses a DC step-down unit 30 inside. The DC section housing 41 is provided with a power input terminal 48 and a DC output terminal 49. The power input terminal 48 is a terminal for taking in the current output from the power supply unit 11 into the DC section housing 41. The power input terminal 48 comprises a high-voltage side power input terminal 48H, which is the high-voltage side terminal, and a low-voltage side power input terminal 48L, which is the low-voltage side terminal. Since the drive system 100 is equipped with two power supply units 11, there are two power input terminals 48 in the DC section housing 41.

[0032] The DC output terminal 49 is a terminal for taking out the current stepped down by the DC step-down unit 30 to the outside of the DC unit housing 41. The DC output terminal 49 includes a high-voltage side DC output terminal 49H, which is the high-voltage side terminal, and a low-voltage side DC output terminal 49L, which is the low-voltage side terminal. There are as many DC output terminals 49 as there are electrical systems 15. In other words, there are eight DC output terminals 49 in the DC unit housing 41, corresponding to the eight electrical systems 15 from the first electrical system 15A to the eighth electrical system 15H.

[0033] The AC unit housing 91 houses the AC conversion unit 50 and the three-phase coil unit 70 inside. The rotating shaft of the three-phase AC motor 80 passes through the AC unit housing 91, and components to be driven, such as a propeller, can be attached to the rotating shaft of the three-phase AC motor 80.

[0034] The AC section housing 91 is equipped with DC input terminals 98. The DC input terminals 98 are terminals for taking in the DC current output from the DC step-down unit 30 into the AC section housing 91. The DC input terminals 98 include a high-voltage side DC input terminal 98H and a low-voltage side DC input terminal 98L. There are as many DC input terminals 98 as there are electrical systems 15. In other words, there are eight DC input terminals 98 in the AC section housing 91, corresponding to the eight electrical systems 15 from the first electrical system 15A to the eighth electrical system 15H.

[0035] The detailed circuit configuration of the drive system 100 is described below. In Figure 3, the DC step-down unit 31 comprises a step-down upper arm 32H, a step-down lower arm 32L, a reactor unit 34, and a capacitor 37. The step-down upper arm 32H is equipped with four step-down switching elements 33. The step-down lower arm 32L is equipped with four step-down switching elements 33.

[0036] The step-down switching element 33 is, for example, a transistor such as a MOSFET with a freewheeling diode connected in antiparallel. The freewheeling diode may be a parasitic diode or a diode provided separately from the parasitic diode.

[0037] The reactor unit 34 is equipped with four reactor elements 35. The reactor unit 34 and the capacitor 37 smooth the voltage output by switching the step-down upper arm 32H and step-down lower arm 32L on and off, thereby stepping down the output voltage.

[0038] The DC step-down unit 31 includes a current sensor 38 and a surge freewheeling switching element 39. The current sensor 38 is a sensor that measures the magnitude of the current stepped down by the DC step-down unit 31. The surge freewheeling switching element 39 is an element that freewheels the surge current generated by the switching of the AC conversion control switch by the AC conversion unit 51. The surge freewheeling switching element 39 is an element in which a freewheeling diode is connected in antiparallel to a MOSFET, similar to the step-down switching element 33.

[0039] The step-down control of the DC step-down unit 31 will be described below. In Figure 4, the step-down upper arm 32H is equipped with four step-down switching elements 33, from the first step-down upper arm switch 33H1 to the fourth step-down upper arm switch 33H4. On the other hand, the step-down lower arm 32L is equipped with four step-down switching elements 33, from the first step-down lower arm switch 33L1 to the fourth step-down lower arm switch 33L4.

[0040] The reactor unit 34 is equipped with four reactor elements 35, from the first reactor element 35R1 to the fourth reactor element 35R4.

[0041] The drain terminal of the step-down switching element 33 forming the step-down upper arm 32H is electrically connected to the high-potential current path of the power supply 11. On the other hand, the source terminal of the step-down switching element 33 forming the step-down lower arm 32L is electrically connected to the low-potential current path of the power supply 11.

[0042] The source terminal of the first step-down upper-arm switch 33H1 is electrically connected to the drain terminal of the first step-down lower-arm switch 33L1. The source terminal of the first step-down upper-arm switch 33H1 and the drain terminal of the first step-down lower-arm switch 33L1 are connected to the first reactor element 35R1. The current path in which the first reactor element 35R1 is provided is the first step-down current path section L1.

[0043] The source terminal of the second step-down upper-arm switch 33H2 is electrically connected to the drain terminal of the second step-down lower-arm switch 33L2. The source terminal of the second step-down upper-arm switch 33H2 and the drain terminal of the second step-down lower-arm switch 33L2 are connected to the second reactor element 35R2. The current path in which the second reactor element 35R2 is provided is the second step-down current path section L2.

[0044] The source terminal of the third step-down upper-arm switch 33H3 is electrically connected to the drain terminal of the third step-down lower-arm switch 33L3. The source terminal of the third step-down upper-arm switch 33H3 and the drain terminal of the third step-down lower-arm switch 33L3 are connected to the third reactor element 35R3. The current path in which the third reactor element 35R3 is provided is the third step-down current path section L3.

