Rotary transformer unit and motor device
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- TDK CORP
- Filing Date
- 2025-01-27
- Publication Date
- 2026-07-30
Smart Images
Figure JP2025002424_30072026_PF_FP_ABST
Abstract
Description
Rotary Transformer Unit and Motor Device
[0001] The present invention relates to a rotary transformer unit used in a wound field magnetic synchronous motor and a motor device including such a rotary transformer unit.
[0002] For example, a motor device includes a wound field magnetic synchronous motor (EESM: Electrically Excited Synchronous Motor). This motor device has a motor stator wound with a winding and a motor rotor wound with a winding. In this motor, the efficiency of the motor can be improved by changing the current flowing through the winding wound around the motor rotor according to the rotational speed of the motor. For example, Patent Document 1 discloses a technique for supplying current to the winding wound around the motor rotor through a rotary transformer and a diode. In this technique, a protection circuit is provided in the motor rotor to protect the diode of the rectifier circuit.
[0003] U.S. Patent Application Publication No. 2017-0070126
[0004] In such a motor device, when an overvoltage is applied to the diode of the rectifier circuit, the diode can be destroyed. Therefore, it is desired to protect the diode.
[0005] It is desirable to provide a rotary transformer unit and a motor device that can protect the diode.
[0006] A rotary transformer unit according to one embodiment of the present invention comprises a switching circuit, a rotary transformer, a rectifier circuit, a current estimation circuit, and a control circuit. The switching circuit has one or more switching elements and is capable of performing switching operations. The rotary transformer has a first winding provided on a stator fixed to a housing, wound in the circumferential direction of a shaft rotatable around a rotation axis and connected to the switching circuit, and a second winding provided on a rotor connected to the shaft and wound in the circumferential direction of the shaft. The rectifier circuit is connected to the second winding and is capable of rectifying the signal supplied from the second winding, and can supply the rectified signal to the second motor winding in a motor having a motor stator including the first motor winding and a motor rotor including the second motor winding. The current estimation circuit is capable of generating an estimated current value by estimating the alternating current transmitted from the first motor winding to the second motor winding based on the first motor current flowing through the first motor winding, the rotational phase of the motor rotor, and the rotational speed of the motor rotor. The control circuit is capable of controlling the switching operation based on the estimated current value so that the current value of the second motor current flowing through the second motor winding falls within a predetermined current range.
[0007] A motor device according to one embodiment of the present invention comprises a motor, a shaft, a switching circuit, a rotary transformer, a rectifier circuit, and a control circuit. The motor has a motor stator including a first motor winding and a motor rotor including a second motor winding. The shaft is connected to the motor rotor and is rotatable about a rotation axis. The switching circuit has one or more switching elements and is capable of performing switching operations. The rotary transformer is provided on the stator fixed to the housing and has a first winding wound in the circumferential direction of the shaft and connected to the switching circuit, and a second winding provided on the rotor connected to the shaft and wound in the circumferential direction of the shaft. The rectifier circuit is connected to the second winding and is capable of rectifying the signal supplied from the second winding and supplying the rectified signal to the second motor winding. The current estimation circuit can generate an estimated current value by estimating the alternating current transmitted from the first motor winding to the second motor winding based on the first motor current flowing through the first motor winding, the rotational phase of the motor rotor, and the rotational speed of the motor rotor. The control circuit can control the switching operation based on the estimated current value so that the current value of the second motor current flowing through the second motor winding is within a predetermined current range.
[0008] According to one embodiment of the present invention, the rotary transformer unit and motor device can protect the diode.
[0009] Figure 1 is a circuit diagram showing an example configuration of a motor device according to one embodiment of the present invention. Figure 2 is a circuit diagram showing an example configuration of a switching control circuit in the inverter circuit shown in Figure 1. Figure 3 is a perspective view showing an example configuration of a rotary transformer shown in Figure 1. Figure 4 is a cross-sectional view showing an example configuration of a stator and rotor shown in Figure 1. Figure 5 is a plan view showing an example configuration of the stator substrate and rotor substrate shown in Figure 3. Figure 6 is an explanatory diagram showing an example of power transmission operation in the rotary transformer shown in Figure 1. Figure 7 is a waveform diagram showing an example of operation of the motor device shown in Figure 1. Figure 8 is a waveform diagram showing another example of operation of the motor device shown in Figure 1. Figure 9 is an explanatory diagram for explaining the operation of the motor device shown in Figure 1. Figure 10 is a flowchart showing an example of operation of the motor device shown in Figure 1. Figure 11 is a waveform diagram showing another example of operation of the motor device shown in Figure 1. Figure 12 is a waveform diagram showing another example of operation of the motor device shown in Figure 1. Figure 13 is a circuit diagram showing an example configuration of a motor device according to a modified example.
[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0011] <Embodiment> [Configuration Example] Figure 1 shows an example configuration of a motor device 1 equipped with a rotary transformer unit according to an embodiment of the present invention. The motor device 1 is connected to an external control device 8 and a DC power supply 9. The external control device 8 is configured to instruct the motor device 1 on the rotational speed. The DC power supply 9 is configured to supply DC power to the motor device 1. The motor device 1 is configured to generate driving force, which is mechanical energy, using the DC power supplied from the DC power supply 9, based on instructions from the external control device 8. The motor device 1 includes a three-phase inverter circuit 10, a rotary transformer unit 20, a motor 90, and a control circuit 99.
[0012] The three-phase inverter circuit 10 is configured to convert the DC power supplied from the DC power supply 9 into three-phase (U-phase, V-phase, W-phase) AC power based on instructions from the control circuit 99. The three-phase inverter circuit 10 includes a switching circuit 11 and a switching control circuit 12.
