SU1156228A1 - Device for braking three-phase induction motor - Google Patents

Abstract

DEVICE FOR BRAKING THREE-PHASE ASYNCHRONOUS MOTOR, containing a contactor with three closing and contacts, ramyakyayuschim and eamikayuosim block contacts, a thyristor, three diodes, a circuitry, two resistors, a capacitor, a relay with winding and a closing contact, one circuitry terminal, one circuitry switch, two resistors, a capacitor, a relay with winding and a closing contact, one circuitry terminal, one circuitry switch, one resistor, two resistors, a capacitor, a relay with a winding and a closing contact, one circuitry circuit, one circuitry, one diode circuit, one circuit breaker, one resistor supply network, other terminals of the contactors of the contactor contacts are connected to the beginnings of the phase windings of the asynchronous electric motor, the ends of which are interconnected, one terminal of the closing co The relay cycle is connected to one terminal of the second closing contact of the coitttor, the thyristor cathode is connected to the first diode's iodine, the thyristor anode is connected to the single terminal of the first resistor, so that, in order to improve reliability and increase braking intensity, a fourth one is entered, five and sixth diodes, a resistor, a capacitor, with the cathode of the first diode connected to the cathode of the second diode and to another terminal of the second closing contact of the contactor, the anode of the second diode connected to another terminal of the closing terminal act of the relay, the other output of the first resistor is connected to one terminal of the opening contact of the contactor, the other terminal of which is connected to the control electrode of the thyristor through the third diode connected in series and the second resistor, the third diode cathode and the second resistor are connected to the first capacitor the cathode of the thyristor and the anode of the fourth diode, the cathode of which is grounded, the cathodes of the fifth and sixth diodes are connected to the anode of the thyristor, the anodes of the fifth and sixth diodes: d are connected to other terminals with From 7 sD D EO of the first and third contactor contacts, one terminal of the closing contact of the contactor is provided with a terminal for connection to a DC source, the other terminal of the closing contact of the contactor is connected via a third resistor to the connection point of one relay coil and the second capacitors, the other terminals of which are combined and intended to connect to a DC source.

Description

The invention relates to electrical engineering and can be used in automated AC electric drives.

A device for braking a three-lag induction motor, comprising a starting contactor with auxiliary contacts and a brake contactor, is known. In the deceleration mode of the asynchronous electric motor, the blocking contacts of the starting contactor short the two phase windings of the electric motor, and the direct current is supplied to the third winding by means of the Ij contactor.

The main disadvantage of the known device is the presence of a special DC source of low voltage.

Closest to the invention is a device for braking a three-phase asynchronous motor containing a contactor with three closing contacts, opening and closing block contacts, a thyristor, three diodes, two resistors, a capacitor, a relay with a winding and a closing contact, one terminal of the closing contacts of the contactor are supplied with leads for connecting the supply mains phases; other terminals of the closing contacts of the contactor are connected to the beginnings of the phase windings of the induction motor, the ends of which are connected between one terminal of the closing contact of the relay is connected to one terminal of the second closing contact of the contactor, the cathode of the thyristor is connected to the anode of the first diode, the anode of the thyristor is connected to one terminal of the first resistor. In the device, braking is performed by the rectified power supply current, thereby eliminating the need for an additional source of dynamic braking 2.

The disadvantages of this device are the limited scope of application. This is due to the use of the zero view of the motor windings and possible damage to the contactor when using relatively large electric motors, low reliability due to the increased heating of the motor windings due to the application of a linear voltage during deceleration and low braking intensity due to the use of only two phase windings of the electric motor

The purpose of the invention is to increase reliability and increase the intensity of braking.

