CONTACTOR AND METHOD FOR PREVENTING WELDING OF CONTACT

PROBLEM TO BE SOLVED: To provide a device and a method which prevent welding between a movable contact and a fixed contact in an electromagnetic contactor. SOLUTION: This contactor 10 has a fixed contact 42 and a movable contact and engages a contact to form a path of the current which flows in the contactor by excitation of an electromagnetic coil 82. Contacts are maintained in the closed position by supplying a low electric power to the coil 82 by using pulse width modulation. The contactor 10 prevents the welding of the contact by a composition of contact material under the low fault current, and is kept in the open position by using magnetic members 62 and 64 until the arc is extinguished by blowing open the contact and contact are sufficiently cooled down under the middle fault current to prevent from the contact from welding. Moreover, under a high fault current, a composition (32, 62 and 64 combined) which blows open the contact and separates an armature 70 from the coil is provided, and the contact is prevented from being reengaged until the coil is excited again.