JPS6037718B2 - Induction motor control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a blind pupil in which an induction motor is controlled in a non-contact manner using a semiconductor such as a thyristor.

Conventionally, as this type of bag hawk, those shown in FIGS. 1 to 5 have been proposed.

In the figure, R, S, and T are three-phase AC power supplies, 1 to 3 are the primary windings of the three-phase induction motor, 4 and 5 are thyristors, 6 and 7 are diodes, and 8a to 8c are energized at the start of elevator startup. normally open contact of the starting magnetic contactor, which is deenergized at the start of deceleration.
9a and 9b are normally open contacts of deceleration electromagnetic contactors which are energized when the elevator starts decelerating and are deenergized when the elevator starts.

At the start of startup, when the startup electromagnetic contactor is energized, the contacts 8a to 8c are closed, so a circuit as shown in FIG. 2 is formed, and the thyristors 4 and 5 are connected in antiparallel to each other. It is inserted between power supply R and winding 1. When the thyristors 4 and 5 are made conductive in this state, the electric motor generates a power running torque as shown in FIG. By controlling the firing angles of the thyristors 4 and 5, the well-known Kuza activation is performed. Thyristor 4
, 5 are fully fired, the motor is operated with all three-phase voltages applied to its primary windings 1-3. In this way, the power running torque of the electric motor can be widely controlled over the range A from the single-phase power running torque curve 12 when the thyristors 4 and 5 are cut off to the power running torque curve 11 when the three-phase full voltage is applied. .

Next, when the starting contactor is deenergized at the start of deceleration, the contacts 8a to 8c open.

Furthermore, when the deceleration electromagnetic contactor is energized, the contacts 9a,
9b is closed. This forms a circuit as shown in FIG. 4, in which the thyristors 4 and 5 and the diodes 6 and 7 constitute a single-phase full-wave rectifier circuit, and direct current flows in the direction of arrow B through the primary windings 1 and 2. As a result, the electric motor generates a braking torque as shown in FIG. If the thyristors 4 and 5 are controlled here, the braking torque can be changed. When the car reaches a predetermined position, the deceleration contactor is deenergized and the contacts 9a and 9b are opened, so the current in the primary windings 1 and 2 is immediately cut off, and a brake (not shown) is applied to the motor. Then the car stops. However, the above device requires five contacts for the sliding door.

Therefore, the equipment is likely to be expensive. Furthermore, if the thyristors 4 and 5 had only the circuit configuration shown in Figure 2, it would be possible to replace them with a single inexpensive bidirectional thyristor, but this would not be possible due to the circuit configuration shown in Figure 4. Therefore, it was necessary to use two expensive thyristors. The present invention aims to improve the above-mentioned drawbacks and provides an induction motor control device that can be constructed at low cost by reducing the number of contacts.

An embodiment of the present invention will be explained below with reference to FIG.
In the figure, 15 is a bidirectional thyristor.

The bidirectional thyristor 15 is connected between the terminal of the primary winding 1 of the motor and the power supply R, and the contact 8c is connected between the terminal of the primary winding 3 and the power supply T. ,2
Both ends of diodes 6 and 7 connected in anti-series are connected between the terminals of . Further, a neutral point of the series circuit of diodes 6 and 7 is connected to a terminal of the primary winding 3 of the motor via a contact 9a.
2. At the start of startup, contact 8c is closed and contact 9a is open, so the circuit is the same as that of FIG. 2, and Kuza startup is performed. At the start of deceleration, contact 8c is opened and contact ga is closed.

Therefore, during the period when the power supply R is positive, R-15 2-6-9a
A half-wave current (in the direction of arrow C) flows through the primary windings 3 and 2 by the circuit 13-21S. During this time, no current flows through the primary winding 1. In addition, during the period when the power supply S is positive, S-7-ga-3
A half-wave current (in the direction of arrow D3) flows through the primary windings 3 and 1 through the circuit 11-15-R. During this time, no current flows through the primary winding 2. These currents flow through the primary windings 2 and 3 due to the flywheel effect of diodes 6 and 7.
Current flows continuously through the primary windings 1 and 3, and a large braking force is generated as in FIG. Note that a single-phase alternating current flows through the primary windings 1 and 2 due to firing of the bidirectional thyristor 15, and the motor also generates single-phase powering torque, but this torque is transferred from the primary winding 3 to the primary winding 2. DC current flowing through
Since the braking torque is smaller than the braking torque generated by the direct current flowing from the primary winding 3 to the primary winding 1, it is canceled out. In other words, Fig. 7 shows typical curves for slippage of single-phase powering torque when a single-phase voltage of the rated voltage is applied to the induction motor and DC braking torque when a DC voltage obtained by rectifying the rated single-phase voltage is applied to the induction motor. Shown below. In the figure, the power running torque is expressed on a scale of one tone of the braking torque. The power running torque and braking torque in FIG. 7 are equal to the torque generated by the motor when the contact 8c is open, the contact 9a is open, and the bidirectional thyristor 15 is fully fired in FIG. 6. Therefore, as is clear from FIG. 7, the DC braking torque is extremely large, at least 20 times the single-phase powering torque. Further, this relationship, that is, the ratio of the single-phase powering torque to the DC braking torque, is the same even when the bidirectional thyristor 15 is controlled to fire. Although the curve in Figure 7 is just an example,
Generally, when performing primary voltage control, the secondary resistance of the motor is increased to facilitate control, and as a result, the difference between braking torque and powering torque becomes particularly large. therefore,
By controlling the firing angle of the bidirectional thyristor 15,
By controlling the braking current, the braking torque of the electric motor can be controlled.

As explained above, the present invention inserts a bidirectional thyristor between the first terminal of the motor and the power supply, and further connects both ends of an anti-series circuit of diodes between the first and second terminals of the motor. Connecting the neutral point of this series circuit to a third terminal of the motor via a contact that closes when the motor decelerates,
Furthermore, a contact that closes when the motor is started is connected between the third terminal and the power source.

This makes it possible to use a relatively inexpensive bidirectional sirensor, and since the number of contacts is only two, the armor can be constructed at a low cost.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of the main part of a conventional induction motor control device, Fig. 2 is a principle circuit diagram at the time of start-up of Fig. 1, Fig. 3 is a diagram of motor running torque vs. slip characteristics at start-up, and Fig. 4 Fig. 5 is a diagram of the principle circuit during deceleration, Fig. 5 is a diagram of motor braking torque vs. slip characteristics during deceleration, Fig. 6 is a circuit diagram showing an embodiment of an induction motor control device according to the present invention, and Fig. 7 is a circuit diagram showing the motor braking torque versus slip characteristic during deceleration. It is a power running torque/braking torque relationship diagram for explaining the relationship between power running torque and zero braking torque in the invention. 1 to 3...Induction motor primary winding, 6,7...Diode, 8c...Starting electromagnetic contactor contact, 9a...
...Magnetic contactor contact for deceleration, 15...Two-way silisk. In addition, the same parts or corresponding parts in the figures are indicated by the same reference numerals. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] 1. Connect three terminals of a three-phase induction motor to a three-phase AC power source, insert a bidirectional thyristor between the first terminal of the motor and the power source, and connect the first terminal and the second terminal of the motor. Connect both ends of a circuit in which diodes are connected in anti-series between the terminals, and connect a contact that closes when the motor decelerates between the neutral point of the series circuit of the diodes and a third terminal of the motor. A control device for an induction motor, wherein a contact that is closed when the motor is started is connected between a third terminal of the motor and the power source.