Analysis and design of 24V DC control contactor

Traditionally, the AC contactor was controlled by exerting continuous DC current to the coil in both magnetic attracting and maintaining process. This would result in the electromagnetic force overloaded, and the wear between the moving contact and static contact intensified. As time went on, the coil heating would become serious, and the lifespan of contactors would be reduced. Therefore, PWM and DC-DC control schemes were used in this paper to achieve the purpose of saving energy and prolong the lifespan of contactors. The design process of PWM and DC-DC control circuits was introduced. By comparing PWM and DC-DC control schemes in performance and cost evaluation, the final plan was determined. Also the system software was completed. The electronic control unit and the whole contactor machine were tested. Compared with contactors by coil direct control, our contactor can save 43.19% energy, and extend the electrical life by 19.30% on average. Compared with similar contactors by electronic control, our contactor can save 17.5% energy, and extend the electrical life by 6.66% on average.