Online stator winding fault diagnosis in inverter-fed AC machines using high-frequency signal injection

The diagnosis of stator winding faults in inverter-fed ac machines using an injected high-frequency carrier signal is presented and analyzed in this paper. Measurement of the resulting high-frequency negative-sequence current (or alternatively of the negative-sequence impedance) is used to detect turn faults at an incipient stage. Though sharing the same physical principles of similar techniques applied to,line-connected machines' the use of a high-frequency signal will be shown to present important advantages, such as providing the same performance almost independently of the fundamental excitation frequency, and drastically reducing the sensitivity to the working condition of the machine, i.e., torque and flux levels.