SU1431001A1 - Method of shorting protection of a.c. thyratron motor - Google Patents

Abstract

This invention relates to electrical engineering, namely, to relay protection. The purpose of the invention is to increase sensitivity and speed. A device for implementing the method comprises a current-to-voltage converter 6, a selective voltage-frequency filter 7, a rectifier 8, a quadrant 9, a reacting element 11. When the circuit closes, the number of turns flowing around the current with frequency f decreases. This causes a decrease in inductive dissipation resistance and an increase in current. The difference between the reference values and the signal, which comes from the output of the smoothing circuit 10, triggers the response of the reacting organ 11 and turns off the ventilator. 1 il. SL

Description

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The invention relates to the field of electrical engineering, namely, to relay protection of AC motors, and can be used to detect short circuits in the windings of the core of a working machine.

The aim of the invention is to increase the sensitivity and speed of protection,

The drawing shows a block diagram of the device that implements the method.

As an example, a valve motor that is powered by a three-phase network is considered. The installation contains a three-phase power supply 1 connected to a valve motor 2, consisting of a frequency converter 3 and a motor 4.

Protection: against short circuits in the windings of the core of the valve motor

The alternating current 5 includes a current-to-voltage measuring converter 6 connected to a selective filter 7 of a voltage with a frequency equal to the ripple frequency of the excited voltage of the power source of the valve motor connected to the rectifier 8 that is output through a quad 9 and the smoothing circuit 10 is connected to a reacting body 11 connected to the output body 12,

; Included in one of the phases at the output of the frequency converter 3 in series with the motor 4, the measuring converter 6 converts into a signal of the magnitude of the current cor. Load converter

6 is a voltage filter 7 having a non-linear amplitude-frequency characteristic; the maximum resistance of the load of the converter b is at the resonant frequency of the filter

The signal from the filter 7 is fed to the rectifier 8, where it is rectified, the pronounced signal is fed to the input of the quadrant 9, where the signal is converted into the corresponding values, which are further integrated by the smoothing circuit 10 and

arrive at the input of the reacting authority 1, to the second input of which a reference (reference) signal is applied

tension The magnitude of the reference voltage is selected based on the condition that the relay operates reliably. The signal received at

output smoothing circuit 10 when the engine with intact windings. During a turn short circuit, the number of turns streamlined by the current with a frequency f decreases, which causes

a decrease in inductive dissipation resistance and current increase. The difference between the reference value and the signal coming from the output of the smoothing circuit 9 in the reacting

The organ 11 is converted into a signal causing its triggering and the selection into the output organ 11 of the signal which is converted (amplified) in the output organ to the parameters

necessary to effect the disconnection of the valve engine 2 from the power source 1.

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Claims (1)

Invention Formula  The method of protection of the AC AC motor from short circuits in the winding of the core, based on the measurement and control of current, converting it into a signal proportional to the monitored parameter, comparing the received signal with a setpoint and when exceeding its generation of a turn-off signal, which, in order to increase sensitivity and speed, is proportional to the monitored parameter current cor, followed by separation from the obtained value of the signal proportional to the component of this current with a frequency equal to the fundamental frequency of the pulsations rectified in accordance with the circuit of the frequency converter of the current, the voltage source of the valve motor power supply.