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Introduction of Fuse
In electronics and electrical engineering, a fuse (from the French fuser, Italian fuso, "spindle") is a type of low resistance resistor that acts as a sacrificial device to provide over current protection, of either the load or source circuit. It’s 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.
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 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 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.
Terms used for Fuses
1. Minimum Fusing Current : It is minimum value of current due to which fuse melts.
2. Current Rating of Fuse : It is maximum value of current due to which fuse does not get melt.
3. Fusing Factor : This is the ratio of minimum fusing current and current rating of fuse.
Therefore, fusing factor = Minimum fusing current / current rating of fuse.
The value of fusing factor is always more than 1.
4. Prospective Current in Fuse: Before melting, the fuse element has to carry the short circuit current through it. The prospective current is defined as the value of current which would flow through the fuse immediately after a short circuit occurs in the network.
5. Melting Time of Fuse or Pre-arcing Time of Fuse: This is the time taken by an fuse wire to be broken by melting. It is counted from the instant, the over current starts to flow through fuse, to the instant when fuse wire is just broken by melting.
6. Arcing Time of Fuse: After breaking of fuse wire there will be an arcing between both melted tips of the wire which will be extinguished at the current zero. The time accounted from the instant of arc initiated to the instant of arc being extinguished is known as arcing time of fuse.
7. Operating Time of Fuse: When ever over rated current starts to flow through a fuse wire, it takes a time to be melted and disconnected, and just after that the arcing stars between the melted tips of the fuse wire, which is finally extinguished. The operating time of fuse is the time gap between the instant when the over rated current just starts to flow through the fuse and the instant when the arc in fuse finally extinguished. That means operating time of fuse = melting time + arcing time of fuse.
Working Principle of Fuse
Fuses operate on the principle of melting when the heat absorbed exceeds its capacity.
Process is usually adiabatic – heat produced goes to heating the fuse wire only.
∴ I2R t = constant,
or I2t = constant.
where R is a constant corresponding to the resistance at the
Time – current characteristic seen corresponds to this expression.
Type of Fuses
The main components of a standard fuse unit consist of the following items:
The major two categories of fuses include:
In order to understand Low voltage fuses better, we can further classify it further into:
Appliction of Fuse
The main usage of fuse is for the protection of the circuit. In a real term scenario, the current flowing through the wires may not be uniform at times. In such cases, your device could get overheated. There is also the chance of a fire if the fuse is not installed.While the technology has advanced with the usage of circuit breaker, fuses are still used in a number of places like cars and basic electrical components.
Our Major Brands of Fuse are