Analysis and Research on Magnetic and Eccentric Characteristics of CRDM Motor

Control Rod Drive Mechanism (CRDM) of the nuclear power plant reactor uses synchronous motor as the key component for electromechanical energy conversion. The unilateral radial magnetic pull of the motor would lead to deformation of motor shaft system and aggravate the bearing wear, which has an important influence on the life of CRDM and the reliability of nuclear reactor operation. In this paper, the mechanism of radial static eccentricity, radial dynamic eccentricity and inclined eccentricity of CRDM motor is analyzed, and the mathematical models for calculating radial and axial magnetic pull are established. The variation rules of radial and axial magnetic pull and their relationship with eccentricity are obtained. The result shows that radial magnetic pull is significantly larger than axial magnetic force for CRDM motor, and is linearly proportional to the eccentricity of the rotor center and nonlinearly proportional to the maximum tilt eccentricity at both ends of the rotor. The conclusion can provide guidance and basis for the optimization and improvement of CRDM motor and shaft system structure design.