APPARATUS MID REVIEWER

for electrical circuits accomplish two main functions namely consistency as well as protection. Protection is assured through detaching power supply in a circuit through overcurrent protection, which removes fire hazards and electrocution. Protection devices used to protect circuits from extreme voltages or currents. This lecture discusses what is a protection device, and types of protection devices used in electrical and electronic circuits.

is an electrical safety device that protects an electric circuit from excessive electric current. Fuses are destroyed during overload conditions. When reasonable to do so (and economically sensible), circuit breakers are used instead because they are not destroyed during overload conditions. It's cheaper to install fuses than circuit breakers, but since fuses need to be replaced and circuit breakers don't, fuses have a higher operational cost.

Contains a thin conductor designed to melt at a low temperature. Once the current reaches a level that can generate enough heat to match or surpass the designed melting point, the connection will break.

Contains two electrical connectors that plug into a circuit and a wire inside that will melt at a certain current.

Screwed directly into a standard fuse socket. To learn more about this type of fuse please see EPB

Referred to as a rejection base (also called type-S), it requires an adapter to fit into a standard fuse socket. Once it is installed it cannot be removed. Fuses with different current ratings will have different threads; therefore, they cannot be replaced with a fuse of a different current rating. To learn more about this type of fuse please see EPB.

_____have a larger element that can handle overcurrent for a relatively short period of time and are unaffected by spikes in the appliance. ______ react instantly to current spikes. Some variants of this fuse are encased in ceramic to withstand high temperatures. Fuses for high voltage applications are filled with sand or oil. This is to prevent arcing between the two ends of the fuse after it has blown. SMD variants of cartridge fuses also exist for direct PCB mounting.

These fuses are specifically designed for automotive systems that run up to __V and occasionally _V. They come in ‘blade’ form (a transparent plastic envelope with flat contacts) and are colour coded according to rated current. Some of these types are also used in other high-power circuits.

Like their name suggests, these fuses are self-resetting. They contain carbon black particles embedded in organic polymers. Normally, the carbon black makes the mixture conductive. When a large current flows, heat is generated which expands the organic polymer. The carbon black particles are forced apart, and conductivity decreases to the point where no current flows. 

is ubiquitous in computer power supplies and phone chargers. They are particularly handy here since replacement is difficult. For the same reason, they are used in aerospace devices. PTCs are easily identified by their _____colour and disc (and occasionally rectangular) shape in their through-hole variants. SMD poly fuses usually come in green with white markings or black with gold markings. PTCs are available in virtually every current rating