METHOD FOR DIAGNOSING DAMAGE TO SQUIRREL-CAGE ROTOR OF INDUCTION MOTOR IN RUN-DOWN MODE

Abstract

The proposed work is intended to deepen the theoretical foundations of constructing systems for diagnos-ing damage to the squirrel-cage rotor of an induction motor in run-down mode. It presents a method for diagnosing dam-age to the rods of a squirrel-cage rotor of an induction motor by means of EMF induced in the stator winding by damped currents in the squirrel-cage winding of the rotor. According to this method, the device is designed on the basis of a personal computer in which a sound card is used as an ADC, and the data is processed in specially created software. Two block diagrams of the device for diagnostics of blood pressure are presented, Information about the damage to the ro-tor is obtained from the EMF of the stator, and the start of the run-down is determined by the difference in its amplitudes or by the closure of the switch block-contacts. In the latter case, when the block-contacts of the load switch are opened, a signal is generated to measure the EMF of the stator winding and this EMF is recorded. This diagnostic system makes it quite easy to diagnose blood pressure with voltage up to 1000 V. However, the need to connect high-voltage AMs to the block-contacts for diagnostics, for example, in switchgear cells, significantly complicates the diagnostic process and so for technological reasons it cannot be used on all AMs. This can be largely avoided, if the beginning of the IM run-out mode is determined by the amplitude difference. The prototype of the rotor bar breakage diagnostics system has shown that its implementation is capable of quite efficiently detecting the rotor bar breakage in the IM run-down mode. In this case, experimental data was obtained both with the use of a computer sound card and an external certified ADC/DAC module. It was found that the measurement error with a sound card is permissible. At the same time, the cost of the entire device is low and is mainly determined by the cost of the PC and software making it affordable for almost any industrial enterprise and non-profit organizations.