KR920004284B1 - Control device of velocity of elevator - Google Patents

Abstract

The apparatus includes a vector controller (14) for performing vector-computations based on the difference between speed command signals and the speed of a 3-phase induction motor (8). A comparator (15) compares the output current value of the vector controller (14) with the input current value of the induction motor (8), and a power factor controller (22) controls power factor for the phase of a 3-phase AC power source based on the output of another comparator (20). Current controllers (16)(24) control current values based on the output of the comparators (15)(23), and sinusoidal pulse width modulation controllers (17)(25) convert AC signals of the current controller (16)(24) to DC currents.

Description

Elevator speed control device

1 is a block diagram showing a speed control device of a conventional elevator.

2 is a circuit diagram of a three-phase induction motor according to FIG.

3 is a graph showing the relationship between voltage and frequency with respect to FIG.

4 is an explanatory diagram showing a variation in the rotational force of the induction motor relative to FIG.

5 is a configuration diagram showing a speed control device of the elevator of the present invention.

6 is a detailed configuration diagram of the vector controller 14 of FIG.

7A and 7B are graphs for explaining speed control by the vector controller 14 of FIG.

* Explanation of symbols for main parts of the drawings

1: 3-phase AC power supply 2, 7: AC reactor

3, 6: current detector 4: converter section

5: inverter section 8: three-phase induction motor

9: pulse encoder 10: position calculator

11: Position commander 12, 15, 20, 23: Comparator

13: Speed Commander 14: Vector Controller

16, 24 Current controller 17, 25: Sinusoidal pulse width modulation controller

18, 26: dead time controller 27: transformer

The present invention relates to the speed control of an AC elevator using power factor control, power regenerative braking, and mutual non-interference control. In particular, the present invention detects the amount of current input to an induction motor for driving a lift by an inverter method and compares the lift with a reference voltage. It relates to a speed control device of an elevator for stably controlling the running speed of.

Conventional speed control apparatus of the elevator is a three-phase induction motor 10 for elevating the elevator 11 connected to the balance weight 13, as shown in Figure 1 attached to the three-phase induction motor 10 the by detecting the rotational speed output from the speed signal speed detector 12, a speed command device (1) of the speed signal (V _T) of said speed detector 12 for outputting a (V _T), the speed command signal (V _P ) And compares the comparator 2 for outputting the difference signal Vs, the difference signal Vs output from the comparator 2 and the speed signal V _T of the speed detector 12, and outputs the sum. Voltage command so that the adder 3, the frequency command signal F corresponding to the addition result of the adder 3, and the frequency command signal F and the straight line d0-d3 shown in FIG. A function generator 4 for generating a signal V, a full-wave rectifying circuit 7 for full-wave rectifying by inputting the difference signal Vs output from the comparator 2, and its rectification A correction circuit 8 for outputting a correction signal Vd proportional to the output of the circuit 7, a correction signal Vd output from the correction circuit 8 and a voltage command signal V of the function generator 4. Is added to output the corrected voltage command signal V 'and the corrected voltage command signal V' and the frequency command signal F outputted from the adder 9 are inputted. A three-phase induction motor 10 is supplied to the three-phase induction motor 10 based on a command of the reference sine wave generator 5 that commands three-phase alternating current to be output, and a command of the reference sine wave generator 5. It is comprised as the inverter part 6.

FIG. 2 is a circuit diagram of a three-phase induction motor according to FIG. In order to input the voltage output from the primary winding 14 and the reactance component of the value X1 and the resistance component of the value r1, the inversely proportional to the reactance component and the slips of the value X2. The secondary winding 15 which consists of the resistance of the value r2 / s mentioned above, and the excitation circuit 16 with one side terminal connected between the primary winding 14 and the secondary winding 15 is comprised.

Referring to the operation of the speed control device of the conventional elevator configured as described above and the problems as follows.

First, when the three-phase induction motor 10 is no load, the speed command signal V _P output from the speed command device 1 becomes the same as the speed signal V of the speed detector 12, and from the comparator 2. The output difference signal Vs becomes zero. For this reason, the voltage command signal V of the function generator 4 is inputted to the reference sine wave generator 5 without being corrected by the correction signal Vd through the rectifier circuit 7 and the correction circuit 8. From the inverter section 6, three-phase alternating current and voltage in the relationship of the straight line d0 shown in FIG. 3 are generated, and the voltage in the primary winding 14 is supplied to the three-phase induction motor 10. Since the drop is small, the secondary organic voltage E2, the frequency Wo, and the relationship (K = E2 / Wo) are almost in the straight line d0 shown in FIG.

