Study Of The Coupled Electromagnetic-Mechanical Stress Field Of Permanent Magnet Synchronous Motor

Permanent magnet synchronous motor magnets are equipped on rotor, and rotor laminations have a large number of slots to separate flux. Sometimes, in order to have the self-starting ability, the rotor surface also installs cage bars, which makes the mechanical strength of the rotor weak further. The motor suffers from mechanical stresses, such as the electromagnetic force, thermal stress and the centrifugal force, when it works in multi-physics coupled field. Especially, the high-speed permanent magnet motor speed is up to tens or even hundreds of thousands per minute. Its rotor laminations and permanent magnets would suffer from huge centrifugal force, so the rotor strength problem is more serious.In order to check whether the permanent magnet synchronous motor rotor structure can meet the requirements of mechanical strength and plasticity under comprehensive stress in multi-physics coupled field, this thesis has a thoroughly investigation on the rotor coupled electromagnetic and mechanical stress field. A 22kW line-start permanent magnet synchronous motor (LSPMSM) and a 11kW high-speed motor are instanced.Firstly, permanent magnetic synchronous motor electromagnetic finite element analyses are carried out.2D electromagnetic models of LSPMSM and high-speed motor are built in ANSOFT Maxwell. Both dynamic characteristics of the LSPMSM under different conditions, such as unload starting, loaded starting, locked and overloaded and the static characteristics of the high-speed motor are calculated.Secondly, the fundamental theory of the the stress field is introduced. It includes the basic concepts of stress, strain, strength theory and main parameters of material mechanical properties, such as elastic modulus, Poisson’s ratio, yield limit. And the rotor stress is analyzed theoretically.Thirdly, analyses of stress fields in the LSPMSM under different conditions are carried out. Based on the LSPMSM electromagnetic simulation models and the calculation results, rotor stress fields of unload starting, loaded starting and overloaded are calculated through the Workbench coupled platform. The strains of the motor under extreme conditions are obtained.Finally, based on the high-speed motor simulation model, the static electromagnetic results are coupled to the stress field combined with material mechanics properties. The stress distribution on the rotor are obtained, and the structure strength of the sheath are checked. This method can be used to design the prototype of the high speed motor.