Author Topic: Fusing three transformers  (Read 1957 times)

0 Members and 1 Guest are viewing this topic.

Offline liquibyteTopic starter

  • Frequent Contributor
  • **
  • Posts: 475
  • Country: us
Fusing three transformers
« on: February 13, 2014, 12:48:39 pm »
I've got a power supply project I'm working one and am wondering how to fuse the thing.  It's going to have three transformers in it.  The two main transformers are 28V @ 4.6A and the auxilliary tranformer is 12.6-0-12.6 @ 2A with everything running off of 60Hz.  I'm still a little confused about the fuse sizes I'd need because I'm not quite grokking the different types and am not sure what the initial inrush would be at worst case.  The two main transformers are going into two seperate supplies with smoothing caps of 15,000uF each but the auxilliary is just going to be powering bog standard linears to power fans, thermal circuitry and displays etc.  I want to fuse everything before the transformers and am lost as to what size and type of fusing arrangement to use.  I'm also not sure if I need to fuse per transformer or just the line before the split.  I'm also wondering if circuit breakers might be a better idea but need some expert opinions on the matter.  Could someone with more experience point me in the right direction?
 

Offline AlfBaz

  • Super Contributor
  • ***
  • Posts: 2184
  • Country: au
Re: Fusing three transformers
« Reply #1 on: February 13, 2014, 12:54:39 pm »
I'd be inclined to protect each transformer separately for starters. If the device developed a fault that caused two transformers to draw no current and the third had a short the single fuse scenario could conceivably allow 15-20 amps to go where normally the max would be 4.6A or 2A
 

Offline KDC

  • Contributor
  • Posts: 23
  • Country: ca
Re: Fusing three transformers
« Reply #2 on: February 13, 2014, 02:09:38 pm »
I'd go with fusing them seperatly as well. Going with fuses no more than 25% greater than the rated current is pretty standard with larger transformers.

It's possible that a time delay type fuse would also work to handle the inrush with no problems with the rated current.
 

Offline liquibyteTopic starter

  • Frequent Contributor
  • **
  • Posts: 475
  • Country: us
Re: Fusing three transformers
« Reply #3 on: February 14, 2014, 02:48:31 am »
I went with 6A x 2 and 2.5A slo-blo and a 3 circuit fuse holder arrangement.  I was going to use circuit breakers but I think I'll hold off on that arrangement until I can do some load testing once everything is together.  Thanks for your help.
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf