Analysis Of CAN Losses And Electromagnetic Force In Canned Induction Motor For Unclear Pump

Canned induction motors are the key power devices of the nuclear power plant.In the background that the third generation nuclear power plant is developing rapidly in China,the design and research of canned induction motor have become an important issue in the development of the third generation nuclear power technology.Canned induction motors have a large unit capacity,work in a special environment.When the motors work in different condition,alternating magnetic field produce large can losses.The accurate calculation of can losses is very important for the electromagnetic design of canned induction motors.In addition,due to the interaction of magnetic flux density and current density,a large electromagnetic force is generated in the can and the stator winding end region.Electromagnetic force can deform and damage the different structures of the motors,posing a great threat to the safe operation of the motors.In this paper,a 5.5MW canned induction motor for nuclear pump is taken as the research object,and the eddy can losses and electromagnetic force of the can and the electromagnetic force in the end winding region are studied.The mechanism of can losses is researched,and the semi-analytical method for calculating can losses is proposed,which can calculate can losses accurately and quickly.The 2-D time-harmonic finite element model are established,and the flux density distribution on can surface is calculated under no load condition,rated load condition and start time,and analysis the each harmonic amplitude.On the basis,the analytical formula of the can losses is deduced,and the can losses under different condition are calculated.By comparing with the result of transient magnetic finite element method,the correctness of the semi-analytical method is verified.The calculating model for electromagnetic force of can is established,combining the 2-D transient magnetic finite element method and the Lorentz force formula,the distribution of the electromagnetic force density of can is obtained.The variation of magnetic flux density,current density and electromagnetic force density with time of different typical points of can in one cycle under rated load is studied.The amplitude values of the electromagnetic force density of the cans are obtained respectively.The 3-D time-harmonic finite element model for electromagnetic force of stator winding end region is established,the electromagnetic force density distribution of stator winding end region is obtained.On the basis,a method of using coordinate transformation to obtain the electromagnetic force density in different directions of the straight section and the involute section of the end winding are proposed,electromagnetic force density distribution of the different directions on different regions is obtained.