Md.Kausher ahmed Electrical department

Advanced electricity Code-6722

Lesson declared Fuse and circuit breaker

Learning outcomes After finished this lesson student will able to # Say about fuse. #Draw fuse. # Explain circuit breaker.

Fuse A miniature time-delay fuse used to protect electronic equipment, rated 3/10 amperes at 250 volts. 1 1/4 inches (about 32 mm) long.

Electronic symbol of fuse

200 A Industrial fuse. 80 kA breaking capacity

Fuse In electronics and electrical engineering, a fuse (from the French fusée, Italian fuso, "spindle"[1]) is a type of low resistance resistor that acts as a sacrificial device to provide overcurrent protection, of either the load or source circuit

Continue,,,,,,,, Its essential component is a metal wire or strip that melts when too much current flows through it, interrupting the circuit that it connects. Short circuits, overloading, mismatched loads, or device failure are the prime reasons for excessive current. Fuses are an alternative to circuit breakers

Continue,,,,,,,,,, A fuse interrupts excessive current ("blows") so that further damage by overheating or fire is prevented. Wiring regulations often define a maximum fuse current rating for particular circuits. Over current protection devices are essential in electrical systems to limit threats to human life and property damage. The time and current operating characteristics of fuses are chosen to

Continue,,,,,,,,,, provide adequate protection without needless interruption. Slow blow fuses are designed to allow harmless short term currents over their rating while still interrupting a sustained overload. Fuses are manufactured in a wide range of current and voltage ratings to protect wiring systems

Continue,,,,,,,,,, and electrical equipment. Self-resetting fuses automatically restore the circuit after the overload has cleared, and are useful in environments where a human replacing a blown fuse would be difficult or impossible, for example in aerospace or nuclear applications.

Renewable fuse

Cartage fuse

Circuit breaker A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or shor circuit. Its basic function is to detect a fault condition and interrupt current flow. Unlike a fuse, which operates once and then must be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation………….

Continue,,,,,,,,,, Circuit breakers are made in varying sizes, from small devices that protect an individual household appliance up to large switchgear designed to protect high voltage circuits feeding an entire city

Fig:Mcb

Feedback #What is star connection? #What is fuse. # What is circuit breaker.

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