Numerical analysis on temperature rise law of electromagnetic coils based on multi-physics field coupling method

Abstract

Coil overheating leads to failures and shortened service life of electromagnetic devices such as clutches. This study establishes a 3D transient electro-thermal coupling model for the coil of an automotive air-conditioning electromagnetic clutch, considering temperature-dependent resistance. The model includes a current module for current distribution and Joule heat calculation, and a heat transfer module for solid heat conduction, convection and radiation. Finally, using the established model, this paper calculates and analyzes the temperature and current evolution of the electromagnetic coil during startup under an ambient temperature of 323.15 K and a constant voltage of 12 V. The results indicate that the coil temperature, current and other parameters change sharply in the initial stage and then tend to be stable. The current drops rapidly from 3.2047 A to 2.7601 A within 10 s, and stabilizes at approximately 2.7449 A at t = 100 s. The resistance variation caused by temperature rise exerts a remarkable effect on the current and temperature field distribution of the coil. The temperature rises are 15.58°C and 13.39°C under constant resistance and temperature-dependent resistance conditions, with a relative difference of 16.36%. The corresponding currents are 3.2047 A and 2.7449 A, differing by 16.75%.