Electrical Characteristics of Relays

Electrical Characteristics of Relays

Rated Coil Voltage- The voltage that the relay is supposed to receive when you energize it.

Set (Operate) voltage- The minimum voltage that the relay needs to close its switch. This will be a little less than the ideal coil voltage.

Rated Power (sometimes called Operating Current)- This is the power that a relay is specifically meant to handle. For example, if a relay is rated at 60W, no more than 60W should be used with the relay. The power rating is the power consumption of the coil, usually expressed in milliwatts, when the relay is energized. Power should not be used for a relay above its power rating. Sometimes the power is expressed in ampere ratings, milliamperes.

Switching Capacity- The maximum amount of current that you can switch with contacts inside the relay. Usually this is for resistive loads, which are attached to the contacts of a relay, example being a light bulb attached to the relay contacts for the relay to power it on. When you use a device that requires a lot of current, such as a motor, the motor takes a big initial surge of current before it gets up to speed. In this case, make sure you choose a relay rated for double the current that the motor draws when it is running.

References
Platt, Charles. Make: Electronics- Learning by Discovery. California: O'Reilly, 2009.