10 Different Types of Electrical Wire and how to Choose One > 자유게시판

When the surrounding temperature gets too high, the composition melts and allows the spring contact mechanism to break the circuit. They contain a fusible, temperature-sensitive composition which holds a spring contact mechanism normally closed. Where several fuses are connected in series at the various levels of a power distribution system, it is desirable to blow (clear) only the fuse (or other overcurrent device) electrically closest to the fault. This means that fuses can only be replaced by the preset (Type S) fuse rating. There are two styles of fuse base that can be screwed into these units: one designed for rewirable fusewire carriers and one designed for cartridge fuse carriers. In a multi-phase power circuit, if only one fuse opens, the remaining phases will have higher than normal currents, and unbalanced voltages, with possible damage to motors. You don't have to oversimplify the answer. Some manufacturers have tested their fuses for up to 63 kA short-circuit current. Special current-limiting fuses are applied ahead of some molded-case breakers to protect the breakers in low-voltage power circuits with high short-circuit levels. Joseph Henry improved it in 1828 by placing several windings of insulated wire around the bar, creating a much more powerful electromagnet which could operate a telegraph through the high resistance of long telegraph wires.

High rupturing capacity fuses can be rated to safely interrupt up to 300,000 amperes at 600 V AC. Fuses are widely used for protection of electric motor circuits; for small overloads, the motor protection circuit will open the controlling contactor automatically, and the fuse will only operate for short circuits or extreme overload. Such tampering will not be visible without full inspection of the fuse. Some companies manufacture resettable miniature thermal circuit breakers, which screw into a fuse socket. Thermal fuses are a 'one shot', non-resettable device which must be replaced once they have been activated (blown). Prestressed concrete poles are often used in coastal areas subject to atmospheric corrosion (one manufacturer claims that "concrete poles are foremost in appearance, durability and maintenance-free service"). While subtransmission circuits are usually carried on overhead lines, in urban areas buried cable may be used. Not all wiring methods approved in the NEC are accepted in all areas of the United States. The Wylex standard consumer unit was very popular in the United Kingdom until the wiring regulations started demanding residual-current devices (RCDs) for sockets that could feasibly supply equipment outside the equipotential zone. Some Wylex standard models were made with an RCD instead of the main switch, but (for consumer units supplying the entire installation) this is no longer compliant with the wiring regulations as alarm systems should not be RCD-protected.

In the UK, older electrical consumer units (also called fuse boxes) are fitted either with semi-enclosed (rewirable) fuses (BS 3036) or cartridge fuses (BS 1361). (Fuse wire is commonly supplied to consumers as short lengths of 5 A-, 15 A- and 30 A-rated wire wound on a piece of cardboard.) Modern consumer units usually contain miniature circuit breakers (MCBs) instead of fuses, though cartridge fuses are sometimes still used, as in some applications MCBs are prone to nuisance tripping. Fuse wire was never used in North America for this reason, although renewable fuses continue to be made for distribution boards. In North America, what are electric cables fuses were used in buildings wired before 1960. These Edison base fuses would screw into a fuse socket similar to Edison-base incandescent lamps. Most circuits in the modern North American home and light commercial construction are wired with non-metallic sheathed (NM) cable designated type. 3. Always buy your charging cable from a reputable retailer or directly from the manufacturer who will put such products through rigorous tests to ensure they meet UK safety standards.

So minor overloads can result in a fuse blowing in minutes, but if there is a large current or short circuit scenario, the fuse will blow in seconds or milli-seconds. The PPTC thermistor is self-resetting in that when current is removed, the device will cool and revert to low resistance. So-called self-resetting fuses use a thermoplastic conductive element known as a polymeric positive temperature coefficient (PPTC) thermistor that impedes the circuit during an overcurrent condition (by increasing device resistance). To prevent installation of fuses with an excessive current rating, later fuse boxes included rejection features in the fuse-holder socket, commonly known as Rejection Base (Type S fuses) which have smaller diameters that vary depending on the rating of the fuse. Over the years MCBs have been made for both styles of base. Existing Edison fuse boards can easily be converted to only accept Rejection Base (Type S) fuses, by screwing-in a tamper-proof adapter. In both cases, higher rated carriers had wider pins, so a carrier couldn't be changed for a higher rated one without also changing the base. One form of fuse box abuse was to put a penny in the socket, which defeated overcurrent protection and resulted in a dangerous condition.