SU1601687A1 - Device for protecting three-phase motor from phase-fault operation - Google Patents

Abstract

The invention relates to electrical engineering and is intended for use in relay protection and automation systems. The purpose of the invention is to increase electrical safety and enhance functionality by providing a comprehensive check of the operability of the ground circuits and power supply each time the electric motor is turned on. When the start button is pressed from the output of the rectifier 2, the voltage is applied to the anode and the control electrode of the lockable thyristor 6. The latter opens, the actuator 12 actuates and contacts 13 connects the electric motor 1 and rectifier 3 to the mains. When releasing the "Start" button, the thyristor 6 is powered from the rectifier 3 and remains in the open state, the contacts 13 are open. When the power supply phase is broken, the thyristor 6 is closed, the actuator 12 returns to its initial state, opens the contacts 13 and disconnects the electric motor 1 from the power supply. When the electric motor 1 is connected to the mains, when the electric motor is operating properly, an additional actuator-relay 22 closes contact 23. When the motor 1 is overloaded, as well as when the motor ground circuit fails, the voltage on the capacitor 11 increases, threshold element 19 is activated, a thyristor 18 connecting the control electrode of the thyristor 6 with an output for connection to the zero point of the supply network. The thyristor 6 is turned off, the actuator 12 returns to its initial state, opening the contacts 13 and disconnecting the electric motor 1 from the mains. 1 il.

Description

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The first rectifier 2 has input terminals for connecting to the appropriate phase supply lines of the electric motor between the power contacts 13 of the actuator 12 and the network terminals. The second rectifier 3 has input terminals for connecting to the appropriate power lines of the phases of the electric motor G between the power contacts 13 of the actuator 12 and the terminals of the electric motor 1. The output of the first rectifier 2 is connected to the first output of the closing contact k of the Start button C, the second output of which is through the anode cathode diode 7. connected to the anode of the first thyristor 6 and through the first resistor 8 to the control electrode of the first thyristor 6, the anode of which is connected to the output of the second rectifier 3, and the cathode is connected to the first terminal of the tangent contact 5 of the Stop button.

The first thyristor 6 is made in the form of a lockable thyristor. The third rectifier 17 is connected to the terminals of the secondary windings of the transformers 14-16 current. The first output of the third resistor 10 connected to the first output of the capacitor II is connected to the positive output of the third rectifier 17 through the second resistor 9, and through the disconnecting anode through the control electrode of the second thyristor 18 through the threshold element 19.

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contact .0 of the Start button is connected to the control electrode of the first thyristor 6. The second output of the opening contact 5 of the Stop button is connected to the second control output of the actuator 12, the first control output of which is connected to the cathode of the second thyristor 18, the second output of the capacitor 11 and to the negative the output of the third straightener 17.

The device has a fourth current transformer 21 intended to connect the corresponding phase of the electric motor 1 to the supply line, an additional actuator-relay 22 with a closing contact 23, a first additional input terminal 2k for connection to the housing of the electric motor 1 and a second additional input terminal 25 for connection to auxiliary earthing switch 2b.

The secondary winding of the fourth current transformer 21 is connected between the first 2k and second 25 additional input pins to the control input of the additional actuator 22, and the second output of the third resistor 10 is connected to the negative output of the third rectifier via the closing contact 23 of the third rectifier 17

The device works as follows.

When the Start button is pressed, the voltage from the output of the rectifier 2 is supplied to the thyristor 6 anode through diode 7. and through the resistor 8 to the control electrode of the thyristor 6. The latter opens, connecting the winding of the actuator 12 to the power buses Executive body 12 it triggers and its contacts 13 closes the power supply circuits of the electric motor 1. Simultaneously with the start of the electric motor 1, power is supplied to rectifier 3.

When contact k of the Start button is opened, the thyristor 6 remains in the open state, current flows through the winding of the actuator 12, and the contacts 13 are closed.

Diode 7 prevents positive voltage from being output from rectifier 3 to control electrode of thyristor 6.

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If one of the phases of the supply voltage is broken, for example, phase A, the rectified voltage decreases to zero and the time interval is 60 hl. Thyristor 6 is closed. The actuator 12 opens the contacts 13 and the motor 1 is disconnected from the network. When the time interval expires, 60 e. hail, in case of a delay in opening the contacts 13, the voltage of phases B and C is applied to the anode of the thyristor 6, but the latter remains in the closed state, since there is no

5 current in its control electrode circuit.

When the electric motor 1 is connected to the AC mains, if the electric motor is functioning properly, it triggers an additional executive element-relay 22 and closes contact 23.

