Classification and Application of Electrical Contacts Silver Contacts

Release time：

2022-10-31 09:47

Classification of electrical contacts
According to the contact mode, electrical contacts can be divided into the following three types
1) Secure the connection contacts. It refers to the electrical contact that cannot move relative between the contact and connected conductors. Such as bus connector, lead connection of electrical equipment, etc.
2) Sliding contact. The contact mode in which the guide bodies can keep in contact with each other but allow one contact surface to move relative to the other is called sliding contact.
For example, the expansion joint of the bus and the brush of the motor are in sliding contact.
3) Breakable contact. If a contact can be closed or opened during normal operation, it is called a breakable contact. The contacts of various switches are disconnectable contacts.
(2) Breakable contacts are classified according to their structure:
1) Butt contact.
Butt contact refers to plane butt joint between moving contact and fixed contact. This contact is more common in old multi oil switches. It is characterized by simple structure and fast crushing speed.
Disadvantages are: the contact surface is unstable, which changes greatly with the change of pressure; No self-cleaning effect during opening and closing; When moving contact and static contact contact, it is easy to rebound. Without auxiliary contact, the main contact is easy to burn out.
2) Socket contact.
Socket contacts are widely used in various low oil circuit breakers, and their structures are shown in the figure below. It has dynamic and static contacts. The moving contact is rod shaped, and the static contact is composed of a plurality of contact fingers, each of which passes through the current; The contact pressure is maintained by spring 2. The advantages of socket contact are: self cleaning function during switching; In the closed state, the contact rod of the moving contact is in contact with the inner side of the contact finger of the static contact. When opening and closing, the arc appears at the ends of the moving contact and the static contact. Therefore, the contact resistance can remain stable in the closed state. When the socket contact passes the short-circuit current, the current flows in the same direction between the fingers and between the fingers and the moving contact rod, so the electromotive force is suction, which increases the pressure between the moving contact and the static contact, and ensures good contact. Therefore, the electrical stability of socket contacts is high. Since the pressure direction of the contact and the moving direction of the moving contact are perpendicular to each other, the bounce is very small when the contact is closed; The end of the contact finger can also be welded with the alloy with high melting point, so that when the short-circuit current is cut off, the metal vapor is reduced.
The main disadvantages of socket contact are: complex structure and difficult manufacturing. When the rated current increases, the closing force of the mechanism will increase (because the pressure of fingers on the moving contact needs to be increased, so the closing resistance will increase); The socket contacts also open longer.