Abstract: A circuit breaker has an insulated casing including an upper casing portion and a lower casing portion. A switching mechanism is attached to a frame which is seated in a positioning recess portion of the lower casing portion. The frame and switching mechanism are captured by extending support arms of the lower casing portion and are fixedly secured thereto to permit operation of the switching mechanism prior to final assembly of the upper and lower casing portions.

Abstract: Disclosed is a circuit breaker switch configuration in which a conducting member in the switch for connecting a switch terminal to a switch contact is shaped to form a loop current path, such that when a current flows in the switch, a magnetic field is established in the vicinity of the switch contacts. Such a magnetic field, which is appropriately oriented, serves to confine a plasma generated by an arc discharge which occurs between the switch contacts when the switch is initially opened. The confinement of the arc discharge plasma by the magnetic field reduces the extent of the plasma and permits the use of smaller arc-extinguishing means in the switch and affords more rapid extinguishment of the arc discharge.