Rotary transformer unit and motor apparatus
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 JP2025002425_30072026_PF_FP_ABST
Abstract
Description
Rotary Transformer Unit and Motor Device
[0006] ,
[0005] ,
[0001] The present invention relates to a rotary transformer unit used in a wound field magnet type synchronous motor and a motor device including such a rotary transformer unit.
[0002] For example, there is a wound field magnet type synchronous motor (EESM: Electrically Excited Synchronous Motor) in a motor device. This motor device has a motor stator wound with a winding and a motor rotor wound with a winding. In this motor, by changing the current flowing through the winding wound around the motor rotor according to the rotational speed of the motor, the efficiency of the motor can be improved. For example, Patent Document 1 discloses a rotary transformer that supplies current to the winding wound around the motor rotor.
[0003] Specification of Chinese Patent Application Publication No. 114094897
[0004] In such a motor device, it is desired to more accurately control the DC component of the current flowing through the winding wound around the motor rotor.
[0005] It is desirable to provide a rotary transformer unit and a motor device that can more accurately control the DC component of the current flowing through the winding wound around the motor rotor.
[0006] A rotary transformer unit according to one embodiment of the present invention comprises a switching circuit, a rotary transformer, a first rectifier circuit, a first current sensor, a second rectifier circuit, a second current sensor, a subtraction circuit, and a switching 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 first 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 a motor winding provided on the motor rotor of a motor. The first current sensor is capable of generating a first signal by detecting the current flowing through the first winding or the second winding. The second rectifier circuit is capable of generating a second signal by performing full-wave rectification operation based on the first signal. The second current sensor can generate a third signal by detecting the AC component of the current flowing through the motor winding. The subtraction circuit can generate a fourth signal by subtracting the third signal from the second signal. The switching control circuit can generate an estimated current value by estimating the DC component of the current flowing through the motor winding based on the fourth signal, and can control the switching operation so that the estimated current value is the same as the target current value.
[0007] A motor device according to one embodiment of the present invention comprises a motor, a shaft, and a rotary transformer unit. The motor has a motor stator and a motor rotor including motor windings. The shaft is connected to the motor rotor and is rotatable about a rotation axis. The rotary transformer unit has a switching circuit, a rotary transformer, a first rectifier circuit, a first current sensor, a second rectifier circuit, a second current sensor, a subtraction circuit, and a switching 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 the shaft 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 first 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 motor winding provided on the motor rotor of the motor. The first current sensor is capable of generating a first signal by detecting the current flowing through the first or second winding. The second rectifier circuit is capable of generating a second signal by performing full-wave rectification based on the first signal. The second current sensor is capable of generating a third signal by detecting the AC component of the current flowing through the motor winding. The subtraction circuit is capable of generating a fourth signal by subtracting the third signal from the second signal. The switching control circuit is capable of generating an estimated current value by estimating the DC component of the current flowing through the motor winding based on the fourth signal, and can control the switching operation so that the estimated current value is the same as the target current value.
[0008] According to one embodiment of the present invention, the rotary transformer unit and motor device make it possible to control the DC component of the current flowing through the windings wound around the motor rotor with greater precision.
[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 a 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 operation of the motor device shown in Figure 1. Figure 8 is a waveform diagram showing an example operation of the rotary transformer unit shown in Figure 1. Figure 9 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, respectively.
[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 current sensor 21, a rectifier circuit 22, a rotary transformer 40, a rectifier circuit 23, a current sensor 24, an amplitude change circuit 25, and a subtraction circuit 26.
[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 the winding 43 (described later) of the rotary transformer 40. Node NB is connected to the other end of the winding 43 of the rotary transformer 40 via the current sensor 21.
[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 of the DC component of the current flowing through the winding 92A of the rotor 92 (described later) of the motor 90. Based on the signal S26 supplied from the subtraction circuit 26, the switching control circuit 32 estimates the DC component of the current flowing through the winding 92A of the rotor 92 of the motor 90, generates an estimated current value, and generates control signals GA to GD so that the estimated current value is the same as the target current value. 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, an AD (Analog to Digital) conversion unit 34, a peak hold unit 35, a subtraction unit 36, a PI (Proportional and Integral) control unit 37, a duty cycle generation unit 38, and a control signal generation unit 39. For the sake of explanation, Figure 2 also shows the control circuit 99 and the subtraction circuit 26.
[0021] The target current value setting unit 33 is configured to generate a signal S33 indicating the target current value based on data regarding the target current value 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. The target current value setting unit 33 then supplies the signal S33 to the subtraction unit 36.
