Eaton Corporation

Walter M Zoller

Peter J Theisen

Edward Louis Wellner

Donald A Link

Michael R Larsen

David S Hunter

In a molded case circuit breaker with an interchangeable thermalmagnetic trip unit, the C-shaped heater transformer core is permanently held in place in the casing by a load bus strap with the gap in the core facing the trip unit. When the interchangeable trip unit is inserted into the molded casing, a magnetically permeable member mounted in the trip unit is aligned in the gap in the heater transformer core. The bimetal of the trip unit is fixed at one end to an electrically conductive sleeve surrounding the magnetically permeable member and forming the secondary of the heater transformer. The length of the magnetically permeable member is selected to establish the current conditions at which the bimetal trips the circuit breaker. The bus strap has an off-set section forming a first shoulder against which one wall of the housing of the interchangeable trip unit seats, and a second shoulder against which a pole piece backed by the heater transformer core seats to fix a gap between the pole piece and the armature in the interchangeable trip unit providing the instantaneous magnetic trip function.

Molded case circuit breaker with interchangeable trip unit having

A subframe is coaxially pivotally mounted with a movable frame of the operating mechanism of a molded case circuit breaker and is locked to the frame by a bell crank pawl which is pivotally mounted on the subframe. A leaf spring assembly rigidly attached to the subframe overlies the movable contact finger to engage the same in the circuit ON condition of the circuit breaker to provide desired contact force. The bell crank pawl is released upon an incrementally small amount of initial movement of the movable contact arm in response to blow-open magnetic repulsion forces to release the movable contact finger for pivotal opening movement relative to the movable frame of the circuit breaker operating mechanism.

Growing community of inventors

Milwaukee, WI, United States of America

Walter M Zoller