JP6391069B2 - Induction superconducting motor control circuit - Google Patents

Description

  The present invention relates to a control circuit for an induction type superconducting motor including a rotor having a superconducting lead-shaped winding formed of a superconducting wire.

  As prior arts related to this type of technical field, for example, there are inventions described in Patent Documents 1 and 2. The invention described in Patent Document 1 is an invention relating to a method of operating a superconducting rotating machine, and controls the voltage applied to the primary winding of the superconducting rotating machine and its frequency. The superconducting rotating machine includes a stator having a winding made of a normal conducting wire, and a superconducting rod-shaped winding made of a superconducting wire is used for the rotor. The invention described in Patent Document 2 is an invention related to the structure of a superconducting rotor.

JP 2013-55733 A International Publication No. 2009/116219 Pamphlet

FIG. 8 of Patent Document 1 describes the relationship between current and voltage flowing in a winding (coil) made of superconducting wire. As shown in FIG. 8 of Patent Document 1, almost no voltage is generated in the winding below the critical current Ic, and the voltage suddenly increases when a current exceeding the critical current Ic flows in the winding. This characteristic is greatly different from that in a normal conductor such as a copper wire, a voltage is generated in proportion to an increase in current according to Ohm's law. On the other hand, according to recent studies, in an oxide-based superconductor typified by yttrium or bismuth, the cooling does not collapse even when a current is passed beyond the critical current Ic, for example, up to twice the critical current Ic. It has been found that as long as it can be used.
As described above, since the characteristics of the superconducting wire are not linear according to Ohm's law, control of the superconducting motor by current control is desired, but the preferred control configuration is not embodied.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a suitable control circuit for an induction type superconducting motor including a rotor having a superconducting lead-shaped winding formed of a superconducting wire. That is.

  The present invention is a control circuit for an induction superconducting motor including a rotor having a superconducting lead-shaped winding formed of a superconducting wire. The control circuit has a phase difference of 120 ° based on a current command forming unit, a frequency command forming unit, a current value command from the current command forming unit, and a frequency value command from the frequency command forming unit. Three sine curve forming sections that form curves, at least two current sensors that detect current values flowing in the U phase, V phase, and W phase of the stator coil, and outputs of the three sine curve forming sections, And three error amplifier units that take a difference from the current value of each corresponding phase detected by the current sensor, and three power units that amplify the outputs of the three error amplifier units. The current value flowing in each phase of the stator coil is feedback-controlled based on the detected current value of each phase.

  ADVANTAGE OF THE INVENTION According to this invention, the suitable control circuit of the induction type | mold superconducting motor provided with the rotor which has the superconducting lead-shaped winding comprised with the superconducting wire can be provided.

1 is a circuit diagram illustrating a control circuit according to a first embodiment of the present invention. It is a circuit diagram which shows the connection of the stator coil shown in FIG. It is a circuit diagram which shows the detail of the power part shown in FIG. It is a circuit diagram which shows the other form of the power part shown in FIG. It is a figure which shows the current-voltage characteristic of the superconducting wire which comprises a superconducting lead | read | reed shape winding and a stator coil. It is a typical circuit diagram of the current drive type inverter concerning a prior art. It is a longitudinal cross-sectional view which shows the structure of the induction type superconducting motor shown in FIG. It is a figure which shows the torque characteristic of the induction type superconducting motor shown in FIG. It is a schematic diagram which shows the electromagnetic phenomenon in the superconducting lead | zound winding of the induction type superconducting motor shown in FIG. It is a circuit diagram which shows the control circuit which concerns on 2nd Embodiment of this invention. It is a circuit diagram which shows the detail of the converter shown in FIG. It is a circuit diagram which shows the control circuit which concerns on 3rd Embodiment of this invention. It is a figure which shows the state in which the motor current is behind with respect to the applied voltage. It is a figure which shows the phase difference of an applied voltage and an electric current from the starting of a motor to synchronous mode.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

(First embodiment)
A control circuit 101 for an induction type superconducting motor according to a first embodiment of the present invention will be described with reference to FIGS.

<Induction type superconducting motor>
First, an induction superconducting motor 1 that is an example of a control target of the control circuit 101 will be described with reference to FIGS.

