Motor drive device and motor

Abstract

The present application provides a motor drive device capable of changing the magnetization state of a variable magnetic force magnet without using a switching element having a large rated current and without adding a switching element. The motor (3) includes a variable magnetic force magnet and a magnetization coil (9) for magnetizing the variable magnetic force magnet. One end of the magnetization coil (9) is electrically or magnetically connected to the connection points of the upper and lower arm switching elements (18A to 18F) of all phases. The control device (2) of the motor drive device (1) includes a magnetization control section that causes a magnetization current to flow through the magnetization coil (9) by forming a period in which the upper arm switching elements (18A to 18C) of all phases or the lower arm switching elements (18D to 18F) of all phases are simultaneously turned on.

Description

Technical Field

[0001] The present invention relates to a motor drive device for driving a motor using a variable magnetic force magnet, and a motor driven by the motor drive device. Background Technology

[0002] In recent years, permanent magnet synchronous motors (PMSMs) have been adopted in electric vehicles and other applications to achieve high efficiency. These motors are suitable for electric vehicles requiring a wide operating range, from low-speed / high-torque to high-speed / low-torque operation. However, at high speeds, field weakening control is necessary, and the resulting copper losses lead to efficiency reduction.

[0003] To address this issue, a variable magnetic force motor (VMFM) is being researched. A VMFM embeds a fixed magnet with high coercivity and unchanged magnetic force / magnetization direction, and a variable magnet with low coercivity and variable magnetic force / magnetization direction, into its rotor. Common methods include directly magnetizing the variable magnet by allowing a magnetizing current to flow through a three-phase coil; and using a magnetizing coil in addition to the three-phase coil, allowing a magnetizing current to flow through the magnetizing coil to change the magnetic force and magnetization direction of the variable magnet (see, for example, Patent Documents 1 and 2). That is, the magnetic force of the variable magnet is increased at low speeds and decreased at high speeds. Therefore, improvements in efficiency and output at high speeds can be expected in a VMFM. Existing technical documents Patent documents

[0004] Patent Document 1: Japanese Patent No. 5921244 Patent Document 2: Japanese Patent No. 5100169 Summary of the Invention The problem to be solved by the present invention

[0005] However, in variable magnetic motors, a larger magnetizing current is required instantaneously when the magnetization state of the variable magnetic magnet changes (magnetizing / demagnetizing) compared to the driving operation. Therefore, in the case of direct magnetization using the aforementioned three-phase coils, a switching element composed of a power semiconductor device with a high rated current is required. Furthermore, in the case of using magnetizing coils, a separate switching element composed of a power semiconductor device with a high rated current must be provided, and there are also issues regarding the margin of the driving voltage relative to the DC voltage.

[0006] The present invention was made to solve the problems of the prior art, and its purpose is to provide a motor drive device that can change the magnetization state of a variable magnetic force magnet without using a switching element with a large rated current and without adding a switching element, as well as a motor driven by the motor drive device. Methods for solving problems

[0007] The motor drive device of the present invention is characterized by an inverter circuit configured by connecting upper arm switching elements and lower arm switching elements in series between the upper arm power line and the lower arm power line in each phase; and a control device that controls the upper and lower arm switching elements of each phase of the inverter circuit to connect the connection points of the upper and lower arm switching elements of each phase to the three-phase coils of the motor, so that three-phase current flows through the three-phase coils. The motor includes two types of permanent magnets: a magnet with high coercivity and a magnet with lower coercivity than the magnet with high coercivity; and a magnetizing coil for changing the magnetization state of the magnet with low coercivity. One end of the magnetizing coil is electrically or magnetically connected to the connection points of the upper and lower arm switching elements of all phases. The control device includes a magnetization control unit that causes magnetizing current to flow through the magnetizing coil during the period when the upper arm switching elements or the lower arm switching elements of all phases are turned on.

[0008] The second invention's motor drive device is characterized in that, in the above invention, the magnetization control unit causes the magnetization current to flow through the magnetization coil by simultaneously turning on the upper arm switching elements of all phases or the lower arm switching elements of all phases.

[0009] The motor drive device of the third invention is characterized in that it includes resonant capacitors, which are respectively connected between the connection points of the magnetizing coil and the upper and lower arm switching elements of each phase. Through the resonant circuit of these resonant capacitors and the magnetizing coil, the three-phase current flows through the magnetizing coil are blocked or suppressed.

[0010] The motor drive device of the fourth invention is characterized in that, in the above invention, it includes an interphase current interruption circuit connected between each resonant capacitor and the magnetizing coil. The interphase current interruption circuit prevents or suppresses the current flowing through the magnetizing coil when an interphase voltage is applied, and allows the current to flow through the magnetizing coil when a voltage is applied that turns on the upper arm switching elements of all phases or the lower arm switching elements of all phases.

[0011] The fifth invention's motor drive device is characterized in that, in the above invention, the phase-to-phase current interruption circuit includes a transformer for phases UVW, wherein the primary and secondary sides of the transformer for phases UVW are of the same polarity, one end of the primary side is connected to each resonant capacitor, one end of the secondary side is connected to a magnetizing coil, the other end of the primary side of the transformer for phase U is connected to the other end of the secondary side of the transformer for phase W or phase V, the other end of the primary side of the transformer for phase V is connected to the other end of the secondary side of the transformer for phase U or phase W, and the other end of the primary side of the transformer for phase W is connected to the other end of the secondary side of the transformer for phase V or phase U.

[0012] The motor drive device of the sixth invention is characterized in that, in this invention, it includes a first neutral point capacitor and a second neutral point capacitor connected in series between the power lines of the upper and lower arms for generating a neutral point, and the other end of the magnetizing coil is connected to the connection point of the first neutral point capacitor and the second neutral point capacitor.

[0013] The motor of the seventh invention is characterized by being driven by the motor drive device of the above inventions, and comprising: a stator on which three-phase coils are wound and mounted; and a rotor provided with a high coercivity magnet and a low coercivity magnet, wherein a magnetizing coil is wound and mounted on the teeth of the stator on which the three-phase coils are wound and mounted.

