A Simple Offline Test for Detecting Rotor Faults in Wound Field Synchronous Machines

Rotor field and damper windings are critical components of wound field synchronous machines (WFSM), where faults can degrade the performance and lead to forced outage of the machine. This necessitates timely and reliable fault detection as false positive indications can cause unwarranted economic losses in case the machine is disassembled prematurely. Applying multiple offline test methods in tandem with online monitoring can minimize the likelihood of false indications. In this letter, a simple offline test method based on the ac impedance of the rotor winding is presented. It is shown that field and damper winding faults can be detected and differentiated without machine disassembly. Experimental testing on three WFSMs verifies that the proposed method can provide a simple test for identifying field and damper winding faults with high sensitivity, and also complement existing tests for improving the reliability of fault diagnosis.