What Is a Power Relay?

Power relay (power relay) is a device that can generate a jump in one or more electrical output circuits when the input (or excitation) meets certain prescribed conditions. Can be used in the neutral point direct grounding system, as the directional element of zero sequence current protection.

Home appliances such as air conditioners often use power relays. The more common ones are the OMRON G4A type and the Panasonic JM type. The most common failure mode of these types of relays is contact bonding ^[1]

The action process of the contact can be divided into two parts: contact closing and contact opening, that is, the pull-in and release processes of the relay. They are cyclically switched at a certain frequency to form the contact opening and closing phenomenon. In the process of contact closure and opening, there are many special physical and chemical phenomena, such as contact resistance, contact jitter and arc.

Principle of action when contacts are closed

When the moving contact and the static contact of the relay are in contact with each other, the contact bounces, that is, the uncontrolled gap opening and closing, and the Joule heat generated by the arc and current at this time greatly affects the relay Opening and closing ability.

Principle of action when contacts are open

When the contact opens and cuts off the load, dazzling sparks and arcs will be generated. The generated arc should continue until the arc voltage drops below the minimum arc voltage value, which will cause greater damage to the contact. The different contact materials and the size of the contact gap directly affect the emission state of the arc electrons and the easiness of occurrence, so they are important conditions for determining the arc. ^[2]

Micro power relay: when contact

Contacts have different electrical contact characteristics and failure phenomena under different load types and different load magnitude conditions. The types of load include capacitive load, motor load, inductive load, DC load, low-level load and dry circuit. Different load types each have their more common forms of failure.

The size of the load is closely related to the failure form and failure mechanism. Under the load of medium power or higher, contact bonding is easy to occur.

There are many defects in the quality of the relay mark pad printing. The specific situation is complex. It may occur single or may occur simultaneously. Find out the cause of the problem, and eliminate the fault one by one, so that the quality of the relay mark pad printing continues to improve ^[3] .