Sensing methods applicable to a 3-phase load transfer contactor

A LOAD transfer contactor is employed in an electric circuit as illustrated in Fig. 1. As is evident from the figure, the purpose of the contactor is to connect a bank of loads to one of two possible power sources. While the contactor could be either manually or automatically controlled, only automatically controlled self-contained contactors are considered in this paper. Also, the contactor could be employed in either a single-phase or a 3-phase circuit, but this paper deals only with 3-phase circuits.