Subharmonics Generated by Space Vector Modulation in Ultrahigh Speed Drives

Failures of ultrahigh speed induction machines (USIM) experienced in the laboratory initiated the current study. The USIM was supplied by voltage source converter controlled by space vector modulation (SVM) to generate electric power by utilizing renewable energy resources. Three different sampling techniques, regular sampled, naturally sampled, and oversampled are investigated by simulations and tests. It was found that subharmonic flux with considerable amplitudes can be generated in USIM. It can cause high level of additional winding copper losses in the rotor that could lead to damage of the machine. The investigation is focused on the generation of subharmonics.