To achieve this goal, the device for braking a three-phase asynchronous motor contains a contactor with three closing contacts, opening and closing block contacts, a thyristor, three diodes, two resistors, a capacitor, a relay with a winding and a closing contact, and one terminal of the closing contacts of the contactor are provided with terminals connection of the supply mains, other terminals of the closing contacts of the contactor are connected to the beginnings of the phase windings of the asynchronous electric motor, the ends of which are interconnected, The terminal of the closing contact is connected to one terminal of the second closing contact of the contactor, the cathode of the thyristor is connected to the anode of the first diode, the anode of the thyristor is connected to one terminal of the first resistor, the fourth, fifth and sixth diodes are inserted, a resistor, a capacitor, and the cathode of the first diode is connected to the cathode of the second diode and to D5: the 7th terminal of the second closing contact of the contactor, the anode of the second diode is connected to another clip of the closing contact of the relay, the other end of the first resistor is connected to one clip of the disconnecting block the contact of the contactor, the other terminal of which is connected through the third diode and the second resistor connected in series to the control electrode of the thyristor; the connection point of the cathode of the third diode and the second resistor is connected via the first capacitor to the cathode of the thyristor and to the anode of the fourth diode whose cathode is grounded; the fifth and sixth diode are connected to the thyristor anode, the anode of the fifth and sixth diodes are connected to other terminals of the first and third closing contacts of the contactor, one closing contact block This contactor is provided with a terminal for connection to a DC source, another terminal of the closing contactor contact through the third pe3

The resistor is connected to the connection point of one terminals of the relay coil and the second capacitor, the other terminals of which are combined and intended for connection to a DC source.

The drawing shows a circuit diagram of the device.

The device contains a contactor with three normally open contacts 1, 2 and 3, an opening blocking contact 4, a closing block contact 5, a thyristor 6, three diodes 7.8 and 9, two resistors 10 and 11, the first capacitor t2, a relay with a winding 13 and -closing contact 14, Some terminals of the closing contacts 1,2 and 3 of the contactor are provided with wires for connecting the phases of the supply network, other clips of the closing contacts 1,2 and 3 of the contactor are connected to the beginnings of the phase windings of the asynchronous electric motor 15, the ends of which are interconnected. One terminal of the closing contactor 14 of the relay is connected to one terminal of the second closing contact 2 of the contactor, the cathode of the thyristor 6 is connected to the anode of the first diode 7, the anode of the thyristor 6 is connected to one output of the first resistor 10, the fourth, five and sixth diodes 16, 17 and 18, the third resistor 19, the second capacitor 20, the cathode of the first diode 7 is connected to the cathode of the second diode 8 and to another lightning switch of the second closing contact 2 of the contactor. The anode of the second diode 8 is connected to another terminal of the closing contact 14 of the relay, the other terminal of the first resistor 10 is connected to one terminal of the contactor I block 4 of the contactor 4, the other terminal of which is connected through the third diode 9 in series and the second electrode 11 thyristor 6, the connection point of the cathode of the third diode 9 and the second resistor 11 through the first capacitor I2 is connected to the cathode of the thyristor 6 and to the anode of the fourth diode 16, whose hodod is grounded, the cathodes of the fifth and sixth diodes 17 and 18 are connected to ano Thyristor b, anodes of the fifth and sixth diodes 17 and 18 are connected to other terminals of the first and third making contacts 1 and 3 contacts 562828. four

torus, one terminal of the closing contact-contact 5 of the contactor is provided with a terminal for connecting a direct current source, another terminal of the closing contact of the contactor 5 of the contactor through the third resistor 19 is connected to the connection point of one winding terminals 13 of the relay and the second capacitor 20J the other ends of which combined and designed to be connected to a direct current source.

The device works in the following way.

The closing contact 14 of the relay prepares the braking circuit and turns on in advance, immediately after the closing contacts 1, 2 and 3 of the contactor are turned on, which start the motor 15, and is disconnected after 20 switching off of the latter with a time delay exceeding (for reliability) the drive stop time. The relay coil 13 is connected via the third resistor 19 by closing the contactor block 5 of the contactor 5 into the DC control circuit, the delay for disconnecting the relay is provided by the second capacitor 20. Other options for disconnecting and holding the relay are possible, for example, by a frequency control relay signal rotation of the motor 15,

During rotation of the motor 15, the thyristor 6 cannot open, because the opening blocking contact 4 of the contactor is open and the control electrode of the thyristor 6 is open. Immediately after disconnecting the contacts 1,2 and 3 of the contactor 6, the thyristor 6 does not open until through the closing contact 14 of the relay , diode 8, motor windings 15, diodes 17 and 18, resistor 10, diode 9 and diode 16 do not charge the capacitor 12, shunting the control transition of the thyristor 6 and thus providing a delay that protects against short circuit of the mains through the arc on closing the con clocks 1,2 and 3 of the contactor after closing the contact block 4, the delay time is determined by the capacitance of the capacitor 12 and the resistance of the resistor 10 ..