[0045] The source terminal of the fourth step-down upper-arm switch 33H4 is electrically connected to the drain terminal of the fourth step-down lower-arm switch 33L4. The source terminal of the fourth step-down upper-arm switch 33H4 and the drain terminal of the fourth step-down lower-arm switch 33L4 are connected to the fourth reactor element 35R4. The current path in which the fourth reactor element 35R4 is provided is the fourth step-down current path section L4.

[0046] In FIG. 5, the on / off states of the step-down switching elements 33 at each timing and the magnitude of the flowing current are illustrated. In this figure, the first step-down upper-arm switch 33H1 is illustrated as SW_H1, and the first step-down lower-arm switch 33L1 is illustrated as SW_L1. Also, the second step-down upper-arm switch 33H2 is illustrated as SW_H, and the second step-down lower-arm switch 33L2 is illustrated as SW_L2. Similarly, the third step-down upper-arm switch 33H3 is illustrated as SW_H3, and the third step-down lower-arm switch 33L3 is illustrated as SW_L3. And the fourth step-down upper-arm switch 33H4 is illustrated as SW_H4, and the fourth step-down lower-arm switch 33L4 is illustrated as SW_L4.

[0047] At timing T1, which is the timing after starting the step-down control, the first step-down upper-arm switch 33H1 and the fourth step-down lower-arm switch 33L4 are switched from off to on. The other step-down switching elements 33 are off. As a result, the current IL1 flowing through the first step-down current path portion L1 gradually increases, and the current IL4 flowing through the fourth step-down current path portion L4 gradually decreases.

[0048] At the next timing T2, the first step-down upper-arm switch 33H1 and the fourth step-down lower-arm switch 33L4 are switched from on to off. Further, the second step-down upper-arm switch 33H2 and the first step-down lower-arm switch 33L1 are switched from off to on. As a result, the current IL2 flowing through the second step-down current path portion L2 gradually increases, and the current IL1 flowing through the first step-down current path portion L1 gradually decreases.

[0049] At the next timing T3, the second step-down upper-arm switch 33H2 and the first step-down lower-arm switch 33L1 are switched from on to off. Further, the third step-down upper-arm switch 33H3 and the second step-down lower-arm switch 33L2 are switched from off to on. As a result, the current IL3 flowing through the third step-down current path portion L3 gradually increases, and the current IL2 flowing through the second step-down current path portion L2 gradually decreases.

[0050] At the next timing T4, the third step-down upper arm switch 33H3 and the second step-down lower arm switch 33L2 are switched from on to off. Furthermore, the fourth step-down upper arm switch 33H4 and the third step-down lower arm switch 33L3 are switched from off to on. As a result, the current IL4 flowing through the fourth step-down current path L4 gradually increases, and the current IL3 flowing through the third step-down current path L3 gradually decreases.

[0051] At the next timing, T5, the fourth step-down upper arm switch 33H4 and the third step-down lower arm switch 33L3 are switched from on to off. Furthermore, the first step-down upper arm switch 33H1 and the fourth step-down lower arm switch 33L4 are switched from off to on. This is the same state as the on / off state of the step-down switching element 33 at timing T1. From T5 onward, the switching of the switches from T2 to T5 is repeated.

[0052] The four buck switching elements 33 forming the buck upper arm 32H have an ON time of 25% of one cycle. That is, the duty cycle of the four buck switching elements 33 forming the buck upper arm 32H is 25%.

[0053] The current IL stepped down by the DC step-down unit 31 is the sum of the current IL1 flowing through the first step-down current path L1, the current IL2 flowing through the second step-down current path L2, the current IL3 flowing through the third step-down current path L3, and the current IL4 flowing through the fourth step-down current path L4. Therefore, the current IL stepped down by the DC step-down unit 31 can be controlled as a stable current without fluctuations over time. The current IL can be controlled by the duty cycle of the step-down switching element 33, and the output current can be increased or decreased according to the output required by the three-phase AC motor 80. Therefore, the duty cycle of the step-down switching element 33 is not limited to 25%. If the duty cycle of the step-down switching element 33 is 25% or more, it becomes a stable current with suppressed fluctuations over time compared to when it is less than 25%. Therefore, when using four buck switching elements 33 each on the buck upper arm 32H and the buck lower arm 32L, for a total of eight buck switching elements 33, it is preferable to set the duty cycle of the buck switching elements 33 to 25% or more. If, for example, n buck switching elements 33 are used on each of the upper and lower arms, it is preferable to set the duty cycle of the buck switching elements 33 to 1 / n or more.

