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Thursday, July 21, 2022

Fuse electrical symbol - Learn with Mr Electro

We shouldn't build a electrical system without protection for it. For a electrical system, there need a protection system in faulty cases such as short circuit condition, overhead condition etc. For a small and medium system in low voltage distribution, fuse is required for their protection. Here we are going to discuss about fuse electrical symbol || Fuse advantage, disadvantage and types. Let's discuss about fuse electrical symbol. 

fuse electrical symbol

Fuse is the simplest and cheapest electrical device that is used for interrupting an electrical circuit under short circuit condition or excessive overload condition i.e. high current magnitudes. Generally, it is used in overload and short circuit  protection of equipment in high voltage (up to 66 KV) and low voltage (up to 400 V) installations/circuits and choose its type as requirement.
Fuse electrical symbol - Learn with Mr Electro

The fuse electrical symbol is the symbol which is used in the electric circuit so that it is easy to understand. You should need to remember the fuse electrical symbol. The fuse electrical symbol is given below: -

Fuse electrical symbol - Learn with Mr Electro

Operation of fuse/fuse element

The fuse's action is depends on the heating effect of the electric current. In normal operation,  when current flowing through the circuit within the safe limits, the heat developed in the fuse element carrying the current is readily dissipated into the surrounding air. Therefore, the fuse element is not working, i.e not melt, at a temperature below its melting point. In case of some fault(short circuit or over load), the heat generated due to the excessive current cannot be dissipated fast enough in environment and the fuse element gets heated & melted. At last, the circuit will break. Thus, it protect a machine or apparatus or an installation from damaged due to excessive current in the circuit in case of short circuit and over load condition.

Advantages of fuse: 

  • It is a cheap electrical protection device.
  • It needs no maintenance.
  • Its operation is inherently completely automatic.
  • It interrupts the short circuit currents without noise, flame, gas or smoke.
  • The minimum time of operation of fuse can be made much smaller as compared with the circuit breakers.
  • The small size of fuse elements imposes current limiting effect under short circuit conditions.
  • Due to its inverse time current characteristic, it is used for overload protection.

Disadvantages of fuse: 

  • After fuse operates, significant time is lost in rewiring or replacing a fuse.
  • It is difficult to choose the fuse size for device protection.
  • The current time characteristic of a fuse cannot always be correlated with other the protected device.

Some points that need to remember in Fuse.

1. Rating :- It is the rms value of current that the fuse can carry continuously without damage or melt which is always less than fusing current. It is expresses in term of Ampere (A) and need to choose right fuse as our load in the system which can carry perfect amount of current for the circuit.

2. Fusing current :- It is the low (minimum) value of current that can damage or melt the fuse which is always more than fuse rating. If this amount of current or higher than that current is flow in the circuit, fuse will be damaged and need new one for replacing it. Here,  I = Kd3/2
where I means fusing current.
K means fuse constant and depends on fusing material.
d means diameter of wire.

3. Fusing factor :- It is the ratio of minimum value of fusing current to the fuse rating. Fusing current is always higher than fuse rating so it's value is always greater than 1.  Generally, its value is between 1 to 2. Formula is given by,

             Fusing factor = the minimum value of fusing current / the fuse rating
There are many types of fuse that are generally used in the system (low voltage and high voltage).

Fuse types

There are many types of fuse. Here we have introduce 5 types of it. They are as follows:-
1. KitKat fuse/rewireable fuse
2. Catbridge fuse
3. Drop out fuse
4. MCB (miniature circuit breaker)
5. MCCB (molded case circuit breaker)
We have already talked about MCCB.

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