[0022] The AD conversion unit 34 is configured to generate a signal S34 by performing AD conversion at a predetermined sampling frequency based on the signal S26 supplied from the subtraction circuit 26.
[0023] The peak hold unit 35 is configured to generate signal S35 by performing a peak hold operation that maintains the peak value in signal S34. This signal S35 corresponds to the estimated current value of the DC component of the current flowing through the winding 92A of the rotor 92 (described later) of the motor 90.
[0024] The subtraction unit 36 is configured to subtract signal S33 from signal S35. The PI control unit 37 is configured to perform PI control based on the subtraction result of the subtraction unit 36. Through this PI control, the inverter circuit 30 is controlled so that the signal value of signal S35 becomes equal to the signal value of signal S33.
[0025] The duty cycle generation unit 38 is configured to generate the switching duty cycle of the switching circuit 31 based on the signal output from the PI control unit 37.
[0026] The control signal generation unit 39 is configured to generate control signals GA to GD based on the switching duty cycle set by the duty cycle generation unit 38.
[0027] 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.
[0028] The current sensor 21 (Figure 1) is configured to detect the current flowing through the winding 43 (described later) of the rotary transformer 40. The current sensor 21 is installed in the path connecting node NB of the switching circuit 31 and the winding 43 of the rotary transformer 40. In this example, the current sensor 21 includes a current transformer. The current sensor 21 is configured to generate a signal S21 corresponding to the current flowing through the winding 43.
[0029] The rectifier circuit 22 is configured to generate a signal S22 by performing full-wave rectification based on the signal S21 supplied from the current sensor 21.
[0030] The rotary transformer 40 has a winding 43 and a winding 47. Winding 43 is provided on the stator 42 (described later), one end of which is connected to node NA of the switching circuit 31, and the other end of which is connected to node NB of the switching circuit 31 via a current sensor 21. Winding 47 is provided on the rotor 46 (described later), one end of which is connected to node NC (described later) of the rectifier circuit 23, and the other end of which is 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.
[0031] 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.
[0032] 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.
[0033] 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.
[0034] 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.
[0035] 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.
[0036] 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.
[0037] 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.
[0038] 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.
[0039] 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.
[0040] 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.
[0041] 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.
[0042] 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.
[0043] FIG. 6 shows the power transmission operation in the rotary transformer 40. The winding 43 of the stator 42 generates a magnetic field based on the AC power supplied from the inverter circuit 30. The portions of the magnetic core 44A close to the shaft 41 and the portions of the magnetic core 44B close to the shaft 41 are magnetically coupled to each other. As a result, in the rotary transformer 40, as shown in FIG. 6, a magnetic path MP passing through the magnetic core 44A and the magnetic core 44B is generated. Then, the winding 47 of the rotor 46 generates AC power based on the magnetic field in this magnetic path MP and supplies the generated AC power to the rectifier circuit 23. In this way, the rotary transformer 40 can transmit AC power from the stator 42 to the rotor 46 by non-contact transmission.
[0044] The rectifier circuit 23 (FIG. 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 substrate (not shown) connected to the shaft 41. The rectifier circuit 23 has diodes DA to DD. The anode of the diode DA is connected to the node NC, and the cathode is connected to the voltage line L21. The anode of the diode DB is connected to the reference voltage line L22, and the cathode is connected to the node NC. The anode of the diode DC is connected to the node ND, and the cathode is connected to the voltage line L21. The anode of the diode DD is connected to the reference voltage line L22, and the cathode is connected to the node ND. The voltage line L21 is connected to one end of the winding 92A of the rotor 92 (described later) of the motor 90. The reference voltage line L22 is connected to the other end of the winding 92A of the rotor 92 of the motor 90 via the current sensor 24.
[0045] The current sensor 24 is configured to detect the AC component of the current flowing through the winding 92A of the rotor 92 (described later) of the motor 90. The current sensor 24 is provided on a substrate (not shown) connected to the shaft 41. The current sensor 24 is provided in a path connecting the reference voltage line L22 and the other end of the winding 92A of the rotor 92 of the motor 90. In this example, the current sensor 24 includes a current transformer. This current transformer has the same configuration as the rotary transformer 40. That is, the substrate on which the current sensor 24 is provided rotates about the rotation axis AZ. Therefore, in the rotary transformer unit 20, in order to transmit the detection result of this current sensor 24 from the rotating system to the fixed system, a current transformer having the same configuration as the rotary transformer 40 is used. The current sensor 24 is adapted to generate a signal S24 corresponding to the AC component of the current flowing through the winding 92A.