[0054] Sufficient time is ensured between switching the step-down switching element 33 on and off and switching it on and off again. That is, in the first step-down upper arm switch 33H1, when switching from off to on at timing T5, the current IL1 flowing through the first step-down current path L1 is zero. Here, switching elements using semiconductors such as MOSFETs generate switching losses when switching on and off. These switching losses tend to increase as the current flowing during on-off switching increases. In other words, the state where the current is zero at the time of on-off switching minimizes switching losses. Therefore, the losses that occur when switching the first step-down upper arm switch 33H1 from off to on can be reduced. In other words, zero-current switching can be achieved when switching the first step-down upper arm switch 33H1 from off to on.

[0055] Furthermore, in the first step-down arm switch 33L1, when switching from on to off at timing T3, the current IL1 flowing through the first step-down current path L1 is zero. Therefore, the losses that occur when switching the first step-down arm switch 33L1 from on to off can be reduced. In other words, zero-current switching can be achieved when switching the first step-down arm switch 33L1 from on to off.

[0056] The other buck switching elements 33 of the buck upper arm 32H are the same as those of the first buck upper arm switch 33H1. That is, zero current switching is achieved when switching from off to on in the buck upper arm 32H. Similarly, the other buck switching elements 33 of the buck lower arm 32L are the same as those of the first buck lower arm switch 33L1. That is, zero current switching is achieved when switching from on to off in the other buck switching elements 33 of the buck lower arm 32L.

[0057] The DC step-down unit 30 performs the same step-down control for each electrical system 15. That is, the step-down switching elements 33 are controlled in the same way and at the same timing from the first DC step-down unit 31A to the eighth DC step-down unit 31H. This makes it possible to supply a stable DC current to each of the eight AC conversion units 51 from the first AC conversion unit 51A to the eighth AC conversion unit 51H.

[0058] In Figure 3, the AC conversion unit 51 comprises an upper arm 52H and a lower arm 52L. The upper arm 52H is equipped with a total of three AC conversion switching elements 53, one for each of the three phases: U-phase, V-phase, and W-phase. The lower arm 52L is also equipped with a total of three AC conversion switching elements 53, one for each of the three phases: U-phase, V-phase, and W-phase. The AC conversion switching elements 53 are elements in which a diode for freewheeling is connected in antiparallel to a MOSFET, similar to the step-down switching elements 33.

[0059] In the upper arm 52H, the drain side of the AC conversion switching element 53 is electrically connected to the high-potential current path. In the lower arm 52L, the source side of the AC conversion switching element 53 is electrically connected to the low-potential current path.

[0060] The three-phase coil section 71 has a total of three coil sections 72, one for each of the three phases. Each coil section 72 is composed of two coil elements 75 arranged in series. The coil section 72 corresponding to the U phase is the U-phase coil section 72U. The coil section 72 corresponding to the V phase is the V-phase coil section 72V. The coil section 72 corresponding to the W phase is the W-phase coil section 72W. The U-phase coil section 72U, the V-phase coil section 72V, and the W-phase coil section 72W are all connected to the neutral point 77. In other words, the U-phase coil section 72U, the V-phase coil section 72V, and the W-phase coil section 72W are connected in a star configuration.

[0061] The coil sections 72 that are in phase are not directly connected in parallel, but are connected in parallel via different AC conversion sections 51 and different neutral points 77. That is, the eight U-phase coil sections 72U are each connected to eight AC conversion sections 51A to 51H and eight neutral points 77A to 77H. The eight V-phase coil sections 72V are each connected to eight AC conversion sections 51A to 51H and eight neutral points 77A to 77H. The eight W-phase coil sections 72W are each connected to eight AC conversion sections 51A to 51H and eight neutral points 77A to 77H. Furthermore, the neutral points 77A to 77H of the different electrical systems 15A to 15H are not directly electrically connected to each other, but can be electrically connected via the AC conversion section 51 and the DC step-down section 31. In other words, by switching the AC conversion switching element 53 or the step-down switching element 33 on and off, the neutral points 77 of different electrical systems 15 can be electrically isolated. Similarly, by switching the AC conversion switching element 53 on and off, the coil sections 72 of different phases can be electrically isolated.

[0062] The AC conversion control of the AC conversion unit 51 will be described below. In Figure 6, the upper arm 52H is equipped with a U-phase upper arm switch 53UH, a V-phase upper arm switch 53VH, and a W-phase upper arm switch 53WH. The lower arm 52L is equipped with a U-phase lower arm switch 53UL, a V-phase lower arm switch 53VL, and a W-phase lower arm switch 53WL.

[0063] The source terminal of the U-phase upper arm switch 53UH and the drain terminal of the U-phase lower arm switch 53UL are electrically connected by the U-phase path section 25U. The U-phase path section 25U includes a U-phase branch section 26U. The U-phase path section 25U electrically connects the U-phase upper and lower arms and the U-phase coil section 72U via the U-phase branch section 26U. The U-phase path section 25U does not include any branch sections other than the U-phase branch section 26U. In other words, the U-phase path section 25U does not electrically connect the U-phase upper and lower arms to any components other than the U-phase coil section 72U.

