Online diagnostics in inverter-fed induction machines using high-frequency signal injection

Fault diagnostics for induction machines using an injected high-frequency carrier signal is presented and analyzed in this paper. Both stator winding fault and broken rotor bar detection is covered. Measurement of the resulting high-frequency negative-sequence current is shown to be capable of detecting both types of faults at their incipient stage. Though sharing similar physical principles to techniques applied to line-connected machines, the use of a high-frequency signal is shown to provide important advantages for inverter-fed machines, such as providing the same performance and drastically reduced sensitivity to the working condition of the machine, i.e., torque and flux levels, and fundamental excitation frequency.