Permanent-Magnet Equivalent Model of Calculating Relay´s Static Attractive Torque Characteristics by Finite Element Method

The permanent magnet (PM) is the key part of the relay. This paper aims to solve the problem of the uneven magnetization for the PM with nonlinear demagnetization curve after magnetizing and demagnetizing. A method partitioning the PM along the magnetization direction and the vertical direction of magnetization according to the condition of the specific magnetization of the PM was presented. By this method, the demagnetization model of the PM was built, the state of the PM magnetization was simulated under the demagnetizing magnetic intensity, and the recoil line and its initial point of each partition of the PM were obtained. Then the characteristic of the recoil line of each partition was used as its magnetic characteristic for the equivalent model of the PM to calculate the static torque characteristics under the demagnetizing magnetic field. Finally, the static torque characteristics of simulation and experiment were compared and the validity of the equivalent model presented was verified.