Electrical switches are used in a variety of applications to control current flow between two points of an electrical circuit. One common application of electrical switches is to control current flow in a power distribution system where the electrical switches are frequently used to isolate various electrical equipment in the power distribution system so that such equipment can be repaired.
Current flow through the electrical switches of a power distribution system is normally on the order of 200-600 amperes. However, large fault currents, such as may be produced by a short circuit condition, occasionally flow in the power distribution system. These fault currents are usually momentary because normally a circuit breaker or other fault sensing device responds to the fault condition by interrupting current flow in the power distribution system. The contacts of the electrical switches in the power distribution system must be able to withstand such momentary fault currents without experiencing substantial deterioration. Also, the contacts of these switches must be able to operate between open and closed states, without substantial adverse effects, while a fault current is flowing through the contacts of the switches. That is, these contacts must retain their integrity when they are closed into a large momentary fault current. Prior switch contacts have been capable of carrying momentary fault currents up to 32,000 amperes. The contacts of the present invention are capable of carrying momentary fault currents of 40,000 amperes.
USPTO Backgrounds
USPTO Backgrounds