[0064] The source terminal of the V-phase upper arm switch 53VH and the drain terminal of the V-phase lower arm switch 53VL are electrically connected by the V-phase path section 25V. The V-phase path section 25V includes a V-phase branch section 26V. The V-phase path section 25V electrically connects the V-phase upper and lower arms and the V-phase coil section 72V via the V-phase branch section 26V. The V-phase path section 25V does not have any branch sections other than the V-phase branch section 26V. In other words, the V-phase path section 25V does not electrically connect any components other than the V-phase upper and lower arms and the V-phase coil section 72V.

[0065] The source terminal of the W-phase upper arm switch 53WH and the drain terminal of the W-phase lower arm switch 53WL are electrically connected by the W-phase path section 25W. The W-phase path section 25W includes a W-phase branch section 26W. The W-phase path section 25W electrically connects the W-phase upper and lower arms and the W-phase coil section 72W via the W-phase branch section 26W. The W-phase path section 25W does not have any branch sections other than the W-phase branch section 26W. In other words, the W-phase path section 25W does not electrically connect any components other than the W-phase upper and lower arms and the W-phase coil section 72W.

[0066] The U-phase path section 25U, the V-phase path section 25V, and the W-phase path section 25W do not electrically connect components of different electrical systems 15. In other words, the different electrical systems 15 are electrically connected by the DC branch section 23, but not electrically connected in other current paths.

[0067] Figure 7 illustrates the on / off states of the AC conversion switching element 53 at each timing. In this figure, the U-phase upper arm switch 53UH is denoted as SW_UH, the V-phase upper arm switch 53VH as SW_VH, and the W-phase upper arm switch 53WH as SW_WH. Additionally, the U-phase lower arm switch 53UL is denoted as SW_UL, the V-phase lower arm switch 53VL as SW_VL, and the W-phase lower arm switch 53WL as SW_WL.

[0068] At a specific timing T1 after AC conversion control has started, the U-phase upper arm switch 53UH is switched from off to on. The V-phase lower arm switch 53VL is originally on, and the other AC conversion switching elements 53 are off. At the next timing T2, the W-phase lower arm switch 53WL is switched from off to on. At the same time, the V-phase lower arm switch 53VL is switched from on to off. At the next timing T3, the V-phase upper arm switch 53VH is switched from off to on. At the same time, the U-phase upper arm switch 53UH is switched from on to off. At the next timing T4, the U-phase lower arm switch 53UL is switched from off to on. At the same time, the W-phase lower arm switch 53WL is switched from on to off. At the next timing T5, the W-phase upper arm switch 53WH is switched from off to on. At the same time, the V-phase upper arm switch 53VH is switched from on to off. At the next timing T6, the V-phase lower arm switch 53VL is switched from off to on. At the same time, the U-phase lower arm switch 53UL is switched from on to off. At the next timing T7, the U-phase upper arm switch 53UH is switched from off to on. At the same time, the W-phase upper arm switch 53WH is switched from on to off.

[0069] The state of the switch at T7 and the state of the switch at T1 are the same, and from T7 onwards, the switching of the switches from T2 to T7 is repeated. This makes it possible to drive the three-phase AC motor 80 with a period of 120 degrees of electrical angle. The three-phase AC motor 80 is energized with a square wave of 120 degrees of electrical angle. During one electrical angle period, the U-phase upper arm switch 53UH is switched on and off only twice: from on to off at T3 and from off to on at T7. For the other AC conversion switching elements 53 as well, the number of times they are switched on and off during one electrical angle period is only two in total: one switch to on and one switch to off.

[0070] The AC conversion unit 50 performs the same AC conversion control at the same timing for all eight electrical systems 15, from the first electrical system 15A to the eighth electrical system 15H. For example, the U-phase upper arm switch 53UH of the first electrical system 15A and the U-phase upper arm switch 53UH of the eighth electrical system 15H will be controlled on and off at the same timing. Such control can be achieved by electrically connecting the gate terminals of the corresponding AC conversion switching elements 53 from the first electrical system 15A to the eighth electrical system 15H. For example, the gate terminals of the eight U-phase upper arm switches 53UH from the first electrical system 15A to the eighth electrical system 15H will be electrically connected.

[0071] In Figure 3, the in-phase coil sections 72 of the eight electrical systems 15, from the first electrical system 15A to the eighth electrical system 15H, are coil sections 72 that generate the same phase back electromotive force. For example, the U-phase coil section 72U of the first electrical system 15A and the U-phase coil section 72U of the eighth electrical system 15H will generate a back electromotive force at the same time. In other words, the U-phase coil section 72U of the first electrical system 15A and the U-phase coil section 72U of the eighth electrical system 15H are coil sections 72 that generate the same phase back electromotive force.