In the nominal mode of operation of the electric motor 1 in the primary windings

5 current transformers I t - 16 nominal currents flow, voltages are induced in the secondary windings, ensuring the charge of the capacitor 11 to a voltage not exceeding the threshold

0 triggered threshold element 19. When overloaded in the circuit of motor 1, the currents in the primary windings of transformers 1 to 16 current increase, the voltages in their secondary windings applied by rectifier 17 and resistor 9 to threshold element 19 proportionally increase. The latter works that. leads to the inclusion of a thyristor 18 and

... turning off the thyristor 6. The executive unit returns to its initial state, opening the contacts 13 and disconnecting the electric motor 1 from the mains.

c When the ground of the electric motor 1 is broken, the relay 22 is turned off, the contact 23 is opened. This causes an increase in the voltage on the capacitor 11. The threshold element 19 is triggered,

Q turns on the thyristor 18 and turns off the thyristor 6. The actuator 12 returns to its initial state, opens the contacts 13 and disconnects the electric motor 1 from the mains.

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Invention Formula

Device to protect a three-phase electric motor from a single phase

operation mode containing three-phase half-wave rectifiers, a start button with a closing contact, a stop button with a break contact, a first thyristor, a diode, at least three resistors and one condensate, an actuator with a first control output for connection to the network zero point and power contacts with leads to connect each power contact to the power line of the corresponding phase of the electric motor, three current transformers, each intended to be connected to the power line of the corresponding phase a motor, a three-phase full-wave third rectifier-v tele, a second thyristor, a threshold element and a disconnecting contact of the Start button, the first rectifier having input terminals for connection to the appropriate phase power lines of the electric motor between the power contacts of the executive body and the network terminals, the second the rectifier has input terminals for connection to the corresponding power lines of the phases of the electric motor between the power contacts of the executive body and the outputs of the electric motor, the output of the first rectifier connected to the first output of the closing contact of the Start button, the second output of which through the anode-cathode of the diode is connected to the anode of the first thyristor, and through the first resistor to the control electrode of the first thyristor, the anode of which is connected to the output of the second rectifier, and the cathode to the first output the break contact of the Stop button, the first thyristor is designed as a lockable thyristor, the third one is rectified connected to the terminals of the secondary windings of current transformers, and

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The first output of the third resistor connected to the first capacitor output is connected to the third output rectifier through a second resistor, and a second thyristor control electrode through the threshold element, the anode of which is connected to the first thyristor control electrode through the break contact of the first thyristor; contact button Stop is connected to the second control output of the executive body, the first control output of which is connected to the cathode of the second thyristor, the second output of the capacitor with a negative output of the third rectifier, that is, in order to increase electrical safety and enhance functionality by providing a comprehensive check of the operability of the ground circuits and power supply at each switching on of the electric motor, a fourth current transformer is introduced into the device to the supply line of the corresponding phase of the electrode, an additional actuator with a closing contact, first, an additional input terminal for connection to the building the motor has a second additional input terminal for connection to the auxiliary earthing, with the secondary winding of the fourth current transformer connected between the first and second additional input terminals in series with the control input of the additional actuator-relay, and the second output of the third resistor through the closing contact of the additional actuator The relay is connected to the negative output of the third rectifier.

Claims (1)

Claim A device for protecting a three-phase electric motor from an out-of-phase operating mode, comprising three-phase half-wave rectifiers, a Start button with a make contact, a Stop button with a make contact, a first thyristor, a diode, at least three resistors and one capacitor, an actuator with a first control an output for connecting 'to the network zero point and power contacts with leads for connecting each power contact to the power line of the corresponding phase of the electric motor, three current transformers, designed Achen for each switching power supply line 15 in the respective motor phases, the third three-phase full-wave rectifier * Tel, the second thyristor, the threshold element and break contact knop- ₂ θ ki Start, wherein the first rectifier having input terminals for connection to respective phases of the motor supply lines between power contacts of the executive body and 25 conclusions of the network, the second rectifier has input terminals for connecting to the corresponding power lines of the phases of the electric motor between the power contacts of the additional organ and the motor leads, the output of the first rectifier is connected to the first terminal of the start contact of the Start button, the second terminal of which is connected through the anode-cathode of the diode to the anode of the first thyristor, and through the first resistor to the control electrode of the first thyristor, whose anode is connected to the output of the second rectifier and the cathode - with the first output of the opening contact of the Stop button, the first thyristor is made in the form of a lockable thyristor, the third rectifier is connected to the terminals of the secondary windings of current transformers, and the first output of the third resistor connected to the first output of the capacitor is connected to the positive output of the third rectifier through the second resistor, and through the threshold element it is connected to the control electrode of the second thyristor, the anode of which is connected to the control electrode of the first thyristor via the start contact of the first thyristor, and the second output of the stop button is open connected to the second control terminal of the actuator, the first control terminal of which is connected to the cathode of the second thyristor, the second terminal of the capacitor and with the negative output of the third rectifier, which means that, in order to increase electrical safety and expand functionality by providing a comprehensive check of the health of the ground and power circuits each time the electric motor is turned on, a fourth current transformer is introduced into the device, designed to be connected to the power line phases of the electric motor, an additional executive organorelay with a closing contact, the first, additional input terminal for connection to the electric housing a motor and a second additional input terminal for connection to an auxiliary earthing switch, wherein the secondary winding of the fourth current transformer is connected between the first and second additional input terminals in series to the control input of the additional actuator-relay, and the second output of the third resistor is connected via the make contact of the additional actuator-relay to negative output of the third rectifier.