Investigation on the accurate calculation of the temperature field of permanent magnet governor and the optimization method of heat conduction

Abstract

Since the heat resistance capacity of permanent magnet governor's key components is poor and high temperature will affect the governor's lifespan, it is extremely necessary to conduct the study on temperature field. Taking the 250 kW permanent magnet governor which is researched and developed independently as an example, the present paper focuses on the present problem of magnetic-thermal unilateralism coupling field's failure of precisely calculating the transmission torque and temperature distribution. The paper proposes adopting bidirectional coupling calculation method, considering temperature's effect on the performance of magnetizer as well as permanent magnet's magnetic field and magnetic characteristics’ influence on temperature field, so as to realize the accurate calculation of magnetic field and thermal field. In addition, simulation results of unilateralism and bidirectional coupling have been verified through experiments. It turns out that the magnetic-thermal bidirectional coupling calculation is closer to the temperature value measured in the experiment, with an error only within 2%, which proves that the bidirectional coupling calculation is more accurate and is of great importance to guiding the design of permanent magnet governor's magnetic field. Meanwhile, as most of the current simulation models neglect the air gap of the connection between the actual magnetizer and the steel disc's rigging screw, the calculation of temperature field is not precise enough. The present paper has conducted a temperature simulation comparison between no air film and air films of varying thicknesses. In this way, it is discovered that the thickness of air film exerts an apparent effect on temperature field, with the highest temperature difference up to 22 ℃. Aiming at the issue of air film's reduction of heat conduction performance, the present paper proposes that the magnetizer disc and steel disc employ explosive welding to form composite board craft, so as to optimize heat condition. In addition, experiments have been conducted for verification. It has been proved that the temperature in the situation where explosive welding heat conduction optimization method is used is lower than the temperature when air film's thickness is 0.15 mm by 7–10 ℃, thereby greatly increasing the efficiency of heat conduction and guaranteeing the steady as well as reliable operation of permanent magnet governor. Keywords: Magnetic-thermal coupling, Temperature field, Explosive welding, Permanent magnet governor