How to Wire a Contactor: 8 Steps (with Pictures) - wikiHow Jul 28, 2015These voltages must be electrically isolated from the standard 120 volts AC. Contactors are used to provide this isolation. Contactors use 120 volt standard power to energize a magnetic coil, which causes a set of internal contacts to close and provide higher power to the equipment. Use these tips to learn how to wire a contactor.Views: 242K How To Wire Contactor And Overload Relay - Contactor How to Wire a 3 Phase Motor With Contactor and Overload Relay. Message: I hope you learn some thing from this post and now you will be able to wire a contactor for 3 phase motor, however i will soon write about more power wiring diagram.