[0013] The switching circuit 11 has switching elements SW1 to SW6. In this example, switching elements SW1 to SW6 are configured using field-effect transistors. However, it is not limited to this, and switching elements SW1 to SW6 may be configured using, for example, insulated-gate bipolar transistors. Switching element SW1 is provided in the path connecting voltage line L11 and node N1 and is configured to perform switching operations based on control signal G1. Switching element SW2 is provided in the path connecting node N1 and reference voltage line L12 and is configured to perform switching operations based on control signal G2. Switching element SW3 is provided in the path connecting voltage line L11 and node N2 and is configured to perform switching operations based on control signal G3. Switching element SW4 is provided in the path connecting node N2 and reference voltage line L12 and is configured to perform switching operations based on control signal G4. Switching element SW5 is provided in the path connecting voltage line L11 and node N3 and is configured to perform switching operations based on control signal G5. The switching element SW6 is provided in the path connecting node N3 and the reference voltage line L12, and is configured to perform switching operations based on the control signal G6. Nodes N1 to N3 are connected to the three windings 91A of the stator 91 (described later) of the motor 90 via the motor 90's current sensor 95 (described later).
[0014] The switching control circuit 12 is configured to control the operation of the switching circuit 11 based on instructions from the control circuit 99. The switching control circuit 12 is configured to include, for example, a microcontroller. The switching control circuit 12 generates control signals G1 to G6 and uses these control signals G1 to G6 to control the operation of the switching circuit 11.
[0015] With this configuration, the three-phase inverter circuit 10 converts the DC power supplied from the DC power supply 9 into three-phase (U-phase, V-phase, and W-phase) AC power. The three-phase inverter circuit 10 then supplies this three-phase AC power to the three windings 91A of the stator 91 (described later) of the motor 90.
[0016] The rotary transformer unit 20 is configured to generate power to be supplied to the windings 92A of the rotor 92 (described later) of the motor 90, based on instructions from the control circuit 99. The rotary transformer unit 20 includes an inverter circuit 30, a rotary transformer 40, a rectifier circuit 23, and a current estimation circuit 24.
[0017] The inverter circuit 30 is configured to generate power to be supplied to the windings 92A of the rotor 92 (described later) of the motor 90 via the rotary transformer 40, based on instructions from the control circuit 99. The inverter circuit 30 includes a switching circuit 31 and a switching control circuit 32.
[0018] The switching circuit 31 has switching elements SWA to SWD. In this example, switching elements SWA to SWD are configured using field-effect transistors. However, it is not limited to this, and switching elements SWA to SWD may be configured using, for example, insulated-gate bipolar transistors. Switching element SWA is provided in the path connecting voltage line L11 and node NA and is configured to perform switching operations based on control signal GA. Switching element SWB is provided in the path connecting node NA and reference voltage line L12 and is configured to perform switching operations based on control signal GB. Switching element SWC is provided in the path connecting voltage line L11 and node NB and is configured to perform switching operations based on control signal GC. Switching element SWD is provided in the path connecting node NB and reference voltage line L12 and is configured to perform switching operations based on control signal GD. Node NA is connected to one end of winding 43 (described later) of the rotary transformer 40. Node NB is connected to the other end of winding 43 of the rotary transformer 40.
[0019] The switching control circuit 32 is configured to control the operation of the switching circuit 31 based on instructions from the control circuit 99. The switching control circuit 32 is configured to include, for example, a microcontroller. The switching control circuit 32 is supplied with data from the control circuit 99 regarding the target current value I1 of the DC component of the current flowing through the winding 92A of the rotor 92 (described later) of the motor 90. Based on this target current value I1 and the estimated current value I2 of the AC current transmitted from the stator 91 of the motor 90 to the winding 92A of the rotor 92, supplied from the current estimation circuit 24, the switching control circuit 32 generates a switching duty cycle D, thereby generating control signals GA to GD. The switching control circuit 32 then uses these control signals GA to GD to control the operation of the switching circuit 31.
[0020] Figure 2 shows an example configuration of the switching control circuit 32. The switching control circuit 32 includes a target current value setting unit 33, a duty cycle generation unit 34, a duty cycle correction unit 35, and a control signal generation unit 36. For convenience of explanation, Figure 2 also shows the control circuit 99 and the current estimation circuit 24.
[0021] The target current value setting unit 33 is configured to set the target current value I1 based on data for the target current value I1 of the DC component of the current flowing through the winding 92A of the rotor 92 (described later) of the motor 90, which is included in the instructions supplied from the control circuit 99.
[0022] The duty cycle generation unit 34 is configured to generate a switching duty cycle D1 based on a target current value I1.
[0023] The duty cycle correction unit 35 is configured to generate a switching duty cycle D by correcting the switching duty cycle D1 based on a target current value I1 and an estimated current value I2 supplied from the current estimation circuit 24. Specifically, as will be described later, the duty cycle correction unit 35 generates a switching duty cycle D by correcting the switching duty cycle D1 based on the target current value I1 and the estimated current value I2 so that the current flowing through the winding 92A of the rotor 92 (described later) of the motor 90 does not become negative.
[0024] The control signal generation unit 36 is configured to generate control signals GA to GD based on the switching duty cycle D supplied from the duty cycle correction unit 35.
[0025] In this way, the switching control circuit 32 generates control signals GA to GD. Based on these control signals GA to GD, the inverter circuit 30 controls the power supplied to the winding 92A of the rotor 92 (described later) of the motor 90 by performing PWM (Pulse Width Modulation) control. In this example, PWM control is used, but it is not limited to this, and phase shift control may also be used. In this case, the switching control circuit 32 generates a phase shift amount instead of a switching duty cycle, and generates control signals GA to GD based on this phase shift amount.
[0026] The rotary transformer 40 has a winding 43 and a winding 47. Winding 43 is provided on the stator 42 (described later), with one end connected to node NA of the switching circuit 31 and the other end connected to node NB of the switching circuit 31. Winding 47 is provided on the rotor 46 (described later), with one end connected to node NC (described later) of the rectifier circuit 23 and the other end connected to node ND (described later) of the rectifier circuit 23. The rotary transformer 40 is configured to transmit power from the stator 42 to the rotor 46.
[0027] Figure 3 shows an example of the external configuration of the rotary transformer 40. Figure 4 shows an example of the cross-sectional configuration of the rotary transformer 40. Figure 5 shows an example of the configuration of windings 43 and 47. The rotary transformer 40 has a shaft 41, a stator 42, and a rotor 46.
[0028] The shaft 41 is connected to the rotor 92 (described later) of the motor 90 and is configured to rotate around the rotation axis AZ in accordance with the driving force generated by the motor 90. The shaft 41 may be directly connected to the rotor 92 of the motor 90, or it may be indirectly connected via other components. Alternatively, the shaft 41 may be formed integrally with the rotor 92 of the motor 90.
