Contact contact form is divided into three point contact and line contact and contact
Point contact contact refers to two conductors in only a little or a very small area of contact on contact (such as ball in the face of a sphere, in the face of plane), the contact is between "point" contact with the "point".Under the same contact pressure, the unit pressure is big, therefore, smaller contact resistance can be obtained. But its poor heat dissipation condition, used in the large current is inappropriate. At the same time, the point contact mechanical strength is weak, only applies to the breaking load of the small contact. Such as much used in the following 10 a relay and contactor and automatic interlocking touch the top of the switch, general control circuit of contact in the form of point contact. Due to small contact area, ensure the working reliability of the contact pressure is lesser also.
Surface contact refers to the surface of the two conductor has a broad contact (such as plane to plane). The contact area and contact pressure are larger. Due to its contact there was no relative slipping between the contact surface in the process of opening and closing, cannot remove oxide film high resistance material, so in such a touch on the leading precious silver piece to be embedded. And surface contact contact resistance is not very stable, when the outside world to contact some damage or improper assembly slightly, will make contact resistance increase greatly. So this application form is less, only used for large current, contact pressure big occasions, such as fixed bus bars, the large capacity of contactor and circuit breaker of the main contact. Knife switch often takes the form of surface contact
Along the line of line contact refers to two conductors or narrower area of contact (such as cylinder to cylinder, cylinder to plane). Under the condition of the same pressure, the line of contact resistance is lower than the previous two. The reason for this is that contact pressure strength and the actual contact area was appropriate to cooperate.Surface contact contact points are more, but stress intensity is small, the point contact pressure intensity is high, but less contact point, so they contact resistance are larger than the line contact condition. In addition, the line contact easy has the sliding and rolling contact, so that contact can improve the working conditions. At the same time, the line contact contact manufacturing, adjusting and assembly are more convenient, thus has been widely used.Used in the medium of dozens to hundreds of Ann Ann current capacity of the electric equipment, such as contactor, automatic switch, and high voltage switch electrical main contactor.
