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Application of Sine Wave Filters with High-Speed, High Power Motors
Decreases in permanent magnet synchronous motor (PMSM) costs are leading to increased utilization in high power applications due to benefits in energy efficiency, partial load efficiency, and decreased motor size. Typically, low pass sine wave filters are used to eliminate switching frequency harmonic content at the output of the variable frequency drive (VFD), minimizing excess heat and voltage stress in the motor. Traditional silicon steel sine wave filters exhibit excessive core losses at high fundamental and switching frequencies, leading to difficulties with overheating and negating the efficiency gains of the sine wave filter. These limitations have led to low adoption rates for sine wave filters in high-speed, high power motor applications. This paper will first discuss the evolution of AC motors, from induction machines to PMSMs. The paper will conclude with a discussion of how properly designed sine wave filters, with optimal materials and construction, can be used to realize substantial benefits in efficiency and reliability when installed in a high-speed, high power motor system.