[Boatanchors] [Milsurplus] Fuses to protect transformers

[Glenn Little]

For fuse selection see:
<http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CCcQFjAA&url=http%3A%2F%2Fwww.schurterinc.com%2Fcontent%2Fdownload%2F339609%2F11198688%2Ffile%2FGuide_to_Fuse_Selection.pdf&ei=IkIhU7mTCMK80gGGxYCgAg&usg=AFQjCNHBM5tQ9F3bo9fkqHNbS4GKvlfg-w&bvm=bv.62922401,d.dmQ&cad=rja>

The voltage marked on the fuse is the voltage that it is guaranteed 
to blow cleanly.
To use the fuse above the rated voltage leaves you open to the fuse 
arcing and not disrupting the circuit as intended.
You see this on fuses blown by lightning or other high voltage surges.
The entire inside surface of the fuse is plated with the conductive 
evaporated fuse element.

Hope this helps

73
Glenn
WB4UIV




At 12:27 AM 3/13/2014, hwhall at compuserve.com wrote:
>For this 40s vintage Link Trainer electronics I'm working on, I'm 
>thinking that it'd be a good idea to fuse not only the primary but 
>the secondary HV winding, since these transformers are not too easy 
>to find anymore. I'm thinking of pigtail fuses inserted in the 
>wiring under the chassis, to maintain appearances. But I'm not sure 
>about what fuse selection would be adequate protection.
>
>Would a 1A fast blow fuse be OK for the secondary that probably 
>delivers around 100ma DC? Or to put it another way, how much over 
>the normal current output should I select a fast blow fuse? The 
>filters are dual section choke input with 15 & 25 mfd caps. I 
>haven't reached the point of firing up the whole thing, so I have to 
>guess for now at the current.
>
>The common fuses I have available are marked 250V and the HV is 
>450V. Can they be relied on to open and not arc?
>
>Any advice? Thanks!!
>
>Wayne
>WB4OGM
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