Contactor is used for protection machine from the circuit which has a much lower power level than the switched circuit, also used to control electric motor, lighting, capacitor, heating. In fact, contactor is one electrically controlled switch, can used in many range voltage and thousands of Amps by AC or DC. It is for making breaking, frequently starting & machine interlocking device, it becomes the delay contactor, mechanical interlocking contactor, star-detla starter. With the thermal overload relay, it is combined into the electromagnetic starter. The contactor is produced according to IEC947-2, VDE0660 & BS5452.