[0029] The stator 42 is fixed to a housing (not shown) of the motor device 1. As shown in Figures 3 and 4, the stator 42 has a magnetic core 44, a substrate 45, and windings 43.
[0030] The magnetic core 44 is constructed using a magnetic material such as ferrite. As shown in Figures 3 and 4, the magnetic core 44 is configured to surround the substrate 45 and the rotor 46. The magnetic core 44 has a magnetic core 44A and a magnetic core 44B.
[0031] As shown in Figure 3, the magnetic core 44A has a ring shape in a plane intersecting the axial direction of the rotation axis AZ. As shown in Figure 4, the magnetic core 44A has a protrusion 44C on its outer circumference in the plane intersecting the axial direction of the rotation axis AZ that projects in the direction in which the magnetic core 44B is provided. Also, as shown in Figure 4, the magnetic core 44A has a protrusion 44D at its end near the shaft 41 that projects in the direction in which the magnetic core 44B is provided. These protrusions 44C and 44D have a ring shape in a plane intersecting the axial direction of the rotation axis AZ.
[0032] The magnetic core 44B, like the magnetic core 44A, has a ring shape in a plane intersecting the axial direction of the rotation axis AZ. Furthermore, like the magnetic core 44A, the magnetic core 44B has a protrusion 44C on its outer circumference in the plane intersecting the axial direction of the rotation axis AZ, projecting in the direction from which the magnetic core 44A is provided. This protrusion 44C has a ring shape in the plane intersecting the axial direction of the rotation axis AZ.
[0033] The magnetic cores 44A and 44B are connected such that the protrusions 44C of magnetic core 44A and magnetic core 44B are in contact with each other. In this way, a cavity is provided inside the magnetic core 44.
[0034] The substrate 45 is, for example, a printed circuit board (PCB). In this example, as shown in Figure 4, the substrate 45 is provided on the surface of the magnetic core 44A that faces the magnetic core 44B. The substrate 45 has a ring shape, as shown in Figure 5. The substrate 45 is fitted onto the outside of the ring-shaped protrusion 44D of the magnetic core 44A, as shown in Figure 4.
[0035] The winding 43 is constructed using pattern wiring provided on the substrate 45 and is wound multiple times along the circumferential direction of the rotation axis AZ. In Figure 5, the area on the substrate 45 where the winding 43 is provided is shaded. The winding 43 may be provided on one of the two surfaces of the substrate 45, or on both surfaces. Furthermore, if the substrate 45 is a multilayer substrate, the winding 43 may be constructed using pattern wiring inside the substrate 45. This winding 43 is connected to the inverter circuit 30 as shown in Figure 1.
[0036] The rotor 46 is connected to the shaft 41 and configured to rotate about the rotation axis AZ. As shown in Figure 4, the rotor 46 is positioned so as to be sandwiched between the magnetic cores 44A and 44B of the stator 42 in the axial direction of the rotation axis AZ. As shown in Figures 4 and 5, the rotor 46 has a substrate 48 and windings 47.
[0037] The substrate 48 is, for example, a printed circuit board. The substrate 48 has a circular shape, as shown in Figure 5. In this example, the size of the substrate 48 is approximately the same as the size of the substrate 45 of the stator 42.
[0038] As shown in Figure 5, the winding 47 is constructed using pattern wiring provided on the substrate 48 and is wound multiple times along the circumferential direction of the rotation axis AZ. In Figure 5, the area on the substrate 48 where the winding 47 is provided is shaded. The winding 47 may be provided on one of the two surfaces of the substrate 48, or on both surfaces. Also, if the substrate 48 is a multilayer substrate, the winding 47 may be constructed using pattern wiring inside the substrate 48. As shown in Figure 5, in this example, the area on the substrate 48 where the winding 47 is provided is approximately the same as the area on the substrate 45 of the stator 42 where the winding 43 is provided. This winding 47 is connected to the rectifier circuit 23 as shown in Figure 1.
[0039] Figure 6 illustrates the power transmission operation in the rotary transformer 40. The windings 43 of the stator 42 generate a magnetic field based on the AC power supplied from the inverter circuit 30. The portion of the magnetic core 44A closest to the shaft 41 and the portion of the magnetic core 44B closest to the shaft 41 are magnetically coupled to each other. As a result, the rotary transformer 40 generates a magnetic path MP through the magnetic cores 44A and 44B, as shown in Figure 6. The windings 47 of the rotor 46 then generate AC power based on the magnetic field in this magnetic path MP and supply the generated AC power to the rectifier circuit 23. In this way, the rotary transformer 40 is able to transmit AC power from the stator 42 to the rotor 46 by contactless transmission.
[0040] The rectifier circuit 23 (Figure 1) is configured to rectify the AC power supplied from the winding 47 of the rotor 46. The rectifier circuit 23 is provided on a circuit board (not shown) connected to the shaft 41. The rectifier circuit 23 has diodes DA to DD. The anode of diode DA is connected to node NC and its cathode is connected to voltage line L21. The anode of diode DB is connected to reference voltage line L22 and its cathode is connected to node NC. The anode of diode DC is connected to node ND and its cathode is connected to voltage line L21. The anode of diode DD is connected to reference voltage line L22 and its cathode is connected to node ND. Voltage line L21 is connected to one end of winding 92A of the rotor 92 (described later) of the motor 90. Reference voltage line L22 is connected to the other end of winding 92A of the rotor 92 of the motor 90.
