Repairing wall warts

Tony Duell ard at p850ug1.demon.co.uk
Fri Feb 17 16:44:16 CST 2006


> 
> On 2/16/2006 at 6:56 PM ard at p850ug1.demon.co.uk wrote:
> 
> >Yes, the standard mains plug over here is rated at 13A, and contains a 
> >cartridge fuse (nromally, 3A, 5A, or 13A). Obviously PSUs with a mains 
> >cable are fitted with such a plug which contains a fuse (even moulded-on 
> >mains plugs [1] have a fuseholder and fuse)
> 
> Are there any appliances in the UK, save for heaters, that draw 13A?  From

A medium-sized PDP11 system :-)

More seriously, the main high-power appliances are all based on heating 
elements. 3kW portable electric heaters are common (both radiant elements 
and fan-assisted ones). Electric kettles tend to be about 2.5kW (so 
around 10A)


> my viewpoint in the US, with 120v mains outlets, appliances are rated at
> less than 15A.  13A at 220v seems to me to be a huge amount of power.  To

What's a typical rating for an electric kettle?

> be sure, we have some 240v appliances, but they're mostly stationary items,
> like ranges (cookers) and clothes dryers and have special (usually a large
> crowfoot) receptacles connected to a single distribution panel circuit.

Tumble driers (and washing machines, dishwashers, which have internal 
water heating elements) are just plugged into a normal 13A socket over 
here (and they may well aproach the 13A maximum). Most electric cookers 
are permanently wired in to a speical circuit, fused at 30A, but there 
are small tabletop cookers that just plug into the 13A socket (and again 
may well draw close to that current when in operation). Water heaters and 
shower heaters are also permanently wired in on special circuits, the 
latter might well be fused at 45A (yes, 9kW shower heaters do exist).

Machine tools, etc are generally connected by a different set of 
connectors. I know them as 'BS4343', they have a CEN number that I can't 
remember. They are colour-coded as to voltage, come in 3, 4, 5 pole 
versions (for 3 phase applications), and come in various ratings up to 
125A. These connectors do not contain fuses.

Industrial portable power tools are 110V over here, operated from an 
isolating transformer with the secondary centre-tapped to ground. The 
idea being that if you accidentally touch a single wire, or the 
insulation of the tool breaks down, the maximum voltage you will get 
across you is 55V which is unlikely to be fatal. The typical transformer 
used for these tools is rated at 3kW (OK, strictly 3kVA). I know my 
father has an angle grinder which draws over 20A at 110V....

-tony



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