From: John Woodgate
Subject: Re: 125 or 250V fuse?
Date: Sun, 29 Sep 2002 10:31:16 +0100
Organization: JMWA Electronics Consultancy
Reply-To: John Woodgate
NNTP-Posting-Date: Sun, 29 Sep 2002 12:38:30 +0000 (UTC)
X-Newsreader: Turnpike (32) Version 4.01 <5Z8C9wtxbnpWyFnyfFzqmVF739>
I read in sci.electronics.design that Alan R. Winstanley
wrote (in )
about '125 or 250V fuse?', on Sat, 28 Sep 2002:
>A definitive answer is published by Littelfuse, here:
>VOLTAGE RATING: The voltage rating, as marked on a
>fuse, indicates that the fuse can be relied upon to safely
>interrupt its rated short circuit current in a circuit where the
>voltage is equal to, or less than, its rated voltage. This system
>of voltage rating is covered by N.E.C. regulations and
>is a requirement of Underwriters Laboratories as a protection
>against fire risk. The standard voltage ratings used by
>fuse manufacturers for most small-dimension and midget
>fuses are 32, 63, 125, 250 and 600.
>In electronic equipment with relatively low output power
>supplies, with circuit impedance limiting short circuit currents
>to values of less than ten times the current rating of
>the fuse, it is common practice to specify fuses with 125 or
>250 volt ratings for secondary circuit protection of 500 volts
Note, however, that this text is definitive in the Americas. The
situation is different in detail in Europe. In particular, small
cartridge fuses (20 x 5 mm and 32 x 6.3 mm) are not normally available,
especially with safety certification valid in Europe, in voltage ratings
other than 250 V.
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
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