Assume that the three-phase induction motor 10 has a heavy load to raise the next elevator (11). Simultaneously from the start to the stop of the three-phase induction motor 10 at this time is the curve g of FIG. That is, it accelerates at time t0-t1, drives at a constant speed at time t1-t2, and decelerates at time t2-t3.

When the three-phase induction motor 10 accelerates, the torque T1 is required as in the fourth degree, the speed signal V _T is smaller than the speed command signal V _P , and the difference signal Vs is a rectifier circuit ( A constant signal is always inputted to the correction circuit 8 by full-wave rectification at 7), and the inverter unit 6 outputs the voltage and frequency of the straight line d1 shown in FIG. On the other hand, a large primary current I1 that matches the torque T1 flows through the three-phase induction motor 10, and a voltage drop occurs in the primary winding 14 by the primary current I1, but the inverter unit ( 6) Since the output voltage of 6) is high, the secondary organic voltage E2 becomes a linear line d0 of FIG. 3 and the time t1-t2 rises at a constant speed as in the case of no load. In this case, the retrograde torque T2 is required. At this time, since the difference signal Vs is smaller than the value at the time of acceleration, the inverter unit 6 outputs a voltage and frequency which can be represented by the straight line d2 as in the third diagram. On the other hand, the voltage drop in the primary winding 14 of the three-phase induction motor 10 is smaller than the acceleration, and the relationship between the secondary organic voltage E2 and the frequency Wo is the straight line d0 of FIG. Will appear. When decelerating the elevator 11 during ascending, the torque T3 becomes smaller than when the three-phase induction motor 10 rises at a constant speed as in the fourth degree.

Therefore, the difference signal Vs is smaller than at a constant speed, and the inverter unit 6 outputs the voltage and frequency indicated by the straight line d2 in FIG. On the other hand, the voltage drop in the primary winding 14 becomes smaller again than at a constant speed, and as a result, the relationship between the secondary organic voltage E2 and the frequency Wo is indicated by a straight line d0 in FIG. In addition, when the elevator 11 that is heavier than the counterweight 13 is lowered, the three-phase induction motor 10 generates the braking torque T11 when the time t0 to t1 is accelerated as in the fourth degree. 12) a speed signal (V _T) is greater than is the value of the speed command signal (V _P) output from the speed command device (1) the difference signal (Vs) is detected from the value is negative.

The difference signal Vs is rectified by the rectifier circuit 7 and then the rectified signal is input to the correction circuit 8 so that the voltage and frequency of the straight line d11 in FIG. 3 are output from the inverter section 6.

On the other hand, the three-phase induction motor 10 flows a primary current I1 suitable for the braking torque T11 and a voltage drop occurs in the primary winding 14 by the primary current I1. As in the case of no load, the voltage E2 generates torques T12 and T13 in the constant speed and deceleration areas as shown in FIG. 4, respectively, and the difference signal between the speed signal V _T and the speed command signal V _P. The voltage command signal V is corrected by the correction signal Vd proportional to the absolute value of (Vs), and the inverter section 6, as shown in the straight line d12 (d13) of FIG. 3, has three phases of voltage and frequency. AC occurs.

Since the voltage drop occurs in the primary winding 14 of the three-phase induction motor 10, the relationship between the secondary organic voltage E2 and the frequency Wo is equal to the straight line d0 of FIG. 3. In this way, the difference between the speed command signal V _P and the speed signal V _T is detected and the voltage command signal V by the speed command signal V _P is added as a correction signal Vd obtained by the absolute value of the difference. As a result of the modification, the proportion of the secondary organic voltage E2 and the frequency Wo of the three-phase induction motor 10 becomes constant, and the torque becomes a value proportional to the secondary current.

Therefore, even if a large torque is applied to the three-phase induction motor, the increase in the primary current is similar to the increase in the torque, and no current is generated to compensate for the drop in the secondary organic voltage.

However, in the conventional speed controller of an elevator, the voltage applied to the excitation circuit of the three-phase induction motor is not accurately controlled, and it does not show the responsiveness to the speed input as in the DC motor. There was a problem that the power is excessively consumed because the voltage of both ends of the main capacitor suddenly rises during the sudden deceleration.

