Research On Halbach Array Hybrid Excitation Pulsed Alternator

Pulsed alternator(PA)integrates inertial energy storage,electromechanical energy conversion and pulsed power conditioning in one unit,which is considered as the most promising pulsed power supply of electromagnetic launch.Hybrid excitation compensated pulsed alternator(HECPA)is a potential research direction with the advantages of high power density,high energy density and high adjustability,due to the topology of hybrid excitation CPA is recently presented,many key issues have not been explored.A novel Halbach array hybrid excitation pulsed alternator is presented in this paper and the following aspects are studied:Analytic method and finite element method(FEM)are used to study the electromagnetic field of the Halbach array hybrid excitation pulsed alternator.Considering power density and energy density,the topology of HECPA is determined.The electromagnetic field of Halbach array permanent magnet(PM)structure are analyzed by analytic method and finite element analysis and its advantages are illustrated.Based on special design method of pulsed alternator,basic electromagnetic parameters of Halbach array HECPA are calculated and the correctness of electromagnetic design is verified by FEM.The electromagnetic field change law and discharge characteristics of different types of CPAs during discharge are analyzed,and the losses and electromagnetic forces distribution of Halbach array HECPA are analyzed.The demagnetization of PMs caused by the armature reaction,electric excitation and high temperature,and the thermal rise caused by windage loss,ohmic loss of compensation shield and armature windings.The demagnetization of PMs caused by external field and thermal field are analyzed by finite element software in details.The demagnetization analysis includes single phase discharge,double phase discharge and sinusoidal load current demagnetization under different thickness of compensation shield.The demagnetization of PMs under different discharge time and discharge cycle of load current are analyzed,the dynamic demagnetization curve of some high risk demagnetization point are used to evaluate partial demagnetization of PMs.Strong pulse current and transient torque are generated during HECPA discharge,so it is a key problem that the thermal rise and electromagnetic forces are accurately analyzed.In order to analyze the thermal field and stress field distribution during discharge,the multi-physics finite element model is established.And the thermal field and stress field of Halbach array HECPA under different discharge modes are analyzed.