[0014] The motor of the eighth invention is characterized by being driven by the motor drive device of the first to sixth inventions, and includes: a stator on which three-phase coils are wound and mounted; and a rotor on which a high-coercivity magnet and a low-coercivity magnet are provided, the low-coercivity magnet being arranged along the circumference of the rotor, and a magnetizing coil being provided in the stator at a position corresponding to the low-coercivity magnet.

[0015] The motor of the ninth invention is characterized by being driven by the motor drive device of the first to sixth inventions, comprising: a stator on which three-phase coils are wound and mounted; and a rotor on which a high-coercivity magnet and a low-coercivity magnet are provided, and a magnetizing coil is provided near the low-coercivity magnet, and the rotor is powered by contact or non-contact. Invention Effects

[0016] According to the present invention, a motor drive device includes: an inverter circuit configured by connecting upper arm switching elements and lower arm switching elements in series between upper arm power lines and lower arm power lines in each phase; and a control device that controls the upper and lower arm switching elements of each phase of the inverter circuit, connects the connection points of the upper and lower arm switching elements of each phase to the three-phase coils of the motor, and allows three-phase current to flow through the three-phase coils. The motor includes two types of permanent magnets: a magnet with high coercivity and a magnet with lower coercivity than the magnet with high coercivity; and a magnetizing coil for changing the magnetization state of the magnet with lower coercivity. One end of the magnetizing coil is electrically or magnetically connected to the connection point of the upper and lower arm switching elements of all phases. The control device includes a magnetization control unit. The magnetization control unit creates a period during which the upper arm switching elements of all phases or the lower arm switching elements of all phases are simultaneously turned on, thereby causing a magnetizing current to flow through the magnetizing coil. Thus, through this magnetization control unit, the upper arm switching elements of all phases or the lower arm switching elements of all phases are simultaneously turned on, for example, as in the second invention, causing a magnetizing current to flow through the magnetizing coil, thereby making the current flowing through the upper arm switching element or the lower arm switching element of one phase one-third of the magnetizing current.

[0017] That is, it can reduce the rated current of the switching element to one-third, and change the magnetization state of a magnet with low coercivity without using a switching element with a large rated current.

[0018] Furthermore, as in the third invention, resonant capacitors are connected between the connection points of the magnetizing coil and the upper and lower arm switching elements of each phase. Through the resonant circuit of these resonant capacitors and the magnetizing coil, the flow of three-phase current through the magnetizing coil is blocked or suppressed, thereby enabling normal motor drive. In addition, the voltage required for the magnetizing current to flow can be suppressed, which can alleviate the limitation on the power supply voltage when magnetizing a magnet with low coercivity during high-speed rotation.

[0019] In this case, as in the fourth invention, an interphase current interruption circuit is connected between each resonant capacitor and the magnetizing coil. If the interphase current interruption circuit prevents or inhibits the current from flowing through the magnetizing coil when an interphase voltage is applied, and allows the current to flow through the magnetizing coil when a voltage is applied that turns on the upper arm switching elements of all phases or the lower arm switching elements of all phases, normal motor drive can be further realized.

[0020] For example, as in the fifth invention, the phase-to-phase current interruption circuit can be constructed using transformers for phases UVW, wherein the primary and secondary sides of the transformers for phases UVW are of the same polarity, one end of the primary side is connected to each resonant capacitor, and one end of the secondary side is connected to the magnetizing coil. Furthermore, the other end of the primary side of the transformer for phase U is connected to the other end of the secondary side of the transformer for phase W or V, the other end of the primary side of the transformer for phase V is connected to the other end of the secondary side of the transformer for phase U or W, and the other end of the primary side of the transformer for phase W is connected to the other end of the secondary side of the transformer for phase V or U.

[0021] Therefore, when an interphase voltage is applied, each transformer in the interphase current interruption circuit functions to suppress currents in the same direction. When a voltage is applied that turns on the upper arm switching elements of all phases or the lower arm switching elements of all phases, each transformer functions to allow currents in the opposite direction to pass directly. At this time, the current passing through is only the component of all phases, so it can be constructed with small-capacity transformers.

[0022] In addition, as in the sixth invention, a first neutral point capacitor and a second neutral point capacitor are provided in series between the power lines of the upper and lower arms for generating a neutral point. The other end of the magnetizing coil is connected to the connection point of the first neutral point capacitor and the second neutral point capacitor, so that there is no need to provide a special switching element in order to magnetize a magnet with low coercivity, and the device can be reduced in size.

[0023] Here, as in the seventh invention, the motor driven by the motor drive device of the above-mentioned inventions comprises: a stator on which three-phase coils are wound and mounted; and a rotor on which a magnet with high coercivity and a magnet with low coercivity are provided, wherein the magnetizing coil is wound and mounted on the teeth of the stator on which the three-phase coils are wound and mounted.

[0024] Alternatively, as in the eighth invention, a low-coercivity magnet can be arranged along the circumference of the rotor, and the magnetizing coil can be placed in the stator at a position corresponding to the low-coercivity magnet. In this case, the low-coercivity magnet can be magnetized over a larger circumferential range, thus mitigating or eliminating the positional limitations of the low-coercivity magnet when magnetizing it.

