RU2239929C2 - Device for controlling three-phase motor incorporating phase-failure protective gear - Google Patents

Abstract

FIELD: electrical engineering; three-phase motor control.

SUBSTANCE: device designed to disconnect three-phase motor from supply mains upon occurrence of phase failure has three-phase optoelectronic relay and three-phase motor that functions as load; in addition it is provided with unit designed to protect motor in case of phase failure in three-phase supply mains or failure of three-phase optoelectronic relay. Protective unit has three leads for monitoring voltage across motor phases and two leads for connecting three-phase optoelectronic relay in series with control circuit. In order to reclose device for normal operation upon elimination of phase failure three-phase optoelectronic relay should be deenergized for short time and then reclosed.

EFFECT: enlarged functional capabilities and operating reliability.

1 cl, 1 dwg

Description

The invention relates to electrical engineering and can be used to control a three-phase electric motor.

A device is known that contains a three-phase optoelectronic relay used to control a three-phase load (J. "Radio" No. 9, 1999, p. 48, Fig. 18).

The disadvantage of this device is the lack of protection of a three-phase load, for example, a three-phase electric motor from phase failure.

The purpose of the invention is the expansion of functionality and improving the reliability of the device by providing a protective shutdown of a three-phase electric motor when the phase of the three-phase supply network breaks.

The drawing shows a circuit diagram of the device.

A device (see drawing) containing an optoelectronic three-phase relay (indicated by “Relay” in the drawing) with input terminals A1, B1, C1 connected to a three-phase supply network with phases Ac, Bc, Cc, output terminals A2, B2, C2 connected to the phases An, Vn, Sn of a three-phase electric motor (marked “M” in the drawing), input plus and minus control terminals, and a DC voltage source is connected to the input positive control terminal through a limiting resistor (indicated in the drawing “Rog”) (in the drawing marked “Vin” ), is additionally equipped with a protection unit with first 1 and second 2 optocouplers, first 3 and second 4 zener diodes, first 5 and second 6 limiting resistors, first 7 and second 8 rectifier diodes, first 9 and second 10 storage capacitors, 11 starting capacitor, shunted the third 12 resistors, the outputs: the first 13 - to connect the input negative control terminal of the optoelectronic three-phase relay, the second 14 negative (common), the third 15, fourth 16, fifth 17 outputs for connecting to the corresponding phases An, Vn, Sn tre phase motor to control the presence of phases, and the input negative control terminal of a three-phase optoelectronic relay connected to the first 13 output of the protection node and through series-connected plus and minus output terminals of the first 1 and second 2 optocouplers, shunted by the starting 11 capacitor and the third 12 resistor, connected to the second 14 output node protection. The positive control terminal of the first 1 optocoupler through the anode-cathode junction of the first 3 zener diodes, the first 5 limiting resistor, the cathode-anode junction of the first 7 diodes and through the third 15 output of the protection node is connected to the An phase of the three-phase electric motor.

The control negative terminal of the first 1 optocoupler and the positive control terminal of the second 2 optocouplers are connected to the phase BH of the three-phase electric motor through the fourth 16 terminal of the protection unit. The negative control terminal of the second 2 optocouplers through the cathode-anode transition of the second 4 zener diodes, the second 6 resistor, the anode-cathode transition of the second 8 diodes and the fifth 17 output of the protection node are connected to the phase Cn of the three-phase electric motor, and the first 9 and second 10 storage capacitors are connected by one terminal with the fourth 16 terminal of the protection node, the other terminals with the cathode of the first 7 and the anode of the second 8 diodes, respectively.

The device (see drawing) operates as follows.

In normal mode, on the input terminals A1, B1, C1 of the optoelectronic three-phase relay, a three-phase symmetrical supply voltage system with phases Ac, Bc, Cc is active. To start the three-phase electric motor in operation, it is necessary to supply + Vin, voltage from the direct current source (for example, using a key element, not shown in the drawing) to the positive input of the optoelectronic three-phase cut through the resistor Rogr. In this case, due to the charging current of the capacitor 11, the control current of the optoelectronic three-phase relay is provided, which, when unlocked, switches the three-phase supply voltage to the terminals An, Vn, Sn of the three-phase motor and, respectively, to the terminals 15, 16, 17 of the protection unit, resulting in a three-phase the electric motor starts. The device uses zener diodes 3 and 4 with a breakdown voltage equal to or greater than half the amplitude value of each of the linear voltages V _AnVn and V _VnCn acting on the corresponding terminals of a three-phase electric motor.