[0041] The current estimation circuit 24 is configured to estimate the alternating current transmitted from the three windings 91A of the stator 91 (described later) to the windings 92A of the rotor 92, based on the current flowing through the three windings 91A of the stator 91 (described later), the rotational phase of the rotor 92 (described later) of the motor 90, and the rotational speed of the rotor 92 of the motor 90. That is, since the three windings 91A of the stator 91 of the motor 90 and the windings 92A of the rotor 92 of the motor 90 are magnetically coupled, an alternating current component is generated in the current flowing through the windings 92A of the rotor 92 in accordance with the alternating current flowing through the three windings 91A. The coupling state between the three windings 91A of the stator 91 of the motor 90 and the windings 92A of the rotor 92 of the motor 90 changes according to the rotational phase of the rotor 92. The current estimation circuit 24 obtains the time change of the magnetic flux (dΦ / dt) based on the coupling state, the current flowing through the three windings 91A of the stator 91, and the rotational speed of the rotor 92. Based on this time change of magnetic flux, the current estimation circuit 24 estimates the alternating current transmitted from the three windings 91A of the stator 91 to the winding 92A of the rotor 92. The current estimation circuit 24 then sequentially supplies the estimated current value I2, which is the instantaneous value of this alternating current, to the switching control circuit 32.
[0042] The motor 90 is a wound-field synchronous motor. The motor 90 has a stator 91, a rotor 92, a rotation phase sensor 93, a rotation speed sensor 94, and a current sensor 95.
[0043] The stator 91 is a so-called stator and is fixed to a housing (not shown) of the motor 90. The stator 91 has three windings 91A. One ends of the three windings 91A are respectively connected to nodes N1 to N3 in the three-phase inverter 10 via the current sensor 95, and the other ends are connected to each other. Three-phase (U-phase, V-phase, W-phase) AC power generated by the three-phase inverter 10 is supplied to the three windings 91A.
[0044] The rotor 92 is a so-called rotor and is configured to rotate about the rotation axis AZ. The rotor 92 has a winding 92A. One end of the winding 92A is connected to the voltage line L21, and the other end is connected to the reference voltage line L22. A signal rectified by the rectifier circuit 23 of the rotary transformer unit 20 is supplied to the winding 92A, and a current flows through it. Thereby, the winding 92A of the rotor 92 is configured to generate a magnetic field corresponding to this current.
[0045] The rotation phase sensor 93 is configured to detect the rotation phase of the rotor 92. Then, the rotation phase sensor 93 supplies a signal indicating the rotation phase of the rotor 92 to the current estimation circuit 24.
[0046] The rotation speed sensor 94 is configured to detect the rotation speed of the rotor 92. Then, the rotation speed sensor 94 supplies a signal indicating the rotation speed of the rotor 92 to the current estimation circuit 24 and the control circuit 99.
[0047] The current sensor 95 is configured to detect the currents flowing through the three windings 91A of the stator 91 respectively. Then, the current sensor 95 supplies a signal indicating the currents flowing through the three windings 91A to the current estimation circuit 24.
[0048] The control circuit 99 is configured to control the operations of the three-phase inverter circuit 10 and the inverter circuit 30 based on an instruction from the external control device 8 and a signal indicating the rotational speed supplied from the motor 90. The control circuit 99 includes, for example, a microcontroller. The control circuit 99 controls the rotational speed of the motor 90 by controlling the operation of the three-phase inverter circuit 10 based on an instruction of the rotational speed from the external control device 8 and a signal indicating the rotational speed in the motor 90. Further, the control circuit 99 generates data on the target current value I1 of the DC component of the current flowing through the winding 92A of the rotor 92 of the motor 90 based on an instruction of the rotational speed from the external control device 8, and supplies this data to the inverter circuit 30. Thereby, the control circuit 99 is configured to control the magnetic field generated by the rotor 92 of the motor 90.
[0049] With this configuration, in the motor device 1, the rotational speed of the motor 90 is controlled based on the three-phase (U-phase, V-phase, W-phase) AC power generated by the three-phase inverter circuit 10, and the magnetic field generated by the rotor 92 of the motor 90 is controlled based on the single-phase AC power generated by the inverter circuit 30. In the motor device 1, for example, when the rotational speed of the motor 90 is low, the magnetic field generated by the rotor 92 of the motor 90 is strengthened, and when the rotational speed of the motor 90 is high, the magnetic field generated by the rotor 92 of the motor 90 is weakened. Thereby, in the motor device 1, the efficiency of the motor 90 can be increased at a wide range of rotational speeds.
[0050] Here, the switching circuit 31 corresponds to a specific example of the "switching circuit" in one embodiment of the present disclosure. The switching elements SWA to SWD correspond to a specific example of "one or more switching elements" in one embodiment of the present disclosure. The rotary transformer 40 corresponds to a specific example of the "rotary transformer" in one embodiment of the present disclosure. The stator 42 corresponds to a specific example of the "stator" in one embodiment of the present disclosure. The rotating shaft AZ corresponds to a specific example of the "rotating shaft" in one embodiment of the present disclosure. The shaft 41 corresponds to a specific example of the "shaft" in one embodiment of the present disclosure. The winding 43 corresponds to a specific example of the "first winding" in one embodiment of the present disclosure. The rotor 46 corresponds to a specific example of the "rotor" in one embodiment of the present disclosure. The winding 47 corresponds to a specific example of the "winding" in one embodiment of the present disclosure. The rectifier circuit 23 corresponds to a specific example of the "rectifier circuit" in one embodiment of the present disclosure. The current estimation circuit 24 corresponds to a specific example of the "estimation circuit" in one embodiment of the present disclosure. Motor 90 corresponds to a specific example of the "motor" in one embodiment of the present disclosure. Stator 91 corresponds to a specific example of the "motor stator" in one embodiment of the present disclosure. The three windings 91A correspond to a specific example of the "first motor winding" in one embodiment of the present disclosure. The current flowing through the three windings 91A corresponds to a specific example of the "first motor current" in one embodiment of the present disclosure. Rotor 92 corresponds to a specific example of the "motor rotor" in one embodiment of the present disclosure. Winding 92A corresponds to a specific example of the "second motor winding" in one embodiment of the present disclosure. The current flowing through winding 92A corresponds to a specific example of the "second motor current" in one embodiment of the present disclosure. Switching control circuit 32 corresponds to a specific example of the "control circuit" in one embodiment of the present disclosure.
[0051] [Operation and Function] Next, the operation and function of the motor device 1 of this embodiment will be described.
