The electrical systems in residential, commercial and industrial applications usually include a panelboard for receiving electrical power from a utility source. The power is then routed through overcurrent protection devices to designated branch circuits supplying one or more loads. These overcurrent devices are typically circuit interrupters such as circuit breakers and fuses which are designed to interrupt the electrical current if the limits of the conductors supplying the loads are surpassed. Interruption of the circuit reduces the risk of injury or the potential of property damage from a resulting fire.
Circuit breakers are a preferred type of circuit interrupter because a resetting mechanism allows their reuse. Typically, circuit breakers interrupt an electric circuit due to a trip condition such as a current overload or ground fault. The current overload condition results when a current exceeds the continuous rating of the breaker for a time interval determined by the trip current. The ground fault trip condition is created by an imbalance of currents flowing between a line conductor and a neutral conductor such as a grounded conductor, a person causing a current path to ground, or an arcing fault to ground.
An example of a ground fault interrupter is a fast acting circuit breaker that disconnects equipment from the power line when some current returns to the source through a ground path. Under normal circumstances all current is supplied and returned within the power conductors. But if a fault occurs and leaks some current to ground, then the ground-fault circuit interrupter (GFCI) will sense the difference in current in the power conductors. If the fault level exceeds the trip level of the GFCI, then the circuit will be disconnected. The trip level for protection of personnel is usually in the range of about 4 mA to 6 mA. The trip level for the protection of equipment is usually about 30 mA.
GFCIs commonly have a push-to-test feature which provides a test circuit located inside the circuit interrupter housing and a externally accessible push-button mounted through the housing. Pushing the button closes the test circuit which simulates a ground fault to check the operation of the circuit interrupter.
The prior art as exemplified in U.S. Pat. No. 4,081,852 issued to Coley et al. and U.S. Pat. No. 4,568,899 issued to May et al. disclose a manual button which closes a test circuit between two wires. The wires lead to the trip circuit and a neutral conductor or to other components such as a circuit board. The wires cause several problems. Routing of the wires during assembly of the circuit breaker requires a disproportionate amount of time and expense and complicates automation of the assembly process. Placement of the wires in close proximity to one another can also lead to arcing during high voltage surges. Any damage to the wiring insulation can lead to a dielectric breakdown and a short condition.
The need arises to overcome the problems associated with using wire leads for connecting a test circuit in GFCIs. The present invention provides a conducting spring which reversibly completes the current path for the test circuit. The conducting spring is inexpensively manufactured and assembly and effectively prevents arcing with other components of the circuit interrupter.
USPTO Backgrounds
USPTO Backgrounds