What Is an Overcurrent Relay?

A relay is an electronic control device. It has a control system (also called an input circuit) and a controlled system (also called an output circuit). It is usually used in automatic control circuits. A type of "automatic switch" for current. Therefore, it plays the role of automatic adjustment, safety protection, and conversion circuit in the circuit.

Current relay is the most commonly used component in power system relay protection. ^[1]

Selection principle of current relay

The power supply voltage of the control circuit, the maximum current that can be provided; The voltage and current in the controlled circuit; The controlled circuit needs several sets of contacts in what form. When selecting a relay, the power supply voltage of the general control circuit can be used as a basis for selection. The control circuit should be able to provide the relay with sufficient working current, otherwise the relay pull-in is unstable.

Current relay use conditions

You can find relevant information to find the model and specification number of the required relay. If you already have a relay at hand, you can check whether it is available based on the information. Finally, consider whether the size is appropriate.

Pay attention to the volume of the appliance

If it is used for general electrical appliances, in addition to considering the volume of the chassis, the small relay mainly considers the circuit board installation layout. For small appliances, such as toys and remote control devices, subminiature relay products should be selected.

Selection conditions for power protection and secondary loop current relays

Auxiliary source current relays need to provide the conditions: contact form (normally open point, normally closed point and the number of switching points), auxiliary voltage level, current setting range, and installation method (in-cabinet installation, panel opening, Rail type).

The conditions that need to be provided for the auxiliary current relay: the contact form (the number of normally open points, normally closed points, and switching points), the current setting range, and the installation method (in-cabinet installation, panel opening type, rail type)