[0072] The coil sections 72, which have the same phase back electromotive force, are not directly connected in parallel, but are electrically connected between them via an AC conversion switching element 53 and a DC step-down unit 31. In other words, the three-phase coil section 71 of the first electrical system 15A and the three-phase coil section 71 of the other electrical systems 15 are electrically connected via at least two AC conversion units 51. The coil sections 72, which have the same phase back electromotive force, are configured to be switchable between an electrically connected state and an electrically isolated state by switching the AC conversion switching element 53 on and off. The above relationship holds true for electrical systems 15 from the first electrical system 15A to the fourth electrical system 15D and for electrical systems 15 from the fifth electrical system 15E to the eighth electrical system 15H. On the other hand, it does not hold true for electrical systems 15 that are not electrically connected to the same power supply unit 11. For example, it does not hold true between the first electrical system 15A and the fifth electrical system 15E, and they are always electrically isolated.

[0073] The operation of the AC conversion control in the AC conversion unit 50 when any of the AC conversion switching elements 53 short-circuits will now be explained. Let's assume that the U-phase upper arm switch 53UH of the first electrical system 15A is short-circuited. In this case, the U-phase upper arm switch 53UH of the first electrical system 15A will always be in the ON state, and therefore current cannot be properly supplied to the three-phase coil section 71 in the first electrical system 15A. Therefore, all the normal AC conversion switching elements 53 of the first electrical system 15A are turned OFF, and all the step-down switching elements 33 of the first DC step-down section 31A are also turned OFF, so that no current flows to the first electrical system 15A. In this state, only the remaining normal AC conversion section 51 is controlled in the same way as under normal conditions. As a result, the three-phase AC motor 80 is driven using the seven electrical systems 15 from the second electrical system 15B to the eighth electrical system 15H.

[0074] The response to a short-circuit failure in any of the AC conversion switching elements 53 is not limited to the failure of the AC conversion switching element 53, but is the same if the coil element 75 fails. That is, current is prevented from flowing through the electrical system 15 that includes the failed coil element 75, and the remaining normal electrical system 15 drives the three-phase AC motor 80. For example, consider the case where the U-phase coil section 72U of the first electrical system 15A has a short-circuit failure. In this case, the AC conversion switching element 53 that supplies current to the U-phase coil section 72U of the first electrical system 15A is switched off, thereby electrically isolating it from the other electrical systems 15. More specifically, the U-phase upper arm switch 53UH and the U-phase lower arm switch 53UL of the first electrical system 15A are switched off. At this time, there is no timing when the U-phase upper arm switch 53UH and the U-phase lower arm switch 53UL are originally turned on at the same time. Therefore, by switching one of the two that is currently on to off, the U-phase coil section 72U of the first electrical system 15A can be electrically isolated from the U-phase coil section 72U of the other electrical system 15.

[0075] The effects of the above-described embodiment will now be explained. According to the above-described embodiment, the AC conversion unit 50 is configured to electrically isolate one coil section 72 from other coil sections 72 that are in phase with it by switching off one AC conversion switching element 53. For example, by switching the U-phase upper arm switch 53UH of the first electrical system 15A from on to off, the U-phase coil section 72U of the first electrical system 15A and the seven U-phase coil sections 72U of the other electrical systems 15 are electrically isolated. Therefore, compared to cases where multiple switching elements must be turned off to electrically isolate one coil section 72 from other coil sections 72 that are in phase with it, electrical isolation can be achieved more quickly.

[0076] Furthermore, in a configuration where multiple switching elements are connected in parallel to switch the power supply to a single coil section 72, there is a possibility that an unintended large current may flow through the switching elements due to a timing difference in the switching control between the multiple switching elements connected in parallel. However, with the configuration of the embodiment described above, the power supply to the coil section 72 can be switched by switching a single switching element. Therefore, the generation of an unintended large current due to a timing difference in the switching control between the switching elements connected in parallel can be suppressed. Consequently, it is easier to prevent the drive system 100 from failing due to an unintended large current.

[0077] Furthermore, since the in-phase coil sections 72 can be electrically isolated from each other, unintended return currents due to impedance variations in the in-phase coil sections 72 do not occur. Therefore, the drive system 100 is more likely to function normally.

[0078] The AC conversion unit 50 comprises one AC conversion unit 51 and one DC step-down unit 31 corresponding to one three-phase coil section 71. In other words, the current flowing through one three-phase coil section 71 is controlled by one AC conversion unit 51 and not by the other AC conversion units 51. Therefore, even if one of the AC conversion switching elements 53 fails, the electrical system 15 including the failed AC conversion switching element 53 can be isolated from other electrical systems. This allows the drive control of the three-phase AC motor 80 to continue.

[0079] The AC conversion unit 51 connects the coil sections 72 of the three-phase coil unit 70 that have the same phase and back electromotive force. Therefore, it is possible to suppress the flow of return current that would occur if the same-phase coil sections 72 of the three-phase AC motor 80 were electrically connected to each other without going through the AC conversion unit 51.

[0080] The motor control device 60 includes an AC section housing 91 that houses the AC conversion unit 50 and the three-phase AC motor 80. Therefore, the AC conversion unit 50 and the three-phase AC motor 80 can be treated as a single integrated device. Consequently, it is easier to assemble them in a suitable location compared to treating the AC conversion unit 50 and the three-phase AC motor 80 as separate devices. In particular, because the electrical load of the AC conversion switching element 53 is small and the amount of heat generated is small, the need to consider constraints regarding heat dissipation structures and the positional relationships between heat-generating components is reduced. Consequently, the AC section housing 91 itself can be easily miniaturized, and the overall miniaturization of the motor control device 60 can be easily achieved.