[0052] (Overall Operation Summary) The control circuit 99 controls the operation of the three-phase inverter circuit 10 and the inverter circuit 30 based on instructions from the external control device 8 and a control signal indicating the rotational speed supplied from the motor 90. Based on instructions from the control circuit 99, the three-phase inverter circuit 10 converts the DC power supplied from the DC power supply 9 into three-phase (U-phase, V-phase, W-phase) AC power and supplies this three-phase AC power to the three windings 91A of the stator 91 of the motor 90. Based on instructions from the control circuit 99, the inverter circuit 30 converts the DC power supplied from the DC power supply 9 into single-phase AC power and supplies this AC power to the windings 43 of the stator 42 of the rotary transformer 40. The rotary transformer 40 transmits the AC power supplied from the inverter circuit 30 from the stator 42 to the rotor 46 by contactless transmission. The rectifier circuit 23 rectifies the AC power supplied from the rotor 46 and supplies the rectified power to the winding 92A of the rotor 92 of the motor 90. The motor 90 generates driving force, which is mechanical energy, based on the three-phase (U-phase, V-phase, W-phase) AC power supplied from the three-phase inverter circuit 10. As a result, the shaft 41 rotates around the rotation axis AZ.
[0053] The rotation phase sensor 93 detects the rotation phase of the rotor 92. The rotation speed sensor 94 detects the rotation speed of the rotor 92. The current sensor 95 detects the current flowing through each of the three windings 91A of the stator 91. The current estimation circuit 24 generates an estimated current value I2 by estimating the alternating current transmitted from the three windings 91A of the stator 91 to the windings 92A of the rotor 92 based on the current flowing through the three windings 91A of the stator 91 of the motor 90, the rotation phase of the rotor 92 of the motor 90, and the rotation speed of the rotor 92 of the motor 90. The switching control circuit 32 generates control signals GA to GD by generating a switching duty cycle D based on a target current value I1 of the DC component of the current flowing through the windings 92A of the rotor 92 of the motor 90, and this estimated current value I2.
[0054] (Detailed Operation) Figure 7 shows an example of the waveform of the current (current I92) flowing through the winding 92A of the rotor 92 of the motor 90, and the waveform of the current (current I43) flowing through the winding 43 of the rotary transformer 40.
[0055] The rectifier circuit 23 of the rotary transformer unit 20 rectifies the AC power supplied from the rotary transformer 40 and supplies the rectified power to the winding 92A of the rotor 92 of the motor 90. Therefore, it is expected that a nearly DC current will flow through this winding 92A. However, as shown in Figure 7, the current I92 flowing through this winding 92A includes an AC component in addition to the DC component. That is, since the three windings 91A of the stator 91 of the motor 90 and the winding 92A of the rotor 92 of the motor 90 are magnetically coupled, an AC component is generated in the current flowing through the winding 92A of the rotor 92 in accordance with the AC current flowing through the three windings 91A.
[0056] Furthermore, the AC component of the current flowing through the winding 92A of the rotor 92 is transmitted to the winding 43 of the rotary transformer 40 via the rectifier circuit 23 and the winding 47 of the rotary transformer 40. As a result, as shown in Figure 7, the amplitude of the current I43 flowing through the winding 43 of the rotary transformer 40 changes in accordance with the current I92.
[0057] Thus, the current I92 flowing through winding 92A includes both a DC component and an AC component. In the motor device 1, the magnetic field generated by the rotor 92 of the motor 90 is controlled by controlling the DC component of the current I92 flowing through winding 92A. Therefore, in the motor device 1, for example, if the DC component is reduced, the current I92 flowing through winding 92A can reach 0A, as shown in Figure 8. If the current I92 becomes negative, current flows through winding 92A from the reference voltage line L22 toward the voltage line L21. In this case, a large reverse voltage may be generated in each of the diodes DA to DD of the rectifier circuit 23.
[0058] Figure 9 shows an example of the waveform of the current I92 flowing through winding 92A and the waveform of the voltage (voltage V92) across the winding 92A. In this example, as a hypothetical case, a rectangular wave current I92 is applied to winding 92A of the rotor 92 of motor 90. When the current I92 decreases rapidly and approaches a negative current, the voltage across winding 92A increases rapidly. In this way, a large reverse voltage is generated in each of the diodes DA to DD of the rectifier circuit 23. As a result, diodes DA to DD may be destroyed.
[0059] Therefore, in the motor device 1, the current estimation circuit 24 generates an estimated current value I2 by estimating the alternating current transmitted from the three windings 91A of the stator 91 to the winding 92A of the rotor 92, based on the current flowing through the three windings 91A of the stator 91 of the motor 90, the rotational phase of the rotor 92 of the motor 90, and the rotational speed of the rotor 92 of the motor 90. Then, the switching control circuit 32 generates control signals GA to GD by generating a switching duty cycle D such that the current I92 flowing through the winding 92A does not become negative, based on a target current value I1 which represents the DC component of the current flowing through the winding 92A of the rotor 92 of the motor 90, and this estimated current value I2.
[0060] Figure 10 shows an example of the operation of the current estimation circuit 24 and the switching control circuit 32. The current estimation circuit 24 and the switching control circuit 32 perform the following processing in each switching cycle.
[0061] First, the switching control circuit 32 generates a switching duty cycle D1 based on the target current value I1 (step S101). Specifically, the target current value setting unit 33 sets the target current value I1 based on data for the target current value I1 of the DC component of the current flowing through the winding 92A of the rotor 92 of the motor 90, which is included in the instructions supplied from the control circuit 99. Then, the duty cycle generation unit 34 generates the switching duty cycle D1 based on that target current value I1.
[0062] Next, the current estimation circuit 24 generates an estimated current value I2 by estimating the alternating current transmitted from the three windings 91A of the stator 91 to the windings 92A of the rotor 92 (step S102). Specifically, the current estimation circuit 24 generates an estimated current value I2 by estimating the alternating current transmitted from the three windings 91A of the stator 91 to the windings 92A of the rotor 92 based on the current flowing through the three windings 91A of the stator 91 of the motor 90, the rotational phase of the rotor 92 of the motor 90, and the rotational speed of the rotor 92 of the motor 90.
[0063] Next, the duty cycle correction unit 35 checks whether the sum of the target current value I1 and the estimated current value I2 is a negative current value (I1 + I2 < 0) (step S103).
