Order feature analysis of electromagnetic noise in a permanent magnet synchronous motor considering current harmonics

Aiming at electromagnetic noise in a permanent magnet synchronous motor (PMSM) as the main noise source of a distributed-drive electric vehicle, firstly, the noise signals of PMSM were measured. The test results showed that the main orders of electromagnetic noise are not only even number orders and the orders in a close vicinity of switching frequency, but also odd number orders and fraction orders ignored as signal burrs in the past. Then, in order to explain the test phenomenon, the air gap magnetic field distribution considering current harmonics was obtained using the way of the magnetomotive multiplied permeance. Radial force wave was obtained with Maxwell's tensor method and was transformed to a radial concentrate force with the 6th order algebraic accuracy using the composite Cotes formula. An analytical model of electromagnetic noise in PMSM considering current harmonics was built. Orders and frequencies of electromagnetic noise were predicted. It was shown that they are 2h_i, 2h_j, 2(2μ-1), (h_i±h_j), (2μ-1±h_i) and (2μ-1±h_j) (h_iand h_j are orders of current harmonics, μ∈N^*); if h_ior h_j is a fraction, the fraction orders of electromagnetic noise occur; the orders and frequencies of noise of PMSM are accurately predicted with the proposed analytical model.