RE: Re: Quick blow fuse

["Mick Furlong" <dorsai@xxxxxxx>]

And I thought they just went boom ;))


> -----Original Message-----
> From: Keith Doxey [mailto:ukha.diyha@xxxxxxx]
> Sent: 18 May 2001 20:11
> To: ukha_d@xxxxxxx
> Subject: RE: [ukha_d] Re: Quick blow fuse
>
>
> Ian,
>
> You are almost right....
>
> Different alloys have different melting points which is what determins
the
> speed of the fuse blowing. All fuses *should* be able to carry
> their maximum
> rating forever, but in reality metal fatigue causes time related
failure.
> The alloy is chosen to blow at the required time interval, for
> instance....
>
> Anti Surge (aka Slow Blow) PSU INPUT PROTECTION
> - will take longer to fail and will withstand a current several times
its
> rating for a short time after which it would still fail. This
> allows surges
> but cuts the power in the event of a prolonged overload. Toroidal
> transformers MUST have Anti Surge fuses fitted to the primary due to
the
> extremely high inrush current. Ordinary fuses die.....quickly! The
spring
> ensures that when the fuse fails the two ends of the wire are
> rapidly pulled
> apart to extinguish any arcing that may take place.
>
> Quick Blow (Clear Glass) GENERAL PURPOSE and PSU OUTPUT PROTECTION
> - fail *fairly quickly* and will not withstand high switch on surges.
Can
> shatter when they fail.
>
> Hi Speed Ceramic (Buff coloured and filled with sand) TRIAC PROTECTION
> - These are designed for protecting semiconductors like triacs. When
lamps
> fail you can get extremely high currents flowing as the filament
> in the lamp
> drops off and shorts out the lamp stem. Quick blow will shatter
> under these
> conditions and will also not fail quick enough to protect the triac.
HSC
> fuses (aka HRC High Rupture Capacity) blow almost instantly and
> protect the
> triac. The fuse wire effectively vapourises in a mini explosion which
is
> contained by the sand in the fuse.
>
> Hope that helps
>
> Keith
>
> > -----Original Message-----
> > From: Ian Lowe [mailto:ian@xxxxxxx]
> > Sent: 18 May 2001 16:51
> > To: ukha_d@xxxxxxx
> > Subject: Re: [ukha_d] Re: Quick blow fuse
> >
> >
> > Keith,
> >
> > As an aside, how does that work? I thought those were quick blow
> > fuses too,
> > with the thought that the spring coil placed the filament under
> > tension such
> > that it was always under slight stress and would (physically)
come apart
> > faster when loaded to failure...
> >
> > if it's an Anti-surge (and I am sure you are right) what's the
> > spring do???
> >
> > Ian.
> >
>
>
>
>
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