[0064] In step S103, if the sum of the target current value I1 and the estimated current value I2 is not a negative current value ("N" in step S103), the duty cycle correction unit 35 uses the switching duty cycle D1 obtained in step S101 as the switching duty cycle D (step S104). Then the process proceeds to step S107.
[0065] In step S103, if the sum of the target current value I1 and the estimated current value I2 is a negative current value ("Y" in step S103), the duty cycle correction unit 35 calculates a correction value ΔD for the switching duty cycle D1 (step S105). Specifically, the duty cycle correction unit 35 first calculates the increase in current that the rotary transformer unit 20 should supply to the winding 92A of the rotor 92 of the motor 90 in order to prevent the current value I92 flowing through the winding 92A from becoming a negative current value. Then, based on that increase in current, the duty cycle correction unit 35 calculates a correction value ΔD for the switching duty cycle D1.
[0066] Then, the duty cycle correction unit 35 calculates the switching duty cycle D by calculating the sum of the switching duty cycle D1 and the correction value ΔD (step S106). The process then proceeds to step S107.
[0067] Then, the control signal generation unit 36 generates control signals GA to GD based on the switching duty cycle D (step S107).
[0068] This completes the process.
[0069] Figure 11 shows an example of the waveform of the current I92 flowing through the winding 92A of the rotor 92 of the motor 90 in the motor device 1. When the current I92 flowing through the winding 92A of the motor device 1 is about to become negative, the rotary transformer unit 20 increases the current flowing through the winding 92A of the rotor 92 of the motor 90 to prevent the current I92 from becoming negative. As a result, reverse voltages are not generated across the diodes DA to DD of the rectifier circuit 23, and the diodes DA to DD are not damaged. Consequently, the motor device 1 can protect the diodes DA to DD.
[0070] In the example shown in Figure 10, step S103 checks whether the sum of the target current value I1 and the estimated current value I2 is a negative current value (I1 + I2 < 0), but it is not limited to this. Alternatively, for example, it may be checked whether the sum of the target current value I1 and the estimated current value I2 is less than a positive threshold Ith (I1 + I2 < Ith). If the sum of the target current value I1 and the estimated current value I2 is less than this threshold Ith, the duty cycle correction unit 35 calculates the increase in current that the rotary transformer unit 20 should supply to the winding 92A of the rotor 92 of the motor 90 so that the current value I92 flowing through the winding 92A does not fall below this threshold Ith. Then, the duty cycle correction unit 35 calculates a correction value ΔD for the switching duty cycle D1 based on that increase in current. In this case, as shown in Figure 12, the current I92 flowing through the winding 92A of the rotor 92 of the motor 90 becomes greater than or equal to the threshold value Ith. As a result, reverse voltage is not generated across each of the diodes DA to DD of the rectifier circuit 23, and therefore the diodes DA to DD are not damaged. Consequently, the motor device 1 can protect the diodes DA to DD.
[0071] Thus, the rotary transformer unit 20 includes a rotary transformer 40 having a switching circuit 31 having one or more switching elements (switching elements SWA to SWD) and capable of performing switching operations, a first winding (winding 43) provided on a stator 42 fixed to the housing and wound in the circumferential direction of a shaft 41 that can rotate around the rotation axis AZ and connected to the switching circuit 31, and a second winding (winding 47) provided on a rotor 46 connected to the shaft 41 and wound in the circumferential direction of the shaft 41, and a motor stator (stator 91) including a first motor winding (three windings 91A) and a second motor The rotary transformer unit 20 includes a rectifier circuit 23 that can supply current to the second motor winding (winding 92A) in a motor rotor (rotor 92) that includes a motor winding (winding 92A), a current estimation circuit 24 that can generate an estimated current value I2 by estimating the alternating current transmitted from the first motor winding (three windings 91A) to the second motor winding (winding 92A) based on the first motor current flowing through the first motor winding (three windings 91A), the rotational phase of the motor rotor (rotor 92), and the rotational speed of the motor rotor (rotor 92), and a control circuit (switching control circuit 32) that can control the switching operation so that the current value of the second motor current flowing through the second motor winding (winding 92A) is within a predetermined range based on the estimated current value I2.
[0072] For example, if a protection circuit is provided in the rectifier circuit 23 to protect diodes DA to DD, the circuit can become complex. Since this rectifier circuit 23 is installed in a rotating system, this protection circuit is also installed in the rotating system. In a rotating system, forces such as centrifugal force are applied, so if the circuit becomes complex in this way, its robustness may decrease.
[0073] On the other hand, in the rotary transformer unit 20, the current estimation circuit 24 generates an estimated current value I2 by estimating the alternating current transmitted from the three windings 91A of the stator 91 of the motor 90 to the winding 92A of the rotor 92, based on the current flowing through the three windings 91A of the stator 91 of the motor 90, the rotational phase of the rotor 92 of the motor 90, and the rotational speed of the motor rotor (rotor 92). Then, the switching control circuit 32 controls the switching operation based on the estimated current value I2 so that the current value of the second motor current flowing through the second motor winding (winding 92A) does not fall below a predetermined current value. As a result, the rotary transformer unit 20 can effectively protect diodes DA to DD without providing a protection circuit to protect diodes DA to DD in the rotating system.
[0074] In the rotary transformer unit 20, the rectifier circuit 23 is capable of allowing current to flow in a predetermined direction through the second motor winding (winding 92A). The current value of the second motor current is positive when the second motor current flows in the predetermined direction through the second motor winding (winding 92A), and the predetermined current range is set to be 0 or greater. In the rotary transformer unit 20, the current value of the current flowing through the winding 92A of the rotor 92 of the motor 90 is controlled to be 0 or greater. As a result, in the rotary transformer unit 20, reverse voltage does not occur across the diodes DA to DD of the rectifier circuit 23, thus protecting the diodes DA to DD.
