The Importance of the Contacts in the Relay

The relay is an electrical appliance that controls on and off of the current in the circuit according to the electrical signal input from the outside world. It can be said that it is a "switch", and the current in the control circuit depends on the "open" and "close" of relay contact part. The reliability and service life of the relay to a large extent depend on how well the contacts work. Therefore, it is necessary to understand and recognize contacts of the relay in order to use it correctly.

 

Relay contact is the most important part of the relay. In the state of normally open or closed, contact part of relay can be simply understood as contact of switch that is normally open or closed to make the signal on or off. Usually the gradient electronic contact can make the relay avoid the contact gap adjustment. It can make up the contact point contact caused by small electronic contact. Of course, their performance is greatly affected by the some factors, such as the material of the contact and type of load and so on.

 

 

Most contacts used in daily life are metal silver contacts. The working process of relay contact includes disconnection process, disconnection state, closing process, and closing state. The requirement for its work is to be able to reliably make and break. Whether the contacts can work reliably or not is contact resistance of the contacts that has the greatest impact. No matter how good the contact is, it is impossible to have no contact resistance, so the contact resistance of the contact is objective.

 

The factors that affect the contact resistance of relay contacts include the size of contact pressure, selection and use of metal contact material, form of contact structure, manufacturing process of the contact, use environment of the contact and the degree of daily maintenance, etc. For relay users, in addition to correct selection, it is also necessary to ensure that the use environment of the relay meets the requirements. Make the relay try to avoid the corrosion of water vapor, dust, and harmful gas, and take measures to reduce the contamination of the contacts, so as to ensure the stability of the contact resistance, and improve the reliability of the contact stamped parts.

 

Another form of contact resistance is film resistance. Because the contacts of relay are exposed to the air for a long time, there will always be compounds produced by dust, water vapor, and chemical gases, which will adhere to the contacts to form a thin film. This is the so-called membrane resistance. So, the conductivity of contacts stamping components will become very poor, and even there is non-conductive in severe cases. Sometimes this phenomenon will be seen in the use. Although the surface of a pair of relay contacts appears to be closed and contacted, the circuit that it controls is not connected, or it is switched on and off, or it is sometimes good and sometimes bad, which will affect the normal operation of the circuit controlled, and it will make it extremely difficult to find fault points.