Design And Analysis Of Axial Flux Permanent Magnet Machine With A New Type Coreless Armature

The disc Machine is a kind of motor whose air gap is flat and the air-gap magnetic fieldis axial，compared with Radial flux Permanent Magnet Machine (RFPM-Machine),it is namedas Axial Flux Permanent Magnet Machine (AFPM-Machine).AFPM-Machine is appliedwidely due to its advantages of compact construction，less axial dimension，and easilyincreasing power by multi-staging.With the topology of AFPM machines,the corelessarmature stator can be manufactured to eliminate the cogging torque and reduce the acousticnoise of machines.Because of non-existing of iron losses，AFPM-machine will give highefficiency running.The windings of power-type (aim at driving) AFPM brushless machineswithout stator core,which is planned to propel underwater vehicles,are directly exposed underthe time-varying air gap magnetic field，so that the eddy current losses in winding conductorsare significant.The eddy-current-losses will make the temperature of armature stator rising,and finally,the efficiency of the AFPM brushless machine will be reduced.It takes importanttheoretical meanings and application value to study on both suppression winding eddy currentloss and calculation method for the coreless armature stator of power-type AFPM brushlessmachines.In this paper,the main research contents and accomplishments are as follows:1、Firstly, the research status quo,present problems and prospect of AFPM-machine aresummarized and analyzed,then,several topologies and geometries of AFPM-machine areintroduced and performance comparison between a conventional RFPM machine and anumber of AFPM machines of different configurations are made,finally,the mechanism of thecopper losss and eddy current loss in coreless armature stator windings of AFPM machine isanalyzed theoretically.2、A novel coreless armature structure is proposed innovatively,in which armaturewindings are made of hot air self-bonding litz wires.This kind of armature windings canreduce eddy current losses of conductor which directly exposed under the time-varying airgap magnetic field in AFPM machines.A prototype of AFPM machine with this novel coreless armature stator structure is designed and its magnetic circuit is calculated using the method ofMathCAD,then the calculation results are analyzed.3、Compared with the conventional segmental equivalent line motor2D finite-elementanalysis（FEA）method,a new method to calculate the winding eddy current loss,namelysegmental3D magnetic FEA method,is proposed. Using this segmental3D magnetic FEAmethod to calculate AFPM machine’s magnetic field will get much more precise results thanusing2D finite-element analysis（FEA）method.Through building coreless stator AFPM3Dmodel by Flux finite software,the armature winding eddy current losses are simulated andcalculated，and the results show that using Litz wires to make AFPM brushless machine’scoreless armature stator can effectively reduce its eddy current losses.4、Through the experiment of the prototype AFPM brushless machine, its eddy currentlosses and mechanical losses are testified and analyzed.Comparing the results betweenexperiment and theoretical calculation，we conclude that the feasibility of design about AFPMmachines，the validity and the accuracy of theoretical calculation method about corelesswinding stators are proved correctly.The research accomplishments in this paper helps tosolve the problem of high temperature rising produced by winding eddy current losses inpower-type AFPM brushless machines with coreless armature stator and make it possible forAFPM machines being used in propelling underwater vehicles.