Reliable Inter Turn Fault Detection on Low Voltage Motors Using SFRA Measurements and Comparison to Surge Testing

Sweep frequency response analysis (SFRA) is a well-known diagnostic tool in the area of power transformer testing. In the past years, several investigations have shown that this technique is highly sensitive to detect various defects in high and low voltage motors too. Although it has been proven that the method can prevent early machine faults, comparisons to other methods and best practices to assess the measurement have hardly been researched, or not at all. The investigations described in this contribution try to close this gap and to propose a practice to assess the winding. Three brand-new stators were manipulated in such a way that single turns can be shortened along different locations in the windings. The results show the possibility to detect faults either by a fingerprint comparison or by a phase to phase comparison. Each setup with and without fault has been measured once with SFRA and once with IFRA, and the results are compared to each other. A sensitivity check proves the SFRA to be highly reliable to detect single inter turn faults. In addition, suggestions for result interpretation are given in this paper too.