SU1262425A1 - Device for locating faults of bars in induction motor squirrel-cage rotor - Google Patents

Abstract

This invention relates to electrical measuring technology. The purpose of the invention is to increase the reliability of the control. The device contains a current sensor 1, amplifier 2, low frequency filter 4 and notch filter 5. Introduction of rectifier 3, null organ 6, sawtooth generator 7, low frequency filters 8 and 12, amplifier 9, threshold element 10, block 11 nonlinearity and indicator 13 increases the stability of the function when determining damage to the rods of a short-circuited rotor of an induction motor in operation mode. 1 il. (L to Od Is9 N9 CD

Description

The invention relates to electrical measuring equipment and can be used to create devices for diagnosing rotor rods of an asynchronous motor in operation. The purpose of the invention is to improve the reliability of control by increasing the STABILITY of operation when determining damage to rods of a short-circuited rotor of an induction motor in the operating mode. The drawing shows a block diagram of the device. The device contains a current sensor 1 connected via a first amplifier 2 connected in series, an amplifier 3, a first low frequency filter 4, a notch filter 5, a null organ 6, a driver 7 of a sawtooth voltage, a third filter 8 low 20

frequency to the first input of the second amplifier 9, to the second input of which the output of the threshold element 10 is connected, and its input is connected to the output of the third low-frequency filter 8. The third input of the second amplifier 9 through the nonlinearity block 11 and the second low-pass filter 12 are connected to the on-board 3. The output of the second amplifier 9 is connected to the indicator 13. In the device, the slip measurement path (1-9) is separated, the path for forming a nonlinear dependence of the motor load as a slip function (11-12), the threshold element 10, the indicator 13. In the first path, the null organ 6, the sawtooth driver 7 and the third low-pass filter 8 convert the slip period into a proportional constant value voltage, and the transmitter 3 provides the ability to filter the signal. The combined use of both paths makes it possible to monitor and measure the degree of damage to the rotor of a running engine.

The device works as follows. Sensor 1 measures the consumption of 50 ki from

engine power or at a constant value of the supply voltage, the value of the current-stator. Amplifier 2, for example, operation, aligns sensor 1 with the input blocks. The signal from Sensor 1 takes the form of an amplitude-modulated signal when the rotor rods are partly broken, so in order to obtain a constant signal proportional to the slip period, first the rectangular pulses are converted into sawtooth voltage in the former 7, then the constant component is extracted in filter 8 from the incoming signal to it. The longer the slip period, the more time to increase

the voltage in the driver 7 of the sawtooth voltage and, accordingly, the constant component at the output of the filter 8 will be more.

When the load on the engine shaft changes, the engine slip changes, and this relationship is non-linear. To improve the accuracy of monitoring the state of the rotor, it is necessary to take into account this dependence of slip on the load. After the termination of the rectifier 3, the signal proportional to the magnitude of the load signal is smoothed in the second low-pass filter 12. The characteristic of the non-linearity block 1 1 provides, in the stunned mode of engine operation, a signal of the magnitude of the slip from the filter 8 and the load from the filter 12 when the value of the load changes. Block 11 nonlinearity can be performed using operational amplifiers and diodes. Signals on the magnitude of the load and slip are sent to the operational amplifier 9. It allows summing the signals arriving at its inputs algebraically, and the signals are connected to the 52 nd to receive a low-frequency signal and a signal should be transmitted to the central pulser 3. Appearance This low frequency with a slip period is caused by the presence of part of the rotor rods. Using the first low-pass filter 4 and the notch filter 5 tuned to the frequency of the supply network, a low-frequency envelope is extracted. A null organ 6, which can be performed on an operational amplifier without feedback or with a non-linear element in feedback (diode, zener diode), converts the alternating signal into square pulses, the duration of which is determined by the low-frequency envelope, i.e. proportional to the slip frequency of the rotor. idling to nominal

Claims (1)

Claim A device for detecting damage to the rods of a squirrel-cage rotor of an induction motor, comprising a current sensor, the output of which is connected to the input of the first amplifier, a first low-pass filter, a notch filter, characterized in that, in order to increase the reliability of control, a rectifier and a zero-organ are introduced into it , sawtooth voltage shaper, second third third low-pass filters, threshold element, nonlinearity block, second amplifier, indicator, while the output of the first amplifier through a rectifier is connected to dams of the first and second low-pass filters, the output of the first low-pass filter is connected to the input of the notch filter, the output of which is connected to the input of the zero-organ, the output of which is connected through the sawtooth voltage generator to the input of the third low-pass filter, the output of which is connected to the input of the threshold element and with the first input of the second amplifier, the second input of which is connected to the output of the threshold element, the third input of the second amplifier is connected to the output of the nonlinearity block, the input of which is connected to the output of the second Oh low-pass filter, the output of the second amplifier is connected to the input of the indicator.