Study On Combined Design And Dynamic Characteristics Of Rotor For MW Class High-Speed Permanent Magnet Motor

High-speed motor has high power density,high efficiency,small size and can drive high-speed load directly.Permanent magnet motor is the first choice of high-speed motor in China because of its wide speed range,high output power and high excitation loss efficiency.However,high-speed motor design is much more complex than conventional motor.The rotor is generally designed to be elongated,while the rotor should have good stiffness and power characteristics.Especially for high-power high-speed motor(output power above MW,speed above 10000 r/min),the rotor will be elongated to ensure better working characteristics of the rotor as it crosses the first order of bending resonance.For permanent magnet motor,its electromagnetic problem is more prominent,because the rotor as the main source of electromagnetic power of motor,not only to ensure that the motor has sufficient output power,but also to ensure the strength of permanent magnet rotor must be considered comprehensively.In this thesis,a high-power and high-speed permanent magnet motor for a direct drive turbine compressor is studied in detail,including the following aspects:(1)In this thesis,the multi-field comprehensive design method of rotor of high-power high speed permanent magnet motor is studied and analyzed,and the key points of rotor design of high-power high speed permanent magnet motor are clarified.(2)Based on electromagnetic power,mechanical strength and bearing-rotor dynamics,a high-power and high-speed built-in permanent magnet rotor model with a rated power of2500 k W and a rated speed of 13500 r/min was designed.First,by giving priority to the optimal length-diameter ratio of high-speed motors,the overall good mechanical characteristics of the motor are guaranteed;Secondly,by prioritizing the electromagnetic design of the rotor structure,the output power requirements of the high-power motor are met,and the stress intensity of the obtained motor rotor structure scheme is compared to meet the stress intensity requirements of the rotor design scheme.Finally,considering the influence of oil film force and inertial mass force of sliding bearing,the vibration mode,critical speed and unbalance response of the rotor are accurately calculated,to adjust the rotor structural parameters,improve the rotor working performance,and ensure the safety and stability of motor operation.(3)By studying the influence of sliding bearings on the vibration characteristics of the rotor system,it is found that more accurate simulation results can be obtained by using the oil-film force coupling method,to explore the influence of different rotor parameters and bearing parameters on rotor amplitude and critical speed,to adjust the rotor design structural parameters and ensure the safety and stability of motor operation.(4)The unbalanced force and unbalanced response of flexible rotor are studied and analyzed.By using Newmark integral method and ANSYS harmonic response analysis module,the unbalanced force and unbalanced response of motor rotor under different eccentricities are calculated.