Low electromagnetic vibration design of double-layer interior permanent magnet machines for electric vehicle

Electromagnetic vibration and noise of driving motor affect the comfort for electric vehicles. Considering low harmonic component and pole design flexibility of double-layer interior permanent magnet (IPM) machines, in this paper, an improved analytical method of no-load air gap flux density for double-layer IPM machines is introduced, and the harmonic spectrum of electromagnetic force is analyzed. A commercial double-layer IPM machine is taken as benchmark, the electromagnetic–structure–sound coupling model is established. The main spatial and temporal order of electromagnetic force for benchmark motor is indicated. Based on this analytical model, a method to minimize the electromagnetic force of specific harmonic component is proposed to reduce electromagnetic vibration and noise, by optimizing parameters of double-layer IPM machine rotor pole without impairing the motor performance. The vibration and noise of the optimized motor under working condition and no-load are compared with the results of the benchmark motor by multi-physics simulation, and validate the proposed optimization approach.