Primary Heat Transport (PHT) pumps in a nuclear power plant are required to be operated with minimum maintenance during their entire life of operation. Thus usage of a gland seal pack operating at high temperature and pressure is not feasible and therefore PHT pumps use thin cans that separate the rotor and stators in order to achieve zero leakage of radioactive coolants. Squirrel cage induction motors having very thin and strong can materials enveloping both rotor and stator are called canned motors. These cans should withstand high pressure of the operating fluid. They should be made of non-magnetic materials and have minimum thickness so that eddy current losses in the cans are as minimum as possible. Limiting hot spot temperatures is the major requirement of thermal design of cage induction motors. Canned motor is an important application of cage induction motor. In a nuclear power plant the maximum hot spot temperatures of motors of Primary Heat Transfer (PHT) pumps have to be limited to be within permissible values which are acceptable to nuclear operators for all the operating conditions. Also motors of PHT pumps have very high power densities, pump liquids at high temperatures and high pressures and are operated for most severe operational transients. Thus thermal design of cage induction motors with cans for which the motors need to be qualified from safety considerations has great importance in the nuclear industry. In the paper, initially thermal design of squirrel cage induction motor a type of totally enclosed fan cooled motor is explained with some assumptions. The thermal design of motor is done using thermal network model and finite element method. The analysis results of above two methods are compared. Later this method will be applied to canned motor for nuclear safety.
展开▼
