JPS62210888A - Controller for induction machine - Google Patents

Abstract

PURPOSE:To eliminate a speed detector, by estimating a rotational speed through the voltage of a condenser and the conductivity of a secondary chopper. CONSTITUTION:Current command i*2 according to a deviation between the signal of a speed command unit 14 and the output signal of a rotational-speed arithmetic-unit 20 is compared with current detection signal i2 by a comparator 16 with hysteresis, and the output of the ON/OFF-control signal of a secondary chopper 3 is generated. By a non-conductivity arithmetic-unit 18, the output signal of the comparator 16 is inverted, and non-conductivity is obtained by performing arithmetic on the average value. Voltage signal EC from a voltage detector 12 for detecting condenser voltage is multiplied by the output signal of the non-conductivity arithmetic-unit 18, and arithmetic operation is performed on slip S, and based on the slip S, a rotational speed is found out by the rotational-speed arithmetic unit 20.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a speed control bag arrangement for a secondary-excitable induction machine, and particularly an induction machine suitable for driving loads such as pumps and fans. The present invention relates to a control device.

[Conventional technology]

As described in Japanese Patent Publication No. 56-25879, the conventional device uses a diode rectifier on the secondary side of the wound induction machine and an on/off operation of a secondary chopper connected to the output thereof. Next, adjust the current and control the torque. The torque is controlled by controlling the on/off operation of the secondary chopper in accordance with the deviation between the speed command and the signal from the speed detector attached to the shaft end of the induction machine.

[Problem that the invention seeks to solve]

According to the above-mentioned conventional technology, a speed detector is required, and installation work to the motor rotating shaft is complicated, and wiring work for a signal line from the speed detector is required.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide an induction machine control device in which the speed detector is omitted.

[Means for solving problems]

The above object is achieved by estimating the rotation speed from the output signal of a voltage detector that detects the voltage of the capacitor and the conduction ratio of the secondary chopper.

[Effect]

The slip of the induction machine is proportional to the secondary voltage, and the DC output voltage (average value) of the forward converter is proportional to this.

On the other hand, the input voltage (instantaneous value) of the secondary chopper is zero when the secondary chopper is on, and equal to the capacitor voltage when the secondary chopper is off. At this time, since the average value of the input voltage of the secondary chopper and the average value of the DC output voltage of the forward converter are balanced, the voltage of the capacitor is expressed by the following equation.

T T Here, Ec: Capacitor voltage, S: Slip, Ezo
: induction machine secondary voltage at s=1, T: secondary chopper on-off period, TON: conduction time, T OFF: non-conduction time If the above equation is expressed by slip S, furthermore, the relationship between slip and rotation speed is as follows: It is expressed as

N= (1-9)・No... (3) Here, No: synchronous speed, N: rotational speed, that is, from the capacitor voltage Ec and non-conduction ratio TOFF/T,
The rotation speed can be determined according to equations (2) and (3). Therefore, the speed detector can be omitted.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, a load 30 such as a pump or a fan is mechanically directly connected to a wound induction machine 1. A diode rectifier 2 is installed on the secondary side of the wound wire induction machine 1, and its output includes a secondary chopper 3 using a self-extinguishing element (transistor, GTO1MO8-FET, etc.), a backflow blocking diode 4, a capacitor 5, and a self-extinguishing element. A regenerative chopper 6 using shaped elements, a free wheel diode 7, and a regenerative inverter 8 using a thyristor are connected. Further, the output of the regenerative inverter 8 is connected to an AC power source via a transformer 9.

The basic operation of this embodiment will be explained. The speed control of the wound induction machine 1 is performed by adjusting the secondary current of the wound induction machine 1 by turning on and off the secondary chopper 3, and controlling the torque that is proportional to the secondary current of the wound induction machine 1. The secondary power of the wound induction machine 1 is supplied to the diode 4 when the secondary chopper 3 is off.
The capacitor 5 is charged through the capacitor 5, and the voltage of the capacitor 5 increases. Therefore, the voltage of the capacitor 5 is detected, and the on/off of the regenerative chopper 6 is controlled so that the voltage value is constant. In this way, the above-mentioned secondary power flows through the regenerative chopper 6 to the regenerative inverter 8, where it is further converted into alternating current power and regenerated into an alternating current power source.

Next, the operation of the control circuit of the secondary chopper 3 will be explained. First, the signal of the speed command device 14 and the rotation speed calculator 20
The deviation of the output signal of is amplified by the speed deviation amplifier 15, and the command signal 12* of the output current of the diode rectifier 2 is output. These 12 umbrellas and the current detection signal 12 from the current detector 11 are compared in a comparator 16 with hysteresis,
An on/off control signal for the secondary chopper 3 is taken out. The signal is amplified by the drive circuit 17 of the secondary chopper 3,
On/off of the secondary chopper 3 is controlled.

