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tabbypurr wrote:
On Tuesday, 28 November 2017 23:08:59 UTC, whit3rd wrote:
On Tuesday, November 28, 2017 at 12:48:01 AM UTC-8, GS wrote:
Commercial isolation transformers get rid of common mode noise, and
since one leg of output is tied to ground, forms a new local
neutral.
That's only true of SOME isolation transformers; the ones used for
bench safety when working on live equipment do NOT make the
neutral-ground connection.
Quite. And building site transformers earth the centre tap.
IOW, they convert the European 240volt system to the American
120V/240V system.
On Thursday, 7 December 2017 21:17:18 UTC, Michael Terrell wrote:
tabbypurr wrote:
On Tuesday, 28 November 2017 23:08:59 UTC, whit3rd wrote:
On Tuesday, November 28, 2017 at 12:48:01 AM UTC-8, GS wrote:
Commercial isolation transformers get rid of common mode noise, and
since one leg of output is tied to ground, forms a new local
neutral.
That's only true of SOME isolation transformers; the ones used for
bench safety when working on live equipment do NOT make the
neutral-ground connection.
Quite. And building site transformers earth the centre tap.
IOW, they convert the European 240volt system to the American
120V/240V system.
They output 110v centre earthed, so nothing is over 55v ac from ground. It was the building site standard until RCDs made 110v not really needed.
Unless they didn't want to replace all their existing power tools?
The wiring is US, even if the transformer is only 50%. Not all of our
power tools are 120 VAC. Some are 240, and others are 480 VAC, three phase.
I think that if 240 volts is really that much more dangerous itOn Fri, 8 Dec 2017 01:14:00 -0500, Michael A Terrell
mike.terrell@earthlink.net> wrote:
Unless they didn't want to replace all their existing power tools?
The wiring is US, even if the transformer is only 50%. Not all of our
power tools are 120 VAC. Some are 240, and others are 480 VAC, three phase.
I've always wondered why so many foreign countries have 240volts as
their standard voltage. We in the U.S. do just fine with 120v, except
for heating devices and some very large motors. So why do they continue
to use 240volts in these foreign countries? If for no other reason, it's
considerably more dangerous.....
I know all too well how getting shocked from 120v feels, and although I
have never gotten shocked by 240v, I know it's a lot worse. Both
voltages can kill a person, but I'd think that 240 kills faster...
I know all too well how getting shocked from 120v
feels, and although I have never gotten shocked
by 240v, I know it's a lot worse.
On Fri, 8 Dec 2017 01:14:00 -0500, Michael A Terrell
mike.terrell@earthlink.net> wrote:
Unless they didn't want to replace all their existing power tools?
The wiring is US, even if the transformer is only 50%. Not all of our
power tools are 120 VAC. Some are 240, and others are 480 VAC, three phase.
I've always wondered why so many foreign countries have 240volts as
their standard voltage. We in the U.S. do just fine with 120v, except
for heating devices and some very large motors. So why do they continue
to use 240volts in these foreign countries? If for no other reason, it's
considerably more dangerous.....
I know all too well how getting shocked from 120v feels, and although I
have never gotten shocked by 240v, I know it's a lot worse. Both
voltages can kill a person, but I'd think that 240 kills faster...
have never gotten shocked by 240v, I know it's a lot worse. Both
voltages can kill a person, but I'd think that 240 kills faster...
On Wed, 22 Nov 2017 14:39:04 -0500, "J.B. Wood" <arl_123234@hotmail.com
wrote:
Hello, and do you have a particular make and model number of device in
mind? An marketed as an AC isolation transformers usually doesn't
provide voltage conversion with input (primary) to output (secondary)
energy transfer solely via magnetic coupling. There are also adjustable
autotransformers (e.g. the venerable Variac brand) that, for example,
takes 120 VAC at input and can provides 0-130 VAC output. The primary
and secondaries of these devices aren't conductively isolated (as an
ohmmeter test will confirm). There are also devices which combine both
isolation and adjustable autotransformer function in one enclosure. Or
you can simply take, say, a 120 VAC-to-120 VAC isolation transformer and
follow it with an adjustable autotransformer, keeping in mind the
maximum AC current/power ratings of the devices. Sincerely,
I reaad on some website where someone took two 120 to 240 volt
transformers, connected both 240 windings together and ended up with 120
on the secondary, completely isolated from the AC line. This makes
sense, for someone who has two such transformers on hand. But would not
make sense to buy two transformers.