[0025] Alternatively, as in the ninth invention, the magnetizing coil can be placed on a rotor near a magnet with low coercivity, and the rotor can be powered by contact or non-contact. In this case, there is the advantage of being able to magnetize regardless of the position of the magnet with low coercivity. Attached Figure Description

[0026] Figure 1 This is a circuit diagram of a motor drive device according to an embodiment of the present invention. Figure 2yes Figure 1 A block diagram of the control device of one embodiment of the motor drive device. Figure 3 This is a partial top sectional view of a motor driven by a motor drive device of the present invention, according to one embodiment. Figure 4 It is a diagram showing the three-phase current waveforms during normal motor drive. Figure 5 It means to Figure 3 The diagram shows the current waveforms of various parts when a variable magnetic force magnet is magnetized. Figure 6 This is a circuit diagram of a motor drive device according to another embodiment of the present invention. Figure 7 It means Figure 6 A diagram showing the specific configuration of the phase-to-phase current cutoff circuit (when a phase-to-phase voltage is applied between U and W). Figure 8 It means Figure 6 A diagram showing the specific configuration of the phase-to-phase current cutoff circuit (the case where a voltage is applied to turn on all phases). Figure 9 This is a partial top sectional view of a motor according to another embodiment driven by the motor drive device of the present invention. Figure 10 yes Figure 9 A 3D view of the stator of a motor. Figure 11 This is a partial longitudinal sectional perspective view of a motor driven by the motor drive device of the present invention. Detailed Implementation

[0027] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Example 1

[0028] Figure 1 This is a circuit diagram of a motor drive device 1 that applies an embodiment of the present invention. Figure 2 This is a block diagram of the control device 2 for the motor drive device 1. Figure 3 This is a partial top sectional view of the motor 3 driven by the motor drive unit 1. In this embodiment, the motor drive unit 1 is mounted on a so-called inverter-integrated electric compressor, which is driven by the motor 3 to a compressor mechanism. The electric compressor, for example, constitutes the refrigerant circuit of a vehicle air conditioning system that regulates the air inside the cabin of an electric vehicle.

[0029] (1) Composition of motor 3 First, refer to Figure 3The structure of the motor 3, which is driven by the motor drive device 1 of the present invention, will be described. In this embodiment, the motor 3 is a permanent magnet synchronous motor (PMSM), such as... Figure 3 As shown, it includes a stator 4 and a rotor 6 rotating inside it. The rotor 6 is mounted on the rotating shaft of the electric compressor and drives the compression mechanism through the rotating shaft.

[0030] The stator 4 of the motor 3 in this embodiment includes a stator core 7 formed by stacking electromagnetic steel plates, three-phase coils 8U, 8V, and 8W (star-connected) wound and mounted on the stator core 7 for each of the UVW phases, and a magnetizing coil 9. The stator core 7 has a plurality of teeth 12 (12 in this embodiment) extending radially inward from the cylindrical yoke portion 11, and the three-phase coils 8U, 8V, and 8W are wound and mounted on each tooth 12. In this embodiment, the magnetizing coil 9 is constructed by connecting two phases of the three-phase coils (in this embodiment, the U-phase three-phase coil 8U and the V-phase three-phase coil 8V) in series and is wound and mounted on the tooth 12.

[0031] In this case, the magnetizing coil 9 uses a thinner coil than the three-phase coils 8U to 8W, resulting in a high number of turns and a space-saving configuration. While the copper losses due to the magnetizing current increase in the magnetizing coil 9, this is considered acceptable due to the instantaneous energization (pulse) described later. Furthermore, based on the torque characteristics of the motor 3 and the magnetization characteristics of the variable magnetic force magnet 13 (described later), the space ratio between the three-phase coils 8U to 8W and the magnetizing coil 9 is optimized.

[0032] On the other hand, the rotor 6 of the motor 3 includes: a rotor core 16; and two types of permanent magnets: a plurality of fixed magnetic magnets 17, which are high-coercivity magnets of the present invention, embedded radially inside the rotor core 16, and a plurality of variable magnetic magnets 13, which are low-coercivity magnets of the present invention, embedded radially outside the fixed magnetic magnets 17. That is, the motor 3 is a variable magnetic force motor (VMFM). In this case, the fixed magnetic magnets 17 are, for example, NdFeB magnets. On the other hand, the variable magnetic magnets 13 are permanent magnets, such as AlNiCo magnets, whose magnetization state (magnetic force magnitude and direction) changes according to the magnetic field. The coercivity of the NdFeB magnet constituting the fixed magnetic magnet 17 is 1000 kA / m, and the coercivity of the AlNiCo magnet constituting the variable magnetic magnet 13 is 120 kA / m. The coercivity of the variable magnetic magnet 13 is lower than that of the fixed magnetic magnet 17.

[0033] Furthermore, in this embodiment, the fixed magnetic magnet 17 is arranged opposite to the aforementioned rotation axis, and the variable magnetic magnets 13 are arranged to extend outward from the radially inner side relative to both sides of the fixed magnetic magnet 17. Moreover, this group of fixed magnetic magnets 17 and two variable magnetic magnets 13 constitutes a magnetic pole, and eight such groups are provided, forming eight magnetic poles.

[0034] (2) Composition of motor drive device 1 Next, the configuration of the motor drive device 1 of the embodiment will be described. The motor drive device 1 of the embodiment includes a three-phase inverter circuit 21 and a control device 2, etc.

[0035] (2-1) Inverter circuit 21 The inverter circuit 21 of this embodiment is a circuit that converts the DC voltage of the DC power supply (vehicle battery: for example, 300V) 23 into a three-phase AC voltage and applies it to the motor 3, thereby allowing three-phase current to flow through the motor 3. This inverter circuit 21 includes a U-phase half-bridge circuit 19U, a V-phase half-bridge circuit 19V, and a W-phase half-bridge circuit 19W. Each phase's half-bridge circuit 19U to 19W individually includes upper arm switching elements 18A to 18C and lower arm switching elements 18D to 18F. Furthermore, each of the switching elements 18A to 18F is connected in reverse parallel with a freewheeling diode 24.

[0036] Furthermore, in the embodiments, each of the switching elements 18A to 18F is composed of an insulated gate bipolar transistor (IGBT) or the like, which is a power semiconductor device in which a MOS structure is assembled to the gate portion.

[0037] Furthermore, the upper ends of the upper arm switching elements 18A to 18C of the inverter circuit 21 are connected to the upper arm power line (positive side bus) 26 of the DC power supply 23. On the other hand, the lower ends of the lower arm switching elements 18D to 18F of the inverter circuit 21 are connected to the lower arm power line (negative side bus) 27 of the DC power supply 23.

[0038] In this case, the upper arm switching element 18A and the lower arm switching element 18D of the U-phase half-bridge circuit 19U are connected in series, the upper arm switching element 18B and the lower arm switching element 18E of the V-phase half-bridge circuit 19V are connected in series, and the upper arm switching element 18C and the lower arm switching element 18F of the W-phase half-bridge circuit 19W are connected in series.

