An actuator (144) for initiating a trip of a circuit breaker. Load current passes through a conductor (66) that is electrically coupled to a contact arm (56) by a braid (62). A thermally responsive bi-metal (64) has a first end portion which is disposed against a portion of the conductor (66) and through which at least a portion of load current carried by the contact arm, the braid, and the conductor passes. The bi-metal further has a second end portion that is disposed in spaced relation to the conductor and is cantilever-mounted on the portion of the conductor via the bi-metal's first end portion. The bi-metal is nominally flat and straight, but increasingly warps as thermal energy in the bi-metal increases. Upon attaining a certain degree of warping, the bi-metal initiates a trip of the circuit breaker by causing the contact arm to swing from a circuit-making to a circuit-breaking condition.