Shaft currents in electric machines fed by solid-state drives

The author discusses the generation of shaft voltages and currents in electric rotating machinery. Those mechanisms of shaft voltage generation that are susceptible to being intensified by solid-state drives are identified. Harmonic generation by solid-state drives is reviewed and categorized for its severity for the most commonly used types of circuit topologies and commutation techniques. Both elements are integrated to ascertain the resulting additional onerous effects that solid-state switched power supplies have on the bearings of electrical machines. Although shaft voltages and currents exist in both AC and DC machines, the author has limited the discussion to AC drives