Fault detection on Induction Machines operated in V/f Scalar Control

This paper presents a new fault detection technique designed for three-phase induction machines operating under Voltage/Frequency scalar control. Electrical and mechanical faults are detected by estimating online the rotor time constant obtained from the magnitude of the stator current and rotor speed measurement. The specific type of fault can be accurately determined by analyzing the observed trends in the rotor time constant variations and identifying the presence of a double-line-frequency pulsation in either the current or speed. This method is simple and effective, does not need other transducers than those already present on a standard V/f electronic power converter, does not affect normal operation, and features good precision in estimating the variation of rotor time constant and robustness.