[sdiy] Mains Voltage Selector Switches & Fusing

[Meslin Frédéric]

Le Tue, 13 Sep 2011 17:38:12 +0200, Richard Gorbutt  
<Richardg at johnhenrys.com> a écrit:

> Some have the fuseholder and voltage selector built into one unit - fuse  
> one way up for 240, the other for 110. but you still have to swap the  
> fuse for a different value. Manufacturers get round it with a printed  
> warning on the back of the unit along with all the other safety  
> warnings- 'use correct value fuse for voltage' etc. most people don't  
> read them anyway. Is especially dodgy going from us to uk voltages and  
> keeping the high value fuse in. I get regular repair work from people  
> who don't read the small print, or change the fuse but not the voltage,  
> or simply use a plug adaptor without changing anything at all. Its not  
> too bad with smpsu wall warts, but plays merry hell with say, a hammond  
> and leslie. Bang/flames/sadface. Doh.
>

Hi,

I thought what was important is the fuse allowed power :

If you have, say a 230v, 375mA, it will let the device use a maximum
of 61 watts, after it burns because of Joule effect.
(230 x 0.375 / sqrt(2) = 61w)

With a 115v, 750mA, it will also let a maximum power of 61 watts.
(115 x 0.750 / sqrt(2) = 61w)

So, as they are calculated for the same maximum power, I think there
is no fuse replacement problem, am I wrong ?

Frédéric