Fuse markings question
Olav Beckmann
I need to replace a fuse in our Mackie 32.8 power supply
which has the following markings: "2.5A L 250V T".
The manual emphasises that I'm supposed to get exactly the same fuse as
has blown out / as is marked onthe back of the power supply.
Now, I understand what the 2.5A, the 250V and the T stand for.
However, I have no idea what the L means and whether it is relevant...
Would there be any potential problem in replacing such a fuse with one
that does not have the "L"??
Any suggestions welcome!
Many thanks!
Olav Beckmann
Tim
"Olav Beckmann" <o...@doc.ic.ac.uk> wrote in message
news:3CD0A66E...@doc.ic.ac.uk...
blow or slow blow.
slo-blo fuses are somtimes marked MDL
CareyD
> However, I have no idea what the L means and whether it is relevant...
> Would there be any potential problem in replacing such a fuse with one
> that does not have the "L"??
The 'T' stands for 'Time lag'. This is the same as anti-surge. The
fuse can withstand brief surges in current such as you get when a
power supply starts up and its filters stabilise. It will fail,
however, if the surge is sustained for a longer duration such as a
fault condition.
'F' stands for 'Fast blow', the same as quick blow. If you put one of
these fuses in it is likely to blow when the power supply is turned
on.
I'm not sure what the 'L' stands for. You should be fine as long as
you use an anti-surge or 'T' fuse of the same rated value.
Regards,
Carey
Olav Beckmann
Thanks very much.
For the record of this newsgroup: someone pointed out to me that the L
denotes a category of breaking capacity (i.e. just how much more than
the nominal current can the fuse "keep out"... OR: For how high a
potential current peak is it safe to use this fuse?). There are 3
categories: Low (L), High (H) and Enhanced (E). Exactly what level of
excess current the L/H/E denotes depends on the fuse type. IEC Standard
EN 60127-2 is the relevant document that lists the exact currents /
factors. Also available as British Standard BS 60127-2, I think.
So, of course your comment above that, as long as the T is there and the
amps / volts are right, things should be fine is absolutely correct,
because given that the Mackie suggests an L fuse, if one ended up using
a H or E fuse, all that would happen is that it offers a bit more
protection in case of extraordinarily high current peaks (but if those
were to happen lots of other things would blow out anyway...).
Thanks again!
--
Dr Olav Beckmann
Research Associate
Department of Computing
Imperial College of Science, Technology and Medicine
180 Queen's Gate, London SW7 2BZ, United Kingdom
Tel.: +44 20 7594 8322, Fax: +44 20 7581 8024
Email: o.bec...@ic.ac.uk
URL: http://www.doc.ic.ac.uk/~ob3/
Craig
electrical
IE if you had a very large overload in a glass fuse - the glass can shatter
where as a ceramic one wouldn't
hence ceramic fuses are sometimes known as HRC (High Rupture Capacity) as
they can withstand the physical shock of the fuse wire exploding
Craig
"Olav Beckmann" <o...@doc.ic.ac.uk> wrote in message
news:3CD12D7...@doc.ic.ac.uk...
Phil Allison
"Craig" <craig....@btinternet.com> wrote in message
news:ab1jhm$eoule$1...@ID-119529.news.dfncis.de...
> I think what you are talking about are physical characteristics rather
than
> electrical
> IE if you had a very large overload in a glass fuse - the glass can
shatter
> where as a ceramic one wouldn't
> hence ceramic fuses are sometimes known as HRC (High Rupture Capacity) as
> they can withstand the physical shock of the fuse wire exploding
>
> Craig
** Garbage. Some ceramic fuses are high rupture and others are not. It
depends on the construction of the fuse inside the ceramic tube.
Non HRC fuses (glass or ceramic) will arc from end to end if
sufficient current is available under a short circuit. HRC ones don't.
Regards, Phil
Craig
From a component catalogue
" Interrupt Rating: The rated breaking capacity of the fuse
(interrupting rating) is the short circuit current at which the fuse can
blow (at the rated voltage) without destruction or arcing being maintained."
I never said that all ceramics are HRC but it is safe to assume a glass one
is not
Craig
"Phil Allison" <bi...@bigpond.com> wrote in message
news:GK_A8.3212$b5.1...@newsfeeds.bigpond.com...
Phil Allison
> Garbage Eh?
** Yes, the breaking capacity of a fuse *is* an electrical
characteristic - opposite of your thesis.
Regards, Phil
BTW Abiguity is error.
Steve Wood
> I think what you are talking about are physical characteristics rather
than
> electrical
> IE if you had a very large overload in a glass fuse - the glass can
shatter
> where as a ceramic one wouldn't
> hence ceramic fuses are sometimes known as HRC (High Rupture Capacity) as
> they can withstand the physical shock of the fuse wire exploding
>
> Craig
>
A lot of high capacity fuses do not use a straight forward "wire", many use
profiled extrusions, designed to blow in different areas under different
fault conditions.
This has several purposes, but predominantly allows the manufacturer to
build in delay/overload curves to suit the application, i.e. motor or
transformer ratings.
Ceramic cartridge fuses do shatter, but require a much higher energy from
the fault. They also tend not to melt during severe fault conditions when
arcing does occur, usually the wrong fuse type has been specified!
