Research On Rotor Structure Strength And Dynamics Of High-speed Permanent Magnet Motor

The High Speed Pm Machine has high efficiency and high power density,which is widely used in the fields of national defense technology and automobile industry.Due to its high speed and rising trend,it is difficult and challenging to meet the requirements of structural strength of rotor parts and analyze its dynamic characteristics in motor design.Once the design is not reasonable,it will cause the failure of rotor parts and resonance and other faults.Therefore,the rotor structure and dynamic characteristics of High Speed Pm Machine are of great significance to the safe operation of the rotor.In this paper,the rotor of a high-speed permanent magnet motor with rated speed of 35000 rpm is simulated,and the rotor strength and dynamics are studied thoroughly.Firstly,the structure of the tabular mount rotor and the built-in rotor of the High Speed Pm Machine is determined,and the optimal interference of the tabular mount rotor selected for the subject is 0.04 mm.The stress analysis of the inner rotor is carried out by using the equivalent ring rule.The influence factors of the strength of the attached rotor and the built-in rotor are studied,and finally the law that the equivalent stress of magnetic steel is proportional to the thickness of sheath is obtained.For the “one” shape built-in rotor,increasing the number of magnetic steel blocks and reinforcing bar thickness can only reduce the equivalent stress of the iron core but not the stress of the magnetic steel.Secondly,the solid element model of rotor is established.Given the boundary conditions,the first 6 natural frequencies of the rotor are extracted.According to the different operating conditions of the rotor of the High Speed Pm Machine,some factors affecting the pre-stress and critical speed of the rotor modes are studied,which is concluded that the effect of rotating centrifugal force on rotor mode is less than that of fluid-solid coupling force.The method of calculating the critical speed is studied in depth and compared with the finite element method,and it is judged that the rotor of the motor selected in this topic will not have resonance phenomenon and can run safely and stably.The control variable method is used to analyze several factors affecting the critical rotor speed,and the relationship between the critical rotor speed and shaft extension length,rotor diameter is inversely proportional,and the bearing stiffness is proportional.Finally,the mass centrifugal force of the rotor is estimated according to the quality grade of the rotor required by the engineering.Observe the first-order vibration shape of the rotor,apply mass centrifugal force to the center of the rotor,and obtain the unbalanced response curve and axis trajectory of the rotor.For the rigid rotor of this kind of High Speed Pm Machine,the first resonance will be generated when the frequency is close to 1100 hz with the gradual increase of the rotational speed.The correctness of the critical rotational speed obtained before is verified.The equivalent stress,life span and damage cloud map of the rotating shaft obtained by simulation meet the requirements.