[0081] The AC conversion unit 50 is configured to electrically isolate the neutral point 77 of one three-phase coil section 71 from the neutral point 77 of another three-phase coil section 71. This prevents current flowing through one three-phase coil section 71 from flowing into another electrical system 15. For example, it prevents current flow such that current flowing through the U-phase coil section 72U of the first electrical system 15A flows through the neutral point 77 to the V-phase coil section 72V of the second electrical system 15B. As a result, the current output from the first DC step-down unit 31A returns to the first DC step-down unit 31A.

[0082] The DC step-down unit 30 is equipped with one DC step-down unit 31 corresponding to one AC conversion unit 51. Therefore, the DC step-down unit 31 can supply a properly adjusted current to the AC conversion unit 51. Consequently, the load on the AC conversion switching element 53 is easily reduced. Furthermore, a configuration can be realized in which there is no need to adjust the amplitude of the AC current in the AC conversion unit 51. Thus, the control of the AC conversion unit 51 can be simplified compared to a configuration without a DC step-down unit 31. As a result, the control cycle of the AC conversion unit 51 can be made more gradual, and the switching loss in the AC conversion switching element 53 can be easily reduced. In addition, if a configuration is adopted in which the current stepped down by one DC step-down unit 31 is supplied to multiple electrical systems 15, the output of the three-phase coil section 71 for each electrical system 15 may be uneven. However, with a configuration in which one DC step-down unit 31 corresponds to one AC conversion unit 51, it is possible to suppress the unevenness of the output of the three-phase coil section 71 for each electrical system 15.

[0083] The DC transformer unit is a DC step-down unit 30. Therefore, even if the output voltage of the power supply unit 11 is too high and exceeds the rated current and rated voltage of the AC conversion switching element 53, it can be stepped down to an appropriate voltage before being supplied to the AC conversion unit 51.

[0084] The motor control device 60 has a power input terminal 48 and a DC output terminal 49, and includes a DC section housing 41 that houses a DC step-down unit 30 inside. Therefore, it is easy to handle a DC step-down unit 30 containing multiple DC step-down units 31 as a single device. Furthermore, by housing the DC step-down unit 30 in a housing different from the AC section housing 91, it is easy to change the combination of the DC step-down unit 30 and the AC conversion unit 50. Consequently, it is easy to provide a motor control device 60 that meets the needs by appropriately combining various DC step-down units 30 with the AC conversion unit 50.

[0085] One electrical system 15 is electrically connected to one of the multiple power supply units 11, and is electrically isolated from the other power supply units 11. Therefore, even if there is a malfunction in one power supply unit 11, the three-phase AC motor 80 can be driven using the electrical system 15 connected to the other power supply unit 11. Furthermore, even if a malfunction occurs in one electrical system 15, it remains electrically isolated from the electrical systems 15 connected to different power supply units 11. Therefore, the electrical systems 15 connected to different power supply units 11 are not affected by the malfunction.

[0086] The AC conversion units 51 of the different electrical systems 15 perform AC conversion control at the same timing. In other words, the U-phase, V-phase, and W-phase are switched at the same timing in the AC conversion units 51 of the different electrical systems 15. Therefore, the AC current converted by each electrical system 15 can similarly drive one three-phase AC motor 80 in the three-phase coil section 71.

[0087] The AC conversion unit 50 controls the three-phase AC motor 80 with a period of 120 degrees electrical angle. Therefore, it is not necessary to switch the AC conversion switching element 53 at a speed faster than the period of 120 degrees electrical angle. Consequently, the switching load on the AC conversion switching element 53 can be reduced compared to when switching at a speed faster than the period of 120 degrees electrical angle. In other words, it is easier to reduce the switching loss of the AC conversion switching element 53.

[0088] In the AC conversion switching element 53, the number of times it switches on and off within one cycle is a total of two: one switch from off to on and one switch from on to off. Therefore, compared to a configuration where the number of on-off switches within one cycle is more than two, the switching load on the AC conversion switching element 53 can be reduced. Consequently, the switching loss of the AC conversion switching element 53 can be easily reduced.

[0089] The upper arm 52H is electrically connected to the lower arm 52L of a different phase via coil sections 72 of multiple phases. Therefore, it is possible to convert DC current to AC current using the AC conversion unit 51.

[0090] The rated current of the AC conversion switching element 53 is smaller than the total current flowing through the three-phase AC motor 80. Furthermore, the rated current of the AC conversion switching element 53 is larger than the value obtained by dividing the total current flowing through the three-phase AC motor by the number of AC conversion units 51 in the AC conversion unit 50. Therefore, when selecting an AC conversion switching element 53, it is easier to secure a wider range of element selection compared to selecting from elements whose rated current is greater than or equal to the total current flowing through the three-phase AC motor 80. In other words, it is easier to select a more preferable switching element by considering performance other than rated voltage and cost. In addition, it is possible to suppress the flow of a current larger than the rated current through the AC conversion switching element 53.

