Field-Circuit Coupled Method Analysis For Electromagnetic Devices And Calculation Of Temperature Field

The DC bias magnetization phenomena is harmful to the characteristics of the transformers on line. It causes the distortion of magnetizing current and the increasing of harmonics leakage magnetic flux and corresponding losses, which in turn result in a series of problems such as the local overheating, insulation damage and system voltage drop. However, the mechanism analysis and the analysis in quantities are still in initial stage as well as the effect of DC bias magnetization has not fully considered in the process of the transformer design. The actual operation of the flameproof motor is also a very complex physical process. The losses are produced inevitably by the motor on operation. The majority of these losses will cause overheating eventually which will increase the temperature. The temperature rise in flameproof induction motor may be harmful for the insulation which directly determines the operation life of the motor and the reliability. With the improvement of electromagnetic theory, the mature of heat transfer knowledge and the development of computer technology, using the fast and convenient method to calculate the electromagnetic and temperature fields accurately in these electromagnetic devices is also imperatively.Based on the principle of DC bias magnetization, this paper uses the pairs of Epstein square coil equipment to further study the core hysteresis loop under the conditions of different operating point and different levels of bias. The hysteresis loop and iron loss curve of the ferromagnetic material under DC bias and AC combined action in actual DC bias are obtained. Taking the saturation characteristics of ferromagnetic materials into account, this paper use the circuit method and the field-circuit coupled method to simulate and calculate the magnetizing current of transformer in the conditions of the DC bias magnetization respectively. The field-circuit coupled model is more practical significance in engineering by comparing the two kinds of simulation results. Then, the loss curve is input to the transformer circuit-field coupled model. Based on the magnetic field calculations, the core loss is calculated and analyzed by programming. Then, the electromagnetic distribution, electromagnetic torque and current of three-phase flameproof induction motor are simulated by using the field-circuit coupled method. As a result, the operation performance of the flameproof motor is calculated. The results are consistent with the design. It is further to validate the correctness of field-circuit coupled method as well as the universality and practicality.This paper combines the knowledge of heat transfer and the finite element method with the actual performance of the motor. The equivalent coefficient of heat conductivity and the coefficient of heat convection in the motor are determined. The 3-D temperature of the flameproof induction motor is calculated by using the finite element method. It can be accurately understanding of the transient temperature distribution of the motor through the calculation of the temperature field in this motor. It is a powerful analytical tool in guiding the design of motor.