By the way, the output signal of the comparator 16 is "1" when 12* is larger than 12 by a predetermined value Δi2 (hysteresis width), and "0" when it is smaller than 12 by Δit.
"When the signal is "1", the secondary chopper 3 is turned on, and when it is "0", the secondary chopper 3 is turned off. The li conduction ratio calculator 18 calculates the non-conduction ratio (TOF) by inverting the output signal of the comparator 16 and calculating the average value.
F/T) related signals are extracted. Here, if the secondary voltage Ego (s=1> is constant in equation (2), the voltage signal E from the voltage detector 12 that detects the capacitor voltage
c, and the output signal TOFF/T of the non-conduction ratio calculator 18
By multiplying according to equation (2), the slip S can be calculated and detected. Further, the rotation speed can be determined by calculating the rotation speed calculation unit 20 according to equation (3) based on this slip S, so that the above-described operation of the secondary chopper 3 becomes possible.

Next, a control circuit for the regenerative chopper 6 will be described. The deviation between the signal of the voltage command unit 21 and the capacitor voltage detection signal is amplified by the voltage deviation amplifier 22 1, and the regenerative inverter 8
outputs a command signal iu for the current flowing through the terminal. This iIII and the regenerative inverter current detection signal i from the current detector 13
are compared in a comparator 23 with hysteresis, and an on/off control signal for the first regeneration chopper 6 is extracted. The signal is amplified by the drive circuit 24 of the regenerative chopper 6, and the on/off of the regenerative chopper 6 is controlled. That is, when the capacitor voltage detection signal becomes larger than the signal from the voltage command unit 21, the on-operation period of the regenerative chopper 6 increases, and accordingly, the discharge current of the capacitor 5, that is, the regenerative inverter current also increases. , the voltage of capacitor 5 is controlled to a predetermined value.

FIG. 2 shows another embodiment of the invention. In Figure 1,
When the AC power supply voltage, that is, the primary voltage of the wound induction machine 1 fluctuates, the secondary voltage also fluctuates, resulting in an error between the calculated rotational speed and the actual speed. This embodiment is designed to compensate for this problem. In other words, the transformation in Figure 2
The lj 25 and the voltage detector 26 are for detecting the AC power supply voltage, and by dividing the output signal thereof and the output signal of the multiplier 19 by the divider 27, it is possible to detect the slip in consideration of the negative voltage. . By manually inputting this signal to the rotational speed calculator 20, it is possible to compensate for errors in detection of the rotational speed due to fluctuations in the AC power supply.

By the way, the secondary voltage of the wound induction machine 1 varies depending on the magnitude of the output current of the diode rectifier 2 due to an internal voltage drop of the induction machine. The embodiment shown in FIG. 3 is designed to compensate for rotational speed detection errors due to this influence. That is, the effect of the voltage drop is calculated by inputting the current detection signal from the current detector 11 to the function generator 29, calculating the amount of output voltage drop of the diode rectifier 2, and adding the output signal to the rotation speed detection signal. can be compensated for.

By the way, in the above-described embodiment, when the deviation between the secondary current command signal T1 and the secondary current 12 is equal to or greater than a predetermined value,
This was a system in which the secondary chopper 3 was turned on and off. However, the present invention is not limited to such a method, and similar operations can be performed using the method described below. That is, the above 1
This method adds the deviations of 2 and 12 to a current deviation amplifier, compares the signal of the amplifier with the carrier wave that determines the on/off frequency of the secondary chopper 3 in a comparator, and extracts the on/off control signal from the comparator. . The output signal of the current deviation amplifier in this case is a signal related to the conduction ratio of the secondary chopper 3, and it is clear that using this signal, the rotation speed can be detected according to equation (2) as in the above-mentioned embodiment. It is.

Note that the reactor 28 connected to the output side of the diode rectifier 2 may be omitted. In that case, the leakage inductance of the wound induction machine 1 acts as a reactor.

〔Effect of the invention〕

According to the present invention, since the speed detector attached to the motor can be omitted, installation work of the speed detector and wiring work of signal lines are not required, and the control device can be simplified and inexpensive. .

[Brief explanation of drawings]

1 to 3 are configuration diagrams each showing an embodiment of the present invention. 1... Induction machine, 2... Diode rectifier, 3...
Secondary chopper, 4... Backflow blocking diode, 5...
Capacitor, 6... Regenerative chopper, 7... Freewheeling diode, 8... Regenerative inverter, 9... Transformer, 1
8...Non-conducting ratio 1st octopus fallen item calculation profit mo2 solid

Claims (1)

[Claims] 1. Connect an induction machine capable of secondary excitation, a secondary chopper for secondary current adjustment to the forward converter connected to the secondary side of the induction machine, and connect a capacitor and diode in parallel with the secondary chopper. In a device comprising a series circuit connected, a regeneration chopper that adjusts the voltage of the capacitor, an inverse converter that converts the output of the chopper to alternating current, and regenerates the power from the capacitor to an alternating current power supply, Control of an induction machine, characterized in that the rotation speed of the induction machine is estimated from the signal regarding the capacitor voltage and the conduction ratio of the secondary chopper, and the rotation speed of the induction machine is controlled using this estimated speed signal. Device.