In view of the conventional problems, the present invention rectifies the three-phase AC power to the DC power in the converter unit, smoothes in the capacitor, converts the AC power into the AC power in the inverter unit, and detects it with the detector. In the vector controller, the current detector The present invention is described in detail according to the accompanying drawings by the phase conversion of the detected current value so that the excitation current and the torque current can be made independently of each other in size by a desired amount.

5 is a configuration diagram showing the speed control device of the elevator of the present invention, and as shown therein, the current detector 3 for detecting current by inputting the three-phase AC power supply 1 through the AC reactor 2 and And a converter unit 4 composed of diodes D1 and D2 and transistors TR1 and TR2 for inputting the three-phase AC power supply 1 of the current detector 3 and then full-wave rectifying the same. A capacitor C1 for smoothing the output of (4), and an inverter section composed of diodes D3 and D4 and transistors TR3 and TR4 in order to convert the DC power smoothed from the capacitor C1 back into AC power. 5) and a three-phase induction motor 8 for elevating the elevator 28 by receiving an AC power output from the inverter unit 5 through the current detector 6 and the noise attenuating AC reactor 7, Pulse encoder 9 for detecting the position of elevator 28 in accordance with the speed of the three-phase induction motor 8 A position calculator 10 for calculating and outputting the position of the elevator 28 by the pulse of the pulse encoder 9, and a position commander 11 for outputting a position command signal to shorten the running speed without harming the elevator. ) And a comparator 12 for comparing the position command signal output from the position commander 11 of the position signal and outputting the difference signal, and correcting the difference signal between the comparator 12 and the three-phase induction. The speed commander 13 outputs the speed command signal after calculating the instantaneous speed of the motor 8, and the three-phase induction motor output from the speed command signal and the pulse encoder 9 of the speed commander 13 ( A vector controller 14 which performs vector operation with a difference from the speed of 8) and a comparator for comparing the current value output from the vector controller 14 with the current value detected by the current detector 6 and outputting the difference signal ( 15) and current control for controlling the difference signal of the comparator 15 (16) and a sine wave pulse width modulation controller 17 and a sine wave pulse width modulation controller 17 for converting an AC signal outputted from the current controller 16 into a DC current which is easy to switch as an input. As the width of the pulse signal changes, the dead time controller 18 for driving the three-phase induction motor 8 by switching the transistors TR3 and TR4 of the inverter unit 5, and the three-phase induction motor 8 The DC voltage detector 21 which detects the DC voltage across the capacitor C1 at the time of sudden deceleration and the DC voltage detected by the DC voltage detector 21 and the preset reference voltage from the reference voltage 19 are applied. A comparator 20 for receiving and comparing the signals and outputting a difference signal, a transformer 27 for detecting and outputting a phase in the three-phase AC power supply 1 through the AC reactor 2, and detecting the same from the transformer 27. The phase and the difference signal output from the comparator 20 The power factor controller 22 for controlling the power factor, the comparator 23 for comparing the output value of the power factor controller 22 with the current value detected by the current detector 3 and outputting the difference signal, and the comparator 23 A current controller 24 for controlling the difference current of the AC signal outputted from the second signal, a sine wave pulse width modulation controller 25 for converting the output of the current controller 24 into a DC current, and the sine wave pulse. The transistors TR1 and TR2 of the converter unit 4 are switched in accordance with the pulse signal output from the width modulation controller 25 to configure the dead time controller 26 for controlling the voltages across the capacitor C1.

6 is a detailed configuration diagram of the vector controller of FIG. 5, in which the pulse output from the pulse encoder 9 of the three-phase induction motor 8 is calculated to rotate the current three-phase induction motor 8. A speed calculator 14b for calculating the number, a comparator 14i for comparing the speed signal of the speed calculator 14b with the speed command signal of the speed commander 13 and outputting the difference signal, and the comparator 14i The three-phase induction motor is inputted by the torque current calculation unit 14a for supplying the torque component current Iqes to the three-phase induction motor 8 by the difference signal of?) And the speed signal calculated by the speed calculation unit 14b. (8) Slip angle frequency calculation section for outputting the slip angle frequency (Ws) by inputting the magnetizing current calculation unit 14c for setting the rated magnetizing current (Ides), the torque current (Iqes) and the rated magnetizing current (Ides) ( 14d) and an integrator 14 which outputs a slip angle θs by integrating the output of the slip angle frequency calculating section 14d. e), a rotor position detector 14g for accumulating the pulses output from the pulse encoder 9 of the three-phase induction motor 8 in one round and outputting the absolute position? r of the current rotor, and the A comparator 14h for comparing the slip angle θs of the integrator 14e with the absolute position θr of the rotor and outputting the isochronous angle θo, the torque current Iqes, the magnetizing current Ides, and the equalizer It consists of a vector calculation part 14f which calculates the magnitude | size and angle of the primary current to be supplied to the three-phase induction motor 8 from the angle (theta) o.

