The principle of power relay
A power relay is a device that can generate jumps in one or more electrical output circuits when the input quantity (or excitation quantity) meets certain specified conditions. It can be used in the neutral point directly grounded system as a directional element for zero-sequence current protection.
The working principle of the power relay is that when a certain voltage or current is applied to both ends of the power relay coil, the magnetic flux generated by the coil passes through the magnetic circuit composed of the iron core, the yoke, the armature, and the working air gap of the magnetic circuit. Suction to the pole face of the iron core, thereby pushing the normally closed contact to disconnect and the normally open contact to close; when the voltage or current across the coil is less than a certain value, and the mechanical reaction force is greater than the electromagnetic attraction force, the armature returns to the initial state, normally The open contact is off and the normally closed contact is on.
Contact principle of power relay
A power relay is a device that can switch in one or more electrical output circuits when the input (or excitation) meets some specific conditions. It can be used in the neutral point directly grounded system as a directional element for zero-sequence current protection.
The action process of the contact can be divided into two parts: the contact closure and the contact opening, that is, the pull-in and release process of the relay, which is cyclically switched at a certain frequency to form the contact opening and closing phenomenon. During the closing and opening of contacts, there are many special physical and chemical phenomena such as contact resistance, contact chatter, and arcing.
The principle of action when the contacts are closed
When the moving contacts and static contacts of the relay are in contact with each other, contact rebound occurs, that is, the uncontrolled opening and closing of the gap occurs. The arc and the Joule heat generated by the energized current at this time greatly affect the opening and closing ability of the relay.
Principles of action when contacts are opened
When the contacts are opened and the load is cut off, dazzling sparks and arcs are generated, and arcing occurs until the arc voltage drops below the minimum arc voltage value, which causes large damage to the contacts. Different contact materials and contact gap dimensions directly affect the radiation state of arc electrons and the ease of occurrence, so they are important conditions for determining arcing.
The role of power relay
Power relays have the advantages of fast action, stable operation, long service life, and small size. Widely used in power protection, automation, motion, remote control, measurement, and communication devices.
Summarized by Easybom.
