| High Speed Permanent Magnet Machines (HSPMMs) with merits of high power density and reduced volume, overcoming shortcomings of conventional machines such as high failure rate and difficult maintenance by reducing gears or bolts when working with high speed prime motors or loads, are widely used in various applications. A series of works on HSPMMs are expanded in this thesis.Firstly, an overview of current research status of HSPMM is presented in terms of the structures and materials, the loss and temperature rise calculation methods, rotor bearings, rotor strength and dynamics. Then the electromagnetic, mechanical and thermal limits on the sizing of the HSPMM are analyzed. Based on these works, the evolving features of machine rotating speeds and power rates under these limits are deduced analytically.Electromagnetic performance calculation methods of HSPMM under different control methods are investigated. Machine performances under brushless DC (BLDC) control, sinusoidal control and six-step control are compared to determine the suitable applications for each control method. Various parameter calculation methods for back electromotive force (EMF), resistances and inductances are presented. Feasible calculation methods for the surface mounted PM (SPM) machine and interior PM (IPM) machine are proposed.The causes of copper loss, iron loss, rotor loss and mechanical loss and their calculation methods are presented based on the proposed parameter calculation methods, considering the special features of HSPMM such as the skin effect. Electromagnetic losses of HSPMM with different control methods are calculated and compared based on the presented methods. The influence of air gap length on electromagnetic losses are investigated.Types of the HSPMM heat dissipation and their features are investigated. The CFD technology is used to build a fluid-solid coupled model to analyze the thermal field of the HSPMM. The HSPMM structure is optimized to reduce the rotor temperature rise. A lumped parameter thermal network (LPTN) model is proposed based on CFD results, then a parameter sensitivity analysis is performed on the rotor temperature. It is found that the rotor temperature rise is most sensitive to the air-gap length and the coercivity of the PM.Different rotor materials and their characteristics and applicable circumstances are analyzed. Engineering rotor strength design methods for the SPM rotor and the IPM rotor are proposed respectively. The rotor strength is investigated further by involving FEM. Then the analysis methods of rotor dynamics of the HSPMM are discussed. Natural frequencies and critical speeds of the rotor under different bearing stiffness are calculated by FEM.The coupling effects for the HSPMM are investigated. An integrated design method based on iterations is proposed, which can calculate the electromagnetic performances, temperature rises, rotor strength and dynamics performances in a decoupled way. Prototypes with power/speed ratings of 75 kW/36 kr/min,140 kW/24 kr/min and 300 kW/18 kr/min for the turbo-blower application are designed based on the proposed integrated design method.Three candidates with different structures are obtained for the 140 kW machine. Performances of the three candidates are compared, showing the most suitable operating condition for each candidate.Three prototypes with different rated power are manufactured. Test bench for the prototypes is built by using the power analyzer. A test method under the load conditions is proposed to measure the back EMF constant, the inductances, temperature rises and electromagnetic torque. Measured results are compared with the calculated results, showing that the integrated design method is feasible and with acceptable accuracy. |
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