RU2291539C2 - Three-phase load control apparatus incorporating phase-failure protective gear and warning device - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: proposed apparatus that incorporates provision for warning about any fault in three-phase supply mains under control by means of warning lights and for protecting load connected thereto, such as three-phase motor, against operation under phase-failure conditions has light-emitting diode matrix, current-limiting components, three-phase mains under control, half-wave rectifier, audible warning device, trimmer resistor, voltage regulator diode, three-phase optoelectronic relay for controlling three-phase motor, thyristor optocoupler, power supply, limiting resistor, and switching component.

EFFECT: enlarged functional capabilities.

1 cl, 1 dwg

Description

The device relates to the field of electrical engineering and can be used to control a three-phase load.

A device for controlling a three-phase electric motor with protection against phase failure (Patent RU 2239929 C2, IPC 7 N 02 N 7/09, publ. 10.11.2004).

A disadvantage of the known device is the lack of alarm about the phase failure of the three-phase supply network.

A device for controlling the presence of three-phase voltages

(AS SU No. 1836769 A3, IPC 7 H 02 N 3/24, publ. 08.23.1993), however, the known device does not contain load protection from phase failure.

Closest to the proposed one is the "Phase imbalance signaling device" (J. "Radio", 2003, No. 11, p. 42, 43).

The disadvantages of the known device are: the lack of response of the light signaling device to the phase imbalance of a controlled three-phase network and the lack of load protection.

The purpose of the invention is the expansion of functionality by providing reliable light signaling of any malfunction of a controlled three-phase network and protecting the load, for example, a three-phase electric motor.

The drawing shows the electrical circuit of the device.

The device contains three pairs of connected counter-parallel single LEDs, one of the conclusions of each of which through the elements 1, 2, 3 of the current limit is connected to phases A, B, C of a controlled three-phase network, to the neutral N of which through a trimming resistor 4, shunted by a zener diode 5, the second leads of all three pairs of LEDs are connected. A half-wave rectifier 6 is connected with its input parallel to the zener diode 5, and the output is connected to an audible warning device 7.

Three pairs of connected counter-parallel single LEDs are combined into three tri-color indicators 8, 9 and 10, each of which includes LEDs 11, 12, 13 of the first and LEDs 14, 15, 16 of the second glow color, emitting to a common fiber. The anodes of the LEDs 11, 12, 13 of the first color of the glow of the first 8, second 9 and third 10 indicators are combined with the cathodes of the LEDs 14, 15, 16 of the second color of the glow of the second 9, third 10 and first 8 indicators, respectively.

The optocoupler 17 contains an LED connected by an anode to the output of the audible warning device, and a photothyristor shunting the control input of the optoelectronic three-phase relay 18, through the power contacts of which a three-phase electric motor 19 is connected to the controlled three-phase network 19. The cathodes of the photothyristor and the optocoupler LED 17, the negative input of the optoelectronic three-phase relay 18 and the negative terminal of the DC power supply 20 are combined and connected to the neutral N.

The positive output of the power source 20 through the limiting resistor 21 and the key element 22 is connected to the positive input of the optoelectronic three-phase relay 18.

The device operates as follows.

In normal mode, a three-phase supply voltage system operates in phases A, B, C. If the LEDs 11, 12, 13 of the first color of the glow are selected, for example, yellow, and the LEDs 14, 15, 16 of the second, which work with them in pair with a common fiber, are blue, then as a result of mixing their emissions in the optical fibers of the three-color indicators 8, 9, 10, the latter glow green, signaling the serviceability of the network phases.

To start the three-phase electric motor in operation, it is necessary to close the key element 22. In this case, power is supplied from the direct current voltage source 20 through the resistor 21 to the control input of the three-phase optoelectronic relay 18, while the relay 18 turns on and starts the three-phase electric motor 19.

When the voltage disappears, for example, on phase A of the supply network due to open circuit or unacceptable “skew” (the two-anode zener diode, which is part of the current limiting element 1, is locked), the LEDs 11 and 15 will stop glowing, as a result of which indicator 8 changes the green glow to blue, and indicator 9 is green to yellow. In this case, the indicator 10 continues to glow green, indicating the presence of a line voltage V _BC or, equivalently, phase voltages V _B and V _C. At the same time, an alternating asymmetry (skew) voltage appears on the resistor 4, which turns the rectifier 6 into a constant, limited by a large phase skew (break) of the zener diode 5. If it exceeds a certain minimum level, the signaling device 7 starts to produce an intermittent signal. At the time of the appearance of this signal, the optocoupler LED 17 is excited, while its photothyristor is unlocked and the control input of the optoelectronic three-phase relay 18 is unlocked, which turns off and de-energizes the three-phase motor 19.

As a sound signaling device 7, for example, two multivibrators on elements of a microcircuit that performs the AND-NOT function and a sound emitter, for example, piezoelectric, can be used.

Trimmer resistor 4 is used to set the threshold of the signaling device 7 and the optocoupler 17.

Thus, the device, while maintaining the function of the prototype, namely, the sound alarm during phase imbalance, additionally provides:

- visual monitoring of the state of each phase of the supply network using three-color indicators;

- protection of a three-phase load, for example, a three-phase electric motor connected to a controlled three-phase network, from operation in an out-of-phase mode and with unacceptable asymmetry of phase voltages.

Claims (1)

A device for controlling a three-phase load with phase distortion protection and an alarm system, containing three pairs of connected counter-parallel single LEDs, one of each of which through the first, second and third current limiting elements are connected respectively to the first, second and third phases of the monitored three-phase network, to the neutral of which, through a trimming resistor, shunted by a zener diode, the second outputs of all three pairs of LEDs are connected, a half-wave rectifier, connected via its input to a parallel specifically to the zener diode, and the output to a sound signaling device, and three pairs of counter-parallel connected LEDs are combined into three tri-color indicators, each of which includes LEDs of the first and second glow colors emitting to a common light guide, anodes of LEDs of the first glow of the first, second and the third two-color indicators are combined with the cathodes of the second-color LEDs of the second, third and first three-color indicators, respectively, an optocoupler, an optoelectronic three-phase relay, through whose contacts are connected to a controlled three-phase network with a three-phase electric motor, a DC power supply, a limiting resistor and a key element, the cathode of the optocoupler LED, the negative input of the optoelectronic three-phase relay and the negative output of the DC power supply combined and connected to the neutral, and the positive output of the power source DC through the limiting resistor and the key element is connected to the positive input of the optoelectronic three-phase relay, characterized in that a The optocoupler LED node is connected to the output of the buzzer, and the optocoupler thyristor shunts the control input of the three-phase optoelectronic relay.