Separation of slip- and high-frequency electromagnetic quantity and its application in rotor loss fine analysis of induction motor

Due to coupled slip- and high-frequency electromagnetic quantity with load conditions, it is difficult to separate the additional iron and copper losses caused by the harmonic field accurately at rotor side of induction motor within a power cycle. To solve this problem, this paper proposes a separation method of rotor electromagnetic quantity with the slip frequency. In this method, the amplitude of flux density or current density with slip-frequency can be solved by Discrete Fourier Transform (DFT) on a spatial field distribution at a random moment, and the polynomial combined high-frequency sine functions are adopted to fit the curves in a power cycle by Least Square Method (LSM); finally, the loss caused by different harmonic fields can be calculated separately and accurately. The correctness of the proposed method is verified by comparing with the computed flux density with a slip cycle, and its application on rotor losses fine analysis is also presented.