SU1686677A1 - Device for braking three-phase induction motor - Google Patents

Abstract

The invention relates to electrical engineering and can be used in electric drives of general industrial mechanisms. The purpose of the invention is to increase reliability. The device contains closing contacts 2, 3 and a three-phase transformer 5, an overcurrent relay with a coil 6 and closing contacts 7-9, diodes 10-12. When the power contact is turned on, its contacts 2-4 connect the electric motor 1 to the network. When translating the motor 1 into the brake mode, contacts 2-4 open. In this case, three circuits of electromagnetic braking are formed: the first winding of the secondary circuit of the transformer 5, the diode 10; the first phase of the motor winding 4 coil 6 and the zero point of the secondary winding of the transformer 5; the second winding of the secondary circuit of the transformer 5, diode 11; second phase motor winding 1 coil 6 and zero point of the secondary winding of the transformer 5; winding of the secondary circuit of the transformer 5, diode 12; the third phase motor winding 1 coil 6 and the zero point of the secondary winding of the transformer 5. Three-wave rectified current flows in three circuits, producing electromagnetic braking of the rotor of the electric motor. 1 il. Yo

Description

The invention relates to electrical engineering and can be used in electric drives of general industrial mechanisms.

The aim of the invention is to increase reliability.

The drawing shows a schematic diagram of a device for braking a three-phase asynchronous motor.

A device for braking a three-phase asynchronous motor, the stator 10th winding of which is connected to a star, contains a linear contactor with three make contacts 2 - 4, some of which are designed to connect to the phase outputs of the stator 15 of the electric motor, other outputs of the make contact of the linear contactors are designed to connect to the phases of the power source, a three-phase transformer 5, a maximum current relay 20 with a coil 6 and three make contacts 7-9, one of the terminals of which are connected to Accordingly, to the other outputs of the closing contacts 2-4 of the contactor, the other conclusions of the making contacts of the relay 25 of the maximum current are connected respectively to one terminal of the primary winding of the transformer 5, the other terminals of which are combined, one terminal of the coil 6 of the relay of the maximum current is designed to connect the star to 30 stator winding 1, the other terminal of the relay coil 6 is connected to a common point of connection of one terminal of the secondary winding of the transformer 5, the other terminals of which are connected to the anodes of the corresponding three diodes 1012, the cathode which are connected to one terminal of the switching contacts of the contactor 2-4.

The device operates as follows.

When the power contactor is turned on, its make contacts 2-4 connect the electric motor to the network. An alternating current flows in the phases of the stator windings 1 of the electric motor. An EMF is induced in the rotor, causing the rotor current and stator magnetic flux to appear, and creates a torque under which the rotor of the electric motor rotates.

To transfer the electric motor from the operating mode to the brake one, open the contacts 2-4 of the linear contactor. In this case, three electromagnetic braking circuits are formed: the first 55 winding of the secondary circuit of transformer 5, diode 10, the first phase of winding 1 of the electric motor, coil 6 of the overcurrent relay and the zero point of the secondary winding of transformer 5: second winding of the secondary target of transformer 5, diode 11 , the second phase of the motor winding 1, the coil 6 of the overcurrent relay and the zero point of the secondary winding of the transformer 5; the third coil 5 of the secondary circuit of transformer 5, diode 12, the third phase of the motor winding 1, coil 6 of the overcurrent relay and the zero point of the secondary winding of transformer 5,

The coil 6 of the overcurrent relay for three circuits is common. A half-wave rectified current flows along three circuits due to the action of EMF of electromagnetic induction, producing electromagnetic braking of the rotor of the electric motor. A total current of 1 _E m = Pem + 12em +! Zem flows through coil 6 of the overcurrent relay, which ensures the accuracy of the overcurrent relay.

When the contacts 7-9 are closed, the overcurrent relay in the secondary circuit of the three-phase transformer 5 passes through the three-phase windings of the electric motor, a half-wave rectified current starts flowing, producing dynamic braking of the electric motor rotor. The braking time of the electric motor is regulated by the value of the armature return coefficient of the overcurrent relay.

The presence of a maximum current relay in the device, its connection between the zero point of the secondary winding of the transformer and the zero point of the stator winding of the electric motor made it possible to ensure the rectified currents of electromagnetic and dynamic braking across all three stator windings of the electric motor.

Claims (1)

Claim A device for braking a three-phase asynchronous electric motor, the stator winding of which is connected to a star containing a linear contactor with three make contacts, some of which are designed to connect to the phase outputs of the stator winding of the electric motor, other outputs of the make contacts of the linear contactor are designed to connect to the phases of the power supply, three diode, characterized in that, in order to increase reliability, a three-phase transformer and a maximum current relay with a coil and with make contacts, some of the outputs of which are connected respectively to other outputs of the make contacts of a linear contactor, other conclusions of make contacts of the overcurrent relay are connected respectively to one output of the primary winding of a three-phase transformer, the other outputs of which are combined into a common point, one output of the coil of the overcurrent relay is intended for connecting the stator winding stars to zero, the other terminal of the overcurrent relay coil is connected to the common connection point of one of the secondary terminals th phase transformer winding, the other terminals of which are connected to anodes of respective diodes, the cathodes 5 are connected to one terminal of the switching contacts of a line contactor. Compiled by E. Peremyslov Editor V. Bugrenkova Tehred M. Morgenthal Corrector O. Kravtsova Order 3610 Circulation Subscription VNIIIPI of the State Committee for Inventions and Discoveries under the State Committee for Science and Technology of the USSR 113035, Moscow, Zh-35, Raushskaya nab., 4/5 Production and Publishing Combine Patent, Uzhgorod, 101 Gagarin St.