Three-pole supplementary protectors protect three circuits from current overloads at the same time. They're UL1077 listed for use as extra protection from electrical damage for devices that already have branch circuit protection or where branch circuit protection isn't required. These protectors follow trip curves to determine when they will interrupt the current. If the current exceeds a device's rating up to a certain factor, the circuit breaker will have a delayed trip to prevent nuisance tripping. If the current exceeds the device's rating at or above that factor, it will immediately trip. They're mounted on standard 35mm DIN rail in applications like luminaires, appliances, control circuits, control power transformers, and other electrical equipment.