Experimental Study on Contact Behavior of Tilted Contact in Air Circuit Breaker

Short-time withstanding current is a key parameter of air circuit breakers. Due to the structure of multiple parallel contacts, the outer movable conductors tilt and slide seriously when withstanding the large short-circuit current. This paper is aimed to investigate the contact behavior of the tilted contact. A new designed experimental setup to measure the minimum repulsion current and the contact resistance of the tilted contact is developed. Contact force and tilt angle can also be measured and adjusted. Based on the measured results and the impression marks of the tilted contact, it is concluded that the repulsion force and the contact resistance are increased seriously when the contact is tilted. During the contact tilting process, the contact type is changed from the line contact to the point contact and the contact center is offset to the edge of the movable contact. In addition, with the help of contact bridge model, it is also found that the contact type transition plays a dominant role on the increase of the repulsion force and contact resistance.