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Posted by Richard Smith on June 25, 2007, 2:13 pm
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Hi
Very "off the wall" question directed to our gifted electricals and
electronics welders...
About 240V to 110V tranformers used with professional power tools here
in the UK - needed by law on building sites - which are heavy - my
3kVA one (?) weighs 19.5kg (43lb). These are "centred-tapped" (to
Earth potential) - so see 55V between Earth and either "hot" wire.
Any "bright sparks" like Iggy - would it be possible to make a
much lighter transformer using inverter technology?
Perhaps chop up the incoming 50Hz AC without rectification at
thousands of Hz, put that through a much smaller and lighter
transformer then rectify the output to an unsmoothed DC to run power
tools?
As all wall sockets rated at 13A with 240V, power available = 240 * 13
= 3120VA - which would be a good capacity for this device.
???
Richard Smith
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Posted by Andrew Mawson on June 25, 2007, 3:20 pm
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> Hi
>
> Very "off the wall" question directed to our gifted electricals and
> electronics welders...
>
> About 240V to 110V tranformers used with professional power tools
here
> in the UK - needed by law on building sites - which are heavy - my
> 3kVA one (?) weighs 19.5kg (43lb). These are "centred-tapped" (to
> Earth potential) - so see 55V between Earth and either "hot" wire.
>
> Any "bright sparks" like Iggy - would it be possible to make a
> much lighter transformer using inverter technology?
>
> Perhaps chop up the incoming 50Hz AC without rectification at
> thousands of Hz, put that through a much smaller and lighter
> transformer then rectify the output to an unsmoothed DC to run power
> tools?
>
> As all wall sockets rated at 13A with 240V, power available = 240 *
13
> = 3120VA - which would be a good capacity for this device.
>
> ???
>
> Richard Smith
110v transformers are NOT required by law on building sites in the UK.
What the regulations call for is the lowest practical safe voltage,
which is often interpreted as 110v. In fact a 240v source through a
30mA RCD is actually also acceptable, as is a 24v supply, which is
even safer but hardly ever used !
AWEM
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Posted by Ignoramus11870 on June 26, 2007, 10:49 am
Please log in for more thread options > Hi
>
> Very "off the wall" question directed to our gifted electricals and
> electronics welders...
>
> About 240V to 110V tranformers used with professional power tools here
> in the UK - needed by law on building sites - which are heavy - my
> 3kVA one (?) weighs 19.5kg (43lb). These are "centred-tapped" (to
> Earth potential) - so see 55V between Earth and either "hot" wire.
You could make a smaller transformer using inverter technology, it
would require a rectifier, high frequency inverter, transformer,
rectifier, and low frequency inverter to make 50 Hz out of many kHz
that inverters operate on, and then some sort of a filter to protect
your tools from voltage spikes caused by high dI/dt inherent in
inverters. Kind of expensive. I definitely do not consider myself to
be very educated on the issue, but I would suppose that in the end you
would not easily afford one. I would invest in a nbice dolly to drag
that transformer around.
i
> Any "bright sparks" like Iggy - would it be possible to make a
> much lighter transformer using inverter technology?
>
> Perhaps chop up the incoming 50Hz AC without rectification at
> thousands of Hz, put that through a much smaller and lighter
> transformer then rectify the output to an unsmoothed DC to run power
> tools?
>
> As all wall sockets rated at 13A with 240V, power available = 240 * 13
>= 3120VA - which would be a good capacity for this device.
>
> ???
>
> Richard Smith
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Posted by Andrew Mawson on June 26, 2007, 12:58 pm
Please log in for more thread options
> On Mon, 25 Jun 2007 18:13:04 GMT, Richard Smith
> > Hi
> >
> > Very "off the wall" question directed to our gifted electricals
and
> > electronics welders...
> >
> > About 240V to 110V tranformers used with professional power tools
here
> > in the UK - needed by law on building sites - which are heavy - my
> > 3kVA one (?) weighs 19.5kg (43lb). These are "centred-tapped" (to
> > Earth potential) - so see 55V between Earth and either "hot" wire.
>
> You could make a smaller transformer using inverter technology, it
> would require a rectifier, high frequency inverter, transformer,
> rectifier, and low frequency inverter to make 50 Hz out of many kHz
> that inverters operate on, and then some sort of a filter to protect
> your tools from voltage spikes caused by high dI/dt inherent in
> inverters. Kind of expensive. I definitely do not consider myself to
> be very educated on the issue, but I would suppose that in the end
you
> would not easily afford one. I would invest in a nbice dolly to drag
> that transformer around.
>
> i
Now THAT'S what I need, a nice Dolly to drag things around for me, she
could also make copious cups of tea, and wipe my fevered brow when it
all gets too much !
AWEM
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Posted by Gunner on June 26, 2007, 1:56 pm
Please log in for more thread options On Tue, 26 Jun 2007 09:49:26 -0500, Ignoramus11870
>I would invest in a nbice dolly to drag
>that transformer around.
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=38137
Btw...it makes a pretty damned good base for a welding cart too. Lots of
guys around here use these to make up welding carts and tool carts to
drag around the back 40.
I think they are currently on sale btw
Gunner
A human being should be able to change a diaper, plan an invasion,
butcher a hog, conn a ship, design a building, write a sonnet,
balance accounts, build a wall, set a bone, comfort the dying,
take orders, give orders, cooperate, act alone, solve equations,
analyze a new problem, pitch manure, program a computer,
cook a tasty meal, fight efficiently, die gallantly.
Specialization is for insects. Lazarus Long
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>
> Very "off the wall" question directed to our gifted electricals and
> electronics welders...
>
> About 240V to 110V tranformers used with professional power tools