Research On Problems Of Electromagnetic And Thermal For Cans In Megawatt Double Canned Induction Motors

Megawatt double canned induction motors are the key power equipment of the nuclear power system.Cans are specific structures in double canned induction motors.Due to the addition of cans,the electromagnetic design of this kind of motors is different from conventional motors.Thus,the accurate analysis of the magnetic,thermal and force problem is the key to the electromagnetic design of this type of motors.A megawatt double canned induction motor is taken as the research object,and problems of can losses,temperature field,dynamic analysis and electromagnetic force are researched combined with the research situation of can electromagnetic,and thermal.The current calculation method of can losses cannot consider the magnetic penetration depth,can eddy current losses stretched out the core segment,circulating current losses between the can and other end structures are rarely reported.Aiming at these problems,the distribution of can losses is researched.A new calculation method of can losses within the core segment which can consider the magnetic penetration depth and end effect of eddy current is proposed.The superposition method is adopted to separate the can eddy current losses stretched out the core segment and circulating current losses between the can and other end structures.The variation of can eddy current losses within the core segment in the entire speed range is revealed.The amplitude and distribution of end can current density are provided,and the influence of the circulating current between the can and other end structures on the amplitude and path of end can current is mastered.The blank of the research on can eddy current losses stretched out the core segment and circulating current losses between the can and other end structures is filled up.On this basis,the relationship between can eddy current losses,circulating current losses and can materials,support cylinder materials,tapered ring materials,clamping plant materials are revealed.The influences of can thicknesses on can eddy current losses,circulating current losses are obtained.Based on these analyses,a decrease method of can losses is proposed and the contribution of this method reducing can losses is provided.The influence of cans on the heat source is studied.Through the research on the nuclear pump cooling system,the inlet boundary condition of the temperature field of double canned induction motors is obtained.The temperature field of double canned induction motors is calculated by finite element method.The distribution of can temperature field is obtained.The characteristics of temperature changes of each structure of double canned induction motors are revealed.The influence of can losses on the motor temperature field is obtained.The relationship between the temperature map,maximum temperature and cooling condition is mastered.Based on this,the optimal cooling condition of double canned induction motors is provided.The mathematical model of double canned induction motors is proposed with the consideration of the stator and rotor can.The voltage equation,flux equation,electromagnetic torque equation and mechanical characteristic equation are established.The calculation method of each parameter in mathematical model is provided.The dynamic process of double canned induction motors is analyzed.The influence of power voltage on motor performance is clarified.The sensitivity threshold of voltage dropped is given.The calculation results and computing time are compared with the flux and simulink co-simulation model.The rationality and high efficiency of mathematical model provided in this paper are verified.The electromagnetic force densities of the stator can,rotor can,stator windings and rotor windings are calculated by the Lorentz force method.The spatial distribution differences of the stator can electromagnetic force density and rotor can electromagnetic force density and its reason are revealed.The dangerous position of the local force of the stator can and rotor can is found.The influence of cans on stator winding electromagnetic force density is studied.The effects of can materials,support cylinder and tapered ring materials and circulating current on the can electromagnetic force density are clarified.The decreasing degree of new method proposed in this paper reducing the can electromagnetic force is provided.The theoretical basis is obtained for the sealing performance of double canned induction motors.