Constant Voltage Transformer Question

[Spehro Pefhany]

On Sun, 2 Jan 2005 15:40:26 +0000, the renowned John Woodgate
<jmw@jmwa.demon.contraspam.yuk> wrote:

I read in sci.electronics.design that Greg Neff <greg@guesswhichwordgoes
here.com> wrote (in <ko0gt0lp9cks961bmfe64qernhralfgodu@4ax.com&gt about
'Constant Voltage Transformer Question', on Sun, 2 Jan 2005:

BTW, I have a question regarding dimming CFLs. One of the effects of
dimming an incandescent lamp is that the colour temperature drops as the
lamp dims. Depending on the application (a romantic dinner for example)
this can be a desired effect. I wonder if this is true for dimmable
CFLs. Has anyone here tried dimmable CFLs, and if so do they have a
pleasant light output when dimmed?

The light comes from the phosphor coating and changes colour very little
with excitation level.

You might have a patent there; a phosphor formulation could be devised
to produce the effect you mention. You'd sell a jillion. (;-)

http://archive.salon.com/sex/world/2001/01/10/light/


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

 

[John Woodgate]

I read in sci.electronics.design that Spehro Pefhany <speffSNIP@interlog
DOTyou.knowwhat> wrote (in <bcagt0lgehqe2dleuijdveskd79oa7p007@4ax.com&gt
about 'Constant Voltage Transformer Question', on Sun, 2 Jan 2005:

http://archive.salon.com/sex/world/2001/01/10/light/

It's very true that there is nothing new under the sun. But Powergen is
a UK electricity supplier company and I've certainly not seen any sign
of the product being marketed.

Maybe it emitted too much mains harmonic stuff. Or caused flicker. (;-)
--
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

 

[John Woodgate]

I read in sci.electronics.design that Watson A.Name - "Watt Sun, the
Dark Remover" <NOSPAM@dslextreme.com> wrote (in <10tg7i5n51j6gbd@corp.su
pernews.com&gt about 'Constant Voltage Transformer Question', on Sun, 2
Jan 2005:

which led me to the conclusion
that all the microwave was doing was switching the magnetron on and off,
and not 'dimming' it on a per cycle basis.

Yes. I don't think you can phase-control a magnetron. DON'T TRY!
--
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

 

[Tam/WB2TT]

"Watson A.Name - "Watt Sun, the Dark Remover"" <NOSPAM@dslextreme.com> wrote
in message news:10tg7i5n51j6gbd@corp.supernews.com...

.....................................
At work I've found this happens with three phase, and I've seen the
neutral wire carrying substantial current, especially when I measure the
current near areas where there is one or more copiers. They seem to
have a very high current draw at times, when the fuser comes on. I've
seen several volts diff between the neutral and ground. Check to see if
you nave a situation where the neutral and ground are not close to the
same voltage. Run appliances to see if that makes a diff. And if you
find that there is, it can be fixed with some rearrangement of the loads
on the breaker panel.

Power Co fixed it. There was a bad splice in the feed coming off the pole
into the house. You have a point about copiers and printers. I had to run a
separate feed to the color laser printer.

Tam
......................

 

[Chuck Harris]

Jim Thompson wrote:
led me to the conclusion

that all the microwave was doing was switching the magnetron on and off,
and not 'dimming' it on a per cycle basis.



AFAIK, that's the way most, if not all, microwaves adjust "power".

...Jim Thompson

Back in the early '80s, a company I worked with made a "precision"
microwave that did the power adjustment on a per cycle basis. It was
a simple thing that could go from 10 to 100% power by dropping full
cycles from the transformer's input.

The nice thing about that microwave was it didn't burn small things
when you were running at reduced power. One demonstration they
used was filling a watch glass with saline and running at 10% power
using a conventional microwave, and then the "precision" microwave.
The conventional microwave would spit and spatter as it blew up the
water around the edges of the puddle, the "precision" microwave heated
everything nice and evenly.

-Chuck Harris

 

[Richard the Dreaded Liber]

On Sun, 02 Jan 2005 17:22:46 +0000, John Woodgate wrote:

I read in sci.electronics.design that Spehro Pefhany <speffSNIP@interlog
DOTyou.knowwhat> wrote (in <bcagt0lgehqe2dleuijdveskd79oa7p007@4ax.com&gt
about 'Constant Voltage Transformer Question', on Sun, 2 Jan 2005:

http://archive.salon.com/sex/world/2001/01/10/light/

It's very true that there is nothing new under the sun. But Powergen is
a UK electricity supplier company and I've certainly not seen any sign
of the product being marketed.

Maybe it emitted too much mains harmonic stuff. Or caused flicker. (;-)

Or, they really _do_ work, and are being withheld from the hoi polloi, so
the lords and ladies get them all to themselves. ;-) Kinda like big oil
suppressing the Pogue carb. ;-)

Cheers!
Rich

 

[Jim Thompson]

On Sun, 02 Jan 2005 16:14:02 -0500, Chuck Harris
<cf-NO-SPAM-harris@erols.com> wrote:

Jim Thompson wrote:
led me to the conclusion
that all the microwave was doing was switching the magnetron on and off,
and not 'dimming' it on a per cycle basis.



AFAIK, that's the way most, if not all, microwaves adjust "power".

...Jim Thompson

Back in the early '80s, a company I worked with made a "precision"
microwave that did the power adjustment on a per cycle basis. It was
a simple thing that could go from 10 to 100% power by dropping full
cycles from the transformer's input.

