Re: UL & fuse rating
- From: legg <legg@xxxxxxxxxxxxxxx>
- Date: Sat, 05 Apr 2008 11:13:27 -0500
On Fri, 4 Apr 2008 20:02:27 -0500, <r.laury@xxxxxxxxxxx> wrote:
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
Your label ratings are the problem - they should reflect AC nominal
line voltages only (1e 110-240). UL testing automatically adds and
subtracts margins for evaluation to reflect typical line voltage
tolerances in the field. If you intend to list operation over the
wider range on your product label, it will be evaluated to those
voltages plus and minus similar margins.
This means it will be evaluated for continuous operation and single
fault abnormals over a 76 to 318VAC range, to carry the extended range
markings, something that you must take into account. This may place
your equipment outside the operating voltage class that you intend it
for.
The fact that your device operates over the range indicated earlier
can be added to your specification, for custmer/client reasurance, but
the label should only reflect the nominal environment, as a wider
range is required simply to claim normal function.
RL
.
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