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From: Cursitor Doom <cd999666@notformail.com>
Newsgroups: sci.electronics.design
Subject: Re: electrical deaths
Date: Sun, 1 Dec 2024 23:59:42 -0000 (UTC)
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On Sun, 1 Dec 2024 22:19:34 +0100, Carlos E.R. wrote:

> On 2024-12-01 21:05, Edward Rawde wrote:
>> "Carlos E.R." <robin_listas@es.invalid> wrote in message
>> news:f1ru1lxdqh.ln2@Telcontar.valinor...
>>> On 2024-12-01 18:29, Cursitor Doom wrote:
>>>> On Thu, 28 Nov 2024 17:58:18 -0800, john larkin wrote:
>>>>
>>>>> On Fri, 29 Nov 2024 01:30:40 +0100, "Carlos E.R."
>>>>> <robin_listas@es.invalid> wrote:
> 
> ...
> 
>>>>>> Jesus!
>>>>>>
>>>>>> Yes, I have seen them. On 220 volts. They were used for
>>>>>> transformers, those that had 120 on one side, 220 on the other,
>>>>>> both being female sockets, so you needed a cable with two male
>>>>>> plugs to connect them to the wall.
>>>>>>
>>>>>> We don't see such transformers anymore, but when I was a kid they
>>>>>> were common, because although most houses were 220 volts, some were
>>>>>> 125, so we had gadgets of both voltages.
>>>>>
>>>>> I've seen them used between two houses, when one had the power shut
>>>>> off.
>>>>
>>>> There are thousands of 240VAC to 110VAC transformers in the UK. You
>>>> can buy or hire them. They are mandatory for site work. IOW, builders
>>>> who need mains power for their drills and saws etc have to use these
>>>> transformers for safety reasons.
>>>
>>> Huh? Why would they want to use their power tools at half the voltage
>>> and at least half the power? Running a 240 volt drill at 110?
>> 
>> No, the power tools will be designed for 115V Building sites require
>> nothing above 60V (the exact number may be 55, not sure) between you
>> and ground.
>> So 240V to 120V isolation transformer with secondary centre tapped to
>> ground.
>> Public display christmas tree lights may require the same. Nothing
>> above 60V so you can't get your hand on the open circuit end end of a
>> string which has 240V on the other end.
> 
> Ah, it is a building code somewhere. USA? Ah, no, you said UK. Well,
> that is a surprise to me. I had no idea.
> 
> But they are using the two semiphases, so 120 volts tools?

Yes, the tools are designed to run at half the normal mains supply 
voltage.

> Interesting idea. Wise. Unless some idiot forgets to install the ground
> connection because he is on a hurry.

Not possible unless someone deliberately tampers with it.
 
> No, here (Spain) we use full voltage (230) at building sites. Some
> machines, like the crane, may have the three phases, ie, 300 volts
> between phases. Of course, I suppose many workers are using battery
> powered tools.

In Spain the ground is usually a *lot* drier than in the UK! I know you 
have your 'cold drop' in October, but the rest of the year is generally 
pretty dry.