| The high speed machine, due to its small volume, high efficiency and great power density, is one of the great concerns in electrical engineering. The PM machine is appropriate for high speed operation due to its simple structure and high power density. It is quite difficult to design such a high speed and high frequency machine than designing a common machine. From the point of view to reduce the centrifugal force and produce the required output power, the rotor should be slender. The rotor should have enough rigidity to avoid spaning the critical speed of bending mode for magnetic-bearing rotor. The rotor strength is more prominent for high-speed PM machine, beacause the PM is not able to withstand large centrifugal forces and must be encapsulated in some high-strength material. Therefore, strength and dynamic character analysis of rotor are key techniques for high-speed PM machine.The research work of this thesis is a part of the project"The distributed high speed generator drove by micro-turbines and its energy conversion system", which is supported by the National Natural Science Foundation of China (No. 50437010). The study of the thesis is concentrated to strength, dynamic characteristic analysis and combined design for high-speed rotor system. The main contents are listed as follows:(1) Rotor design of high-speed PM machine is investigated based on combined mechanical with electromagnetic and dynamic properties analysis. First, rotor external diameter can be considered according to the surface velocity. The variation range of rotor diameter is determined according to mechanical constraints based on stress analysis. Then, in accordance with output power, rotor structure and axial length are selected by electro-magnetic analysis. The rotor length is determined together with rigidity and dynamics requests. The end, the optimized design of the rotor structure is carried on based on strength, rigidity and the electromagnetism requests.(2) The nonlinear contact FEA model of rotor is established to calculate the stress for different operation conditions and determinate suitable interference fit between PM and enclosure. The satisfied strength structure of rotor is choosed by stress analysis.(3) In order to calculate the rotor critical speeds accurately, the FEA model of magnetic-bearing rotor is established, which influences of detrusion and rotational inertia are considered simultaneously. The anisotropic material properties in FEA model are definited. According to the suspension character of magnetic-bearing system, the magnetic-bearings stiffness in FEA model is obtained by exciting experiment. Influences of stiffness and structural parameters to critical speeds and vibration modes of rotor are analysed. The design method of rotor changing magnetic-bearing stiffness and design parameter to avoid resonance is investigated.(4) The FEA model of multi-span rotor system coupled by flexible couplings is established. The spring element simulates the axial, radial and torsional stiffness of elastic coupling. The influences of stiffness and structure parameters of the coupling on the critical speeds of rotor system are analyzed. The method to avoid resonance of rotor system through changing the structure parameter and supporting stiffness of parts is investigated.(5) Vibration is the bottleneck of stable operation for high-speed machine. The methods of reducing and suppression vibration are researched by vibration analysis. The combined FEA and Newmark method is used to calculate the non-linear unbalance response due to the unbalanced force. The simulation results of different vibration frequencies are verified by tests.(6) In the no-load and load conditions, the electrical and magnetic properties of motor and generator, vibration displacement, vibration spectrum, orbit of rotor and shafting, vibration acceleration of frame and so on are measured.
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