  As shown in FIG. 7, the induction type superconducting motor 1 includes a cylindrical casing 50, an annular stator 51 fixed to the inner peripheral surface of the casing 50, and a disk shape that closes both openings of the casing 50. Brackets 52a and 52b, and a rotor 56 rotatably supported by the brackets 52a and 52b via bearings 53a and 53b.

The stator 51 has an annular stator core 54 formed by laminating electromagnetic steel plates such as silicon steel plates in the axial direction, and a stator coil 55 provided in a slot of the stator core 54. The stator coil 55 is formed by winding an oxide superconducting wire represented by yttrium or bismuth. The wire constituting the stator coil 55 may be a metal-based superconducting wire represented by NbTi or Nb ₃ Sn and other superconducting wires, or a normal conducting wire such as a copper wire.

  The rotor 56 is disposed inside the stator 51 with a predetermined gap between the rotor 56 and the stator 51. The rotor 56 includes a hollow cylindrical rotor core 57 formed by laminating electromagnetic steel sheets such as silicon steel sheets in the axial direction, a superconducting lead-shaped winding 58 housed in a slot of the rotor core 57, and a normal conductor. A shape winding 59 and a rotating shaft 60 attached coaxially to the rotor core 57 are provided. The diameter of the superconducting lead-shaped winding 58 is smaller than the diameter of the normal conducting lead-shaped winding 59, and the superconducting lead-shaped winding 58 is arranged closer to the rotation center than the normal conducting lead-shaped winding 59.

The superconducting lead-shaped winding 58 is made of an oxide-based superconducting wire typified by yttrium or bismuth. The wire constituting the superconducting lead-shaped winding 58 may be a metal-based superconducting wire represented by NbTi or Nb ₃ Sn and other superconducting wires. The normal conducting lead-shaped winding 59 is composed of a normal conducting wire such as a copper wire. It is preferable to stabilize the rotation of the normal conducting lead winding 59 together with the superconducting lead winding 58 as in this embodiment. However, only the superconducting lead winding 58 is provided to provide normal conduction. The cage winding 59 may be omitted. That is, there is no need for the normal lead wire 59.

  The rotating shaft 60 is rotatably supported by the brackets 52a and 52b via the bearings 53a and 53b.

  The stator 51 and the rotor 56 are cooled by conduction cooling by a refrigerator, immersion cooling by liquid nitrogen or liquid helium, and the stator coil 55 and the superconducting lead-shaped winding 58 are brought into a superconducting state.

  FIG. 5 is a diagram showing current-voltage characteristics of the superconducting wires constituting the superconducting lead-shaped winding 58 and the stator coil 55. The horizontal axis is the current flowing through the superconducting wire, and the vertical axis is the generated voltage. For example, a current value that generates 10 μV / m is called a critical current Ic. As shown in FIG. 5, in the superconducting wire, the voltage generated suddenly does not increase, but the generated voltage increases as the current increases. For this reason, the critical current Ic is a current value that generates 10 μV / m, which can be practically called zero voltage generation. The characteristic of this non-linear curve 200 may be expressed by an n value. As the current value approaches Ic, the current value increases in a non-linear manner. When the current value exceeds Ic, the voltage change becomes considerably large and is strongly influenced by the non-linear component. The impedance of the coil is a combination of the inductance and is proportional to the current. Therefore, since the current is determined by a certain proportional coefficient with respect to the applied voltage (alternating current), the current can be regarded as the same sine curve as the applied voltage. This is an outline except for phase shift, load fluctuation, etc. In any case, a sine curve current flows in each phase (U phase, V phase, W phase) of the coil. On the other hand, when a current exceeding the critical current Ic is passed through the superconducting wire by the conventional method, the current flowing through each phase is distorted. In the vicinity of the apex of the sine curve, a voltage is generated due to an increase in current and the current decreases. An unbalanced current flows in the U phase, the V phase, and the W phase.

  Here, FIG. 6 is a typical circuit diagram of a current-driven inverter according to the prior art. A large reactor 201 is arranged upstream of three sets of power elements that perform PWM control on each phase (U phase, V phase, W phase), and the total sum of currents flowing into each phase is controlled to be difficult to change. By providing the reactor 201 with an inductance much greater than the inductance of the motor coil, the current flowing into each phase is balanced. The disadvantage of this circuit is that there is a large loss due to the reactor 201 having a very large inductance, and the sum of the currents of the three phases is balanced, but the sine curve coming from the non-linear component of the superconducting coil is seen for each phase. The distortion cannot be removed.