[0039] Furthermore, the connection points of the upper arm switch element 18A and the lower arm switch element 18D of the U-phase half-bridge circuit 19U are connected to the three-phase coil 8U of the U phase of the motor 3, the connection points of the upper arm switch element 18B and the lower arm switch element 18E of the V-phase half-bridge circuit 19V are connected to the three-phase coil 8V of the V phase of the motor 3, and the connection points of the upper arm switch element 18C and the lower arm switch element 18F of the W-phase half-bridge circuit 19W are connected to the three-phase coil 8W of the W phase of the motor 3.

[0040] In the embodiment, the connection point of the upper arm switching element 18A and the lower arm switching element 18D of the U-phase half-bridge circuit 19U is also electrically connected to one end of the U-phase resonant capacitor 28U; the connection point of the upper arm switching element 18B and the lower arm switching element 18E of the V-phase half-bridge circuit 19V is also electrically connected to one end of the V-phase resonant capacitor 28V; and the connection point of the upper arm switching element 18C and the lower arm switching element 18F of the W-phase half-bridge circuit 19W is also electrically connected to one end of the W-phase resonant capacitor 28W.

[0041] (2-2) Resonant circuit 31 The other ends of the resonant capacitors 28U to 28W for each phase of UVW are connected to each other and then connected to one end of the magnetizing coil 9. That is, the resonant capacitors 28U to 28W for each phase of UVW are electrically connected between the magnetizing coil 9 and the connection points of the upper and lower arm switching elements 18A and 18D, the upper and lower arm switching elements 18B and 18E, and the upper and lower arm switching elements 18C and 18F, respectively. Thus, the magnetizing coil 9 is electrically connected to the connection points of the upper and lower arm switching elements 18A and 18D, the upper and lower arm switching elements 18B and 18E, and the upper and lower arm switching elements 18C and 18F through the resonant capacitors 28U to 28W.

[0042] Each resonant capacitor 28U to 28W, together with the magnetizing coil 9, constitutes a resonant circuit 31 (LC resonant circuit). The resonant point of this resonant circuit 31 is set to the frequency of the magnetizing voltage (described later) or a value near it but far from the frequencies of the three-phase voltages (U-phase voltage Vu, V-phase voltage Vv, and W-phase voltage Vw, described later). Therefore, the resonant circuit 31 is configured as follows: it presents a low impedance to the magnetizing voltage, allowing the magnetizing current to flow through the magnetizing coil 9; and it presents a high impedance to the three-phase voltages, preventing the three-phase current from flowing through the magnetizing coil 9 or suppressing the three-phase current from flowing through the magnetizing coil 9.

[0043] Furthermore, a series circuit of a first neutral point capacitor 32 and a second neutral point capacitor 33 is connected between the upper arm power line 26 and the lower arm power line 27 of the DC power supply 23. The first neutral point capacitor 32 and the second neutral point capacitor 33 are capacitors of the same capacitance, and their connection point becomes the neutral point potential of the motor 3 (the neutral point potential of the star-connected three-phase coils 8U to 8W). Moreover, the other end of the magnetizing coil 9 is connected to the connection point of these first neutral point capacitors and second neutral point capacitors 32 and 33.

[0044] (2-3) Control device 2 Next, refer to Figure 2 The configuration of control device 2 will be described. Control device 2 is composed of a microcomputer with a processor. In this embodiment, it receives operation commands and speed commands from vehicle ECU 34 and motor current (phase current) from motor 3. Based on these, it controls the on / off state (switching) of each switching element 18A to 18F of inverter circuit 21. Specifically, it controls the gate voltage applied to the gate terminals of each switching element 18A to 18F.

[0045] The control device 2 in this embodiment includes a motor control unit 35, a PWM signal generation unit 36, a gate driver 37, a magnetization control unit 38, and a magnetization PWM signal generation unit 39. Additionally, the control device 2 includes a current sensor (not shown) for measuring the motor current (phase current) of each phase required to detect the magnetic pole position of the rotor 6 of the motor 3, namely, U-phase current Iu, V-phase current Iv, and W-phase current Iw. This information is input to the motor control unit 35.

[0046] The motor control unit 35 calculates and generates three-phase modulation voltage command values ​​Vu' (hereinafter, U-phase voltage command value Vu'), Vv' (hereinafter, V-phase voltage command value Vv'), and Vw' (hereinafter, W-phase voltage command value Vw') for generating the three-phase voltages applied to each of the three-phase coils 8U to 8W of the motor 3 by vector control based on the electrical angle, current command value and phase current of the motor 3.

[0047] The PWM signal generation unit 36 ​​takes into input the three-phase modulation voltage command values ​​Vu', Vv', and Vw' calculated by the motor control unit 35, and generates and outputs PWM signals as drive command signals for the U-phase half-bridge circuit 19U, V-phase half-bridge circuit 19V, and W-phase half-bridge circuit 19W of the inverter circuit 21 by comparing the magnitude of these three-phase modulation voltage command values ​​Vu', Vv', and Vw' with the magnitude of the carrier signal (e.g., a sawtooth wave carrier).

[0048] The magnetization control unit 38 receives a magnetization command and the position information of the rotor 6 from the motor control unit 35. When a magnetization command is received from the magnetization control unit 38, it generates magnetization voltage command values ​​Vum', Vvm', and Vwm' to generate a magnetization voltage Vm. The magnetization voltage Vm is used to allow a pulsed magnetization current Im, which is used to change the magnetization state (magnetizing / demagnetizing) of the variable magnetic force magnet 13, to flow through the magnetization coil 9. In this case, based on the position information of the rotor 6, the magnetization control unit 38 generates the magnetization voltage command values ​​Vum', Vvm', and Vwm' at the moment when the variable magnetic force magnet 13 reaches the position corresponding to the magnetization coil 9.

