[sdiy] Fuse 101

[Tim Ressel]

Peter,

Ah yes, fuses. For dynamite you should use a ... oh
wait, I'll bet you mean the other kind...

Seriously, fuses are funny. If you put 1A of current
through a 1A fuse, it will not blow. The way fuses are
rated is the amount of delay before blowing verses the
current overage. In other words, for 150% current the
delay will be X, for 200% current the delay will be Y.

My rule of thumb is to calculate the power of the
secondary of the power supply to be fused, add 20% for
efficiency, and calculate the primary current. Then I
use the next bigger fuse.

You should fuse the 'primary' i.e. the incomming AC
power, and fuse it as close to the wall as possible.
Right where the power cord comes into the box, before
the power switch, is the best.

Hope that helps.

==Tim


--- Peter Grenader <pgrenader at mksound.com> wrote:
> 
> The first step in correcting any chronic condition
> is coming out of denial.
> That being said, I have an admission to make:
> 
> I have bad (read: terrible) power supply hygiene.
> 
> But...I am trying to do something about it! 
> Currently my modular is being
> powered by no less than 5 supplies, all unboxed,
> just sitting there waiting
> to get knocked over by the dog.  My 15 volt line is
> covered satisfactorily-
> my 12 volt line is a mess: Two Doepfer supplies and
> two little Power 1's,
> which have been tied together to form a +12 to -12
> string.
> 
> I have just ordered a Condor 1.5 amp bipolar supply
> for the 12 volt line to
> compliment the one I already have for the 15 volt
> line - and, I've ordered a
> nice aluminum chassis box to house them both in.
> 
> Now comes the question of fuses.  They are all
> fused, but I am not sure they
> are fused correctly.
> 
> If I am running up to the current rail on the
> secondary side (1.5 amp), what
> do you suggest I use for the promary fuse value? 
> shoud I underrate this a
> bit to assure my fuse does it's job, should I use a
> slo-blo or standard?
> 
> Any input on this would be helpful.
> 
> best,
> 
> Peter 
> 
> 
> 


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