SU811473A1 - Electric motor reversing device - Google Patents

Description

one

The invention relates to electrical engineering, in particular, to devices for reversing electric motors of DC valve electric drives mainly in the field winding.

A device for reversing an electric motor across an excitation winding with capacitive disconnection 1 is known. However, when powered by a controlled rectifier, the excitation winding by capacitance by capacity is excluded, especially when controlled with a large range.

The closest in technical drying, effect and effect achieved is a device for reversing an electric motor, in which the field winding is connected to a reversible thyristor converter on two fully controlled bridges 2.

With a constant shunting of the excitation winding with a discharge resistor, the latter cannot be chosen high enough to reduce losses, since the thyristors of the controlled rectifier may not be closed when the control is removed, their pulses. Therefore, the decay time of the current in the field winding is increased. In addition, the drying, control of the passage of current through a zero value with

By helping, the current sensor complicates the logic unit and reduces the reliability of the device.

The aim of the invention is to accelerate the decay of the current in the winding and to increase the reliability of the device.

This goal is achieved by the fact that in the open circuit of the thyristor groups with straightening, the bodies on the DC side include the forced switching node, the charging circuit is switched, its capacitor is connected to the AC network.

FIG. 1 shows a circuit with one group of thyristors, a reverser and a switching unit with a discharge of its capacitor and a thyristor; in fig. 2 is a circuit with two groups of thyristors connected to the bridge, and a forced switching node with a discharge of its capacitor through the winding of the drossel.

The device contains a controlled thyristor rectifier 1, a forced switching node 2, including a suppressor thyristor 3, a commutation capacitor 4 and a thyristor 5, and a reverser including thyristors 6 and 7. The forced switching unit 2 is connected to an open thyristor circuit groups on the DC side, and the charge circuit 8 is switched, its capacitor is connected to the AC network. An excitation winding 9, shunted by voltage suppressor 10, is connected to the rectifier 1 through a reverser.

When a reverse command is given, the control pulses from thyristors 5 and 6 or 7 (depending on which ones were included) are removed, and simultaneously a pulse is applied to unlock the thyristor 3. Condenser 4 is discharged, thyristors 5, 6 or 7 are locked, and the current in this circuit almost instantly drops to zero, and the current in the excitation winding under the action of the emf self-induction begins to flow, decreasing through the voltage suppressor 10. In this case, the higher the stabilizer voltage, the faster the current in the excitation winding decreases.

From the moment the reversal command is given, the time delay for turning on the thyristors 5, 7 or 6 starts, which is longer than the recovery time of the thyristor locking properties by the time of the current falling through the thyristors when they are locked. Thyristors 5, 7, or 6 can then be turned on, but they turn on when the current in the field winding drops to zero, thereby preventing the opening of all the inverter thyristors, i.e., the through-current mode.

In the second variant, when reversing, pulses are removed from the controlled rectifier from the group previously operating, and at the same time a pulse is applied to the opening of the quenching thyristor 3. The capacitor 4 is discharged through the primary winding of the drossel. The voltage induced in the secondary winding has a opposite direction to the current flowing through the circuit section: the controlled rectifier is the middle point of the secondary windings of the throttles. The current in this circuit also almost instantly decreases to zero, and the current in the excitation winding closes through the voltage suppressor 10. After a similar time lag, you can turn on the second group of thyristors of the controlled rectifier 1. In this circuit it is necessary to take into account that the flow of a constant the excitation winding current through the secondary windings of the throttles magnetizes it somewhat.

Due to the forced disconnection of the field winding from the mains, the current in it drops to zero much faster under the effect of the voltage stabilization on the voltage limiter. In this case, it is not necessary to control the passage of current through zero; it is enough to turn on the second

a group of thyristors with a time delay for restoring the thyristor locking properties, which is necessary in any other schemes. Even if by this time the current in the field winding does not decrease to

The zero, previously not working group will not turn on, as the counter voltage on the limiter will be applied to the thyristors. This increases the reliability of the device. The logical switching device in this case is simplified, since its function is to turn on the quenching thyristor simultaneously with the removal of the control pulses from the working thyristor group and to apply control pulses to the thyristors of the previously inactive group with a delay.

Claims (2)

1.Ivanchuk B.P. et al. Semiconductor-controlled drives. Thyristor amplifiers in electric drive circuits. M., “Energie, 1966, p. 37, fig. 13.6. 2. USSR author's certificate number 251074, cl. H 02P 13/16, 1970 (prototype). ABOUT 5 V "} 40