[0046] The amplitude change circuit 25 is configured to generate a signal S25 by amplifying or attenuating the signal S24 supplied from the current sensor 24. The gain factor of the amplitude is set according to, for example, the ratio of the number of turns of the winding 43 and the number of turns of the winding 47 in the rotary transformer 40. The amplitude change circuit 25 is configured using, for example, an amplifier circuit or a voltage dividing circuit using a plurality of resistance elements.
[0047] The subtraction circuit 26 is configured to generate a signal S26 by subtracting the signal S25 from the signal S22.
[0048] The motor 90 is a wound-field synchronous motor. The motor 90 has a stator 91, a rotor 92, and a sensor 93.
[0049] 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 the nodes N1 to N3 in the three-phase inverter 10, 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.
[0050] The rotor 92 is a so-called rotor and is configured to rotate around 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 via the current sensor 24. The winding 92A is supplied with a signal rectified by the rectifier circuit 23 of the rotary transformer unit 20, and current flows. As a result, the winding 92A of the rotor 92 generates a magnetic field corresponding to this current.
[0051] The sensor 93 is configured to detect the rotational speed of the rotor 92. The sensor 93 then supplies a signal indicating the rotational speed of the rotor 92 to the control circuit 99.
[0052] The control circuit 99 is configured to control 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 signal indicating the rotational speed supplied from the motor 90. The control circuit 99 is configured to include, 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 the rotational speed instructions from the external control device 8 and a signal indicating the rotational speed in the motor 90. The control circuit 99 also generates data on the target current value of the current flowing through the winding 92A of the rotor 92 of the motor 90 based on the rotational speed instructions from the external control device 8, and supplies this data to the inverter circuit 30. In this way, the control circuit 99 controls the magnetic field generated by the rotor 92 of the motor 90.
[0053] In this configuration, the motor device 1 controls the rotational speed of the motor 90 based on the three-phase (U-phase, V-phase, W-phase) AC power generated by the three-phase inverter circuit 10, and controls the magnetic field generated by the rotor 92 of the motor 90 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 slow, the magnetic field generated by the rotor 92 of the motor 90 is strengthened, and when the rotational speed of the motor 90 is fast, the magnetic field generated by the rotor 92 of the motor 90 is weakened. As a result, the motor device 1 can increase the efficiency of the motor 90 over a wide range of rotational speeds.
[0054] 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 current sensor 21 corresponds to a specific example of the "first current sensor" in one embodiment of the present disclosure. The rectifier circuit 22 corresponds to a specific example of the "second rectifier circuit" in one embodiment of the present disclosure. The rectifier circuit 23 corresponds to a specific example of the "first rectifier circuit" in one embodiment of the present disclosure. The current sensor 24 corresponds to a specific example of the "second current sensor" in one embodiment of the present disclosure. The amplitude changing circuit 25 corresponds to a specific example of the "amplitude changing circuit" in one embodiment of the present disclosure. The subtraction circuit 26 corresponds to a specific example of the "subtraction circuit" in one embodiment of the present disclosure. Signal S21 corresponds to a specific example of the "first signal" in one embodiment of the present disclosure. Signal S22 corresponds to a specific example of the "second signal" in one embodiment of the present disclosure. Signals S24 and S25 correspond to a specific example of the "third signal" in one embodiment of the present disclosure. Signal S26 corresponds to a specific example of the "fourth signal" in one embodiment of the present disclosure. The motor 90 corresponds to a specific example of the "motor" in one embodiment of the present disclosure. The stator 91 corresponds to a specific example of the "motor stator" in one embodiment of the present disclosure. The 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 a "motor winding" in one embodiment of the present disclosure. Switching control circuit 32 corresponds to a specific example of a "switching control circuit" in one embodiment of the present disclosure.
[0055] [Operation and Function] Next, the operation and function of the motor device 1 of this embodiment will be described.
[0056] (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. The sensor 93 of the motor 90 supplies a signal indicating the rotational speed of the motor 90 to the control circuit 99.
