Unformatted text preview: s switches, fuses, circuit breakers, relays and
other equipment. A brief account of these devices is given below. However, the reader may find the
detailed discussion on them in the subsequent chapters.
1. Switches. A switch is a device which is used to open or close an electrical circuit in a
convenient way. It can be used under full-load or no-load conditions but it cannot interrupt the fault
currents. When the contacts of a switch are opened, an *arc is produced in the air between the
contacts. This is particularly true for circuits of high voltage and large current capacity. The switches
may be classified into (i) air switches (ii) oil switches. The contacts of the former are opened in air
and that of the latter are opened in oil.
(i) Air-break switch. It is an air switch and is designed to open a circuit under load. In order to
quench the arc that occurs on opening such a switch, special arcing horns are provided. Arcing horns
are pieces of metals between which arc is formed during opening operation. As the swi...
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- Spring '12
- Electrical Engineering, Short circuit, Fuse, Circuit breaker