JPH01321891A - Controller of wound-rotor induction motor - Google Patents

Abstract

PURPOSE:To suppress amplitude of beat current as soon as possible providing a secondary winding current is a dominant wave by connecting a bridge circuit provided with a self-arc-extinguishing type element to a secondary circuit of a wound-rotor induction motor in parallel. CONSTITUTION:A bridge circuit 27 provided with a self-arc-extinguishing type element is connected to a secondary circuit of a motor 1 through a transformer 20 in parallel with a three full-wave rectifying circuit 3. A dominant wave secondary current operation circuit 22 performs operations of the dominant wave secondary current of the motor 1. A harmonic current operation circuit 23 performs operations of a harmonic current reference signal according to a square wave current signal of slip frequency detected by a current detector 21 and a dominant wave secondary current signal. A current controlling circuit 25 turns the self-arc-extinguishing type element of the bridge circuit 27 ON/OFF through a gate circuit 26 to control the current supplied to a DC reactor 28 so that variation between a detection signal of a current detector 24 and a harmonic current reference signal is reduced to 'zero'.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to a control device for a wound induction motor that controls the speed of the wound induction motor using a static Servius method.

(Prior art) A conventional wound type positive conduction motor using the stationary Servius method (
FIG. 4 shows a control device for a motor (hereinafter also referred to as an electric motor). In Fig. 4, a three-phase full-wave rectifier 3 is connected to the secondary winding of the motor 1.
is connected. A silice inverter 5 for converting the DC output into AC at the power frequency is connected to the DC output side of the three-phase full-wave rectifier 3 via a DC reactor 4.

The alternating current that is the output of the silice inverter 5 is converted into a wi source via a transformer 6. A current flowing through a Servius circuit consisting of a three-phase full-wave rectifier 3, a DC reactor 4, and a thyrisk inverter 5 is detected by a current detector 7.

The speed reference setter 8 is used to set a reference value for the rotational speed (hereinafter also simply referred to as speed) of the electric motor 1.

The speed control circuit 9 calculates the deviation between the setting signal from the speed reference setter 8 and the detection signal from the speed detector 2, and outputs a current reference signal that makes this deviation zero. Current control circuit 10
calculates the deviation between the current reference signal that is the output of the speed control circuit 9 and the detection signal from the current detector 7, and outputs a phase control signal that makes this deviation zero. Based on this phase control signal, the phase controller 11 gives a firing pulse to the thyrisk inverter 5. In the control device configured as described above, a square wave current of 120 @ energization as shown in FIG. 5 flows through each phase (U, V, W) of the motor secondary winding.

(Question 8 to be solved by the invention) However, for such a square wave current, (6n±1)sf(
However, nml, 2. ) contains harmonic currents. Among them, the content of the fifth harmonic component with n=1 is the largest, and this component appears on the power supply side of the motor as (1-6s)f (where S is slip and f is the power supply frequency).

This harmonic component of (1-6s)f interferes with the power supply frequency f, and in particular, when f--f or equal to 0, the motor-order laminar flow becomes a low-frequency beat current.

In systems where the short-circuit impedance of the power supply is large (power supply capacity is small), the amplitude of the beat current increases due to the reactance voltage drop, causing problems such as interference with lighting equipment connected to the same system and generation of flicker. was there.

The present invention has been made in view of the above problems, and provides a control device for a wound type positive conduction motor that can suppress the amplitude of the beat current as much as possible regardless of the specific speed of the motor. The purpose is to

[Structure of the invention]

(Means for Solving the Problems) The present invention provides a rectifier that rectifies the secondary power of a wound positive conduction motor, an inverter that converts direct current that is the output of the rectifier into alternating current at the power frequency, and a wound positive conduction motor. speed control means for outputting a current reference for an input current of an inverter such that the deviation between the detected value of the rotational speed of the inverter and the reference value is zero; and a first current control means for adjusting the firing frequency of the inverter.
Based on a bridge circuit having a self-arc-extinguishing element connected in parallel to the secondary circuit of a winding positive conduction motor, a detected value of the secondary voltage and a detected value of rotational speed of the winding positive conduction motor, and a current reference. A fundamental wave secondary current calculation means for calculating the fundamental wave secondary current of each phase of the wound positive conduction motor, a first current detector for detecting the input current of the rectifier, and an output of the first current detector. and harmonic current calculation means for calculating a harmonic current reference based on the output of the fundamental wave secondary current calculation circuit;
a second current detector that detects the input current of the bridge circuit; The present invention is characterized by further comprising a second current control means for controlling the current.

(Function) According to the control device for a wound type positive conduction motor according to the present invention configured as described above, a harmonic compensation current flows from the bridge circuit, a square wave current flows to the Servius circuit consisting of a rectifier and an inverter, and the aforementioned By combining the harmonic compensation current and the harmonic compensation current, a fundamental wave current flows through the secondary winding of the motor.

As described above, according to the present invention, the amplitude of the beat current can be suppressed as much as possible regardless of the specific speed of the motor.