[0049] In this embodiment, the magnetization PWM signal generation unit 39 receives the magnetization voltage command values ​​Vum', Vvm', and Vwm' output by the magnetization control unit 38. This also generates and outputs a magnetization PWM signal that serves as the drive command signal for the U-phase half-bridge circuit 19U, V-phase half-bridge circuit 19V, and W-phase half-bridge circuit 19W of the inverter circuit 21. In this embodiment, the magnetization PWM signal is a signal that simultaneously turns on the upper arm switching element 18A of the U-phase half-bridge circuit 19U, the upper arm switching element 18B of the V-phase half-bridge circuit 19V, and the upper arm switching element 18C of the W-phase half-bridge circuit 19W (i.e., the upper arm switching elements of all phases) (while the lower arm switching elements 18D to 18F of all phases are turned off).

[0050] Furthermore, the PWM signal for magnetization is not limited to the above, and can also be a signal that simultaneously turns on the lower arm switching element 18D of the U-phase half-bridge circuit 19U, the lower arm switching element 18E of the V-phase half-bridge circuit 19V, and the lower arm switching element 18F of the W-phase half-bridge circuit 19W (i.e., the lower arm switching elements of all phases) (in this case, the upper arm switching elements 18A to 18C of all phases are turned off).

[0051] The magnetization PWM signal output by the magnetization PWM signal generation unit 39 is superimposed on the PWM signal output by the PWM signal generation unit 36 ​​and input to the gate driver 37. The gate driver 37 generates the gate voltages of the upper arm switching element 18A and lower arm switching element 18D of the U-phase half-bridge circuit 19U, the gate voltages of the upper arm switching element 18B and lower arm switching element 18E of the V-phase half-bridge circuit 19V, and the gate voltages of the upper arm switching element 18C and lower arm switching element 18F of the W-phase half-bridge circuit 19W based on the PWM signal superimposed with the magnetization PWM signal.

[0052] Furthermore, each switching element 18A to 18F of the inverter circuit 28 is turned on / off driven according to the gate voltage output from the gate driver 37. That is, if the gate voltage is in the on state (a specified voltage value), the switching element turns on; if the gate voltage is in the off state (zero), the switching element turns off. In the case where the switching elements 18A to 18F are the aforementioned IGBTs, the gate driver 37 is a circuit for applying the gate voltage to the IGBT according to the PWM signal, and is composed of an optocoupler, a logic IC, a transistor, etc.

[0053] Furthermore, the voltage at the connection point of the upper arm switching element 18A and the lower arm switching element 18D of the U-phase half-bridge circuit 19U is applied (output) as the U-phase voltage Vu (three-phase voltage) to the U-phase three-phase coil 8U of the motor 3; the voltage at the connection point of the upper arm switching element 18B and the lower arm switching element 18E of the V-phase half-bridge circuit 19V is applied (output) as the V-phase voltage Vv (three-phase voltage) to the V-phase three-phase coil 8V of the motor 3; and the voltage at the connection point of the upper arm switching element 18C and the lower arm switching element 18F of the W-phase half-bridge circuit 19W is applied (output) as the W-phase voltage Vw (three-phase voltage) to the W-phase three-phase coil 8W of the motor 3.

[0054] Furthermore, the voltage at the connection point of the upper arm switching element 18A and the lower arm switching element 18D of the U-phase half-bridge circuit 19U, the voltage at the connection point of the upper arm switching element 18B and the lower arm switching element 18E of the V-phase half-bridge circuit 19V, and the voltage at the connection point of the upper arm switching element 18C and the lower arm switching element 18F of the W-phase half-bridge circuit 19W are respectively applied (output) to the magnetizing coil 9 of the motor 3 via the resonant capacitors 28U to 28W.

[0055] (3) Operation of control device 2 (3-1) During normal motor drive Next, refer to Figure 4 , Figure 5 The actual control actions of control device 2 will be explained. Figure 4 This represents the waveforms of the three-phase currents Iu, Iv, and Iw during normal motor driving, where the three-phase voltages (phase voltages of each phase UVW) based on the PWM signal output by the PWM signal generation unit 36 ​​are applied to the three-phase coils 8U to 8W of the motor 3. During normal motor driving, by applying phase-to-phase voltages, three-phase currents Iu, Iv, and Iw, each with a phase offset of 120°, flow through each coil 8U to 8W of the motor 3.

[0056] In addition, Figure 4The magnetizing current Im at this time is also shown. The voltage at the connection point of the upper arm switching element 18A and the lower arm switching element 18D of the U-phase half-bridge circuit 19U, the voltage at the connection point of the upper arm switching element 18B and the lower arm switching element 18E of the V-phase half-bridge circuit 19V, and the voltage at the connection point of the upper arm switching element 18C and the lower arm switching element 18F of the W-phase half-bridge circuit 19W, that is, the three-phase voltages (U-phase voltage Vu, V-phase voltage Vv, W-phase voltage Vw) in this case are also applied to the magnetizing coil 9 of the motor 3 via the resonant capacitors 28U to 28W. However, as described above, the resonant point of the resonant circuit 31 composed of each resonant capacitor 28U to 28W and the magnetizing coil 9 is set to a value far from the frequency of the three-phase voltages (U-phase voltage Vu, V-phase voltage Vv, W-phase voltage Vw), so the impedance becomes high for the three-phase voltage. Therefore, the magnetizing current Im does not flow through the magnetizing coil 9 or the magnetizing current Im hardly flows through the magnetizing coil 9. Therefore, motor 3 is driven normally.

[0057] (3-2) Magnetization of the variable magnetic force magnet 13 Next, in Figure 5 The diagram shows the current waveforms of each component when the magnetization control unit 38 outputs magnetization voltage command values ​​Vum, Vvm, and Vwm, and the magnetization PWM signal control unit 39 outputs a magnetization PWM signal based on these magnetization voltage command values ​​Vum, Vvm, and Vwm, in order to magnetize the variable magnetic magnet 13. Furthermore, as described above, the magnetization control unit 38, based on the position information of the rotor 6, causes a pulse-shaped magnetization current Im of a predetermined width to flow through the magnetization coil 9 at the moment the variable magnetic magnet 13 reaches the position corresponding to the magnetization coil 9, thereby magnetizing the variable magnetic magnet 13. At this time, in this embodiment, as described above, the upper arm switching element 18A of the U-phase half-bridge circuit 19U, the upper arm switching element 18B of the V-phase half-bridge circuit 19V, and the upper arm switching element 18C of the W-phase half-bridge circuit 19W (i.e., the upper arm switching elements of all phases) are simultaneously turned on. Furthermore, the lower arm switching elements 18D to 18F of all phases are turned off at this time.

