# Transformer protection on secondary



## Wireless (Jan 22, 2007)

What is a good way to fuse the secondary side at 5a? Right now there is a ceramic fuse block in which the minimum is 15a. Two transformers burnt up already presumably due to the lack of proper fuse sizes.


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## frenchelectrican (Mar 15, 2007)

Wireless said:


> What is a good way to fuse the secondary side at 5a? Right now there is a ceramic fuse block in which the minimum is 15a. Two transformers burnt up already presumably due to the lack of proper fuse sizes.


If ya don't mind expand this question and what type of transfomer it is if open core and what voltage you are running and I know there are cermaic fuse block they do take smaller fuse if have to.

And what va rating this one?

Merci,
Marc


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## varmit (Apr 19, 2009)

In less than 30 amp applications, I like to use "CC" fuses in a din rail mounted fuse holder. These take minimal space.


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## frenchelectrican (Mar 15, 2007)

varmit said:


> In less than 30 amp applications, I like to use "CC" fuses in a din rail mounted fuse holder. These take minimal space.


That true that one way I do that and some transfomer I ran into couple of them are " Top loader " so that mean the fuse will be on top of transfomer and this useally found with open control transfomer but for other types it will varies.

Merci,
Marc


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## McClary’s Electrical (Feb 21, 2009)

Wireless said:


> What is a good way to fuse the secondary side at 5a? Right now there is a ceramic fuse block in which the minimum is 15a. Two transformers burnt up already presumably due to the lack of proper fuse sizes.


 

Please elaborate. I'm thinking there's another problem.


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## Southeast Power (Jan 18, 2009)

My question would be more along the lines of why is the transformer so overloaded?
A fuse will not help you.........................


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## brian john (Mar 11, 2007)

Determine the load and proper KVA rating, with proper primary and secondary fusing, as noted CC or KTK's, call your local Graingers.


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## Jlarson (Jun 28, 2009)

Wireless said:


> What is a good way to fuse the secondary side at 5a? Right now there is a ceramic fuse block in which the minimum is 15a. Two transformers burnt up already presumably due to the lack of proper fuse sizes.


Me thinks you are overloading the transformer and you need to figure out the load's requirements and you will probably need to up size the transformer. But if you really want to try 5 amp fuses just some 5 amp class CC fuses and the proper fuse block should work fine.


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## varmit (Apr 19, 2009)

If two transformers have burnt up, assuming that they are wired correctly, there is most likely an overload on the transformer. If that is the case, only installing smaller fuses will be making a fuse tester. Try to determine the actual load and size a replacement xfmr. appropriately.


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## Wireless (Jan 22, 2007)

480v primary 120v secondary .5KVA. I realize there is something causing the overload, but if there had been a proper sized fuse it would have not burnt the transformer. So far there was a loose connection to the coil of one contactor and a jammed contactor on the other.


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## Wireless (Jan 22, 2007)

brian john said:


> Determine the load and proper KVA rating, with proper primary and secondary fusing, as noted CC or KTK's, call your local Graingers.


 
It's funny that you mention Grainger, they are the first place I called for the contactors but blanked on calling them for the fuse holders!


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## caddie (Oct 29, 2010)

I'm pretty sure you are not supposed to fuse the secondary side of a transformer. The protection, if any, should be on the high voltage side, where the current is low.


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## varmit (Apr 19, 2009)

caddie said:


> I'm pretty sure you are not supposed to fuse the secondary side of a transformer. The protection, if any, should be on the high voltage side, where the current is low.


Depending on the VA or KVA rating you may be required to fuse the primary and secondary. I don't have my code book handy, but from memory I believe that any transformer rated 500 VA and larger, requires primary and secondary fusing.

Oops your Canadian. The world may be different there.


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