[0057] The current sensor 21 generates signal S21 by detecting the current flowing through the winding 43 of the rotary transformer 40. The rectifier circuit 22 generates signal S22 by performing full-wave rectification based on the signal S21 supplied from the current sensor 21. The current sensor 24 generates signal S24 by detecting the AC component of the current flowing through the winding 92A of the rotor 92 of the motor 90. The amplitude change circuit 25 generates signal S25 by amplifying or attenuating the signal S24 supplied from the current sensor 24. The subtraction circuit 26 generates signal S26 by subtracting signal S25 from signal S22. The switching control circuit 32 generates an estimated current value by estimating the DC component of the current flowing through the winding 92A of the rotor 92 of the motor 90 based on the signal S26 supplied from the subtraction circuit 26, and generates control signals GA to GD so that the estimated current value becomes the same as the target current value.
[0058] (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.
[0059] 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.
[0060] Furthermore, the AC component of the current I92 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.
[0061] The rotary transformer unit 20 generates an estimated current value by estimating the DC component of the current flowing through the winding 92A of the rotor 92 of the motor 90, based on the AC component of the current flowing through the winding 43 of the rotary transformer 40. The rotary transformer unit 20 then controls the current flowing through the winding 92A of the rotor 92 so that the estimated current value becomes the same as the target current value.
[0062] Figure 8 shows an example of the operation of the rotary transformer unit 20. Figure 8 shows an example of the waveforms of the signal S21 output by the current sensor 21, the signal S24 output by the current sensor 24, the signal S26 output by the subtraction circuit 26, and the signal S35 output by the peak hold section 35 of the switching control circuit 32. Since signals S21, S24, S26, and S35 are signals that indicate current, these signals are shown converted to current.
[0063] The current sensor 21 generates a signal S21 as shown in Figure 8 by detecting the current flowing through the winding 43 of the rotary transformer 40. The waveform of this signal S21 corresponds to the waveform of the current I43 shown in Figure 7. The rectifier circuit 22 generates a signal S22 by performing full-wave rectification based on this signal S21.
[0064] The current sensor 24 generates a signal S24 as shown in Figure 8 by detecting the AC component of the current flowing through the winding 92A of the rotor 92 of the motor 90. The waveform of this signal S24 corresponds to the waveform of the AC component among the DC component and AC component included in the waveform of the current I92 shown in Figure 7. The amplitude changing circuit 25 generates a signal S25 by amplifying or attenuating this signal S24.
[0065] The subtraction circuit 26 generates the signal S26 shown in Figure 8 by subtracting the signal S25 from the signal S22.
[0066] The AD conversion unit 34 of the switching control circuit 32 generates signal S34 by performing AD conversion at a predetermined sampling frequency based on signal S26. The peak hold unit 35 generates signal S35 by performing a peak hold operation that maintains the peak value in signal S34. This signal S35 corresponds to the estimated current value of the DC component of the current flowing through the winding 92A of the rotor 92 of the motor 90.
[0067] In other words, the waveform of signal S21 includes the DC component of the current intended to flow through the winding 92A of the rotor 92 of the motor 90, and the AC component of the current flowing through the winding 92A. On the other hand, the waveform of signal S24 includes the AC component of the current flowing through the winding 92A, but does not include the DC component. Therefore, the rotary transformer unit 20 can estimate the DC component of the current flowing through the winding 92A by performing subtraction based on these two signals S21 and S24.
[0068] The rotary transformer unit 20 controls the current flowing through the rotor winding 92A so that the estimated current value becomes the same as the target current value. As a result, the rotor 92 of the motor 90 in the motor device 1 can generate an appropriate magnetic field. Consequently, the efficiency of the motor 90 in the motor device 1 can be increased.
[0069] 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, a first rectifier circuit (rectifier circuit 23) connected to the second winding (winding 47) and capable of rectifying the signal supplied from the second winding (winding 47) and supplying the rectified signal to a motor winding (winding 92A) provided on the motor rotor (rotor 92) of the motor 90, and a function for detecting the current flowing through the first winding (winding 43). The system includes a first current sensor (current sensor 21) capable of generating a first signal (signal S21), a second rectifier circuit (rectifier circuit 22) capable of generating a second signal (signal S22) by performing full-wave rectification based on the first signal (signal S21), a second current sensor (current sensor 24) capable of generating a third signal (signals S24, S25) by detecting the AC component of the current flowing through the motor winding (winding 92A), a subtraction circuit 26 capable of generating a fourth signal (signal S26) by subtracting the third signal (signal S25) from the second signal (signal S22), and a switching control circuit 32 capable of generating an estimated current value by estimating the DC component of the current flowing through the motor winding (winding 92A) based on the fourth signal (signal S26), and controlling the switching operation so that the estimated current value becomes the same as the target current value. This allows for more precise control of the DC component of the current flowing through the winding 92A wound around the motor rotor.
