What is general relay? General relay is an abstract concept in physics. Many people may not know what is general relay. Relays are usually used in automatic control circuits. In fact, it is an "automatic switch" that uses a small current to control the operation of a large current. Therefore, it plays the functions of automatic regulation, safety protection and circuit conversion in the circuit.
Functions of general relay:
Relay is an electrical control device, which causes a predetermined step change in the electrical output circuit when the input becomes a specific requirement. It interacts between the control system (also known as input loop) and the controlled system (also known as output loop). Usually used in automatic control circuit, it is actually an "automatic switch", which uses small current to control high current operation. Therefore, it plays the functions of automatic regulation, safety protection and circuit conversion in the circuit.
1. Expand the control range: if the control signal of the multi contact relay reaches a certain value, multiple circuits can be switched, disconnected and opened at the same time according to different forms of contact groups.
2. Amplification: for example, sensitive relay, intermediate relay, etc., a small control quantity and high power control circuit can be used.
3. Integrated signal: for example, when multiple control signals are input to the multi winding relay in the specified form, the comparison is integrated to achieve the predetermined control effect.
4. Automatic remote control and monitoring: for example, relays on automation equipment and other electrical appliances can form program control circuits to realize automatic operation.
Working principle of general power relay:
Power relay is a device that can be switched by one or more electric output circuits when the input (or excitation) meets some specific conditions. It can be used as the directional element of zero sequence current protection in neutral point direct grounding system. The action process of contacts can be divided into two parts: contact closure and contact disconnection, that is, the process of pull in and release of relays, which are cycled and switched at a certain frequency, resulting in contact separation and closure. There are many special physical and chemical phenomena in the process of contact closing and opening, such as contact resistance, contact jitter and arc discharge.
The action principle of the contact when closing: 1. When the dynamic and static contacts of the relay contact each other, the contact rebound occurs, that is, the uncontrolled gap opening and closing. At this time, the Joule heat generated by the arc and the energized current greatly affects the opening and closing ability of the relay; 2. When the contact is opened and the load is cut off, dazzling sparks and arcs will be generated, causing great damage to the contact until the arc voltage drops below the minimum arc voltage.
When using the relay, it should be emphasized that if the relay falls or is impacted accidentally during installation, its electrical and mechanical parameters may change greatly. If there are serious hidden dangers, try to detect them in time before use.