5 11 enters 1 time from the network

energy is stored in the capacitor 12 and the stagnation stability increases as the

five

The moment the thyristors are turned on (the start of engine braking) depends on transient switching processes, since the initial charging of capacitor 12, while the arc on the power contacts has not extinguished, does not occur from a single-phase single-wave rectifier circuit, but from a two-phase rectifier circuit.

After extinguishing the arc at contacts 1.2 and 3 and charging the capacitor 12, the thyristor 6 is switched on by the current coming from the engine 15 which starts working as a generator due to the energy stored in it before it is disconnected from the network, creating a braking moment until until the magnetic flux is attenuated. In this case, the current from the two phase windings of the engine 15 through the diodes 17 and 18 first flows through the input circuit of the thyristor 6, through the resistor 10, the auxiliary contact A, the diode 9, the resistor 11, the control of the transition of the thyristor 6, the diode 7 and the third phase of the engine 15 , and after switching on the thyristor 6 through a short-circuited circuit formed by the windings of the engine 15, diodes 17 and 18, the thyristor 6 and diode 7. Simultaneously, a way appears for the braking current from the network to the wire to give half-periods through contact 14 of the relay, diode 8, windings the motor 15, the diodes 17 and 18, the thyristor 6 and the bridge 16 to the ground (in zero gadfly feed network). In this case, after the termination of the magnetic deceleration (when the magnetic flux is attenuated), the effectiveness of the continuing dynamic deceleration contributes

562286

the fact that the energy stored previously in capacitor 12 and added to the conductive part of the period to the nonconducting half-life energy maintains

5 the thyristor 6 is open, it is discharged to its input circuit through the resistor 11, regardless of whether the current closing through the diode 7 is sufficient due to the motor self-induction EMF,

in order to keep the thyristor 6 open during the entire braking time. After the end of braking, contact 14 of the relay completely disconnects the motor from the network. Hot contact 14

5 relays operate under light conditions, since they disconnect the half-wave current; however, when choosing the type of relay, one should, however, take into account the power of the first motor.

W The proposed device is suitable not only for electric motors, the windings of which are connected by a star and {lead four output ends, but also for having only three output

45, the end, and also when the windings are connected in delta, since the device does not need a lead end from the neutral.

The invention reduces overheating

30, due to the supply of braking circuits by phased voltage across the diode, the cathode of which is grounded instead of LIIN, a decrease in voltage affects little, because the braking current even in this case exceeds the optimum value. j

Claims (1)

A THREE-PHASE ASYNCHRONOUS ELECTRIC MOTOR BRAKING DEVICE, comprising a contactor with three make contacts, an open and close block contact, a thyristor, three diodes, two resistors, a capacitor, a relay with a winding and a make contact, one terminal of the make contact for the contactor is equipped with an output terminal , other terminals of the contactor contacts of the contactor are connected to the beginnings of the phase windings of the induction motor, the ends of which are interconnected, one terminal contact of the contactor e is connected to one terminal of the second make-contact contact, the cathode of the thyristor • connected to the anode of the first diode, the anode of the thyristor is connected to one terminal of the first resistor, characterized in that, in order to increase reliability and increase the braking intensity, the fourth , fifth and sixth diodes, a resistor, a capacitor, the cathode of the first diode connected to the cathode of the second diode and to another terminal of the second make contact of the contactor, the anode of the second diode connected to another terminal of the make contact of the relay, The output terminal of the first resistor is connected to one terminal of the opening contact block of the contactor, the other terminal of which is connected in series through the third diode and the second resistor to the thyristor control electrode, the connection point of the cathode of the third diode and the second resistor is connected through the first capacitor to the thyristor cathode and to the fourth anode the diode whose cathode is grounded, the cathodes of the fifth and sixth diodes are connected to the thyristor anode, the anodes of the fifth and sixth diodes are connected to other terminals of the first and third respectively rd _g for abutting the contactor contacts, one clamp closing the auxiliary contact of the contactor is provided with a terminal for connection to a DC source, the other clamp closing the auxiliary contact of the contactor via a third resistor connected to the connection point of one of the relay coil terminals and second-> capacitor, the other terminals of which are combined and designed to be connected to a direct current source.