[0091] The example given illustrates a case where power is supplied to a total of eight electrical systems 15, four on each side, using two power supply units 11. However, the method of power supply is not limited to the example described above. For example, a configuration in which power is supplied to eight electrical systems 15 using one power supply unit 11 is also possible.

[0092] <Second Embodiment> This embodiment is a modification based on the preceding embodiment. In this embodiment, the DC step-down unit 30 is replaced with a DC step-up unit 230 as the DC transformer unit.

[0093] Figure 8 shows a power supply unit 211, a current path unit 20, a DC boost unit 230, an AC conversion unit 50, and a three-phase AC motor 80. In this figure, the DC boost unit 231 is shown as CNV. The power supply unit 211 is a DC power supply that outputs less power than the power supply unit 11.

[0094] The DC boost unit 230 is a device that transforms the voltage output from the power supply unit 211 and increases it to a voltage that can drive the three-phase AC motor 80, that is, it boosts the voltage. The DC boost unit 230 is equipped with eight DC boost units 231. The DC boost unit 230 provides an example of a DC transformer unit. The DC boost unit 231 provides an example of a DC transformer unit.

[0095] The first electrical system 15A is configured by electrically connecting the first DC boost unit 231A, the first AC converter 51A, and the first three-phase coil unit 71A. The second electrical system 15B is configured by electrically connecting the second DC boost unit 231B, the second AC converter 51B, and the second three-phase coil unit 71B. The third electrical system 15C is configured by electrically connecting the third DC boost unit 231C, the third AC converter 51C, and the third three-phase coil unit 71C. The fourth electrical system 15D is configured by electrically connecting the fourth DC boost unit 231D, the fourth AC converter 51D, and the fourth three-phase coil unit 71D.

[0096] The fifth electrical system 15E is configured by electrically connecting the fifth DC boost unit 231E, the fifth AC converter 51E, and the fifth three-phase coil unit 71E. The sixth electrical system 15F is configured by electrically connecting the sixth DC boost unit 231F, the sixth AC converter 51F, and the sixth three-phase coil unit 71F. The seventh electrical system 15G is configured by electrically connecting the seventh DC boost unit 231G, the seventh AC converter 51G, and the seventh three-phase coil unit 71G. The eighth electrical system 15H is configured by electrically connecting the eighth DC boost unit 231H, the eighth AC converter 51H, and the eighth three-phase coil unit 71H.

[0097] The DC boost unit 230 performs the same boost control for each electrical system 15. That is, the first DC boost unit 231A to the eighth DC boost unit 231H perform the boost control in the same way and at the same timing. Therefore, the AC conversion unit 50 converts the DC voltage boosted by the DC boost unit 230 into AC in each electrical system 15.

[0098] The effects of the above-described embodiment will now be explained. According to the above-described embodiment, the DC transformer unit is a DC boost unit 230. Therefore, even if the power supply unit 211 cannot output the voltage required to drive the three-phase AC motor 80, the three-phase AC motor 80 can be driven by boosting the voltage to the required level.

[0099] <Other Embodiments> The disclosures in this specification and drawings are not limited to the exemplary embodiments. The disclosures include the exemplary embodiments and variations thereon by those skilled in the art. For example, the disclosures are not limited to combinations of parts and / or elements shown in the embodiments. The disclosures are implementable in a variety of combinations. The disclosures may have additional parts that can be added to the embodiments. The disclosures include those in which parts and / or elements of the embodiments have been omitted. The disclosures include substitutions or combinations of parts and / or elements between one embodiment and another. The scope of the disclosed technical areas is not limited to the descriptions of the embodiments. Some of the scope of the disclosed technical areas are indicated by the claims and should be understood to include all modifications within the meaning and scope equivalent to the claims.

[0100] The disclosures in the specification and drawings are not limited by the claims. The disclosures in the specification and drawings encompass the technical ideas described in the claims and extend to a wider and more diverse range of technical ideas than those described in the claims. Therefore, a variety of technical ideas can be extracted from the disclosures in the specification and drawings without being bound by the claims.

[0101] (Disclosure of Technical Ideas) This specification discloses several technical ideas as described in the following paragraphs. Some paragraphs may be written in a multiple dependent form, where subsequent paragraphs optionally refer to preceding paragraphs. Furthermore, some paragraphs may be written in a multiple dependent form, where they refer to other multiple dependent forms. These paragraphs written in multiple dependent forms define several technical ideas.

[0102] (Technical Concept 1) A motor control device for controlling a multiphase AC motor (80) having a multiphase coil unit (70) having a plurality of multiphase coil sections (71) in which coil sections (72) of different phases are electrically connected to each other, comprising: a current path section (20) that forms a current path between a power supply unit (11, 211) and the multiphase AC motor; and an AC conversion unit (50) having a plurality of AC conversion sections (51) capable of converting the DC current of the power supply unit into AC current, wherein the AC conversion unit is configured to electrically isolate one coil section from other coil sections that are in the same phase by switching off one AC conversion switching element.

