Motor Starters and Contactors

16 Control Relays

are magnetic devices that are used to remotely switch loads. They are functionally identical to a magnetic , save that control relays lack and built-in protection.

Control relay.

Since magnetic-motor starters are limited in the number of , control relays are used where additional contacts are required to switch low-level current loads such as , motor starters, or other relays.

Some control relays are the latching-type relay, in that after energizing the coil, the relay contacts remain mechanically latched in the closed position, even after power is removed from the coil. To open the relay contacts, the coil requires the momentary energization of a second coil to unlatch the coil.

The advantage of this type of relay is that it is not necessary to keep the coil continuously energized, which results in quieter operation and less current drawn from the source.


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Basic Motor Control by Aaron Lee and Chad Flinn is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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