The influence of winding capacitance on high frequency time harmonic losses in induction motors

An experimental study of motor current and power for time harmonic frequencies up to 100-200 kHz has been carried out. It is shown that motor losses can be significantly increased at frequencies above the first resonance by the very nonuniform voltage distribution along the winding turns. Tests on small motors (up to ten horsepower) indicate that the first resonance can occur as low as 20 kHz but is more typically in the range of 50-70 kHz. The tests also demonstrate that equivalent magnetic connections, i.e., series vs. parallel connection for dual voltage motor designs, can have very different high-frequency characteristics and that variations in system grounding result in significant changes in resonant frequencies and losses.<
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