Rotor fault detection in field oriented controlled induction machines

The employment of inverter-fed induction machines in industrial plants is growing thanks to the continuously decreasing costs related to power electronics devices and microcontrollers. It is well known that a sudden failure in an asynchronous machine employed in a continuous process may cause severe profit losses: the possibility to early detect incipient faults is vital in order to avoid this scenario. The most widely studied induction machine fault is by far the rotor bar breakage. Many papers have been written about methods allowing the detection of rotor defects. However, very few of them are specifically devoted to inverter-fed machines and does not take account the effect of the control technique and possibly feedback loops. In previous work the authors have presented two rotor fault indexes which evaluate the ratio between the amplitude of the electrical power oscillation drawn by the induction machine and its average value. Both of the indexes have proven to be effective with open loop and closed loop V/f control as well as with a sensorless vector control strategy. In this paper, the applicability of the aforementioned diagnostic techniques to field oriented controlled induction machines will be discussed.