US Patent 7492564 Protection apparatus for an electrical load

The trip unit of a circuit breaker provides overload protection for a contactor used to energize a load such as a motor while still providing conventional protection for the wiring serving the motor. The trip unit of the circuit breaker eliminates the need for a separate overload relay by generating a pre-trip signal that opens the contactor when the circuit breaker I2t long delay function reaches a selected percentage, such as about 85%, of the trip value.