Collection:Undervoltage Release Coils

An under voltage release is an optional device that is installed in circuit breakers. It triggers a power trip if the power drops below a predetermined level. Usually, it's between 70 and 35 percent of the UV rating. It is not powered by the circuit breaker, instead It receives power from an alternative source such as a battery. Although originally designed for coal mines, it can be used in any domain operating in heavy industry.

An under voltage release device is composed of a solenoid magnet with a moving arm fixed to a spring loaded latch. This latch holds a spring-biased plunger, which, when released, contacts the trip bar to trip the breaker.

The magnetic force can overcome the spring force as long as the voltage to the solenoid magnet is normal. This will prevent the trip bar's release. The magnetic force is overcome if the voltage drops below the preset level or cuts off. This force releases the plunger and then trips the power.