ASYNCHRONOUS MOTOR CAGE FAULT-DETECTION THROUGH ELECTROMAGNETIC TORQUE MEASUREMENT

In this article a new method is presented allowing the diagnostic of bar or ring rupture of a cage of asynchronous machine. It is shown that a modelling of the asynchronous machine taking into account each bar and each portion of ring of the cage allows to consider the influence of a rupture upon the expression to the instantaneous electromagnetic torque. It has been put up an instrumentation permitting the measurement of this tor que. The spectral analysis of the parameter leads to the diagnostic of a cage rupture by discriminating this fault from other faults, particularly mechanical ones. It is also observed that ruptures influence greatly the electromagnetic torque. The peak variation of the significant spectral lines is so important that it allows the detection of a first rupture without the need of a very sophisticated instrumentation.