[0058] At this time, if the U-phase upper arm current flowing through the upper arm switching element 18A is set to Ipu, the V-phase upper arm current flowing through the upper arm switching element 18B is set to Ipv, and the W-phase upper arm current flowing through the upper arm switching element 18C is set to Ipw, then the resonant point of the resonant circuit 31, which is composed of each resonant capacitor 28U~28W and the magnetizing coil 9 as described above, is set to the frequency of the magnetizing voltage Vm or near it. Therefore, the impedance of the resonant circuit 31 becomes extremely small or extremely low relative to the magnetizing voltage Vm, and the magnetizing current Im flows through the magnetizing coil 9.

[0059] Furthermore, the magnetizing current Im at this time becomes the sum of the upper arm currents Ipu (U phase), Ipv (V phase), and Ipw (W phase), which is three times their sum (Im = Ipu + Ipv + Ipw). Moreover, this pulsed, large magnetizing current Im (refer to...) Figure 5 ( ), correctly change the magnetization state of the variable magnetic magnet 13.

[0060] As described above, the motor drive device 1 of the present invention drives a motor 3 equipped with a variable magnetic magnet 13 and a magnetizing coil 9 for magnetizing the variable magnetic magnet 13. One end of the magnetizing coil 9 is connected to the connection point of the upper and lower arm switching elements 18A to 18F of all phases. The control device 2 is equipped with a magnetization control unit 38. The magnetization control unit 38 simultaneously turns on the upper arm switching elements 18A to 18C of all phases or the lower arm switching elements 18D to 18F of all phases, so that the magnetizing current Im flows through the magnetizing coil 9. Therefore, through the magnetization control unit 38, the upper arm switching elements 18A to 18C of all phases or the lower arm switching elements 18D to 18F of all phases are simultaneously turned on, so that the magnetizing current Im flows through the magnetizing coil 9. As a result, the current (Ipu, Ipv, Ipw) flowing through the upper arm switching elements 18A to 18C or the lower arm switching elements 18D to 18F of one phase becomes one-third of the magnetizing current Im.

[0061] That is, the rated current of the switching elements 18A to 18F can be reduced to one-third, and the magnetization state of the variable magnetic magnet 13 can be changed without using a switching element with a larger rated current.

[0062] Furthermore, in this embodiment, resonant capacitors 28U to 28W are respectively connected between the magnetizing coil 9 and the upper and lower arm switching elements 18A to 18F of each phase. Through the resonant circuit 31 of these resonant capacitors 28U to 28W and the magnetizing coil 9, the three-phase currents Iu, Iv, and Iw are prevented or suppressed from flowing through the magnetizing coil 9, thus enabling normal motor drive. In addition, the voltage required to flow through the magnetizing current Im can be suppressed, and when the variable magnetic force magnet 13 is magnetized at high speed, the limitation on the power supply voltage can be alleviated.

[0063] Additionally, in this embodiment, a first neutral point capacitor 32 and a second neutral point capacitor 33 are provided in series between the upper and lower arm power lines 26 and 27 for generating a neutral point, and the other end of the magnetizing coil 9 is connected to the connection point of the first neutral point capacitor and the second neutral point capacitor 32 and 33.

[0064] Here, if all the upper arm switching elements 18A-18C of all phases are simultaneously turned on as in the embodiment, and if the other end of the magnetizing coil 9 is not connected to the connection point of the neutral point capacitors 32 and 33 as in the embodiment, a special switching element is required between the other end and the lower arm power line 27. However, by connecting the other end of the magnetizing coil 9 to the connection point of the neutral point capacitors 32 and 33 as in the embodiment, there is no need to provide a special switching element for magnetizing the variable magnetic force magnet 13, thus enabling device reduction. Example 2

[0065] then, Figure 6 This is a circuit diagram illustrating a motor drive device 1 according to another embodiment of the present invention. In this diagram, [the device is used in conjunction with...] Figures 1-5 The same reference numerals denote the same components, and descriptions are omitted. In this embodiment, an interphase current cutoff circuit 41 is provided between each resonant capacitor 28U to 28W and the magnetizing coil 9.

[0066] In the above embodiment, the resonant capacitors 28U to 28W are connected in series with the magnetizing coil 9 to form a resonant circuit 31. However, there is a risk that a slight three-phase current may flow due to the imbalance of each component. The phase-to-phase current cutoff circuit 41 is provided to eliminate or suppress this situation.

[0067] The phase-to-phase current interruption circuit 41 is as follows: it blocks or suppresses the current flowing through the magnetizing coil 9 when a phase-to-phase voltage is applied; and it allows current to flow through the magnetizing coil 9 when a voltage is applied that turns on the upper arm switching elements 18A-18C of all phases or the lower arm switching elements 18D-18F of all phases. Figure 7 The specific configuration of the phase-to-phase current cutoff circuit 41 is shown in the figure.

[0068] The phase-to-phase current interruption circuit 41 in this embodiment is composed of three transformers 46 to 48 for each of the U, U, and W phases. The primary side 46P and the secondary side 46S of the transformer 46 used for the U phase are of the same polarity. The primary side 47P and the secondary side 47S of the transformer 47 used for the V phase are also of the same polarity. The primary side 48P and the secondary side 48S of the transformer 48 used for the W phase are also of the same polarity.

[0069] Furthermore, one end of the primary side 46P of the U-phase transformer 46 is connected to the resonant capacitor 28U, one end of the primary side 47P of the V-phase transformer 47 is connected to the resonant capacitor 28V, and one end of the primary side 48P of the W-phase transformer 48 is connected to the resonant capacitor 28W. Additionally, one end of the secondary side 46S of the U-phase transformer 46, one end of the secondary side 47S of the V-phase transformer 47, and one end of the secondary side 48S of the W-phase transformer 48 are connected to the magnetizing coil 9.

