Research On Hybrid Magnet Field Modulation Machine

Field modulation machines(FMMs)have the advantage of high torque production at low speed operation,which is desired for direct-drive applications,such as power generation,robot joint drive,and large telescope drive.This dissertation proposes a new hybrid magnet FMM(HM-FMM)which combines FMM with the conception of hybrid magnet(HM)excitation.Further study of electromagnetic design method,analytical modeling and electromagnetic characteristics are significant in both theory and engineering application values.The structure characteristics and modulation mechanism of FMM are investigated based on comprehensive analysis of the state of the art of field modulation machines at home and abroad.Then,a R/S design method for multi-port FMM(MPFMM)is proposed.An analytical model is established for analyzing the electromagnetic field and cogging torque in the MPFMM with multi-PM-excitation and multi-modulation layer.Combined with the concept of HM,a new HM dual-stator FMM(HM-DSFMM)is proposed whose working harmonics,electromagnetics characteristics and demagnetization risk of PM are investigated and evaluated.A 12-slot/10-pole HM-DSFMM prototype is designed.The rationality and reliability of its electromagnetic design are verified by analytical,finite-element-analysis(FEA)predicted and experimental results.The main research work and achievements of the dissertation are as follows:(1)The research background and significance of the subject are introduced,and the state of the art and latest progress of HM machines and FMMs at home and abroad are comprehensively presented and analyzed.(2)The structural characteristics of magnetic gears(MGs)and FMM are summarized.The evolution process from MG to motor is given.A R/S design method suitable for MPFMM is proposed.The modulation mechanism and operation principle of MG and FMM are studied in depth.The calculation formula of working harmonics of MPFMM with multi-PM-excitation and multi-modulation layers is derived.The electromagnetic characteristics of permanent magnet(PM)excitation structures commonly used in FMM are analyzed.Pole slot combinations of fractional slot concentrated winding suitable for DSFMM are investigated.(3)An analytical model of multi-PM-excitation and multi-modulation layer FMM is built.The slotless stator model is used to calculate the equivalent air gap permeance under different PM excitations.Then,the electromagnetic field and the electromagnetic characteristics of the machine are analyzed.The cogging torques of the MPFMM under single PM excitation and dual PM excitation are compared and analyzed using energy method for revealing the effect of multi-PM-excitation for cogging torque.(4)The calculation constraints of the working point and volume of each PMs in HM excitation are studied.The magnetic field characteristics of each HM excitation are compared and analyzed.The working point variation law of each PM with different thickness in the HM excitation is given.The electromagnetic characteristics of the HM-FMM with different HM excitation combinations are studied.(5)A new HM-DSFMM is proposed and its electromagnetic design is given.The electromagnetic characteristics of the optimized machine are calculated.The electromagnetic properties of four typical machines designed by R/S design method are compared.The risk assessment of PM demagnetization is carried out.A 12-slot/10-pole HM-DSFMM prototype is manufactured and tested to verify the rationality of the design.