[0103] (Technical Concept 2) The motor control device according to Technical Concept 1, wherein the AC conversion unit is configured to switch between a state in which the coil portions of the multiphase coil unit, which have in-phase back electromotive forces, are electrically connected and a state in which they are electrically separated, by switching the AC conversion switching element on and off.

[0104] (Technical Concept 3) A motor control device according to Technical Concept 1 or Technical Concept 2, comprising an AC section housing (91) having a DC input terminal (98) and housing the AC conversion unit and the multiphase AC motor inside.

[0105] (Technical Concept 4) The motor control device according to any one of Technical Concepts 1 to 3, wherein the AC conversion unit is configured to electrically separate the neutral point (77) of one of the multiphase coil sections from the neutral point of the other multiphase coil section.

[0106] (Technical Concept 5) The motor control device according to any one of Technical Concepts 1 to 3, wherein the AC conversion unit is configured to electrically separate one of the multiphase coil sections from the other multiphase coil section.

[0107] (Technical Concept 6) A motor control device according to Technical Concept 4 or Technical Concept 5, comprising a DC transformer unit (30, 230) having a plurality of DC transformer units (31, 231) that transform the DC voltage output from the power supply device, wherein the DC transformer unit has one DC transformer unit corresponding to one AC converter.

[0108] (Technical Concept 7) The motor control device according to Technical Concept 6, wherein the DC transformer unit is a DC step-down unit (30) having a plurality of DC step-down units (31) that step down the DC voltage output from the power supply device.

[0109] (Technical Concept 8) A motor control device according to Technical Concept 6 or Technical Concept 7, comprising a DC section housing (41) having a power input terminal (48) and a DC output terminal (49), and housing the DC transformer unit inside.

[0110] (Technical Concept 9) A motor control device according to any one of Technical Concepts 6 to 8, comprising a plurality of electrical systems (15) each having one DC transformer and one AC converter, wherein the electrical systems are electrically connected to one of the plurality of power supply devices and electrically isolated from the other power supply devices.

[0111] (Technical Concept 10) A motor control device according to Technical Concept 9, wherein the AC conversion units of different electrical systems perform AC conversion control on each other at the same timing.

[0112] (Technical Concept 11) The AC conversion unit is a motor control device according to any one of Technical Concepts 1 to 10, which controls the multiphase AC motor with a period of 120 degrees of electrical angle.

Claims

1. A motor control device for controlling a multiphase AC motor (80) comprising a multiphase coil unit (70) having a plurality of multiphase coil sections (71) in which coil sections (72) of different phases are electrically connected to each other, comprising: a current path section (20) that forms a current path between a power supply unit (11, 211) and the multiphase AC motor; and an AC conversion unit (50) having a plurality of AC conversion sections (51) capable of converting the DC current of the power supply unit into AC current, wherein the AC conversion unit is configured to electrically isolate one coil section from other coil sections of the same phase by switching off one AC conversion switching element.

2. The motor control device according to claim 1, wherein the AC conversion unit is configured to switch between a state in which the coil portions of the multiphase coil unit, which have in-phase back electromotive forces, are electrically connected and a state in which they are electrically separated, by switching the AC conversion switching element on and off.

3. The motor control device according to claim 1, comprising an AC section housing (91) having a DC input terminal (98) and housing the AC conversion unit and the multiphase AC motor inside.

4. The motor control device according to claim 1, wherein the AC conversion unit is configured to electrically separate the neutral point (77) of one of the multiphase coil sections from the neutral point of the other multiphase coil section.

5. The motor control device according to claim 1, wherein the AC conversion unit is configured to electrically separate one of the multiphase coil sections from the other multiphase coil section.

6. A motor control device according to claim 4 or 5, comprising a DC transformer unit (30, 230) having a plurality of DC transformer units (31, 231) for transforming the DC voltage output from the power supply, wherein the DC transformer unit comprises one DC transformer unit corresponding to one AC converter.

7. The motor control device according to claim 6, wherein the DC transformer unit is a DC step-down unit (30) having a plurality of DC step-down units (31) that step down the DC voltage output from the power supply device.

8. The motor control device according to claim 6, further comprising a DC section housing (41) having a power input terminal (48) and a DC output terminal (49), and housing the DC transformer unit inside.

9. The motor control device according to claim 6, comprising a plurality of electrical systems (15) each having one DC transformer and one AC converter, wherein the electrical systems are electrically connected to one of the plurality of power supply devices and electrically isolated from the other power supply devices.

10. The motor control device according to claim 9, wherein the AC conversion units of different electrical systems perform AC conversion control at the same timing with respect to each other.

11. The motor control device according to any one of claims 1 to 5, wherein the AC conversion unit controls the multiphase AC motor with a period of 120 degrees of electrical angle.

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