Lumped radial force characteristics reconstruction for switched reluctance machines through scaling flux-linkage characteristics

This paper presents a simple and practical method to estimate the lumped radial force characteristics for the switched reluctance machines (SRMs). Firstly, the relationship between the square root of the lumped radial force and the flux-linkage is discussed and analyzed. With the geometry data of the studied SRM, the above relationship under nominal airgap length and nominal material magnetic property conditions can be obtained through the finite element analysis (FEA) software. Since the radial flux density dominates the magnitude of the radial force and it concentrates on the overlapping area, the above relationship is analyzed to be roughly held when the airgap length and/or material magnetic property vary. Based on this relationship obtained from FEA and the actual measured flux-linkage characteristics, the lumped radial force can be easily reconstructed for the actual SRMs regardless of the possible airgap length variation and material magnetic property deviation during the manufacturing process. Simulation results on the 8/6 SRM and 12/8 SRM verify that the proposed method provides good radial force estimation results when the airgap length is reduced or increased up to 50%. Superior estimation results are also observed on the condition that the magnetic BH curve is linearly varied by ±25%. The accurate and simple radial force estimation method proposed in this paper provides a solid basis for the radial-force-shaping-based advanced control methods to suppress the acoustic noise.