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ELECTRICAL SAFETY DESIGN |
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Conductors and Overcurrent Devices |
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| Electric current is the flow of electrons through a conductor. The size of
the wire is the main determinate in deciding how much current can safely flow through a
conductor. A larger wire can carry more current safely. If too much current flows through
a conductor, excess heat is produced. If the circuit is not protected, the heat may
continue to build until it reaches a temperature high enough to destroy the insulation and
cause a fire. The National Electrical Code specifies the allowable current flow permitted in certain-sized conductors. Ampacity is the term used to describe the current-carrying capacity of a conductor. The size of the fuse or circuit breaker required to provide protection is determined by the ampacity of the conductor in the circuit to be protected and the type of load that is on the circuit. Fuses and circuit breakers are designed to protect equipment and facilities against overcurrent and overheating, but they also provide considerable protection against shock in most situations. The basic idea of a protective device is to make a weak link in the circuit. A fuse acts as a weak link that is the first piece of the system to be destroyed. In the case of a circuit breaker, a set of contacts open the circuit and stops the flow of current. Unlike a fuse, a circuit breaker can be re-used by re-closing the contacts. |
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