[0075] In the rotary transformer unit 20, the motor 90 further includes a current sensor 95 capable of detecting a first motor current flowing through the first motor winding (three windings 91A), a rotational phase sensor 93 capable of detecting the rotational phase of the motor rotor (rotor 92), and a rotational speed sensor 94 capable of detecting the rotational speed of the motor rotor (rotor 92). The current estimation circuit 24 is capable of generating an estimated current value I2 by estimating the alternating current transmitted from the first motor winding (three windings 91A) to the second motor winding (winding 92A) based on the first motor current detected by the current sensor 95, the rotational phase detected by the rotational phase sensor 93, and the rotational speed detected by the rotational speed sensor 94. In this way, the current estimation circuit 24 can generate an estimated current value I2 by estimating the alternating current transmitted from the first motor winding (three windings 91A) to the second motor winding (winding 92A) based on the detection results of the current sensor 95, the rotational phase sensor 93, and the rotational speed sensor 94. This allows the rotary transformer unit 20 to protect diodes DA to DD.
[0076] [Effects] As described above, this embodiment includes a switching circuit having one or more switching elements and capable of performing switching operations; a rotary transformer having a first winding provided on a stator fixed to a housing and wound in the circumferential direction of a shaft rotatable around a rotation axis and connected to the switching circuit, and a second winding provided on a rotor connected to the shaft and wound in the circumferential direction of the shaft; a rectifier circuit connected to the second winding and capable of rectifying the signal supplied from the second winding and supplying the rectified signal to the second motor winding in a motor having a motor stator including the first motor winding and a motor rotor including the second motor winding; a current estimation circuit capable of generating an estimated current value by estimating the alternating current transmitted from the first motor winding to the second motor winding based on the first motor current flowing through the first motor winding, the rotation phase of the motor rotor, and the rotation speed of the motor rotor; and a control circuit capable of controlling the switching operation based on the estimated current value so that the current value of the second motor current flowing through the second motor winding becomes a value within a predetermined current range. This protects the diode.
[0077] In this embodiment, the rectifier circuit is capable of allowing current to flow in a predetermined direction in the second motor winding. The current value of the second motor current is positive when the second motor current flows in the predetermined direction in the second motor winding, and the predetermined current range is set to be 0 or greater, thereby protecting the diode.
[0078] In this embodiment, the motor further includes a current sensor capable of detecting a first motor current flowing through a first motor winding, a rotational phase sensor capable of detecting the rotational phase of the motor rotor, and a rotational speed sensor capable of detecting the rotational speed of the motor rotor. The current estimation circuit is capable of generating an estimated current value by estimating the alternating current transmitted from the first motor winding to the second motor winding based on the first motor current detected by the current sensor, the rotational phase detected by the rotational phase sensor, and the rotational speed detected by the rotational speed sensor. This protects the diode.
[0079] [Modification] In the above embodiment, the motor 90 is equipped with a current sensor 95, a rotational phase sensor 93, and a rotational speed sensor 94, and the current estimation circuit 24 estimates the alternating current transmitted from the three windings 91A of the stator 91 to the winding 92A of the rotor 92 based on the detection results of these sensors, but it is not limited to this. Alternatively, as shown in the motor device 1A in Figure 13, a three-phase inverter circuit may estimate the current flowing through the three windings 91A in the stator 91 of the motor 90, the rotational phase of the rotor 92 of the motor 90, and the rotational speed of the rotor 92 of the motor 90, and the current estimation circuit may estimate the alternating current transmitted from the three windings 91A of the stator 91 to the winding 92A of the rotor 92 based on these estimation results. This motor device 1A comprises a three-phase inverter circuit 10A, a rotary transformer unit 20A, and a motor 90A.
[0080] The three-phase inverter circuit 10A has a switching control circuit 12A. Similar to the switching control circuit 12 in the above embodiment, the switching control circuit 12A is configured to control the operation of the switching circuit 11 based on instructions from the control circuit 99. The switching control circuit 12A also performs the operation of estimating the current flowing through the three windings 91A in the stator 91 of the motor 90, the rotational phase of the rotor 92 of the motor 90, and the rotational speed of the rotor 92 of the motor 90. In other words, the switching control circuit 12A controls the operation of the switching circuit 11. The operation of the switching circuit 11 corresponds to the operating state of the motor 90A. Therefore, the switching control circuit 12A can estimate the current flowing through the three windings 91A in the stator 91 of the motor 90, the rotational phase of the rotor 92 of the motor 90, and the rotational speed of the rotor 92 of the motor 90. The switching control circuit 12A then supplies these estimation results to the current estimation circuit 24 of the rotary transformer unit 20A.
[0081] The rotary transformer unit 20A has a current estimation circuit 24A. The current estimation circuit 24A is configured to estimate the alternating current transmitted from the three windings 91A of the stator 91 of the motor 90 to the windings 92A of the rotor 92, based on estimation results of the current flowing through the three windings 91A of the stator 91 of the motor 90, the rotational phase of the rotor 92 of the motor 90, and the rotational speed of the rotor 92 of the motor 90, which are supplied from the switching control circuit 12A.
[0082] The motor 90A includes a stator 91, a rotor 92, and a rotational speed sensor 94. This motor 90A is the same as the motor 90 according to the above embodiment, but without the rotational phase sensor 93 and the current sensor 95.
[0083] In the rotary transformer unit 20A, the first motor winding (three windings 91A) includes three windings 91A, each supplied with three AC signals from the three-phase inverter circuit 10A. The three-phase inverter circuit 10A can calculate the first motor current, rotation phase, and rotation speed. The current estimation circuit 24A can generate an estimated current value I2 by estimating the AC current transmitted from the first motor winding (three windings 91A) to the second motor winding (winding 92A) based on the first motor current, rotation phase, and rotation speed calculated by the three-phase inverter circuit 10A. Even in this case, the rotary transformer unit 20A can protect diodes DA to DD.
[0084] Although the present invention has been described above with reference to embodiments, the present invention is not limited to these embodiments and various modifications are possible.
[0085] For example, the circuit configuration of the switching circuit 31, the shape of the rotary transformer 40, and the circuit configuration of the rectifier circuit 23 shown in each of the above embodiments are examples only and are not limited to the disclosed circuit configurations and shapes.
[0086] The effects described herein are illustrative only, and the effects of this disclosure are not limited to those described herein. Therefore, other effects may be obtained with respect to this disclosure.