  FIG. 8 is a diagram showing torque characteristics of the induction type superconducting motor 1. When the superconducting lead-shaped winding 58 enters a superconducting state, the superconducting guide-shaped winding 58 captures the magnetic flux of the rotating magnetic field generated by the stator 51, thereby generating a synchronous torque (this magnetic flux capturing state is shown in FIG. 9B). . At this time, the induction-type superconducting motor 1 rotates by the synchronous torque main drive and exhibits a torque characteristic corresponding to a portion A (= synchronous region (synchronous rotation)) of FIG.

  If a large load is applied to the induction superconducting motor 1 in the synchronously rotating state, the superconducting coil winding 58 shifts to the magnetic flux flow state shown in FIG. 9A, and the induction superconducting motor 1 is rotated by the induced torque main movement. To do. At this time, the induction type superconducting motor 1 exhibits a torque characteristic corresponding to a portion B (= slip region (induction rotation)) in FIG. Note that if the load on the induction superconducting motor 1 is excessive, the step-out occurs.

<Control circuit>
As shown in FIG. 1, the control circuit 101 of the induction type superconducting motor of this embodiment includes a current command forming unit 2, a frequency command forming unit 3, three sine curve forming units 4 (4a, 4b, 4c), three The error amplifier unit 5 (5a, 5b, 5c), three power units 6 (6a, 6b, 6c), and three current sensors 7 (7a, 7b, 7c) are provided.

  In FIG. 1, the induction type superconducting motor 1 is shown in a simplified manner. With respect to the stator coil 55, the U phase, the V phase, and the W phase are each represented by one coil, that is, the stator coils 55a, 55b, and 55c. Actually, for example, four coils are connected in series, or some coils are reversely connected to create a rotating magnetic field, but these are collectively represented by one coil. doing. Further, the superconducting lead-shaped winding 58 and the like constituting the rotor 56 are not shown in FIG.

  The current value command from the current command forming unit 2 to the sine curve forming unit 4 may be variable as well as a constant value.

  The frequency command forming unit 3 determines the frequency of the sine curve created by the sine curve forming unit 4. If the motor is designed at a commercial frequency, the rated operation is 60 Hz or 120 Hz. When suppressing the rotation speed, the frequency value command from the frequency command forming unit 3 is set to 30 Hz, for example. Alternatively, the start frequency of the motor may be set to 0 and swept to a predetermined frequency. In this case, the frequency value command from the frequency command forming unit 3 is 0 at the start of the motor, and the frequency command forming unit 3 also has a function of sweeping from a frequency value command of 0 to a predetermined frequency at the start. .

  The sine curve forming unit 4b forms a sine curve so that the phase is 120 ° later than that of the sine curve forming unit 4a, and the sine curve forming unit 4c is 120 ° later than the sine curve forming unit 4b. The sine curve amplitude is obtained from the current value command from the current command forming unit 2, and the sine curve frequency is obtained from the frequency value command from the frequency command forming unit 3 by each sine curve forming unit 4 a, 4 b, 4 c.

  The current sensors 7a, 7b, and 7c detect current values flowing through the stator coils 55a (U phase), 55b (V phase), and 55c (W phase), respectively. Although a shunt resistor may be used as the current sensor 7, it is preferable to use a non-contact type current sensor.

  The error amplifier units 5a, 5b, and 5c receive the outputs of the sine curve forming units 4a, 4b, and 4c, respectively, and the current values detected by the current sensors 7a, 7b, and 7c as feedback signals, respectively. 4b, 4c, and current control values for each phase (U phase, V phase, W phase) through the power units 6a, 6b, 6c.

  Since the current control command value from the sine curve forming units 4a, 4b, and 4c is a sine curve, if the control loop has an infinite gain, the stator coil 55 that is a load has non-linear characteristics. Even so, the current flowing there is corrected and controlled to a sine curve. An infinite gain is impossible, but if a sufficiently large gain is given, the current flowing through the stator coil 55 is corrected and controlled to a sufficiently practical sine curve.

