On-line detection of stator winding short-circuit faults in a PM machine using HF signal injection

This paper presents a high frequency (HF) injection scheme to detect short-circuits faults in the stator winding of a VSI-fed permanent magnet (PM) machine. The proposed approach is derived from sensorless control schemes based on HF voltage signal injection for tracking position in a surface-mount PM machine. In this paper the method of space-modulation profiling (SMP) is used to obtain a magnetic signature of the machine operating under healthy conditions. This signature can then be compared with the on-line measured saliency profile during normal operation to detect any abnormality in the drive's performance. The main application of the presented scheme is for the detection of windings problems such as insulation breakdowns and short circuits. Experimental results are shown for the case of a PM servo drive where incipient and full short-circuit faults have been emulated and successfully detected. Due to its relatively simple implementation and since no additional transducers are required, this approach presents an interesting alternative for condition monitoring.