Study Of Eddy Losses And Thermal Stress On Shielded CAN In Canned Motor With New Phase-shifted Structure

The canned motor called packless pump motor, which is equipped with metal shieldingcan has been widely used in the nuclear and chemical industry. It has many advantages such ascompletely leak-free, safe, reliable, low maintenance and low noise etc. The shielding can is agood weldability, corrosion resistance, non-magnetic metal material, cutting the rotating statormagnetic field generating induced electromotive force and eddy current, causing eddy losses,high temperature rise and thermal stress, which affects the security of motor. this paperpresents a new kind two-cell phase-shifted canned motor structure based on the idea ofeliminating induced electromotive force on the shielded can. The two coaxial connected statorwindings affected by the rotating magnetic field of induction motor circumferentially changingpole pitch in space，produce two equal but opposite induction electromotive force in theshared stator shielded can，which can cancel each other，suppress the eddy losses, lowertemperature rise on it, and improve the reliability and safety of the canned motor．Firstly, reviewed the development of the packless pump motor, introduces the operatingprinciples and characteristics of the mechanical structure. Described the phase-shiftedstructure’s feasiblity through calculating the formula of eddy loss. Compared with thetraditional one and summarized the characteristics of the new structure of the phase-shiftedmotor. Designed and completed the verification experiment for the phase-shifted motor.Secondly, analysed the traditional and novel phase-shifted motor eddy current field usingansoft by the finite element analysis method. Compared the results including stator core losses,copper losses，eddy losses on the can and the distribution of the eddy current with thetraditional structure’s. Summarized the reason of the unexpected effect, and proposed theimprovement ideas.Finally, Analyzed the temperature rise and thermal stress of the traditional andphase-shifted motor’s can using Ansys Workbench co-simulation method. Load the lossescurve of main parts to the temperature field simulation model, then calculated the temperaturedistribution characteristics and the temperature variation curve of motor components includingiron core, winding, casing and the shielding sleeve, from starting to rated opreation. Comparedthe temperature distribution characteristic of the phase-shifted motor with the traditional. Then,based on the temperature characteristics, simulated the thermal stress on the can when it’s starting and rated running. It’s showed that the phase-shifted packless pump motor has abetter stress character than the traditional through comparison of the stress field result. Soit’s concluded that the phase-shifted motor has higher safety and more reliable.