  Control by the error amplifier 5 is not limited to proportional control (P control), but an integral term is added as PI control, or a differential term is added as PID control.

  Here, regarding the sine curve forming unit 4, when a circuit is constructed discretely, an integrating DAC (digital / analog converter) that substantially integrates and outputs an analog value obtained from an input voltage and digital data; If there is a ROM, the sine curve forming unit 4 can be configured. The ROM stores the sine curve data corresponding to the address, and inputs the digital value of the sine curve to the integrating DAC while changing the address. The function of changing the ROM address is the role of the frequency command forming unit 3, and the input voltage input to the integrating DAC is the output of the current command forming unit 2. Recently, inexpensive microcomputers are frequently used. Rather than such a discrete circuit, the current command forming unit 2, the frequency command forming unit 3, the sine curve forming unit 4, and the error amplifier unit 5 are functions of the microcomputer board, and 3 from the DAC or the like built in the microcomputer. One analog signal may be output to control the power unit 6.

  As shown in FIG. 3, the power unit 6 is configured by an analog circuit, for example, and includes a voltage amplification unit 14 and two bipolar transistors 15 and 16. At the time of plus, one bipolar transistor 15 is turned on and the other bipolar transistor 16 is cut off. The merit of configuring the power unit 6 with such an analog circuit is that the waveform is very beautiful as compared with PWM control described later.

  FIG. 4 shows an example in which the power unit 6 is configured by PWM control (Pulse Width Modulation). Note that PWM control is a known control method. The power unit 6 shown in FIG. 4 includes a separation circuit 20, a reference wave generator 18, comparators 19a and 19b, an upper drive circuit 21, a lower drive circuit 22, and power MOSFETs 23 and 24.

  The reference wave generator 18 outputs a sawtooth waveform or a triangular waveform. The command value (current command value) from the error amplifier unit 5 is separated into a plus side and a minus side by the separation circuit 20, and the minus side is inverted, and the command value and the output waveform from the reference wave generator 18 are generated. The comparators 19a and 19b compare each other, and a PWM signal that is turned on when the command value is larger than the reference voltage and turned off when it is smaller is output from the comparators 19a and 19b. The lower drive circuit 22 uses a circuit whose ON and OFF are reversed.

  Instead of the power MOSFETs 23 and 24, IGBTs (Insulated Gate Bipolar Transistors) may be used as the power elements. A simple buffer may be provided in front of the power element.

  Some of the functions of the microcomputer incorporate the PWM signal, and the functions of the current command forming unit 2, the frequency command forming unit 3, the sine curve forming unit 4, the error amplifier unit 5, and the power unit 6 are part of the microcomputer function. Furthermore, a configuration in which the power MOSFETs corresponding to the power MOSFETs 23 and 24 in FIG. 4 are directly controlled or a simple buffer is added between them may be employed.

(Second Embodiment)
FIG. 10 is a circuit diagram showing the control circuit 102 of the induction superconducting motor 1 according to the second embodiment of the present invention. The same components as those of the control circuit 101 of the first embodiment shown in FIG. 1 are denoted by the same reference numerals (the same applies to the control circuit 103 of the third embodiment shown in FIG. 12).

In the present embodiment, there are two current sensors 7 (current sensors 7a and 7b). Since each coil is star-connected as shown in FIG. 2, the current value flowing through one phase is a value obtained by adding the current values flowing through the other two phases. The control circuit 102 includes a converter 8 and adds currents I _U and I _V flowing through the U phase and V phase, and inverts plus and minus to obtain a current I _W flowing through the W phase. Input as feedback signal.

  As shown in FIG. 11, the converter 8 includes an operational amplifier 10. The resistors 11, 12, and 13 are usually of the same value, for example, 10 kΩ. When the outputs of the current sensors 7a and 7b are input to the operational amplifier 10, they are added and inverted.

  Note that the converter 8 shown in FIG. 11 can also be used on the current command side. Although illustration is omitted, for example, when a converter 8 is inserted instead of the sine curve forming unit 4c and the outputs of the sine curve forming units 4a and 4b are input to the operational amplifier 10, an output of the same waveform as the output of the sine curve forming unit 4c is output. Is obtained. This output may be input to the error amplifier unit 5c. In this case, the converter 8 becomes a W-phase sine curve forming section.

