SU1387159A1 - A.c. drive - Google Patents

Abstract

The invention relates to electrical engineering and can be used in electric drives for cranes of any industrial purpose. The aim of the invention is to increase reliability. This goal is achieved by using only three diodes 14, 15 and 16, connected to the middle leads of the induction resistor 11, to create a current loop during start and stop of the electric drive. Due to the discharge of the capacitor 10, the relay closure 17 is activated and, by contact 18, connects the thyristor 12 to the stator make-up circuit with the dynamic braking current. 1 il.

Description

i

(/

Os os

ate

;about

The invention relates to electrical engineering and can be used in electric drives for cranes of any industrial purpose.

The purpose of the invention is to increase reliability.

The drawing shows a diagram of the drive.

The AC drive contains a three-phase synchronous motor 1, the phases of the stator winding of which are connected to a power source through contacts 2–4 of the power contactor, a brake contactor with two closing contacts 5 and 6. The first diode 7 is connected in parallel to contact 2 of the power contactor In one of the phases of the stator winding and the anode is connected to the anode of the first thyristor 8, with one of the phases of the stator winding and with one of the terminals of the first resistor 9, the other output of which is through the first locking contact, contact 5 of the brake contactor and is connected to the control electrode of the first thyristor 8, the cathode of which is connected to one of the plates of the capacitor 10. The actuator also contains a three-phase induction rheostat 11, one of the terminals of which is connected to the phases of the rotor winding. The second thyristor 12 with the series-connected second resistor 13 shunts the contact 4 of the power contactor in another phase of the stator winding. The average leads of the induction rheostat 11 are connected respectively to the anodes of the second 14, third 15 and fourth 16 diodes, the cathodes of which are combined into a common point and connected to another plate of the capacitor 10, to a different phase of the stator winding and to a single output through the second contact b of the brake contactor. coils 17 of the relay, the other output of which is connected to the common connection point of the other outputs of the three-phase induction rheostat 11, and the cathode of the first thyristor 8. The closing contact 18 of the relay is connected by one output to the control unit ektrodom second thyristor 12, the anode of which through the third resistor 19 is connected to the other terminal of the make contact 18 relay.

The drive works as follows.

When starting the engine, contacts 2-4 close, the stator windings of the electric motor are connected to the power source. In the rotor winding, an emf is induced and a current limited by the resistance of the induction rheostat 11 flows through the rotor circuit. As the acceleration increases, the frequency of the emf induced in the rotor decreases, and the resistance of the induction rheostat decreases, the electric drive accelerates according to the characteristics close to the excavator.

With dynamic braking, disconnect contacts 2-4 and close contacts 5

and 6. The discharge current of the previously charged Capacitor 10 flows through the relay coil 17 and along the circuit: a positive capacitor plate 10, two stator windings

electric motor, resistor 9, closed contact 5, control electrode junction - thyristor cathode 8, negative capacitor plate 10, providing the initial control current of the thyristor 8. The relay closes its contact 18, the thyristor 12, driven by the network, opens according to the principle of amplitude-phase control, providing a constant feed current in the stator windings rectified according to a half-wave circuit. The thyristor 8 is opened by the voltage received from the cathodes of the diodes 14-16, and a self-excitation current flows through the stator windings. Thus, a feed current and a self-excitation current flow simultaneously across the stator windings. This provides intensive and economical engine braking. The capacitor 10 provides a more reliable opening of the thyristor 8 and the operation of the coil 17 of the relay at the first moment of the start of deceleration.

Decreasing speed decreases

EMF induced in the rotor of the electric motor. When the voltage becomes insufficient for supplying / powering the coil 17 of the relay, it opens its contact 18, the thyristor 12 closes, and the feed current stops flowing into the stator windings. The voltage in the rotor is further reduced, the thyristor 8 is closed, the electric motor is stopped.

Thus, the electric drive allows the mechanical characteristics of an excavator-type drive, stable dynamic braking with combined excitation from self-excitation current and charging current with an economical thyristor operating mode, automatic termination of the dynamic braking mode.

40

Claims (1)

Invention Formula An AC motor drive containing a three-phase asynchronous motor, the phases of the stator winding of which, through the contacts of a power contactor, are intended to be connected to a power source, a braking contactor with two closing contacts, three resistors, one diode, the first of which is connected parallel to the contact of the power contactor in one of the phases the stator winding and the anode is connected to the anode of the first thyristor, with one phase of the stator winding and with one output of the first resistor, the other output of which is through the first The closing contact of the brake contactor is connected to the control electrode of the first thyristor, the cathode of which is connected to one capacitor plate, a three-phase induction rheostat, some of the terminals of which are connected to the rotor winding phases, the second thyristor is connected in series with the second resistor and shunts the contact of the power contactor in another phase of the stator winding, different that, in order to increase reliability, a relay with a coil and with a closing contact is inserted into it, a three-phase induction rheostat is made with average leads, each of which is connected to with the anodes of the second, third and fourth diodes, the cathodes of which are combined into a common point and yen with a different capacitor plate, with a different stator winding phase and through a second contact contact of the brake contactor — with one output of a relay coil, the other output of which is connected to the common connection point of the other outputs of the three-phase induction rheostat, and the cathode of the first thyristor; with the control electrode of the second thyristor, the anode of which through the third resistor is connected to another output of the closing relay contact.