[0070] In addition, the other end of the primary side 46P of the U-phase transformer 46 is connected to the other end of the secondary side 48S of the W-phase transformer 48, the other end of the primary side 47P of the V-phase transformer 47 is connected to the other end of the secondary side 46S of the U-phase transformer 46, and the other end of the primary side 48P of the W-phase transformer 48 is connected to the other end of the secondary side 47S of the V-phase transformer 47.

[0071] In the above composition, refer to Figure 7 , Figure 8 The operation of the phase-to-phase current interruption circuit 41 in the embodiment will be explained. For example, when the upper arm switching element 18A of the U-phase half-bridge circuit 19U is turned on and the lower arm switching element 18F of the W-phase half-bridge circuit 19W is turned on, thus applying a phase-to-phase voltage to the phase-to-phase current interruption circuit 41, the current is to be... Figure 7 The current flows from phase U to phase W as shown by the dashed arrow. However, at this time, transformers 46-48 function to suppress currents in the same direction. Therefore, the current does not flow through magnetizing coil 9, and the current flowing from phase U to phase W is also suppressed. Figure 7 (The dashed arrow in the middle).

[0072] On the other hand, when a voltage is applied to the phase-to-phase current cutoff circuit 41 to simultaneously turn on the upper arm switching elements 18A to 18C of all phases, the current is as follows: Figure 8 The flow is indicated by dashed arrows. At this time, each transformer 46-48 functions to allow current in the opposite direction to pass directly, so that the current of all phases flows through the magnetizing coil 9. The current passing through at this time becomes only a component of all phases, so the phase-to-phase current interruption circuit 41 can be constructed by small-capacity transformers 46-47. The same applies when a voltage is applied that simultaneously turns on the lower arm switching elements 18D-18F of all phases.

[0073] Furthermore, not limited to the above connection examples, it is also the same to connect the other end of the primary side 46P of the U-phase transformer 46 to the other end of the secondary side 47S of the V-phase transformer 47, connect the other end of the primary side 47P of the V-phase transformer 47 to the other end of the secondary side 48S of the W-phase transformer 48, and connect the other end of the primary side 48P of the W-phase transformer 48 to the other end of the secondary side 46S of the U-phase transformer 46.

[0074] Thus, if an interphase current cutoff circuit 41 is connected between each resonant capacitor 28U-28W and the magnetizing coil 9, and if the interphase current cutoff circuit 41 prevents or suppresses the current flowing through the magnetizing coil 9 when an interphase voltage is applied, and allows the current to flow through the magnetizing coil 9 when a voltage is applied that turns on the upper arm switching elements 18A-18C of all phases or the lower arm switching elements 18D-18F of all phases, then normal motor drive can be further realized. Example 3

[0075] Next, refer to Figure 9 as well as Figure 10 Another embodiment of the motor 3 driven by the motor drive device 1 of the present invention will be described. Furthermore, in each figure, it is assumed that... Figure 3 Components indicated by the same reference numerals have the same or identical functions. Additionally, the three-phase coils 8U to 8W are shown cut off at the end face of tooth 12 in each figure. Furthermore, in... Figure 9 The image shows a cross-section of the fixed magnetic magnet 17, the magnetization coil 9, and the variable magnetic magnet 13.

[0076] In this embodiment, the fixed magnetic magnet 17 is disposed radially outside the rotor core 16 and at both axial ends of the rotor core 16. Figure 9 (Only one end is shown). Furthermore, the variable magnetic force magnet 13 is arranged circumferentially inside the rotor core 16. And, as described above, the magnetic poles are formed by the fixed magnetic force magnet 17 and the variable magnetic force magnet 13.

[0077] Furthermore, in this embodiment, a slot 51 is formed in the circumferential direction on the inner circumferential surface of the stator core 7 at a position corresponding to the variable magnetic force magnet 13, and a magnetizing coil 9 is disposed in this slot 51. In addition, in this embodiment, the magnetizing coil 9 is arranged along the entire circumference of the inner circumferential surface of the stator core 7. With this configuration, the variable magnetic force magnet 13 can be magnetized over a wide circumferential range in a three-dimensional magnetic circuit manner via the magnetizing coil 9. Therefore, limitations related to the magnetic pole position of the rotor 6 when magnetizing the variable magnetic force magnet 13, i.e., the position of the variable magnetic force magnet 13 of the rotating rotor 6, can be mitigated or eliminated. Example 4

[0078] Next, refer to Figure 11 Another embodiment of the motor 3 driven by the motor drive device 1 of the present invention will be described. Furthermore, in each figure, it is assumed that... Figure 3 , Figure 9 , Figure 10 The same reference numerals denote parts that have the same or identical functions.

[0079] In this embodiment, the variable magnetic magnet 13 is arranged opposite to the aforementioned rotation axis, and the fixed magnetic magnets 17 are arranged to extend radially outward from both sides of the variable magnetic magnet 13. Furthermore, this group of eight variable magnetic magnets 13 and two fixed magnetic magnets 17 constitutes a magnetic pole.

[0080] Furthermore, the magnetizing coil 9 is not located on the stator core 7, but is located on the rotor core 16 surrounding each variable magnetic force magnet 13. Additionally, in Figure 11 The end face of the variable magnetic force magnet 13 is shown by cutting the magnetizing coil 9 through the end face of the rotor core 16. In this way, by placing the magnetizing coil 9 on the rotor core 16, magnetization can be achieved without being limited by the magnetic pole position of the rotor 6, i.e., the position of the rotating variable magnetic force magnet 13.

[0081] However, in this case, the magnetizing coil 9 is powered by a slip ring or brush (contact), or by a rotary transformer in a non-contact manner.

