SU1427475A1 - Arrangement for starting and operating a three-phase induction motor in incomplete-phase duty of three-phase supply mains - Google Patents

Abstract

The invention relates to electrical engineering and is intended to ensure the start-up and operation of a three-phase asynchronous electric motor in the case of an incomplete phase supply network. The purpose of the invention is to increase the reliability of power supply by increasing the permissible operating time of the consumer in an incomplete phase mode. When the voltage disappears in one of the phases after applying voltage to the electric. rotor motor contacts 6 relays 3 minimum voltages are opened, and contacts 10 are closed. The damaged phase is connected through the closed contact 15 of the time relay 14 to the neutral wire of the network, as a result of which the engine is started. At the same time, a bias voltage appears between -. the solid zero point 13 and the neutral wire of the network, the bare 14 point receives power. Then, after starting the contact, contact 15 of the time relay 14 disconnects the disconnected phase from the neutral wire of the network, as a result of which the zero sequence current does not flow through the electric motor and an additional heating of the electric motor windings does not occur. 1 il. WITH S

Description

The invention relates to techniques for relay protection and emergency automation in electrical installations, and in particular to devices for starting and operating a three-phase asynchronous electric motor in an out-of-phase mode of a power supply network.

The purpose of the invention is to increase the reliability of power supply by increasing the permissible operating time of the consumer in an out-of-phase mode.

The drawing shows a control circuit for the start-up and operation of a three-phase asynchronous electric motor When the power mode of a three-phase electric network is not fully fan-operated.

The first 2, second 3 and third 4 undervoltage relays are connected to the supply network 1. The closing contacts 5, 6 and 7 of the undervoltage relay 2, 3 and 4 are respectively connected to the supply circuit of the three-phase asynchronous electric motor 8. Between each phase of the mains 1 and the terminal for connecting the neutral wire after contacts 5, 6 and 7 of relay 2, 3 and 4 of the minimum voltage, respectively, are disconnected contacts 9, 10 and 11 of the indicated relays, a standard circuit 12 for starting an electric motor, an artificial zero point 13, a time relay 14. NC 15 of the time relay 14 is connected between the connection point of NC 9, 10 and 11 of the relays 2, 3 and 4 of the minimum voltage.

Artificial zero point 13 can be made in the form of three capacitors or resistors.

The device operates as follows.

Under normal operating conditions of the supplying three-phase electric network, the voltages of phases A, B, C are equal in amplitude and are unfolded in phase by 120. A standard control circuit applies voltage to the trigger circuit 12. The undervoltage relays 2, 3 and 4 are activated, close their contacts 5,6,7 and open the contacts 9, 10 and 11. The three-phase asynchronous motor 8 starts up and works in normal mode.

When the voltage disappears, for example, in phase B in the supply network 1, after switching on the standard start-up circuit 12, the contacts 6 of the minimum voltage relay 3 open. The contacts 10 of the relay 3 of the minimum · voltage are closed, and the phase B of the electric motor is connected via the closed contact 15 of the time relay 14 to the zero wire of the electric network 1, as a result of which the motor starts.

Simultaneously, when an out-of-phase mode occurs, a bias voltage appears between the artificial zero point 13 and the neutral wire of the supply network 1, as a result of which the time relay 14 is supplied with power. After starting the electric motor 8, contact 15 of the time relay 14 disconnects phase B from the neutral wire of the network, as a result of this, the zero sequence current does not flow through the electric motor 8 and there is no additional heating of the motor windings.

Thus, the proposed device, in comparison with the prototype, can reduce the magnitude of the currents flowing through the windings after starting the electric motor, and thereby increase the duration of the three-phase asynchronous electric motor and increase the maximum torque during the non-phase operation of the power supply network.

Claims (1)

Claim A device for starting and operating a three-phase asynchronous electric motor when the supply phase of a three-phase network is out of phase, comprising a fault phase detection unit, made in the form of three undervoltage relays with make contacts for connecting the induction motor power and disconnect contacts for connecting to the corresponding phase conductors of the network from the motor side, connected to a star, while the conclusions of the coils of the undervoltage relay are connected to the terminals for connecting between zero and vuyuschimi phase conductors at the power supply with respect to its switching contacts, olichayuscheesya in that, in order to increase reliability of power supply by increasing the allowable time of the user in the unbalance additionally introduced time relay coil is connected between the newly introduced ³ 1427475 ⁴ artificial neutral point and a terminal for connecting to the neutral wire of the network, and the NC contact of the time relay is connected in series between the common point of the indicated star of the NC contacts of the relay e minimum voltage and a terminal for connecting to the neutral wire of the network.