Evaluation of the Applicability of Frequency Response Analysis to Rotating Electric Machines

There is an increasing interest in identifying alternative options for testing rotating machines with the high demand for reliability-critical applications such as electric propulsion and renewable energy generation. The applicability of frequency response analysis (FRA) of impedance to quality assurance and maintenance testing of rotating electric machines is being actively studied, as it has been proven to be a non-invasive and versatile test for identifying anomalies in transformers. In this work, a comprehensive analysis on the applicability of FRA testing for different types of electric machines is given. Testing on different stator (random/hairpin/ form-wound), rotor slot (open/closed), rotor core (cylindrical/ salient pole), and permanent magnet (PM) (surface/interior PM) designs are performed with and without the rotor inserted. The applicability of FRA to rotating machine testing are given for different stator and rotor design combinations based on the test results. In addition, the influence of the rotor position and guidelines on interpretation based on phase or sister unit comparison is presented.