SU1387096A1 - Device for protecting 3-phase electric motor against abonrmal condition - Google Patents

Abstract

The invention relates to electrical engineering. The purpose of the invention is to increase reliability. As the winding temperature of the electric motor 6 increases above the allowable values, the resistance of thermistors 3 increases sharply, the control unit 1 operates and shuts off the electric motor 6. When the phase in the supply network is disconnected, the voltage at the output of the asymmeter 7 and diode bridge 8 increases, the transistor 12 closes, shunt the thermistor 3 circuit , and the control unit 1 srabaS (L so oo o so 05

Description

Tbmaef. When the temperature of the elements of the node 5 increases above the allowable values, due to the heating from the electric motor, the resistance of the thermistor 4 sharply increases, and the control unit 1 triggers. 1 Il.

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The invention relates to electrical engineering and can be used to protect three-phase, electric motors from abnormal conditions.

The purpose of the invention is to increase the reliability of the device.

The drawing shows an electrical diagram of a device for a three-phase electric motor.

The device contains a control unit 1 with a switch with clips 2 for connecting a winding thermistor 3 circuit, a thermistor 4, is located in node 5, reacting to an open phase and installed directly on the electric motor 6.

Node 5 contains a resistor asymmetric 7, a diode bridge 8, a trimming resistor 9, a capacitor U, a resistor & p 11, and a transistor 12.

The device has two stable states: normal and state of operation. As the winding temperature of the electric motor 6 increases above the permissible values, the resistance of the thermistors 3 increases sharply, the control unit 1 triggers and breaks the circuit of the magnetic starter coil, disconnecting the electric motor from the mains. The control unit 1 is also triggered when a short circuit occurs in the thermistor resistors.

The node works as follows.

With a symmetrical power supply, the voltage between the zero point of the asymmeter 7 and the neutral wire of the network is minimal and the transistor 12 is closed. When a phase is broken in the supply network, the voltage at the output of the asymmeter 7 and the diode bridge 8 increases, the transistor 12 opens, shunt the circuit of thermistors 3 and 4, i.e. an artificial closure occurs in the thermistor circuit, which leads to the activation of control unit 1. The magnitude of the voltage at the base of the transistor is regulated by a resistor 9. For a more precise adjustment of the circuit, when the supply voltage changes in series with resistor 9, it is desirable to turn on the zener diode. The diode bridge 8 serves to isolate the asymmetric 7 input signal and power the control unit 1. As the temperature of the elements of the node 5 increases above the allowable values, the resistance of the thermistor 4 sharply increases due to heating from the electric motor, causing control unit 1 to trip. The device also protects the motor from operation with unacceptable asymmetry.

power network.

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Claims (1)

Invention Formula A device for protection of a three-phase electric motor against an abnormal mode, comprising a block regulating for phase loss with leads for connecting to a power supply network, a switch control unit, the first and second wires of which are connected to the switch coil terminals with a terminal for connecting to the neutral wire of the network, and a circuit control switch one pin connected to the phase wire, and the other pin connected 35 with the third and fourth step of the switch control unit, characterized in that, in order to increase reliability, the unit reacting to the phase wrench contains a resistor 40 asymmetry with leads for connecting to the supply mains phases, zero point asymmetry is connected to the first input of the rectifying bridge, the second input output of which 45 is provided with a terminal for connecting to the neutral wire of the network, the output 313870964 the outputs of the rectifier bridge with the resistor, the emitter and the collector are connected to the first resistor for connecting the first resistor to the unit water thermistors in the winding of the electronic control switch, collector The motor through the trimmer re-transistor is connected to the thermistor and connected to the base plate, the other output of which connects the emitter of the transistor, between which the resistors are also connected to the second head of the mentioned terms.