[0082] Furthermore, in the embodiment, when the magnetizing current Im flows through the magnetizing coil 9, all the upper arm switching elements 18A-18C of all phases or all the lower arm switching elements 18D-18F of all phases are simultaneously turned on. However, the moments of switching on or off can also be staggered. That is, as long as the period during which all the upper arm switching elements 18A-18C of all phases or all the lower arm switching elements 18D-18F of all phases are turned on is such that the magnetizing current Im flows through the magnetizing coil 9 through all the upper arm switching elements 18A-18C of all phases or all the lower arm switching elements 18D-18F of all phases, the effects of the present invention can be achieved. However, it is preferable that they are turned on simultaneously as in the embodiment.

[0083] In addition, in the embodiment, the magnetizing coil 9 is electrically connected to the connection points of the upper and lower arm switching elements 18A to 18F of all phases (through resonant capacitors 28U to 28W), but it is not limited to this. A non-contact power supply device can also be used to magnetically connect the magnetizing coil 9 to the connection points of the upper and lower arm switching elements 18A to 18F of all phases, so that the magnetizing current Im flows through the magnetizing coil 9 in a non-contact manner through the upper arm switching elements 18A to 18C of all phases or the lower arm switching elements 18D to 18F of all phases.

[0084] Furthermore, in the embodiments, the present invention is applied to a motor drive device for driving control of the motor of an electric compressor, but it is not limited thereto. The present invention is also effective for driving control of motors in various devices with variable magnetic force magnets. Explanation of reference numerals in the attached figures:

[0085] 1: Motor drive unit; 2: Control unit; 3: Motor; 4: Stator; 6: Rotor; 7: Stator core; 8U~8W: Three-phase coils; 9: Magnetizing coil; 13: Variable magnetic force magnet (low coercivity magnet); 16: Rotor core; 17: Fixed magnetic force magnet (high coercivity magnet); 18A~18F: Upper and lower arm switching elements; 21: Inverter circuit; 26: Upper arm power line; 27: Lower arm power line; 28U~28W: Resonant capacitor; 31: Resonant circuit; 32, 33: First neutral point capacitor, second neutral point capacitor; 35: Motor control unit; 36: PWM signal generation unit; 37: Gate driver; 38: Magnetization control unit; 39: Magnetization PWM signal generation unit; 41: Phase-to-phase current cutoff circuit; 46: Transformer for U phase; 47: Transformer for V phase; 48: Transformer for W phase.

Claims

1. A motor drive device, characterized in that, The motor drive device includes: an inverter circuit configured by connecting upper arm switching elements and lower arm switching elements in series between the upper arm power line and the lower arm power line in each phase; and a control device that controls the upper and lower arm switching elements of each phase of the inverter circuit, connecting the connection points of the upper and lower arm switching elements of each phase to the three-phase coils of the motor, so that three-phase current flows through the three-phase coils. The motor comprises: a magnet with high coercivity; two permanent magnets with lower coercivity than the magnet with high coercivity; and a magnetizing coil for changing the magnetization state of the magnet with lower coercivity, one end of the magnetizing coil being electrically or magnetically connected to the connection point of the upper and lower arm switching elements of all phases. The control device includes a magnetization control unit that causes a magnetization current to flow through the magnetization coil during the period when the upper arm switching element of all phases or the lower arm switching element of all phases is turned on.

2. The motor drive device according to claim 1, characterized in that, The magnetization control unit causes the magnetization current to flow through the magnetization coil by simultaneously turning on the upper arm switching elements of all phases or the lower arm switching elements of all phases.

3. The motor drive device according to claim 1, characterized in that, The motor drive device includes a resonant capacitor, which is connected between the magnetizing coil and the connection points of the upper and lower arm switching elements of each phase. The resonant circuit of these resonant capacitors and the magnetizing coil prevents or suppresses the flow of the three-phase current through the magnetizing coil.

4. The motor drive device according to claim 3, characterized in that, The motor drive device includes an interphase current interruption circuit, which is connected between each of the resonant capacitors and the magnetizing coil. The phase-to-phase current interruption circuit prevents or inhibits the current flowing through the magnetizing coil when a phase-to-phase voltage is applied, and allows the current to flow through the magnetizing coil when a voltage is applied that turns on the upper arm switching elements of all phases or the lower arm switching elements of all phases.

5. The motor drive device according to claim 4, characterized in that, The phase-to-phase current interruption circuit includes a transformer for phases UVW. The primary and secondary sides of the transformer for phases UVW are of the same polarity. One end of the primary side is connected to each of the resonant capacitors, and one end of the secondary side is connected to the magnetizing coil. The other end of the primary side of the transformer used for the U phase is connected to the other end of the secondary side of the transformer used for the W phase or the V phase. The other end of the primary side of the transformer used for phase V is connected to the other end of the secondary side of the transformer used for phase U or phase W. The other end of the primary side of the transformer used for the W phase is connected to the other end of the secondary side of the transformer used for the V phase or the U phase.

6. The motor drive device according to claim 1, characterized in that, The motor drive device includes a first neutral point capacitor and a second neutral point capacitor connected in series between the power lines of the upper and lower arms for generating a neutral point. The other end of the magnetizing coil is connected to the connection point of the first neutral point capacitor and the second neutral point capacitor.

7. A motor, characterized in that, The motor is driven by the motor drive device according to any one of claims 1 to 6. The motor comprises: a stator on which the three-phase coils are wound; and a rotor having the high-coercivity magnet and the low-coercivity magnet. The magnetizing coil is wound and mounted on the teeth of the stator on which the three-phase coil is wound and mounted.

8. A motor, characterized in that, The motor is driven by the motor drive device according to any one of claims 1 to 6. The motor comprises: a stator on which the three-phase coils are wound; and a rotor having the high-coercivity magnet and the low-coercivity magnet. The low-coercivity magnets are arranged circumferentially along the rotor. The magnetizing coil is located in the stator at a position corresponding to the magnet with low coercivity.

9. A motor, characterized in that, The motor is driven by the motor drive device according to any one of claims 1 to 6. The motor comprises: a stator on which the three-phase coils are wound; and a rotor having the high-coercivity magnet and the low-coercivity magnet. The magnetizing coil is disposed on the rotor near the low coercivity magnet and is powered by contact or non-contact.

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