(Example) An example of the present invention will be described below with reference to the drawings. Components that are the same as those of the conventional speed control device shown in FIG. 5 are designated by the same reference numerals, and the explanation thereof will be omitted. As shown in FIG. 1, the control device for the wound induction motor of this embodiment has a self-extinguishing element connected to the secondary circuit of the motor 1 in parallel with a three-phase full-wave rectifier circuit 3 via a transformer 20. A bridge circuit 27 is connected. The input current of the three-phase full-wave rectifier 3 is detected by the current detector 21, and the input current of the three-phase full-wave rectifier 3 is detected by the current detector 21.
The input current of 7 is detected by the current detector 24. The fundamental wave secondary current calculation circuit 22 calculates the fundamental wave secondary current of the electric motor 1 based on the output signal of the speed control circuit 9, the detection signal of the speed detector 2, and the secondary voltage of the electric motor 1. An example of this fundamental wave secondary current calculation circuit 22 is shown in FIG. The fundamental wave secondary current calculation circuit 22 shown in FIG. 3 inputs a secondary voltage signal obtained by connecting each phase of the motor secondary winding via a transformer 221 to a divider 224.

Detection signal of speed detector 2 of electric motor 1 and synchronous speed setter 2
By dividing the setting signal of 22 by the slip signal obtained by inputting it to the slip detector 223, it is possible to obtain a constant fundamental wave secondary current frequency signal for each phase, which is independent of the motor speed. A fundamental wave secondary current signal can be obtained by multiplying this fundamental wave secondary current frequency signal by the output signal (current reference signal) of the speed control circuit 9 shown in FIG. 1 in a multiplier 225. FIG. 3 shows one embodiment of the motor secondary U-phase winding, and other V-phase and W-phase windings can be obtained in the same manner.

Referring again to FIG. 1, the harmonic current calculation circuit 23 receives the square wave current signal of the slip frequency detected by the current detector 21 (see symbol A in FIG. 2(a)) and the fundamental wave secondary current calculation circuit 22. A harmonic current reference signal (see symbol C in FIG. 2(b)) is calculated based on the fundamental wave secondary current signal which is the output of.

The current control circuit 25 controls the gate circuit 2 so that the deviation between the detection signal of the current detector 24 and the harmonic current reference signal becomes zero.
6, the self-extinguishing element of the bridge circuit 27 is turned on and off to control the current flowing to the DC reactor 28.

In the control device for the wound induction motor configured in this manner, a harmonic current C shown in FIG. 2(b) flows to the bridge circuit 27. Therefore, the secondary winding current of the motor 1 is the current A flowing through the three-phase full-wave rectifier 3 shown in FIG. 2(a).
and the harmonic current C flowing to the bridge circuit 27 are combined to form the waveform shown by the dotted line in FIG. 2(a), that is, the fundamental wave current.

As described above, according to this embodiment, the motor secondary winding current can be made into the fundamental wave current by flowing the harmonic compensation current in the motor secondary winding circuit, and the harmonic current can be suppressed. I can do it.

Furthermore, a specific speed (for example, l/3 or l/6 of the slip frequency)
Even if the motor is driven in the vicinity of Flickering of lighting equipment can be prevented.

〔Effect of the invention〕

According to the present invention, by flowing a harmonic compensation current through the motor secondary winding circuit, the motor secondary winding current can be made into a fundamental wave current, and the amplitude of the beat current can be adjusted regardless of the specific speed of the motor. can be suppressed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a control device for a wound induction motor according to the present invention, FIG. 2 is a graph showing the input current and harmonic current reference of the Servian circuit, and the motor secondary winding current, and FIG. The figure is a block diagram showing a fundamental wave secondary current calculation circuit according to the present invention, FIG. 4 is a block diagram showing a conventional wound induction motor control device, and FIG. 5 is a block diagram showing each phase of a conventional motor secondary winding. 3 is a graph showing a square wave current flowing through the circuit. DESCRIPTION OF SYMBOLS 1... Electric motor, 2... Speed detector, 3... Three-phase full-wave rectifier, 4... DC reactor, 5... Sirisk inverter, 6... Transformer, 7... current detector,
8...Speed setter, 9...Speed control circuit, 10...
-Current control circuit, 11... Phase control circuit, 20...
Transformer, 22... Fundamental wave secondary current calculation circuit, 23...
・Harmonic current calculation circuit, 24...Current detector, 25・
...Current control circuit, 26...Gate circuit, 27...
Bridge circuit, 28...DC reactor. Applicant's agent Mr. Sato Figure 1 Figure 2 Figure 3

Claims (1)

[Scope of Claims] A rectifier that rectifies the secondary power of the wound induction motor, an inverter that converts the direct current that is the output of the rectifier into alternating current at the power supply frequency, and a detected value of the rotational speed of the wound induction motor. speed control means for outputting a current reference of the input current of the inverter such that the deviation from the reference value is zero; and ignition of the inverter so that the deviation between the detected value of the input current of the inverter and the current reference becomes zero. a first current control means for adjusting the frequency; a bridge circuit having a self-extinguishing element connected in parallel to a secondary circuit of the wound induction motor; , a fundamental wave secondary current calculation means for calculating a fundamental wave secondary current of each phase of the wound type induction motor based on a detected value of the secondary voltage and a detected value of the rotational speed of the wound type induction motor, and the current reference; a first current detector that detects the input current of the rectifier; and a harmonic that calculates a harmonic current reference based on the output of the first current detector and the output of the fundamental secondary current calculation circuit. current calculation means; a second current detector for detecting the input current of the bridge circuit; 1. A control device for a wound induction motor, comprising: second current control means for controlling a gate of a self-extinguishing element.