US 5,341,191 A · Molded case current limiting circuit breaker

Abstract

A molded case circuit breaker having current limiting capabilities optimized for relatively smaller frame sizes. More specifically, one aspect of the invention relates to a two-piece carrier assembly for carrying the main and arcing contact arms which allows the main and arcing contacts to be blown open during short circuit conditions. The two-piece carrier assembly includes an inner carrier and an outer carrier pivotally connected together. The contact arms are carried by the inner carrier. When sufficient magnetic repulsion forces are exerted on the contacts due to a short circuit condition, the inner carrier pivots relative to the outer carrier to allow the contact arms to blow open. In order to control the amount of force required for blow open, a compression spring loaded cam assembly is provided. Another important aspect of the invention relates to a contact spring housing which relocates the contact springs away from the separable contacts to protect the springs from damage, for example, from heat due to contact separation. In order to improve the interruption time of the circuit breaker for relatively large overcurrents, such as a short circuit, a reverse current loop is provided which generates sufficient magnetic repulsion forces to blow open the separable contacts in a relatively short period of time. Within the restraints of the physical dimension of a relatively smaller breaker frame size, additional features have also been incorporated. More specifically, an improved rating plug assembly is provided with a one-piece plunger, relatively easier to manufacture than known designs which utilize two-piece plungers. Another aspect of the invention relates to an auxiliary cam plate for controlling the motion of the crossbar at the remote end in a four pole circuit breaker. The cam plate compensates for bending of the crossbar to improve the contact force in the remote pole. Lastly, a molded interphase barrier forms a gas barrier within the circuit breaker and maintains its position during assembly relatively better than known interphase barriers.

Claims21

Dependent claims

A molded case circuit breaker comprising:

a molded housing;
a plurality of pairs of separable main contacts carried by said housing, each pair defining a movably mounted main contact and a fixed main contact means;
a plurality of movably mounted contact arms for carrying said movably mounted main contacts, rotatably mounted for movement defining a closed position, an open position, a trip position, and a blow open position;
an operating mechanism, operably coupled to said plurality of movably mounted contact arms, for controlling movement of said plurality of movably mounted contact arms defining a closed position, an open position and a trip position;
and
a line side conductor formed as a generally straight member adjacent said plurality of movably mounted contact arms and defining a contact portion adjacent one end carrying said fixed main contact means and forming a line side terminal on an opposing end, said line side conductor including a predetermined number of cut outs for reversing, relative to the direction of electrical current flow from the line side terminal, the direction of electrical current flow in said contact portion adjacent said plurality of movably mounted contact arms, thereby forming a reverse current loop which generates sufficient magnetic repulsion forces to blow open said plurality of movably mounted contact arms when said electrical current reaches a predetermined magnitude.

3 more elements

Dependencies are inferred from the claim text.

Molded case current limiting circuit breaker

Life of this patent

Molded case current limiting circuit breaker

Life of this patent

Abstract

Claims21