Abstract: A magnetic trip means for automatically opening a circuit breaker contact upon the occurrence of predetermined fault current conditions is constructed of a stationary yoke, an armature biased away from the yoke and movable toward the yoke for tripping of the switch, an actuating coil in series with the contacts, and a sealed capsule coaxial with the coil for obtaining selected tripping characteristics. Within the sealed capsule there is a movable magnetic core biased to a normal position extending substantially outside the coil. The core is movable inside of the coil toward the armature upon the occurrence of overload current conditions with movements of the core toward the armature being retarded in a controlled manner. Control is obtained by closely spacing the outer cylindrical wall of the core and the inner cylindrical wall of the capsule, and additionally by utilizing a viscous fluid within the capsule.

Abstract: A unitized combination motor starter is provided with a single insulated housing wherein a plurality of pole units are disposed side-by-side. Each pole unit includes a circuit breaker contact section and a contactor contact section. A spring powered mechanism for circuit breaker operation is disposed on one side of the pole units and an electromagnet for contactor operation is disposed on the other side of the pole units. The current carrying elements of each pole unit are arranged to provide a current loop having relatively close opposing arms so that large mechanical forces accompany high magnitude current flow. These forces are directed so as to produce a blow-off effect at the circuit breaker contacts, resulting in current limiting action to protect the contactor contacts.