The Influence of Air Gap Thickness between the Stator and Rotor on Nuclear Main Pump

摘要

The canned motor pumps are commonly used as main umps in nuclear primary circuit systems, because the typically outward leakage clearance in general centrifugal pumps does not exist in the canned motor pumps. The longer air gap thickness between the motor stator and the rotor, the more cooling liquid flowing through the air gap, which results the heat exchange becomes better between the motor and the cooling liquid and the temperature rise of the motor is lower. These are all good for improving the motor efficiency at the angle of the view, the temperature rise. From another angle of the view, the electromagnetism, the longer thickness between the motor stator and the rotor, the weaker interaction between the stator and rotor magnetic fields, which results the Lorentz force becomes weaker and the torque becomes smaller, and also the motor efficiency becomes lower. Therefore, there is an optimum value of the air gap thickness between the stator and the rotor, to balance the temperature rise and the electromagnetism interaction. In this paper with the case of 30kW canned motor, the coupled analysis of the heat exchange and the electromagnetic performance was studied. The influence of the air gap thickness on the motor temperature rise and on the electromagnetic performance was discussed respectively, and then the optimum value of the air gap thickness was given.