power relay contact system

For a contact power relay, the contact is its actuator, which is the part it uses to tear and connect the circuit: the reliability and life of the power relay's work depend to a large extent on the quality of the contact's work. Therefore, we must pay full attention to this problem in order to correctly design and use it to provide the most reliable automatic devices for national economy and national defense construction.

There are four working states of contacts: (1) closed state; (2) open process; (3) open state; (4) closed process. 

The basic requirements for its work are simply: "divide" reliably and "close" reliably. Ideally, the contactWhen it is in the closed state, it is best to conduct electricity like a whole conductor: when it is disconnected, the current immediately becomes zero; when it is closed, the circuit immediately conducts normally; when it is in the open state, it has good insulation properties and can withstand higher voltages. . However, "contradiction exists universally", and in the simple form of movement such as the connection and disconnection of contacts (ie, integration and separation), many special physical and chemical phenomena occur, which are full of contradictions and struggles. For example, when the conduction is closed, the contact part always has contact resistance,

When this resistance is too large to a certain extent, it may lead to a power failure (the on-current becomes too small); it is often accompanied by arcs or sparks when it is disconnected, and in severe cases, it may cut off continuously and cause the entire electrical appliance or the entire equipment to burn; In the process, there will be mechanical bumps, which will cause the contacts to bounce and a series of very short arcs will appear, and even the contacts will be welded together; if the insulation strength is not enough in the disconnected state, it may be re-breakdown by overvoltage.

"All contradictions exist objectively, and our task is to reflect and resolve them as accurately as possible." To this end, we will first analyze the contradictory essence of each working stage of the contact according to the different working states, and then generalize and analyze its overall problems.