RU1817186C - Device for protecting three-phase-wound-rotor motor against rotor circuit breakage - Google Patents

Abstract

Usage: in the protection schemes of electrical machines from phase failure. The device provides a clear diagnosis of the malfunction, reduces the severity of the accident, recovery costs. SUMMARY OF THE INVENTION: Depending on the type of drive malfunction, the pulse duration generated by the operating circuit will vary. At the moment of starting the electric motor, the frequency of the rotor and stator voltages coincide, which is a control circuit consisting of a rectifier unit 10, which transmits positive half-waves of the network, a shaper 11, which converts them into rectangular pulses, and a selector. 12, which controls the frequency of the rotor voltage according to the pulse duration, a shaper 13, which expands the selector pulses. The pulse of the expander 13 at the input opens the input C of the counter 7, fe s. with

Description

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which the first working pulse from pulse former 2 delays, and the second passes to the input of the pulse generating unit 4, which generates pulses for the counter 7. The trailing edge of the second working pulse counter 3 closes, the generator stops working, and the information from the counter 7 on the inputs JK memory 5 or b, it is rewritten that the invention relates to electrical engineering, in particular to devices for protecting an electric motor with a phase rotor from breaking the rotor chain, used mainly in multi-motor drives ah.

The purpose of the invention is to increase operational reliability by ensuring separation of the open signal in the phase windings of the rotor from the open in the starting rheostat.

The invention is illustrated in the drawing, in which Fig. 1 shows a block diagram of a device; Fig. 2 shows voltage diagrams at the output of the rectifier unit: a - with a functioning electric motor; b - when the rotor winding is broken; in - at breakage of starting rheostat.

The device comprises a three-phase rectifier unit 1, a pulse generator 2, a pulse counter 3, a pulse generation unit 4, two memory elements 5 and 6, a binary pulse counter 7, two actuating relays 8 and 9, a single-phase rectifier block 10, a pulse generator. 11, pulse selector 12, pulse expander 13.

The device operates as follows. The voltage from the starting rheostats is applied to the input of the rectifier unit 1, which transmits positive pulses (Fig. 2) of different durations, depending on the nature of the damage, to the input of the pulse shaper 2, where they are converted to rectangular pulses and are present at the input of the pulse counter 3, which expects at the input R the resolution of their count from the output of the pulse shaper 13. The resolution of the count only occurs when the motor starts up from standstill. At the initial moment of starting time, the rotor voltage frequency coincides with the stator voltage frequency and is fed to the input of a single-phase rectifier unit 10, which transmits positive sinusoidal pulses from

an actuating relay 8 or 9 is activated, respectively, an open in the rotor winding to the rotor rings or an open circuit of the starting rheostats. With a working motor, only one working pulse will be present at the output of driver 2, which will not pass to the output of counter 3, and relays 8, 9 will not be turned on. 2 ill.

which pulse shaper 11 forms rectangular pulses. These pulses are extracted by a pulse selector 12 in the form of pulses of very short duration, which are fed to the input of a pulse expander 13 to increase their duration to 3 seconds. The pulse expander 13 at the input opens the input C of the pulse counter 3, which is the first working pulse from the output

the pulse former 2 delays, and the second passes to the input of the pulse generating unit 4 operating in standby mode. The pulse generating unit 4 generates rectangular pulses, which are counted by the binary counter 7 until the end of the second pulse. The output of the pulse counter 3 is closed by the trailing edge of the working pulse. 5 or 6 is overwritten at the j-K inputs from binary counter 7 to memory element 5 or 6. The actuating relays 8 or 9 included in the output of the memory elements are activated. The actuating relay 8 is triggered by a break in the rotor winding to the rotor rings, b in FIG. 2, and relay 9 is triggered by a break in the chain of starting rheostats, in FIG. 2. If the electric motor is working, then at the output of the pulse former 2 there will be only one working pulse that will not pass to the output of the pulse counter 3, the executive relays 8, 9 will not turn on.

Formula A device for protecting an asynchronous three-phase electric motor with a phase rotor from breaking the rotor circuit, comprising a three-phase rectifier unit, the output of which is connected to the input of the pulse former, a pulse generating unit and an actuator relay, characterized in that, with the aim of increasing

operational reliability by ensuring the separation of the open signal in the phase windings of the rotor from the open in the starting rheostat, it is additionally equipped with a pulse counter, a binary pulse counter having four outputs, two memory elements and a control circuit connected to the terminals for connecting to the phase wires of the rotor winding and consisting of sequentially cor single-phase rectifier units, a second pulse shaper, a pulse selector and a pulse expander, the output of which is connected the second inputs of the pulse counter, the binary counter pulses and fourth inputs

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memory elements, wherein the output of the pulse former is connected to the first input of the pulse counter, the output of which is connected to the input of the pulse generating unit and the second inputs of two memory elements, the output of the pulse generating unit Y is connected to the first input of the binary counter, having four outputs connected to the first and third inputs

by two memory elements, / a j xbfl1 of a three-phase rectifier unit is connected between the terminals for connection with the phase terminals of the motor rotor and the zero point of connection of the starting rheostats.