Resonant Transformer

A

Andy

Guest
Andy writes:

Older style constant voltage output power supplies sometimes
used a device called a "resonant transformer".

They seem to work well, and many RV systems use them.

I just haven't been able, yet, to get a good gut feeling
of an explanation of how a resonant transformer, without
any electronics other than rectifier diodes, can maintain
a regulated output D C voltage.

If anyone here has a good feel for this, and can provide
an explanation, I would be most happy to learn this principle.
Thank you,

Andy W4OAH
 
Andy wrote:
Andy writes:

Older style constant voltage output power supplies sometimes
used a device called a "resonant transformer".

They seem to work well, and many RV systems use them.

I just haven't been able, yet, to get a good gut feeling
of an explanation of how a resonant transformer, without
any electronics other than rectifier diodes, can maintain
a regulated output D C voltage.

If anyone here has a good feel for this, and can provide
an explanation, I would be most happy to learn this principle.
Thank you,

Andy W4OAH
Click to expand...
Very simple.
A resonant transform trashes the waveform by dinking with the third and
other harmonics.

These have been illegal in most civilized countries for decades.
And even in parts of New Mexico.


--
Many thanks,

Don Lancaster
Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
voice: (928)428-4073 email: don@tinaja.com

Please visit my GURU's LAIR web site at http://www.tinaja.com
 
On Thu, 06 Jan 2005 16:21:14 -0700, Don Lancaster <don@tinaja.com>
wrote:

Very simple.
A resonant transform trashes the waveform by dinking with the third and
other harmonics.

These have been illegal in most civilized countries for decades.
And even in parts of New Mexico.
Click to expand...
Why would anyone want to make a particular type of transformer (of all
things) *illegal* for God's sake? Why the proscription??

--

"What is now proved was once only imagin'd." - William Blake, 1793.
 
Paul Burridge wrote:
On Thu, 06 Jan 2005 16:21:14 -0700, Don Lancaster <don@tinaja.com
wrote:

Very simple.
A resonant transform trashes the waveform by dinking with the third and
other harmonics.

These have been illegal in most civilized countries for decades.
And even in parts of New Mexico.

Why would anyone want to make a particular type of transformer (of all
things) *illegal* for God's sake? Why the proscription??

--

"What is now proved was once only imagin'd." - William Blake, 1793.
Click to expand...
IEE 455 or some such. I've got the exact reference somewhere in Tech
Musings

Thou shalt not trash thy power line with harmonics if thine power is
above 50 watts.
The law now in Europe for a decade and the US for several years.

Which is what modern power factor correction is all about.

Resonant transformers are ridiculously above the harmonic limits.


--
Many thanks,

Don Lancaster
Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
voice: (928)428-4073 email: don@tinaja.com

Please visit my GURU's LAIR web site at http://www.tinaja.com
 
Paul Burridge wrote:
On Thu, 06 Jan 2005 16:21:14 -0700, Don Lancaster <don@tinaja.com
wrote:


Very simple.
A resonant transform trashes the waveform by dinking with the third and
other harmonics.

These have been illegal in most civilized countries for decades.
And even in parts of New Mexico.


Why would anyone want to make a particular type of transformer (of all
things) *illegal* for God's sake? Why the proscription??
Click to expand...
There are some here, up to ~5000va; no mention of them being contraband:


http://www.sola-hevi-duty.com/products/powerconditioning/cvs.htm
Power Conditioner - Sola/Hevi-Duty - Constant Voltage Transformers

--
john
 
Hi John,

There are some here, up to ~5000va; no mention of them being contraband:


http://www.sola-hevi-duty.com/products/powerconditioning/cvs.htm
Power Conditioner - Sola/Hevi-Duty - Constant Voltage Transformers
Click to expand...

Unless I misunderstand something, I read under "Operating
Characteristics" that the input current without a load can be up to 50%
or more of the full load current. Whoa!

Regards, Joerg

http://www.analogconsultants.com
 
I read in sci.electronics.design that Don Lancaster <don@tinaja.com>
wrote (in <41DDC7EA.C85B178C@tinaja.com>) about 'Resonant Transformer',
on Thu, 6 Jan 2005:
Very simple.
A resonant transform trashes the waveform by dinking with the third and
other harmonics.
Click to expand...
Agreed that's very simple, but is it an explanation?
These have been illegal in most civilized countries for decades. And
even in parts of New Mexico.
Click to expand...
I don't know of any law against them in Europe that's been in place for
decades. Higher-power examples (e.g. 250 VA) probably won't meet EN
61000-3-2.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk
 
Joerg wrote:
Hi Paul,

Why would anyone want to make a particular type of transformer (of all
things) *illegal* for God's sake? Why the proscription??



Probably because it could mess up the power grid if you had too many of
those online. Depending on how well they are equipped with caps, input
inductors and the like their input current can deviate so much from
sinusoidal that it could become a problem. I had seen one where the
lamps connected to the same power phase actually began to 'sing'.

That is also a reason why power factor correction (PFC) is mandatory for
heavy duty gear in some countries. Meaning you can't just slap in a
rectifier plus some large electrolytics and then happily run your big
switcher from that like in the good old days. In the same way that you
can't replace the muffler on an MG-B with a couple of straight pipes for
that nice loud roar...

Regards, Joerg

http://www.analogconsultants.com
Click to expand...
I bet those "singing" lamps were switchers (ie: had solid state
controllers).
 
Hi Robert,

I bet those "singing" lamps were switchers (ie: had solid state
controllers).
Click to expand...
Nope, plain old incandescent bulbs. No switchers, just switches ;-)

And the singing was nearly gone when the res xfmr was loaded with
something heavy. So theoretically you could do morse code via load on-off.

Regards, Joerg

http://www.analogconsultants.com
 
I read in sci.electronics.design that Don Lancaster <don@tinaja.com>
wrote (in <41DDDFBD.2B840010@tinaja.com>) about 'Resonant Transformer',
on Thu, 6 Jan 2005:

IEE 455 or some such.
Click to expand...
Did you mean 'IEEE'?

I've got the exact reference somewhere in Tech
Musings

Thou shalt not trash thy power line with harmonics if thine power is
above 50 watts.
Click to expand...
No. Not in Europe.

The law now in Europe for a decade
Click to expand...
Since 1998 there has been control of mains harmonics emissions in
Europe. But nothing there about 50 W.

and the US for
several years.
Click to expand...
Only IEEE 519 and that applies to sites, not individual pieces of
equipment. The US adamantly refuses to produce a 120 V 60 Hz version of
IEC 61000-3-2.
Which is what modern power factor correction is all about.

Resonant transformers are ridiculously above the harmonic limits.
Click to expand...
Low power ones may not violate the Class A limits of IEC/EN 61000-3-2,
which are absolute current limit, so very lax for low-power stuff.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk
 
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