Westinghouse KT3400T Thermal Magnetic Trip Unit

The Westinghouse KT3400T Thermal Magnetic Trip Unit is a 400A replaceable trip accessory for KT-series circuit breakers. This dual-function device provides thermal (overload) protection and magnetic (short-circuit) protection, enabling the breaker to trip quickly on high fault current while allowing normal operation during typical overloads. As a component of the Cutler-Hammer/Westinghouse protection lineup, the KT3400T is designed to fit compatible KT-type breakers and to restore specified trip characteristics when replacement is required. Its 400A rating identifies the current at which the unit operates, making it suitable for medium- to large-load circuits within electrical distribution panels that employ KT-series protection. By offering a modular trip unit, it supports maintenance and lifecycle management by replacing the trip element without replacing the entire breaker assembly.