Under the influence of the positive half-wave, the voltage V _{AnVn is} in the circuit: terminal 15, diode 7, resistor 5, zener diode 3, terminal 16 the input control current of the optocoupler 1 flows.

When a positive half-wave of voltage V _{VNSn appears} along the circuit: terminal 16, zener diode 4, resistor 6, diode 8, terminal 17, the input control current of the optocoupler 2 occurs.

The optocouplers 1 and 2 are unlocked and their outputs connected in the forward direction bypass the capacitor 11, ensuring the continuity of the control current of the optoelectronic three-phase relay after the charge of the capacitor 11. The capacitors 9 and 10 provide an open state of the optocouplers 1 and 2 at negative half-waves of linear voltages V _AnVn and V _Ext .

When the voltage disappears on one of the phases An, Vn, Sn of a three-phase electric motor, the device operates as follows.

For example, due to the breakdown of the Ac phase of the three-phase supply network or a malfunction of the optoelectronic three-phase relay, terminal A2 of the latter and the phase An of the three-phase motor disappears.

In this case, the phase Вн of the three-phase electric motor has a positive potential relative to the phase Сн in the positive half-wave of the linear voltage V _ВнСн , while the de-energized phase An of the three-phase electric motor has a negative potential relative to the phase Вн. Therefore, the input control current of the optocoupler 1 is terminated, the latter is turned off and, interrupting the control current of the optoelectronic three-phase relay, turns off the three-phase motor.

When the voltage disappears in the phase Cn, the linear voltages V _AnBn and V _{VnCn are} also in antiphase, which prevents the input control current from flowing through optocoupler 2, the latter is turned off and, interrupting the control current of the optoelectronic three-phase relay, turns off the three-phase motor.

When the voltage disappears at the phase Vn, the linear voltages V _AnVn and V _VnSn coincide in phase, but the amplitude is less than the breakdown voltage of zener diodes 3 and 4, which prevents the input control currents from flowing through optocouplers 1 and 2, the latter are disconnected and interrupting the control current of the optoelectronic three-phase relay turn off the three-phase electric motor.

After eliminating the cause of the phase malfunction, to turn on the device in normal operation, it is necessary to briefly turn off the voltage + Vvx and turn it on again.

Thus, the device provides a protective shutdown and non-inclusion of a three-phase electric motor when the voltage disappears on one of its phases due to a break in the corresponding phase of the supply three-phase network or a malfunction of the optoelectronic three-phase relay.

Claims (1)

A device for controlling a three-phase motor with phase-loss protection, containing an optoelectronic three-phase relay with input terminals connected to a three-phase supply network, and output terminals connected to the phases of a three-phase electric motor, input positive and negative control terminals, and to the input positive control terminal through a limiting a resistor is connected to a DC voltage source, characterized in that it is additionally equipped with a protection unit with first and second optocouplers, the first and zener diodes, first and second limiting resistors, first and second rectifier diodes, first and second storage capacitors, a starting capacitor, a shunted third resistor, outputs: the first to connect the input negative control terminal of the optoelectronic three-phase relay, the second negative (common), third, fourth , fifth conclusions for connection to the corresponding phases of a three-phase electric motor for monitoring the presence of phases, and the input negative control terminal of a three-phase an optoelectronic relay is connected to the first output of the protection node and through the positive and negative outputs of the first and second optocouplers connected in series, shunted by the starting capacitor and the third resistor, connected to the second output of the protection node, the positive control terminal of the first optron through the anode - cathode transition of the first zener diode, first limiting resistor, the cathode-anode junction of the first diode and through the third terminal of the protection node is connected to one of the phases of the three-phase electric motor, the control negative terminal the first optocoupler and the control positive output of the second optocoupler through the fourth output of the protection unit are connected to the second phase of the three-phase electric motor, the negative control output of the second optocoupler through the cathode – anode transition of the second zener diode, the second resistor, the anode – cathode transition of the second diode and the fifth output of the protection unit are connected to the third phase of a three-phase electric motor, with the first and second storage capacitors connected to the fourth terminal of the protection unit by one terminal, and by the other terminals to the cathode of the first and the anode of the second iodov respectively.