Tuesday, April 1, 2014

Fuse Standards and their classification

For Low Power Fuses Electrical Standard IEC 60269 is followed.
There are 4 volumes for this standard.
è   1.For General Requirement
è   2.For fuses for industrial and commercial applications
è   3.Fuses for residential applications
è   4.Fuses to protect semiconductor devices.

IEC 60269-1 – Low-voltage fuses – Part 1: General requirements
IEC 60269-2 – Low-voltage fuses – Part 2: Fuses mainly for industrial application – Examples of standardized systems of fuses A to I
IEC 60269-3 – Low-voltage fuses – Part 3: Fuses mainly for household and similar applications – Examples of standardized systems of fuses A to F
IEC 60269-4 – Low-voltage fuses – Part 4: Supplementary requirements for fuse-links for the protection of semiconductor devices
IEC 60269-5 – Low-voltage fuses – Part 5: Guidance for the application of low-voltage fuses
IEC 60269-6 – Low-voltage fuses – Part 6: Supplementary requirements for fuse-links for the protection of solar photovoltaic energy systems

As per IEC standard
1.The replaceable element is called a fuse link 
2.The assembly of fuse link and fuse holder is called a fuse.

The standard identifies application categories which classify the time-current characteristic of each type of fuse. 

As clear from above fuse which clearly suggest gL- gG description let us study what does this means:-

The application category is a two-digit code.
The first letter is a if the fuse is for short-circuit protection only; an associated device must provide overload protection.
The first letter is g if the fuse is intended to operate even with currents as low as those that cause it to blow in one hour. These are considered general-purpose fuses for protection of wires.

The second letter indicates the type of equipment or system to be protected:
D – North American time-delay fuses for motor circuits, UL 248 fuses
G – General purpose protection of wires and cables
M – Motors
N – Conductors sized to North American practice, UL 248 fuses
PV – Solar photovoltaic arrays as per 60269-6
R, S – Rectifiers or semiconductors as per 60269-5
Tr – Transformers

Thus after studying we find that fuse can be used for applications General purpose protection of wires and cables.

Any fuses built to the IEC 60269 standard and carrying the same application category (for example, gG or aM) will have similar electrical characteristics, time-current characteristics, and power dissipation as any other, even if the fuses are made in the packages standardized to the earlier national standards. Fuses of the same application category can be substituted for each other provided the voltage rating of the circuit does not exceed the fuse rating.

The tests recommended on Fuses by IEC 60269 are:
1.Temperature rise & power dissipation test
2.Non-fusing & Fusing test
3.Verification of rated current test
4.Overload test
5.Verification of Time Current Characteristics and Gates