A molded case circuit breaker having thermal and magnetic trip means. A moving contact support structure is disposed about the magnetic trip means so as to cause current flowing through the circuit breaker contacts to pass twice through the magnetic circuit of the magnetic trip means. The moving contact support structure includes resistance material operable upon overcurrent conditions through the contacts to aid in heating the thermal trip means. An operating mechanism includes an operating spring in compression which acts as one leg of a toggle linkage and stores energy to operate the contacts with a snap action.
