Investigation Of The Flux Adjustment Capability In The Hybrid Excited Switching Flux Permanent Magnet Machines

In this paper,the flux adjustment capability of hybrid excited switching flux permanent magnet(HESFPM)machines is systematically studied.Two types 12/10 HESFPM machines with different locations of field windings have been designed and compared to investigate their electromagnetic performance and flux adjustment capability.In the first HESFPM machines(HESFPM-1),partial permanent magnets(PMs)are replaced by dc field windings,while in the other one(HESFPM-2)the dc field windings are placed outside the conventional switching flux permanent magnet(SFPM)machine.The HESFPM-2 machine exhibits much larger slot area for dc field windings than HESFPM-1 machine,which indicates higher flux enhancing or weakening capability.In the design of machine,the slot area ratio of HESFPM-2 machine has a wide range,so the influence of the change of machine size on the slot area is more obvious,and the design of machines is more flexible.In addition,the comparison of torque and flux adjustment capability between the HESFPM machines is also carried out at the same flux adjustment coefficient and output torque.The influences of different lengths of PM,widths of PM,stator tooth widths,the width of iron flux bridge on torque and flux adjustment capability have been investigated.The influences of different rotor pole numbers on the flux adjustment capability of HESFPM machines are investigated.12/10 and 12/14 HESFPM machines with different rotor pole numbers and winding configurations have been designed and compared to investigate their electromagnetic performance and flux adjustment capability.The topologies and winding connections of 12/10 and 12/14 HESFPM machines are described firstly.The influence of field currents on the flux adjustment capability is presented as well as the influence of the slot area ratio between the field and armature windings.It shows that at the same structures of stator and same slot area ratio,the 12 stator pole HESFPM machine with rotor pole number of Ns+2 exhibits higher torque and better flux adjustment capability than the HESFPM machine with rotor pole number of Ns-2.In addition,the effects of different field excitations densities,the slot area ratio of between the field and all windings,the width of iron flux bridge on the torque performance and flux adjustment capability of E-core HESFPM machines are analyzed.For E-core HESFPM machine,the stator adopts E-type structure,E-core HESFPM machine is proposed by employing DC excitation coils on the middle teeth of stator E-core which have no magnet,the slot area of the machine is occupied by armature winding and DC excitation winding respectively,which improves the utilization ratio of permanent magnet,slot area and the torque density of the machine.Finally,a 12/10 and 12/14 HESFPM prototype machine was designed and manufactured in this paper.The back EMF and torque experiments under different field excitations of the HESFPM prototype were carried out to verify the torque performance and flux adjustment capability simulation results of HESFPM machine.