Thermal analysis of contactors with voltage feedback system

Based on the similarities and differences of thermal analysis issues between the intelligent and general AC contactors, a thermal analysis model considering influences of both main conductor loop and electromagnetic system is constructed for the intelligent contactor. According to the alternating turn-on and turn-off characteristics of the coil circuit controlled by the pulse-width modulation, the model constructs a set of differential equations with magnetic circuit method to describe characteristics of the electromagnetic system and its thermal source model by subsequently solution to these equations. Linking with the features common of the two kinds of contactors, the extension of the thermal analysis method of general contactor to intelligent contactor is demonstrated as well. With the proposed thermal analysis model, the steady-state temperature rise of an actual intelligent contactor by an optimized coil and core parameter is evaluated and compared with the measurement. The analysis results show that the temperature rise of the miniaturized electromagnetic system of the intelligent AC contactor can be decreased effectively compared with the general AC contactor to meet the requirements of national standards.