Transformer Fuse size Calculator

In distribution networks generally, we need to use fuse for protecting power and distribution transformers. fuse’s maximum current rating depends on what load is connected through the secondary side of the transformer. when the current flowing through the fuse increases to its maximum value, the fuse starts to melt due to the heat produced. from the following, 3 Phase Transformer Fuse size Calculator we can find the copper fuse size in SWG(standard wire gauge) and ampere after selecting the rating and voltage of primary and secondary of the transformer.

Transformer Fuse size Calculator

Transformer Full Load Current and Copper Fuse Size Calculator

Once the rated current of the transformer is known and using the following SWG chart we can find no. of SWG fuse wire.

3 Phase transformer fusing size chart

In the following chart, SWG no. of copper wire/ aluminum/iron wire/ tin wire has to be used to protect the transformer given. using the above calculator first get the current rating of the transformer then select SWG no. of fuse wire from following the 3 Phase transformer fusing chart –

What is SWG

The full form of SWG is the Standard Wire Gauge system. This wire gauge standard comes from Britain and is frequently referred to as the British Wire Gauge system or the Imperial Wire Gauge standard. It has been used as the only measuring standard in the UK since 1884. Its derivational history has also effectively circumscribed the usage of the standard to mainly Britain and its surrounding areas.

Difference Between SWG and AWG

SWG vs AWG

As we know the size of the fuse wire come in mm2 which is always in fraction due to which it is not easy to remember fuse size in mm2. So, Wire size standards are important as it gives an easy-to-remember numerical chart of commonly used wire sizes. The problem with standards is that they are not compatible with each other. A good example of this is the SWG and AWG standards. The main difference between SWG and AWG is where they originated from. SWG was derived from the British Standard Wire Gauge, dropping the British part eventually. In comparison, AWG stands for the American Wire Gauge and it originates from North America, which is composed of the US and Canada.

When it comes to the actual cable sizes, the two are actually not equivalent in size. In general, an SWG wire would be bigger than an AWG wire of the same gauge. For example, with a gauge value of 1, an SWG wire would have a diameter of 0.3 inches while an AWG wire would have a diameter of 0.2893.

How to calculate fuse size

To calculate fuse size for any transformer we need to know the maximum current carrying capacity of that transformer. and after that using chart we can find fuse wire size.

For 100 kva, 3 phase transformer primary and secondary current calculation or current Capacity of the distribution transformer on the LT(415 v) side can be calculated as follow-

100 kva transformer load capacity–

 100 kva=√3.x 415v x I x cos @

LT Side max. current capacity

I= 100×1000 / 1.732 X 415v= 139 amp

H T Side max. current capacity shall be-

 I= 100×1000 / 1.732 X 11000 v= 5.25 amp

Hence, fuse size according to chart

Fuse size for secondary / 415V side = 16 no. copper fuse

Fuse size for primary / 11 kV side = 32 no. copper fuse

conclusion

Fuse is essential to save distribution and power transformer both. but rating and size of the fuse must be according to the load on the transformer. The above fuse rating calculator is set according to the full load current of the transformer. and calculator is for copper made fuse.