[0070] For example, the system could be configured to detect the current in the winding 92A of the rotor 92 of the motor 90, which includes both DC and AC components, and to obtain the DC component based on the detection result. However, in this case, it is necessary to transmit the detection result of the current, which includes both DC and AC components, from the rotating system to the stationary system, which can complicate the circuit configuration. Furthermore, if the DC component is obtained by performing moving average processing or filtering processing based on the current, which includes both DC and AC components, delays may occur, making it difficult to obtain the DC component in a timely manner.
[0071] On the other hand, the rotary transformer unit 20 is configured to detect the AC component of the current flowing through the winding 92A of the rotor 92 of the motor 90. This allows the current detection results to be easily transmitted from the rotating system to the stationary system. Based on the current flowing through the winding 43 of the rotary transformer 40 and the AC component of the current flowing through the winding 92A of the rotor 92 of the motor 90, the DC component of the current flowing through the winding 92A is estimated. This allows the DC component of the current flowing through the winding 92A to be estimated in a timely manner using a simple method. As a result, the rotary transformer unit 20 can more accurately control the DC component of the current flowing through the winding wound on the motor rotor.
[0072] Furthermore, the rotary transformer unit 20 is further equipped with an amplitude changing circuit 25 that can change the amplitude of the third signal (signal S24) by amplifying or attenuating the third signal (signal S24). The first current sensor (current sensor 21) is capable of detecting the current flowing through the first winding (winding 43). The subtraction circuit 26 is capable of generating a fourth signal by subtracting the third signal (signal S25), whose amplitude has been changed by the amplitude changing circuit 25, from the second signal (signal S22). As a result, the rotary transformer unit 20 can appropriately remove the AC component, and thus more accurately estimate the DC component of the current flowing through the winding 92A. Consequently, the rotary transformer unit 20 can more accurately control the DC component of the current flowing through the winding wound around the motor rotor.
[0073] [Effect] 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 the 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 first rectifier circuit connected to the second winding and capable of rectifying the signal supplied from the second winding and supplying the rectified signal to a motor winding provided on the motor rotor of the motor, and a device for detecting the current flowing through the first winding. The system includes a first current sensor capable of generating a first signal, a second rectifier circuit capable of generating a second signal by performing full-wave rectification based on the first signal, a second current sensor capable of generating a third signal by detecting the AC component of the current flowing through the motor winding, a subtraction circuit capable of generating a fourth signal by subtracting the third signal from the second signal, and a switching control circuit capable of generating an estimated current value by estimating the DC component of the current flowing through the motor winding based on the fourth signal, and controlling the switching operation so that the estimated current value becomes the same as the target current value. This makes it possible to control the DC component of the current flowing through the winding wound on the motor rotor more accurately.
[0074] In this embodiment, an amplitude changing circuit is further provided that can change the amplitude of the third signal by amplifying or attenuating the third signal. The first current sensor is capable of detecting the current flowing through the first winding. The subtraction circuit is capable of generating a fourth signal by subtracting the third signal, whose amplitude has been changed by the amplitude changing circuit 25, from the second signal. This makes it possible to control the DC component of the current flowing through the winding wound on the motor rotor more accurately.
[0075] [Modification 1] In the above embodiment, a current sensor 21 is provided to detect the current flowing through the winding 43 of the rotary transformer 40, but the embodiment is not limited to this. Instead, for example, as shown in the motor device 1A in Figure 9, a current sensor is provided to detect the current flowing through the winding 47 of the rotary transformer 40. This motor device 1A includes a rotary transformer unit 20A. The rotary transformer unit 20A includes an inverter circuit 30, a rotary transformer 40, a current sensor 21A, a rectifier circuit 22, a rectifier circuit 23, a current sensor 24, and a subtraction circuit 26.
[0076] The current sensor 21A is configured to detect the current flowing through the winding 47 of the rotary transformer 40. The current sensor 21A is installed in the path connecting the winding 47 of the rotary transformer 40 and node ND of the rectifier circuit 23. In this example, the current sensor 21A includes a current transformer. This current transformer has the same configuration as the rotary transformer 40. That is, in the rotary transformer unit 20A, a current transformer having the same configuration as the rotary transformer 40 is used to transmit the detection result of the current sensor 21A from the rotating system to the stationary system. The current sensor 21A is configured to generate a signal S21 corresponding to the current flowing through the winding 47.