(Third embodiment)
FIG. 12 is a circuit diagram showing the control circuit 103 of the induction superconducting motor 1 according to the third embodiment of the present invention.

  In the present embodiment, the phase difference detection circuit 30 that obtains the phase difference between the phase of the voltage waveform (sine curve) applied to the stator coil 55a and the phase of the current waveform (sine curve) detected by the current sensor 7a. A (phase difference detection unit) is further provided.

  The phase difference is a value indicating how much the current waveform detected by the current sensor 7a is advanced or delayed with respect to the voltage waveform applied to the stator coil 55a ("applied voltage waveform"- "Current waveform"). That is, the phase difference becomes a positive value when the current waveform is delayed from the applied voltage waveform, and becomes a negative value when the current waveform is advanced.

  Here, when the superconducting lead-shaped winding 58 is in the magnetic flux trapping state shown in FIG. 9B, the permanent current continues to flow through the loop of the superconducting lead-shaped winding 58, so that the rotor 56 functions as a permanent magnet. If the rotor 56 becomes a permanent magnet, the induction superconducting motor 1 behaves as a synchronous motor. However, since the induction superconducting motor 1 does not have an angle detector that detects the position (angle) of the rotor 56, commutation control cannot be performed.

  When the load is light, the magnetic field of the rotor 56 catches up with the rotating magnetic field of the stator 51, and the motor efficiency decreases. Further, when the load is heavy, the rotor 56 rotates with a delay from an appropriate angle, so that the motor efficiency also decreases. When the load becomes heavier, the resistance to the load is further lost due to a reduction in the efficiency of the motor, resulting in a step-out.

  If the phase difference between the phase of the applied voltage waveform and the phase of the current waveform is small, the load is light. If the phase difference is large, the load is heavy. Can be detected by detecting the phase difference between the applied voltage and the current.

  The detected phase difference signal is input to the current command forming unit 2, and the output of the current command forming unit 2 is variably controlled. An appropriate value (for example, 20 °) of a predetermined phase difference is set as a target value. If the detected phase difference is larger than the target value, the generated torque is increased by increasing the current value command from the current command forming unit 2. . If the detected phase difference is smaller than the target value, the generated torque is reduced by reducing the current value command.

  Thus, by controlling the current value command based on the phase difference between the applied voltage and the current, the magnetic field generated by the rotor 56 magnetized by the permanent current is an appropriate amount with respect to the rotating magnetic field generated by the stator 51. Rotate with a delay.

  In this way, not only does the step out due to insufficient torque, but the current of the minimum necessary without causing the rotor 56 to catch up with the rotating magnetic field more than necessary by reducing the motor efficiency by flowing a large current through the coil. Thus, the induction superconducting motor 1 can be driven. FIG. 13 is a diagram illustrating a state in which the current 42 flowing through the stator coil 55a is delayed with respect to the voltage 41 applied to the stator coil 55a. In this figure, the current 42 is delayed by about 40 ° with respect to the applied voltage 41.

  Since the phase difference between the applied voltage and the current is the same for all of the U phase, the V phase, and the W phase, for example, only the U phase may be detected as in the present embodiment. Instead of the applied voltage, an induced voltage produced by the induction superconducting motor 1 may be used. That is, the phase difference between the phase of the induced voltage waveform of the induction superconducting motor 1 and the phase of the current waveform detected by the current sensor 7a may be detected and used for current control. This is because the applied voltage and the induced voltage behave slightly differently, but the phase difference from the current waveform can be handled equally.

  Next, FIG. 14 shows the applied voltage (waveform) to the stator coil 55 and the current (waveform) flowing from the start of the induction superconducting motor 1 until the induction superconducting motor 1 enters the synchronous mode. It is a figure which shows an example of the behavior of a phase difference with). The horizontal axis of FIG. 14 is time. The vertical axis represents the phase difference. Part B (slip mode) in FIG. 14 corresponds to part B in FIG. Part A (synchronous mode) in FIG. 14 corresponds to part A in FIG.

  In the example shown in FIG. 14, the phase of the current flowing through the stator coil 55 is delayed by 20 ° from the phase of the voltage applied to the stator coil 55 when the motor is started. This delay of 20 ° is an example, and is often delayed by about 20 to 60 °.

