In this dissertation, the High Speed Axial Flux Permanent Magnet Machines (HSAFPMMs) are analyzed based on the analytical and lumped parameters network approaches. A series of works on HSAFPMMs are expanded in this thesis such as the magnetic flux densities calculation, the losses and thermal analysis, the vibration and mechanical verification, etc. The works in this thesis hold significant value for the theory development and engineering application of HSAFPMMs.
The fruits and the main contributions of this thsis are as follows:
1. A traditional AFPM motor with semi-closed slots and symmetric N-S poles is taken as the prototype to evaluate the performances of four magnetic analytical approaches. To be more precise, the real conformal mapping, the complex conformal mapping (CM), the Schwarz-Christoffel (SC) Mapping and the subdomain (SD) approach are modeled under Cartesian coordinate system. The pros and cons of each method are demonstrated after comparing the cogging torque, back EMFs, etc. Finally, the current sheet approach is adopted to calculate the armature field which completes the computational system of relative permeance method. The main contribution of this section is using the SC model to calculate the relative permeance function. The reason why K plane is necessary and the detailed processes are shown in thesis.
2. The subdomain model for HSAFPMMs with Halbach PM array is solved under Cartesian coordinate system. Afterwards, the back EMFs, cogging torque, output torque of AFPM motor are analyzed. Based on the magnetic flux density calculated as in previous section, the iron loss and PM eddy current loss are obtained by magnetic reluctance circuit and analytical model respectively. The main contribution of this section is the SD model which can be used for any Halbach array and magnetization directions. Moreover, the armature calculation method proposed in thesis can be easily adapted for any winding structures.
3. Based on computational fluid dynamics (CFD), the friction loss and heat transfer coefficient of HSAFPMMs are researched and the detailed equations are given in the thesis. Based on the previous study, the lumped parameters thermal network (LPTN) considering magnet-thermal coupling is developed. Finally, the accuracy of CFD model is validated by comparing the results with that obtained by LPTN. The main contributions of this section include the prediction of temperature in the airgap and the heat transfer coefficient via fitting method, which shows higher accuracy and can reduce the matrix dimension.
4. The vibration of HSAFPMMs is studied in this thesis. The reasons resulting in the vibration and noise are explained firstly. Moreover, the Maxwell tensor which is the main source of vibration is studied. Secondly, the differences of the calculation of nature frequency between radial flux and axial flux machines are pointed out. Afterwards, the nature frequency, stiffness and damping ration are calculated based on the thin plate theory. Finally, the frame velocity is obtained using mechanical network which considering the forces in different teeth. The work is then compared with the FE model.
5. The mechanical issues are examined by using analytical approach. More precisely, a new assembling approach is proposed based on the axial force research and the stability of rotor system are checked by rotor dynamics as well as the thickness of rotor back-plate. The rotor eccentricities are also considered in the thesis. The flux densities, flux linkages and back EMFs are modeled by SC approach. The main contribution of this section is the eccentricity model, which was firstly developed by SC approach, and the proposed model is fast and have acceptable accuracy.
6. The detailed assembling procedures of HSAFPM machine are reported in the thesis, it consists the detailed handing method of AMM stator core, Halbach PMs and windings. Afterwards, the back EMFs and temperature rise under direct current were tested to verified the models mentioned above. The new assembling approach in the thesis for the stator core and PMs was proposed, the results show that this approach is effective.