There was an old patent using two neon sign type transformers back to back.
The problem with isos, you get higher voltage with no load than normal, and
droop 10-20% with load..
oldschool@tubes.com> wrote:
I reaad on some website where someone took two 120 to 240 volt
transformers, connected both 240 windings together and ended up with 120
on the secondary, completely isolated from the AC line. This makes
sense, for someone who has two such transformers on hand. But would not
make sense to buy two transformers.
There was an old patent using two neon sign type transformers back to back.
The problem with isos, you get higher voltage with no load than normal, and
droop 10-20% with load..
On Sunday, 10 December 2017 08:48:23 UTC, GS wrote:
There was an old patent using two neon sign type transformers back to back.
I can't imagine how that could be worth patenting. Many patents have no value.
The problem with isos, you get higher voltage with no load than normal, and
droop 10-20% with load..
It would take an unusually tiny transformer to be that badly regulated.
On 12/10/2017 8:14 AM, tabbypurr wrote:
On Sunday, 10 December 2017 08:48:23 UTC, GS wrote:
There was an old patent using two neon sign type transformers back to back.
I can't imagine how that could be worth patenting. Many patents have no value.
The problem with isos, you get higher voltage with no load than normal, and
droop 10-20% with load..
It would take an unusually tiny transformer to be that badly regulated.
"Neon sign transformer"
They are DESIGNED to be baldy regulated.
High voltage to strike the initial arc, then sag down to
a sustaining voltage.
Same design with fluorescent ballast transformers.
Both are designed for a specific purpose, not to be used in some
bastardized lash up.
On Sunday, 10 December 2017 08:48:23 UTC, GS wrote:
oldschool@tubes.com> wrote:
I reaad on some website where someone took two 120 to 240 volt
transformers, connected both 240 windings together and ended up with 120
on the secondary, completely isolated from the AC line. This makes
sense, for someone who has two such transformers on hand. But would not
make sense to buy two transformers.
There was an old patent using two neon sign type transformers back to back.
I can't imagine how that could be worth patenting. Many patents have no value.
The problem with isos, you get higher voltage with no load than normal, and
droop 10-20% with load..
It would take an unusually tiny transformer to be that badly regulated.
NT
On Sunday, 10 December 2017 08:48:23 UTC, GS wrote:
oldschool@tubes.com> wrote:
I reaad on some website where someone took two 120 to 240 volt
transformers, connected both 240 windings together and ended up with 120
on the secondary, completely isolated from the AC line. This makes
sense, for someone who has two such transformers on hand. But would not
make sense to buy two transformers.
There was an old patent using two neon sign type transformers back to back.
I can't imagine how that could be worth patenting. Many patents have no value.
I think I missed something in middle, like carbon trace resistors.
The problem with isos, you get higher voltage with no load than normal, and
droop 10-20% with load..
It would take an unusually tiny transformer to be that badly regulated.
NT
tabbypurr> wrote:
On Sunday, 10 December 2017 08:48:23 UTC, GS wrote:
oldschool@tubes.com> wrote:
I reaad on some website where someone took two 120 to 240 volt
transformers, connected both 240 windings together and ended up with 120
on the secondary, completely isolated from the AC line. This makes
sense, for someone who has two such transformers on hand. But would not
make sense to buy two transformers.
There was an old patent using two neon sign type transformers back to back.
I can't imagine how that could be worth patenting. Many patents have no value.
The problem with isos, you get higher voltage with no load than normal, and
droop 10-20% with load..
It would take an unusually tiny transformer to be that badly regulated.
NT
In my experience 10% droop is pretty good. 15% more common. I'm just
talking transformers in general. A Feroresonant one will do good.
Greg
In my experience 10% droop is pretty good. 15% more common. I'm just
talking transformers in general. A Feroresonant one will do good.
Sola-type CV transformers put out a wretched wave-form.
If your connected device is sensitive to mains noise,
they will not work out so well.