Abstract: A coil produces a magnetic field in response to an applied voltage which suspends a core in a predetermined position above a trip arm. The trip arm is pivotally mounted between a normally reset position and a tripped position. In the absence of an undervoltage condition, the magnetic field produced by the coil exerts a sufficient force to suspend the core against gravity above a first free end of the trip arm. A second free end of the trip arm is adapted to trip a circuit breaker when the trip arm is rotated from the reset position to the tripped position. When an undervoltage condition occurs, the core drops onto the first free end of the trip arm and the second free end pivots to trip the breaker.The coil is normally energized for maintaining the core suspended against gravity and heat is produced in the coil as a result of current flow therein. A cooling convection air path facilitates heat dissipation in the coil.