Analysis Of The Eddy Current Losses In The Permanent Magnet Of Yokeless And Segmented Armature Axial Flux Motor

The Yokeless and Segmented Armature(YASA)topology is a new type of axial flux motor.The YASA motor has no stator yoke and end windings,less iron loss and a high fill factor which all increase torque density and efficiency of the machine.Thus,the topology is highly suited for electric vehicle,renewable energy,flywheel energy storage and some high performance applications as its compact structure,high power density and a series of advantages.The permanent magnets(PMs)are the magnetic excitation source in the permanent magnet synchronous motor(PMSM).Due to the effect of time harmonics of stator current and space harmonics of air gap magnetic field,the loss in permanent magnets is considerable and leads the partial overtemperature.The machine’s temperature rise will affect not only its service life,its insulation,but also its operational reliability.YASA has ten poles,so it will generate much more eddy current loss at the same speed and the high frequency.It is necessary to design a special way to reduce the magnet temperature generating by the eddy current loss.Different from traditional radial flux electrical machine,YASA is a kind of axial flux electrical machine.That makes it difficult for axial flux electrical machine to simplify the three-dimensional electromagnetic field analyzation down to twodimensional analyzation.the structure of axial flux electrical machine with one stator between two rotors is firstly introduced.The distribution of magnetic field and the parameters of the main magnetic circuit are analyzed on the basic of magnetic circuit model.The causes of eddy current loss and its influencing factors was analysed thoroughly.The expression of magnet eddy current loss and other parameters were showed and calculated respectively.The magnet surface groove of YASA axial flux motor is discussed in this paper.Several factors influences were studied including the groove depth,groove method and groove number.Then the calculated results from the analytic method were compared with those calculated by three dimensional finite element method to analysis the eddy current loss of the different groove methods.Compared with the air gap flux density of the rated load,a reasonable magnet surface groove method and number was chosen.