  In this case, the induction-type superconducting motor 1 rotates at a phase difference of 20 ° between the applied voltage and the current for a while and enters a synchronous mode when the rated rotation is reached, and the phase changes according to the load. The induction superconducting motor 1 rotates in a sliding mode when it is started. The induction superconducting motor 1 is rotated at the maximum current at the time of starting. That is, the current value command from the current command forming unit 2 is the maximum current value command when the induction superconducting motor 1 is started. The “maximum current (maximum current value)” refers to a current (current value) necessary to rotate the induction superconducting motor 1 to the rated rotation with a requested load. In the present invention, the current (current value) required for the induction superconducting motor 1 to reach the synchronous mode from the slip mode and the “maximum current (maximum current value)” can be defined.

  A point P in FIG. 14 is not a sliding mode, for example, a point having a phase difference of 10 °. The phase difference at point P = 10 ° is set as a determination value for determining the synchronization mode. When the phase difference decreases from 20 ° in the sliding mode from 10 ° to 10 °, the target value of the phase difference is set to 10 °, for example, and the current value flowing into the stator coil 55 is controlled so that the phase difference is 10 °. Try to stabilize. Specifically, as described above, the phase difference signal detected by the phase difference detection circuit 30 is input to the current command forming unit 2, and the output of the current command forming unit 2 is variably controlled. If the phase difference of 10 ° is set as a target value (threshold value) and the detected phase difference is larger than 10 °, the generated torque is increased by increasing the current value command from the current command forming unit 2. If the detected phase difference is smaller than 10 °, the current value command is reduced to reduce the generated torque. The determination value for the synchronization mode determination may be different from the target value after the synchronization mode determination. In addition, after the above determination, in any case (regardless of the magnitude of the phase difference with respect to the target value), the current value command is smaller than the maximum current value command.

  In the case of the induction superconducting motor 1, the phase difference in the sliding mode is 20 °, and the most efficient phase difference in the synchronous mode is 20 °. Therefore, the control for setting the target value of the phase difference to 10 ° is control at a point where the efficiency is slightly lower than the maximum efficiency of the motor, but is control with a margin for not entering the slip mode.

  According to this control, when the phase difference is smaller than the sliding mode by a predetermined angle (20 ° −10 ° = 10 ° in the above embodiment), it is determined that the induction superconducting motor 1 is in the synchronous mode, After that, by changing the current value command from the current command forming unit 2 so that the phase difference approaches its target value (10 ° in the above embodiment), the slip mode is erroneously entered due to load fluctuation or the like. As a result, stable synchronous mode operation of the induction superconducting motor 1 can be realized.

(Operation and effect of the invention)
(1) The present invention is a control circuit for an induction type superconducting motor including a rotor having a superconducting lead-shaped winding formed of a superconducting wire. The control circuit has a phase difference of 120 ° based on a current command forming unit, a frequency command forming unit, a current value command from the current command forming unit, and a frequency value command from the frequency command forming unit. Three sine curve forming sections that form curves, at least two current sensors that detect current values flowing in the U phase, V phase, and W phase of the stator coil, and outputs of the three sine curve forming sections, And three error amplifier units that take a difference from the current value of each corresponding phase detected by the current sensor, and three power units that amplify the outputs of the three error amplifier units. The current value flowing in each phase of the stator coil is feedback-controlled based on the detected current value of each phase.

  According to this configuration, distortion of the current (sine curve waveform) flowing through each phase (U phase, V phase, W phase) due to the non-linear characteristics of the superconducting wire can be removed. Since the current can be suppressed, the induction superconducting motor can be stably rotated. In addition, since current control can be performed without using a large reactor (see FIG. 6), an efficient circuit configuration is obtained.

(2) In the present invention, there are two current sensors, and the current values flowing in two phases of the U phase, V phase, and W phase of the stator coil are detected by the two current sensors, respectively. The remaining one-phase current value is preferably obtained by adding and inverting the detection values of the two current sensors. According to this configuration, the control circuit can be manufactured at low cost.

(3) In the present invention, there are three current sensors, and the current values flowing in the U phase, V phase, and W phase of the stator coil can be detected by the three current sensors, respectively. preferable. According to this configuration, the current value control can be made robust.

(4) Further, in the present invention, it is preferable that the three power units are PWM controlled.