--
Regards
Steve Wood
Audio Reality Ltd.
Phil Allison
"Steve Wood" <wood...@hotmail.com> wrote in message
news:vIrB8.8358$C5.23...@monolith.news.easynet.net...
> A lot of high capacity fuses do not use a straight forward "wire", many
use
> profiled extrusions, designed to blow in different areas under different
> fault conditions.
> This has several purposes, but predominantly allows the manufacturer to
> build in delay/overload curves to suit the application, i.e. motor or
> transformer ratings.
>
> Ceramic cartridge fuses do shatter, but require a much higher energy from
> the fault. They also tend not to melt during severe fault conditions when
> arcing does occur, usually the wrong fuse type has been specified!
** The ceramic HRC fuses I have come across use stranded wires combined
with fine silica sand to act as arc quenching. There are, no doubt,
numerous ways to skin this particular cat, however breaking a potential 1
to 3 thousand amp AC arc is no simple matter.
Regards, Phil
Steve Wood
>
> ** The ceramic HRC fuses I have come across use stranded wires
combined
> with fine silica sand to act as arc quenching.
I've never seen stranded wire in a fuse, the sand is very common, also helps
absorb some mechanical shock .
Does make a mess when the fuses really blow ;-)
> There are, no doubt, numerous ways to skin this particular cat,
>however breaking a potential 1 to 3 thousand amp AC arc is no simple
matter.
>
Agreed, hence the reason fuse manufactures are using profiled extrusions in
place of simple wires.
It was some 10 - 15 years ago that i read up on this, and have no idea where
to find the data, from what i remember the fuse is extruded as a profiled
ribbon, and then cut into thin strips. The profile is designed to create
weak points, these allow clean breaks and reduce arcing.
FWIW I was thinking of fault conditions far higher than 1 - 3 thousand amps.
Over the last 10 years or so I have been involved in repairing and building
control panels for large industrial refrigeration plants, several of these
have used multi magawat compressors driven by large electric motors, drawing
well in excess of 600amps per phase at 415V. Fault conditions here run well
into the 10s of thousands of Amps.
Arthur Dent
> Hi,
>
> I need to replace a fuse in our Mackie 32.8 power supply
> which has the following markings: "2.5A L 250V T".
>
> The manual emphasises that I'm supposed to get exactly the same fuse as
> has blown out / as is marked onthe back of the power supply.
>
> Now, I understand what the 2.5A, the 250V and the T stand for.
> However, I have no idea what the L means and whether it is relevant...
> Would there be any potential problem in replacing such a fuse with one
> that does not have the "L"??
It's a relatively new marking on IEC standard fuses. You're obviously
familiar with the other figures.
L means Low beaking capacity.
H - the other other alternative means High breaking capacity ( large
rupture current ).
As you only need an L rated fuse it doesn't matter about the breaking
capacity in your case. Just make sure you get an identical IEC type fuse.
H type fuses sometimes used to be called HRC or HBC - high breaking/rupture
capacity and are typically made with a ceramic body to contain the arc on
fault.
Other posters - please note that US 'slo-blo' is *NOT* the same as
IEC/European 'T' - time lag. The characteristics are different.
Graham ( sorry about the alias )
Arthur Dent
> Garbage Eh?
>
> From a component catalogue
> " Interrupt Rating: The rated breaking capacity of the fuse
> (interrupting rating) is the short circuit current at which the fuse can
> blow (at the rated voltage) without destruction or arcing being maintained."
>
> I never said that all ceramics are HRC but it is safe to assume a glass one
> is not
I tend to prefer your explanation better - however H rated fuses are indeed
available in glass construction - often with a sand infill. Personally I feel
more confident with the ceramic ones though.
Graham
Phil Allison
"Arthur Dent" <babe...@SiriusCyberneticsCorp.com> wrote in message
news:3CD75929...@SiriusCyberneticsCorp.com...
> Olav Beckmann wrote:
>
> > Hi,
> >
> > I need to replace a fuse in our Mackie 32.8 power supply
> > which has the following markings: "2.5A L 250V T".
> >
> > The manual emphasises that I'm supposed to get exactly the same fuse as
> > has blown out / as is marked onthe back of the power supply.
> >
> > Now, I understand what the 2.5A, the 250V and the T stand for.
> > However, I have no idea what the L means and whether it is relevant...
> > Would there be any potential problem in replacing such a fuse with one
> > that does not have the "L"??
>
> It's a relatively new marking on IEC standard fuses. You're obviously
> familiar with the other figures.
>
> L means Low beaking capacity.
>
> H - the other other alternative means High breaking capacity ( large
> rupture current ).
>
> As you only need an L rated fuse it doesn't matter about the breaking
> capacity in your case. Just make sure you get an identical IEC type fuse.
>
> H type fuses sometimes used to be called HRC or HBC - high
breaking/rupture
> capacity and are typically made with a ceramic body to contain the arc on
> fault.
** Really, unless they are sand filled to quench the arc they cannot
be HRC types.
>
> Other posters - please note that US 'slo-blo' is *NOT* the same as
> IEC/European 'T' - time lag. The characteristics are different.
** Really, that *is* tantalising. Can you elaborate?
Regards, Phil