In the figure, reference numeral 30 denotes a traction mechanism, and 29 denotes a balance weight of the elevator 28.

Referring to the effects of the present invention configured as described above are as follows.

The three-phase AC power source 1 has a direct current in the inverter unit 4 composed of diodes D1 and D2 and transistors TR1 and TR2 through the current detector 3 after the current waveform is improved through the AC reactor 2. Fully rectified by a power supply, smoothed by the capacitor C1, and applied to the input side of the inverter unit 5, where a pulse signal is output from the sinusoidal pulse width modulation controller 17 controlled by the current controller 16, and then dead. Since the transistors TR3 and TR4 of the inverter unit 5 are selectively switched through the time controller 18, the DC power applied to the input side thereof is converted into AC power again, and then the current detector 6 and the noise attenuation alternating reactor. The seven-phase induction motor 8 is driven, and the induction motor is driven to drive the elevator 28 up or down through the traction mechanism 30.

At this time, the speed of the three-phase induction motor 8 is detected by the pulse encoder 9 and applied to the position calculator 10, whereby the position calculator 10 calculates the position of the elevator 28 with the pulse of the pulse encoder 9. When the position commander 11 applies a position command signal to the comparator 12 that shortens the driving speed without harming the most elevating person, the comparator 12 is then sent to the comparator 12. After comparing the position signal of the position calculator 10 and the position command signal of the position commander 11, the difference signal is applied to the speed commander 13, and the speed commander 13 receives the signal as an input. After calculating the instantaneous speed of the most suitable three-phase induction motor 8, the speed command signal is applied to the comparator 14i of the vector controller 14 as shown in FIG. The pulse signal output from the pulse encoder 9 of FIG. When the speed signal of the three-phase induction motor 8 is calculated by the speed calculator 14b and applied to the comparator 14i, and applied to the magnetization current calculator 14c, the comparator 14i receives the speed command signal and the speed. After comparing the present speed signals of the three-phase induction motor 8 output from the calculating section 14b, the difference signal is sent to the torque current calculating section 14a, and the torque current calculating section 14a transmits the three-phase induction motor 8. By determining how much torque is supplied to the vector, the vector operator 14c calculates the speed signal and applies the rated magnetizing current Ides to the vector operator 14f, while the slip angle frequency operator 14d is the torque. The slip angle frequency Ws is obtained by calculating the torque current Iqes of the current operation unit 14a and the rated magnetization current Ides of the magnetization current operation unit 14c.

이다. 이와같이 슬립각주파수연산부(14d)에서 슬립각주파수(Ws)를 구하고, 적분기(14e)에서 적분하여 상기 슬립각(θs)을 구한 후 비교기(14h)에 인가하면 비교기(14h)는 펄스엔코더(9)에서 출력된 펄스를, 회전자의 한바퀴내에서 누적시켜서 현재의 회전자절대위치(θr)를 계산하는 회전자위치검출부(14g)의 출력과 비교하여 그 등기각(θo)을 벡터연산부(14f)는 토오크전류(Iqes), 정격자화전류(Ides) 및 등기각(θo)으로부터 출력단자(Iu)(Iv)(Iw)를 통해 3상유도전동기(8)에 공급할 1차전류의 크기와 각도를 벡터연산하여 가장 적절한 전류치를 비교기(15)의 타측입력에 인가시키게 되고, 이때 3상유도전동기(8)의 입력전류를 전류검출기(6)에서 검출하여 비교기(15)의 일측입력에 인가시키게 됨에 따라 그 비교기(15)는 벡터제어부(14)의 벡터연산부(14f)에서 출력된 전류치와 전류검출기(6)에서 검출된 전류치를 비교하여 그 차를 전류제어기(16)에서 제어하고, 이후 정현파펄스폭변조제어기(17)를 거쳐 아날로그값이 스위칭하기에 편한 직류 전원으로 바뀌고, 이것은 데드타임제어기(18)에서 인버터부(5)의 트랜지스터(TR3, TR4)가 암쇼트(Arm Short)가 일어나지 않도록 제어된 후 정현파펄스폭변조제어기(17)의 펄스신호폭의 변화에 따라 인버터부(5)에 구성된 트랜지스터(TR3, TR4)의 온-오프시간을 제어하여 3상유도전동기(8)에 일정한 교류전원이 인가되어 구동된다.That is, when the mutual inductance of the three-phase induction motor 8 is M, the resistance of the rotor is Rr, the inductance of the rotor is Lr, the slip angle is θs, and the slip angle frequency is Ws.