[0087] Furthermore, this disclosure may take the following forms:
[0088] (1) A rotary transformer having one or more switching elements and a switching circuit capable of performing switching operations; a first winding provided on a stator fixed to a housing and wound in the circumferential direction of a shaft rotatable around a rotation axis and connected to the switching circuit; a second winding provided on a rotor connected to the shaft and wound in the circumferential direction of the shaft; a rectifier circuit connected to the second winding and capable of rectifying the signal supplied from the second winding and supplying the rectified signal to the second motor winding in a motor having a motor stator including a first motor winding and a motor rotor including a second motor winding; a current estimation circuit capable of generating an estimated current value by estimating the alternating current transmitted from the first motor winding to the second motor winding based on a first motor current flowing through the first motor winding, the rotational phase of the motor rotor, and the rotational speed of the motor rotor; A rotary transformer unit comprising a control circuit capable of controlling the switching operation such that the current value of the second motor current flowing through the second motor winding becomes a value within a predetermined current range based on the estimated current value. (2) The rotary transformer unit according to (1), wherein the rectifier circuit is capable of allowing current to flow in a predetermined direction in the second motor winding, the current value of the second motor current is a positive value when the second motor current flows in the predetermined direction in the second motor winding, and the predetermined current range is 0 or greater. (3) The rotary transformer unit according to (1) or (2), wherein the motor further comprises a current sensor capable of detecting the first motor current flowing through the first motor winding, a rotational phase sensor capable of detecting the rotational phase of the motor rotor, and a rotational speed sensor capable of detecting the rotational speed of the motor rotor, and the current estimation circuit is capable of generating the estimated current value by estimating the alternating current transmitted from the first motor winding to the second motor winding based on the first motor current detected by the current sensor, the rotational phase detected by the rotational phase sensor, and the rotational speed detected by the rotational speed sensor.(4) The rotary transformer unit according to (1) or (2), wherein the first motor winding includes three windings to which three AC signals are supplied from a three-phase inverter circuit, the three-phase inverter circuit is capable of calculating the first motor current, the rotation phase, and the rotation speed, and the current estimation circuit is capable of generating the estimated current value by estimating the AC current transmitted from the first motor winding to the second motor winding based on the first motor current, the rotation phase, and the rotation speed calculated by the three-phase inverter circuit. (5) A motor having a motor stator including a first motor winding and a motor rotor including a second motor winding; a shaft connected to the motor rotor and rotatable about a rotation axis; a switching circuit having one or more switching elements and capable of performing switching operations; a rotary transformer having a first winding provided on the stator fixed to the housing, wound in the circumferential direction of the shaft and connected to the switching circuit, and a second winding provided on the rotor connected to the shaft and wound in the circumferential direction of the shaft; a rectifier circuit connected to the second winding and capable of rectifying a signal supplied from the second winding and supplying the rectified signal to the second motor winding; a current estimation circuit capable of generating an estimated current value by estimating the alternating current transmitted from the first motor winding to the second motor winding based on a first motor current flowing through the first motor winding, the rotation phase of the motor rotor, and the rotation speed of the motor rotor; A motor device comprising a control circuit capable of controlling the switching operation such that the current value of the second motor current flowing through the second motor winding becomes a value within a predetermined current range, based on the estimated current value.
Claims
1. A rotary transformer having one or more switching elements and a switching circuit capable of performing switching operations; a first winding provided on a stator fixed to a housing and wound in the circumferential direction of a shaft rotatable around a rotation axis and connected to the switching circuit; a second winding provided on a rotor connected to the shaft and wound in the circumferential direction of the shaft; a rectifier circuit connected to the second winding and capable of rectifying the signal supplied from the second winding, and capable of supplying the rectified signal to the second motor winding in a motor having a motor stator including a first motor winding and a motor rotor including a second motor winding; and a current estimation circuit capable of generating an estimated current value by estimating the alternating current transmitted from the first motor winding to the second motor winding based on a first motor current flowing through the first motor winding, the rotational phase of the motor rotor, and the rotational speed of the motor rotor. A rotary transformer unit comprising a control circuit capable of controlling the switching operation so that the current value of the second motor current flowing through the second motor winding becomes a value within a predetermined current range, based on the estimated current value.
2. The rotary transformer unit according to claim 1, wherein the rectifier circuit is capable of allowing current to flow in a predetermined direction in the second motor winding, the current value of the second motor current is positive when the second motor current flows in the predetermined direction in the second motor winding, and the predetermined current range is 0 or greater.
3. The rotary transformer unit according to claim 1, wherein the motor further comprises a current sensor capable of detecting a first motor current flowing through the first motor winding, a rotational phase sensor capable of detecting the rotational phase of the motor rotor, and a rotational speed sensor capable of detecting the rotational speed of the motor rotor, and the current estimation circuit is capable of generating the estimated current value by estimating the alternating current transmitted from the first motor winding to the second motor winding based on the first motor current detected by the current sensor, the rotational phase detected by the rotational phase sensor, and the rotational speed detected by the rotational speed sensor.
4. The rotary transformer unit according to claim 1, wherein the first motor winding includes three windings, each supplied with three AC signals from a three-phase inverter circuit, the three-phase inverter circuit is capable of calculating the first motor current, the rotation phase, and the rotation speed, and the current estimation circuit is capable of generating the estimated current value by estimating the AC current transmitted from the first motor winding to the second motor winding based on the first motor current, the rotation phase, and the rotation speed calculated by the three-phase inverter circuit.
5. A motor having a motor stator including a first motor winding and a motor rotor including a second motor winding; a shaft connected to the motor rotor and rotatable about a rotation axis; a switching circuit having one or more switching elements and capable of performing switching operations; a rotary transformer having a first winding provided on the stator fixed to the housing, wound in the circumferential direction of the shaft and connected to the switching circuit, and a second winding provided on the rotor connected to the shaft and wound in the circumferential direction of the shaft; a rectifier circuit connected to the second winding and capable of rectifying the signal supplied from the second winding and supplying the rectified signal to the second motor winding; a current estimation circuit capable of generating an estimated current value by estimating the alternating current transmitted from the first motor winding to the second motor winding based on a first motor current flowing through the first motor winding, the rotational phase of the motor rotor, and the rotational speed of the motor rotor; A motor device comprising a control circuit capable of controlling the switching operation so that the current value of the second motor current flowing through the second motor winding becomes a value within a predetermined current range, based on the estimated current value.