(5) The present invention further includes a phase difference detection unit that obtains a phase difference between the voltage applied to the stator coil or the induced voltage of the induction superconducting motor and the current detected by the current sensor. When the phase difference becomes smaller by a predetermined angle than in the case of the mode, it is determined as the synchronous mode. After the determination, when the phase difference is larger than the target value of the phase difference, In the case of increasing and decreasing, it is preferable that the current value command from the current command forming unit is decreased.

  According to this configuration, it is possible to prevent the slip mode from being erroneously entered due to a change in the load acting on the induction type superconducting motor, and as a result, a stable synchronous mode operation of the induction type superconducting motor can be realized. In addition, a large current does not flow through the coil, and the rotor does not catch up with the rotating magnetic field more than necessary, thereby reducing the motor efficiency. That is, the induction type superconducting motor can be driven with the minimum necessary current.

  The phase difference is a value indicating how much the current waveform detected by the current sensor is advanced or delayed with respect to the applied voltage waveform to the stator coil when the applied voltage to the stator coil is applied. That is. When the induced voltage of the induction superconducting motor is applied, it is a value indicating how much the current waveform detected by the current sensor is advanced or delayed with respect to the induced voltage waveform of the induction superconducting motor. These values (phase differences) are positive values when the current waveform is delayed, and negative values when the current waveform is advanced.

(6) Further, in the present invention, the current value command from the current command forming unit is set to the maximum current value command until the phase difference becomes a predetermined angle smaller than that in the slip mode from the start of the induction type superconducting motor. And after the said determination, it is preferable that the said current command formation part is comprised so that it may become a current value command smaller than the said maximum current value command.

  According to this configuration, wasteful current consumption after entering the synchronous mode can be suppressed.

1: Inductive superconducting motor 2: Current command forming unit 3: Frequency command forming unit 4: Sine curve forming unit 5: Error amplifier unit 6: Power unit 7: Current sensor 51: Stator 55: Stator coil 56: Rotor 58: Superconducting lead-shaped winding 101: Control circuit (control circuit for induction superconducting motor)

Claims (4)

A control circuit for an induction-type superconducting motor having a rotor having a superconducting lead-shaped winding formed of a superconducting wire,
A current command forming unit;
A frequency command forming unit;
Based on the current value command from the current command forming unit and the frequency value command from the frequency command forming unit, three sine curve forming units each forming a sine curve with a phase difference of 120 °,
At least two current sensors for detecting a current value flowing in each of the U phase, V phase, and W phase of the stator coil;
Three error amplifier units that take the difference between the outputs of the three sine curve forming units and the current values of the corresponding phases detected by the current sensor;
Three power units for amplifying the outputs of the three error amplifier units;
With
Feedback control of the current value flowing in each phase of the stator coil based on the detected current value of each phase ,
A phase difference detection unit for obtaining a phase difference between the voltage applied to the stator coil or the induced voltage of the induction superconducting motor and the current detected by the current sensor;
When the phase difference is smaller than the slip mode by a predetermined angle, it is determined as the synchronous mode. After the determination, when the phase difference is larger than the target value of the phase difference, the current value from the current command forming unit When the command is increased and the command is small, the current value command from the current command forming unit is configured to be small.
From the start of the induction type superconducting motor until the phase difference is smaller than the sliding mode by a predetermined angle, the current value command from the current command forming unit is set as the maximum current value command, and after the determination, A control circuit for an induction type superconducting motor , wherein the current command forming unit is configured to have a current value command smaller than a maximum current value command . In the control circuit of the induction type superconducting motor according to claim 1,
There are two current sensors,
The current values flowing in two of the U phase, V phase, and W phase of the stator coil are detected by the two current sensors, and the remaining one phase current values are detected by the two current sensors. A control circuit for an induction superconducting motor, characterized in that the value is obtained by adding and inverting the value. In the control circuit of the induction type superconducting motor according to claim 1 ,
There are three current sensors,
A control circuit for an induction type superconducting motor, wherein the current values flowing in the U phase, V phase, and W phase of the stator coil are respectively detected by the three current sensors. In the control circuit of the induction type superconducting motor according to any one of claims 1 to 3,
A control circuit for an induction type superconducting motor, wherein the three power units are PWM controlled.

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