to be. In this way, the slip angle frequency Ws is obtained from the slip angle frequency calculating unit 14d, and the slip angle? S is obtained by integrating the integrator 14e, and then applied to the comparator 14h. ) Is compared with the output of the rotor position detector 14g, which accumulates the pulse output from the rotor within one turn of the rotor and calculates the current rotor absolute position θr, and compares the registered angle θo with the vector operator 14f. ) Is the magnitude and angle of the primary current to be supplied to the three-phase induction motor 8 through the output terminals Iu (Iv) (Iw) from the torque current Iqes, the rated magnetizing current Ides, and the isochronous angle θo. The vector operation is performed to apply the most appropriate current value to the other input of the comparator 15. At this time, the input current of the three-phase induction motor 8 is detected by the current detector 6 and applied to the one input of the comparator 15. As a result, the comparator 15 checks the current value and the current test output from the vector operation unit 14f of the vector control unit 14. The current value detected at the outlet 6 is compared and the difference is controlled by the current controller 16, and then, via the sinusoidal pulse width modulation controller 17, the analog value is changed into a DC power supply which is easy to switch, which is a dead time controller. In operation 18, the transistors TR3 and TR4 of the inverter unit 5 are controlled such that arm short does not occur, and then the inverter unit 5 according to the change of the pulse signal width of the sine wave pulse width modulation controller 17. By controlling the on-off time of the transistors TR3 and TR4 configured in the above, a constant AC power is applied to the three-phase induction motor 8 to be driven.

Here, if the three-phase induction motor 8 decelerates rapidly, the reverse current accumulates in the capacitor C1 through the AC reactor 7, the current detector 6, and the diode D4 of the inverter unit 5, and eventually the capacitor The voltage at both ends of C1 rises.

When the increased DC voltage is detected through the DC voltage detector 21 and applied to one input of the comparator 20, the comparator 20 is larger than the reference voltage preset in the reference voltage 19, and then power regeneration is performed. Will be done. Thereafter, the power factor controller 22 controls the phase of the three-phase AC power supply 1 detected through the difference signal and the transformer 27 compared with the comparator 20, and the power factor control 22 of the comparator 23 is controlled. The output value is compared with the current value detected by the current detector 3, the difference signal is controlled by the current controller 24, and then the analog value is converted into a DC power supply via the sinusoidal pulse width modulation controller 25, which is dead. In the time controller 25, the transistors TR1 and TR2 of the converter unit 4 are controlled so as not to cause a dark short, and then configured in the converter unit 4 according to the change in the pulse signal width of the sinusoidal pulse width modulation controller 25. When the transistors TR1 and TR2 are turned on, current is reversed to control the power factor of the capacitor C1 so that the power factor is close to " 1 ". On the other hand, in the vector controller 14, non-interference control so that the rated magnetization current Ides and the torque current Iqes can be independently made without a time delay by the phase change of the current value detected by the current detector 6, respectively. Will be

(모터의 극수쌍)ㆍ

ㆍIdesㆍIqes로 표시되므로 여기서 정격자화전류(Ides)와 토오크전류(Iqes)가 모두 양의 값일때는 지령치 방향대로 돌려는 힘이 발생된다.7a and b show an example in which the speed command signal of the speed commander 13 is controlled by the vector controller 14, and if the speed command signal output from the speed commander 13 is 1500 RPM, the pulse encoder ( If the actual rotation speed of the three-phase induction motor 8 detected from 9) is 1000 RPM, the slip angle θs, rated magnetization current Ides and torque current Iqes as shown in FIG. Is a positive value, and the torque T applied to the three-phase induction motor 8 is

(Pole pair of motors)

Since Ides and Iqes are displayed, when the rated magnetizing current Ides and the torque current Iqes are both positive values, a force that is turned in the direction of the command value is generated.

At this time, magnetization current (Ides) is generated as much magnetization current as necessary, and torque current (Iqes) is a positive current proportional to the difference between the speed command signal and the actual rotation speed of the three-phase induction motor (8) three-phase induction It is synthesized and applied to the electric motor 8. Therefore, the three-phase induction motor 8 rotates at a speed that matches the speed command signal of the speed commander 13 within the shortest time.

