Actuator assembly with calibration means and electrical power switch apparatus incorporating the actuator assembly with calibration means

An actuator assembly for an electrical power switch apparatus, the actuator assembly having a housing and a plunger positioned within the housing where the plunger is movable between a set position and an actuated position. The plunger includes a compression spring to provide a pre-load thereto that biases the plunger away from the set position and toward the actuated position. A magnet contained in the housing and positioned proximate to the plunger establishes a magnetic force which overcomes the pre-load of the compression spring and maintains the plunger in a set position. A coil assembly, that when energized, produces an electromagnetic force which bucks the magnetic force established by the magnet allowing the plunger to be propelled by the compression spring to the actuated position. A screw extends through an opening in the plunger for engagement with the compression spring so that rotation of the screw results in the adjustment or calibration of the pre-load of the compression spring.