Re: UL & fuse rating




<r.laury@xxxxxxxxxxx> wrote in message
news:NNOdnUDNRpZEUmvanZ2dnUVZ_uSgnZ2d@xxxxxxxxxxxxxx
Hi Group:

I've just finished designing a new switching power supply.
It' rated at 90VAC - 277VAC input and 12V@xxxxxxx =30W output.
I've completed all the EMC test and am preparing for
UL Class 2 approval. The nominal input current at 277VAC is around
.53amps.
The fuse I've selected is a 5mm pigtail, 1.5amp fast action rated at 250V.
There are no 5mm glass fuses in the US rated higher than 250V.
I can find them in other countries, but Little Fuse, Bussman ect
does not make them. How do all of the other power supply
MFG with universal input fuse their products? I'll be talking with UL next
week
and I'm sure I'll find out but, I would like to get a heads up.

Any input appreciated

RonL
Wow talk about coincidence! I've just finished research and writing a page
all about fuses for the club website (will be uploaded on Sunday)

Here is an excerpt from webpage about the voltage rating:

Voltage rating.
The voltage rating has no effect on the current rating but is important.
When a fuse blows an arc is developed between the two ends of the broken
fuse element and if the voltage across these ends is high enough, the arc
will be maintained and the current will not be interrupted. This condition
could result in considerable damage to the equipment, even melting of the
fuse body and / or fire. Arcs are readily produced in high voltage circuits
or where inductive loads are being used and in these conditions the voltage
rating of a fuse must not be exceeded.

Fuses can be used for their current rating at all voltages (AC and DC, there
is no real difference where a fuse is concerned) up to their maximum
voltage. When it is known for certain that although the circuit has a high
voltage present the power available is limited, it is possible to use a fuse
at a higher voltage than that for which it is rated. This is common practice
in domestic electronic equipment and quite safe. However, if you have any
doubt, keep within the voltage ratings given by the manufacturers.


Read the whole page from Sunday on:

Highfields Amateur Radio Club Website:
http://highfields-arc.co.uk

It will be in Constructors Corner, full URL for that page will be:
http://highfields-arc.co.uk/constructors/fuses.htm

But don't forget it won't be there until Sunday!
HTH

Brian MW0GKX



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