SU1317542A2 - Device for protection of three-phase electric motor - Google Patents

Abstract

This invention relates to electrical engineering, in particular, to relay protection. The purpose of the invention is to increase the speed of protection in the mode of braked rotor. This is due to the fact that if during the operation of an electric motor, a braked rotor mode arises, the voltages on the secondary windings of transformers 1 increase, the thyristor 9 is triggered, the zener diode 19 is punched and with a slight delay the voltage across the delay element 18 and contact 17 is applied to the control electrode of the thyristor 6, which, when opened, leads to the actuation of the actuator 4. 1 sludge. SL with SP 1H

Description

one . The invention relates to electrical engineering and is intended for use in agricultural objects.

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The purpose of the invention is to increase the speed of protection in the mode of inhibited rotor.

The drawing shows a schematic diagram of the device.

The device contains current transformers 1 connected to the difference of the phase currents of the protected motor 2, an annular balanced detector 3 connected to the secondary windings of transformers 1, an actuator 4 connected between the middle points of the secondary windings of transformers 1. Parallel to the resistor 5 of one of the detector 3 arms the first is turned on thyristor 6. The first resistor 7 is connected to the cathode of the divider 8. Controlling the rectifier on the second thyristor 9 is connected to the secondary winding of one of the transformers 1, the output of the rectifier It is connected to the RC-circuit of a second resistor 10, third resistor 11 and the control circuit 12. kondensatora- rectifier formed divider 13 voltage. The device has a two-input diode element OR 14, a time relay 15 with a response time setting element 16 and a closing contact 17 in the output circuit, a time delay unit 18, a zener diode 19, a quarter resistor 20.

The control electrode of the first thyristor 6 is connected to a chain of the first resistor 7 and dynistor 8 connected in series through the serially connected closing contact 17 of the time relay 15 and the output of the first input of the OR 14 element. The input of the time delay unit 18 is connected to the cathode through the anode-cathode the second thyristor 9, and the output of the -block 18 is connected to the second input of the element OR 14. The fourth resistor 20 is connected between the control electrode and the cathode of the first thyristor 6, and the control input of the relay

15 time connected to the terminals of the secondary winding of one of the transformers 1 current. Using the element

The 16 relay 15 is tuned to the amount of time it takes for the transceiver to exceed the duration of the transition process when the motor is started.

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The device works in the following way.

When the power of the electric motor 2 is turned on, the starting currents of the electric motor flow at the start-up stage in the primary windings of the transformers 1. Under the action of inrush currents in the secondary windings of transformers 1, increased voltages are excited, in connection with which the thyristor 9 is triggered and the capacitor 12 is quickly charged, Zener diode 19 is punctured simultaneously, and the voltage through delay element 18 pos5

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five

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stubs to the second input of the element OR 14. In addition, the voltage from the secondary winding of the transformer 1 is fed to the control input of the relay 15-time, which is triggered after the end of the starting process, when the motor current decreases to the operating value. By the time the relay 15 closes and closes the contact 17, the voltage on the secondary windings of transformers 1 decreases to operating values, the thyristor 9 closes, the capacitor 12 discharges, the time delay unit 18 returns to its initial state of readiness to receive the next input signal from the thyristor cathode 9. Thus, during normal start-up of the electric motor, actuator 4 does not work.

35 If during operation of the electric motor a braked rotor mode occurs, for example, due to jamming of the working body of the agricultural machine, the voltage on the secondary windings of transformers 1 reappears, the thyristor 9 is triggered, the zener diode 19 penetrates and with a slight delay the voltage through block 18 and end 45 cycle 17 is applied to Yu. to the thyristor electrode 6. The latter opens, which leads to the unbalancing of the ring detector 3 and the operation of the actuator 50 by 4. The electric motor 2 is disconnected from the network. :

If an overload occurs during the steady state operation of the electric motor through the thyristor 9 is55

There is a floating charge of capacitor 12, while the zener diode 19 does not work. When the capacitor 12 reaches the voltage

The dynistor 8 positive voltage enters through the OR element and the contact 17 to the control electrode of the thyristor 6. The latter, turning on, wakes up the operation of the executive unit 4 and turns off the electric motor.

When a two-phase operation mode occurs, the voltage at the output of the phase detector 3 sharply increases and the actuator 4 triggers without delay by disconnecting the electric motor 2 from the network.

The positive effect of the invention is that the protection speed increases when the braked rotor mode occurs after a period of prolonged operation of the electric motor. As a result, the insulation overheat is prevented and the reliability and service life of the electric motor increases.

Claims (1)

Invention Formula The device for protection of the three-phase electric motor on an auth.St. 771794, Editor S. Lisin Compiled by O. Orlov Tehred M. Khodanych Proofreader I. Musk Order 2429/49 Circulation 618 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow Zh-35, Raushsk nab., 4/5, Production and printing company, Uzhgorod, Projecto st., 4 characterized in that, in order to increase the speed of protection in the braked mode of the rotor, a two-input diode element OR, a time relay with an element for setting the response time and a closing contact in the output circuit, a time delay unit, a zener diode and a fourth resistor are introduced, while controlling the first thyristor is connected to a chain of a series-connected first resistor and a dynistor through a series-connected make contact time relay | p and output — the first input of the SHSh element, the input block the time delay through the anode-cathode of the Zener diode is connected to the cathode of the second thyristor, and the output of the time delay unit to the second input of the OR element, the fourth resistor is connected to the control electrode and the cathode of the first thyristor, and the control input of the time relay is connected | To the secondary windings of one of the current transformers.