On Tue, 27 Sep 2005 20:44:10 +0800, Xiaofan Chen wrote:

> I am not so sure whether the map is really that accurate.

I'm sure - this sort of thing changes surprisingly often.
 
Not long ago the voltage in most countries on the Continent of Europe was specified as 220V +/- 6%, and in the 
UK it was 240V +/- 6%.  In order to standardise it was decided that the nominal voltage would be 230V +/- 10%, 
so without actually changing anything we are now "the same" as the Continent (except that the limits are one 
or two volts different).  At home I regularly see voltages in the upper 240s just as I always have.  It means 
that designers of mains operated equipment know what they have to contend with, and by allowing for 207 to 
253V they can sell the same devices anywhere in Europe (subject to CE marking, of course! :-)

> I had to developed some seperate product for Japanese market
> since it is said that the mains voltage is slightly lower than
> the North America (100V versus 110V nomainal and 10% ripple).
> 
> In China the norminal is 220V and in Singapore norminal is 230V.
> So we often have to consider 253V as the higher end of
> AC voltage. The 3V extra than 250V may cause problem with
> the certification body since some relay manufacturers specify
> the isolation voltage (re-inforced insulation) to be 250V.

Hang on!  We're talking about AC RMS voltages - surely isolation has to be tested against *peak* voltages, 
which will be over 300V in the ranges we're talking about.

Cheers,


Howard Winter
St.Albans, England


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