[0077] In this rotary transformer unit 20A, both the current sensor 21A and the current sensor 24 are provided on the secondary side of the rotary transformer 40. Therefore, the amplitude changing circuit 25 can be omitted in this rotary transformer unit 20A. The subtraction circuit 26 is configured to generate signal S26 by subtracting signal S24 from signal S22.
[0078] 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.
[0079] 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.
[0080] 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.
[0081] Furthermore, this disclosure may take the following forms:
[0082] (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 first rectifier circuit connected to the second winding and capable of rectifying the signal supplied from the second winding and supplying the rectified signal to a motor winding provided on the motor rotor of the motor; a first current sensor capable of generating a first signal by detecting the current flowing through the first winding or the second winding; a second rectifier circuit capable of generating a second signal by performing full-wave rectification operation based on the first signal; a second current sensor capable of generating a third signal by detecting the AC component of the current flowing through the motor winding; and a subtraction circuit capable of generating a fourth signal by subtracting the third signal from the second signal. A rotary transformer unit comprising a switching control circuit capable of generating an estimated current value by estimating the DC component of the current flowing through the motor winding based on the fourth signal, and controlling the switching operation so that the estimated current value is the same as a target current value. (2) The rotary transformer unit according to (1), further comprising an amplitude changing circuit capable of changing the amplitude of the third signal by amplifying or attenuating the third signal, the first current sensor capable of detecting the current flowing through the first winding, and the subtraction circuit capable of generating the fourth signal by subtracting the third signal whose amplitude has been changed by the amplitude changing circuit from the second signal. (3) The rotary transformer unit according to (1), the first current sensor capable of detecting the current flowing through the second winding.(4) A motor having a motor stator and a motor rotor including motor windings; a shaft connected to the motor rotor and rotatable about a rotation axis; and a rotary transformer unit, wherein the rotary transformer unit has one or more switching elements and is 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 the shaft 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 first 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 motor windings; a first current sensor capable of generating a first signal by detecting the current flowing through the first winding or the second winding; and a second rectifier circuit capable of generating a second signal by performing full-wave rectification based on the first signal. A motor device comprising: a second current sensor capable of generating a third signal by detecting the AC component of the current flowing through the motor winding; a subtraction circuit capable of generating a fourth signal by subtracting the third signal from the second signal; and a switching control circuit capable of generating an estimated current value by estimating the DC component of the current flowing through the motor winding based on the fourth signal, and controlling the switching operation so that the estimated current value is the same as the target 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 first rectifier circuit connected to the second winding and capable of rectifying the signal supplied from the second winding and supplying the rectified signal to a motor winding provided on the motor rotor of the motor; a first current sensor capable of generating a first signal by detecting the current flowing through the first winding or the second winding; a second rectifier circuit capable of generating a second signal by performing full-wave rectification operation based on the first signal; a second current sensor capable of generating a third signal by detecting the AC component of the current flowing through the motor winding; and a subtraction circuit capable of generating a fourth signal by subtracting the third signal from the second signal. A rotary transformer unit comprising a switching control circuit capable of generating an estimated current value by estimating the DC component of the current flowing through the motor winding based on the fourth signal, and controlling the switching operation so that the estimated current value is the same as the target current value.
2. The rotary transformer unit according to claim 1, further comprising an amplitude changing circuit capable of changing the amplitude of the third signal by amplifying or attenuating the third signal, wherein the first current sensor is capable of detecting the current flowing through the first winding, and the subtraction circuit is capable of generating the fourth signal by subtracting the third signal, whose amplitude has been changed by the amplitude changing circuit, from the second signal.
3. The rotary transformer unit according to claim 1, wherein the first current sensor is capable of detecting the current flowing through the second winding.
4. A motor having a motor stator and a motor rotor including motor windings; a shaft connected to the motor rotor and rotatable around a rotation axis; and a rotary transformer unit, wherein the rotary transformer unit has one or more switching elements and is capable of performing switching operations; a rotary transformer having a first winding provided on a stator fixed to a housing, wound in the circumferential direction of the shaft 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 first 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 motor windings; a first current sensor capable of generating a first signal by detecting the current flowing through the first winding or the second winding; and a second rectifier circuit capable of generating a second signal by performing full-wave rectification based on the first signal. A motor device comprising: a second current sensor capable of generating a third signal by detecting the AC component of the current flowing through the motor winding; a subtraction circuit capable of generating a fourth signal by subtracting the third signal from the second signal; and a switching control circuit capable of generating an estimated current value by estimating the DC component of the current flowing through the motor winding based on the fourth signal, and controlling the switching operation so that the estimated current value is the same as the target current value.