ㆍIdesㆍIqes로 되는데 여기서 정격자화전류(Ides)는 항상 양의 값이나 토오크전류(Iqes)는 부의값을 가지므로 3상유도전동기(8)는 지령치방향의 반대방향으로 돌려는 힘이 발생된다. 이때 토오크전류(Iqes)의 값은 3상유도전동기(8)의 회속도가 서서히 줄어 속도지령치에 가까와짐이 따라 그 양이 줄어들게 되고 속도가 같아질때 토오크전류(Iqes)는 제로(zero)가 된다.In addition, if the speed command signal of the speed commander 13 is 1500 RPM and the actual rotation speed of the three-phase induction motor 8 detected from the pulse encoder 9 is 2000 RPM, the vector of FIG. By the calculation unit 14f, the angle θ _T formed by the slip angle θs, the rated magnetizing current Ides, and the torque current Iqes becomes a negative value as in the seventh diagram, and the torque _T at this time is similarly

ㆍ Ides and Iqes, where the rated magnetizing current (Ides) always has a positive value and the torque current (Iqes) has a negative value, so the three-phase induction motor (8) generates a force that rotates in the direction opposite to the command value direction. . At this time, the value of torque current Iqes decreases as the rotation speed of the three-phase induction motor 8 gradually approaches the speed command value, and the torque current Iqes becomes zero when the speed is the same. .

As described above, the present invention can reduce the cost of system installation cost because the power installation capacity is reduced compared to the conventional elevator control device, and it is possible to remove the noise generated by the induction motor by switching the transistor of the inverter unit and the converter unit at high speed. There is a characteristic that can feel the lift.

Claims (2)

The three-phase AC power supply 1 is full-wave rectified in the converter section 4, and smoothed in the condenser C1, followed by a pulse encoder 9, a position calculator 10, a position commander 11, a comparator 12 and In the elevator control apparatus for controlling the inverter unit 5 by the speed command signal calculated by the speed commander 13 to drive the three-phase induction motor 8 with the three-phase AC power generated therein, the speed commander The vector controller 14 which performs vector operation with the difference between the speed command signal of (13) and the speed of the three-phase induction motor 8 output from the pulse encoder 9, and the output current value of the vector controller 14 and The comparator 15 comparing the input current value of the three-phase induction motor 8 detected by the current detector 6 and the direct current detecting the voltage between both ends of the capacitor C1 when the three-phase induction motor 8 decelerates rapidly. The voltage detector 21 and the DC voltage of the DC voltage detector 21 and the reference voltage set in advance from the reference voltage 19 are compared. Power factor controller 22 for power factor controlling the comparator 20, the difference voltage of the comparator 20, and the phase of the three-phase AC power supply 1 detected from the transformer 27, and the power factor controller 22. A comparator 23 for outputting a difference signal by comparing the output value of the output signal with the input current value of the converter section 4 detected by the current detector 3 and a current for controlling the difference signal of the comparators 15 and 23. Controllers 16 and 24, sinusoidal pulse width modulation controllers 17 and 25 for converting AC signals of the current controllers 16 and 24 into direct current, and the sinusoidal pulse width modulation controllers 17 and 25. And a dead time controller (18) (26) for controlling dead time in order to prevent dark shorting of the transistors of the converter section (4) and the inverter section (5) in accordance with the pulse signal of the apparatus. A speed comparator (14b) for calculating a current speed by calculating a pulse of said pulse encoder (9), and a comparator for comparing a speed signal and a speed command signal of said speed calculator (14b). 14i) and the torque current calculating section 14a for supplying the torque current Iqes to the three-phase induction motor 8 by the difference signal of the comparator 14i, and the speed signal of the speed calculating section 14b. The magnetizing current calculating unit 14c for setting the magnetizing current Ides, the slip angle frequency calculating unit 14c for calculating the torque current and the magnetizing current to obtain a slip angle frequency Ws, and the slip angle frequency are integrated and slipped. Rotor position for accumulating the integrator 14e for obtaining the angle θs and the pulse output from the pulse encoder 9 of the three-phase induction motor 8 in one round to obtain the absolute position θr of the current rotor. Comparing the detection unit 14g with the slip angle and the absolute position, the equivalence angle θo is obtained. And a comparator (14h) and a vector controller (14f) rotor vector controller for calculating the magnitude and angle of the current from the torque current, the magnetizing current, and the angle of registration.

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