The nice thing about that microwave was it didn't burn small things
when you were running at reduced power. One demonstration they
used was filling a watch glass with saline and running at 10% power
using a conventional microwave, and then the "precision" microwave.
The conventional microwave would spit and spatter as it blew up the
water around the edges of the puddle, the "precision" microwave heated
everything nice and evenly.

-Chuck Harris

I did a neon light dimmer that way... feed the transformer with full
cycles (to avoid saturation), and switched them in and out as groups
(with TRIACs).

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[Rich Grise]

On Sun, 02 Jan 2005 17:24:13 +0000, John Woodgate wrote:

I read in sci.electronics.design that Watson A.Name - "Watt Sun, the
Dark Remover" <NOSPAM@dslextreme.com> wrote (in <10tg7i5n51j6gbd@corp.su
pernews.com&gt about 'Constant Voltage Transformer Question', on Sun, 2
Jan 2005:
which led me to the conclusion
that all the microwave was doing was switching the magnetron on and off,
and not 'dimming' it on a per cycle basis.

Yes. I don't think you can phase-control a magnetron. DON'T TRY!

I've seen series-modulated magnetrons in military jamming transmitters,
but they have real DC for the plates. The rectifier in the last microwave
oven I took apart was half of a voltage doubler, and the maggie was the
other diode.

Fil. winding
C----| |--+----+UUU+
C C | | |
C D v Fil. If you think I'm going to try to draw
C --- Anode a magnetron, think again. ;-)
C | |
C-----+---+------+
|
GND

I wouldn't even want to try integral-cycle control with a klooge like
that!

Cheers!
Rich

 

[Jeff]

"Jim Thompson" <thegreatone@example.com> wrote in message
news:ikkbt0pjrt88is8loksicrm969oj15l4b7@4ax.com...

On Fri, 31 Dec 2004 22:11:24 +0000, John Woodgate
jmw@jmwa.demon.contraspam.yuk> wrote:

I read in sci.electronics.design that Jim Thompson
thegreatone@example.com> wrote (in <05ibt0t5kanq8gb9is8ke29novbq3ehbqm@
4ax.com&gt about 'Constant Voltage Transformer Question', on Fri, 31 Dec
2004:
I have 5x 75W halogen floods just over the cooking area... 15' up,
that's barely adequate.

You won't get a household-type CFL with as much light output as a 75 W
halogen. Do the luminaires have to be 15 feet up?

That's where the ceiling is ;-) (They're recessed PAR3 floods.)

Have you considered low voltage Halogen's? They used to come with a linear
transformer, to drive the halogen bulb at 12V. Common wattages were/are 20
and 50W. Newer ones use a SMPS with a crude unrectified output. Power
density of such SMPS is extremely high. We have a under cabinet low voltage
halogen system, which uses 3 x 20W bulbs, all run off of a single SMPS
that's about 1" x 3/4" x 2", including the standard size replaceable fuse!
Most of these newer low voltage halogens with the SMPS should last much
longer, since the SMPS should give a regulated output, and the filaments in
the halogen bulbs are much heavier for a given wattage.

Three 35 W (or so; I
don't know what ratings are available for 120 V) linear fluorescent
tubes would give you more light, but you would need to arrange a
suitable luminaire.

John, at least here in Canada/US, fluoro tubes are rated for 40W, for a
standard 4' tube. Energy saver tubes, which seem to be the only ones that
are commonly available now are rated for 34W, which fit the same fixture
without modification. The 34W tubes are junk, since the seem to only give
out 1/2 the light. New, T8 fluorescent tubes are rated for 32W, and are
significantly brighter then the older 40W tubes, they are also much
skinnier, with a diameter of about 1".

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[Jim Thompson]

On Mon, 03 Jan 2005 00:06:09 GMT, "Jeff" <levy_jeff@hotmail.com>
wrote:

[snip]

Have you considered low voltage Halogen's? They used to come with a linear
transformer, to drive the halogen bulb at 12V. Common wattages were/are 20
and 50W. Newer ones use a SMPS with a crude unrectified output. Power
density of such SMPS is extremely high. We have a under cabinet low voltage
halogen system, which uses 3 x 20W bulbs, all run off of a single SMPS
that's about 1" x 3/4" x 2", including the standard size replaceable fuse!
Most of these newer low voltage halogens with the SMPS should last much
longer, since the SMPS should give a regulated output, and the filaments in
the halogen bulbs are much heavier for a given wattage.


[snip]

Helluva good idea! Maybe automotive headlamps? They're quite rugged.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[Jeff]

"Jim Thompson" <thegreatone@example.com> wrote in message
news:hc4ht0513b6tc60nu6mutodcjtog8ieah4@4ax.com...

On Mon, 03 Jan 2005 00:06:09 GMT, "Jeff" <levy_jeff@hotmail.com
wrote:

[snip]

Have you considered low voltage Halogen's? They used to come with a
linear
transformer, to drive the halogen bulb at 12V. Common wattages were/are
20
and 50W. Newer ones use a SMPS with a crude unrectified output. Power
density of such SMPS is extremely high. We have a under cabinet low
voltage
halogen system, which uses 3 x 20W bulbs, all run off of a single SMPS
that's about 1" x 3/4" x 2", including the standard size replaceable
fuse!
Most of these newer low voltage halogens with the SMPS should last much
longer, since the SMPS should give a regulated output, and the filaments
in
the halogen bulbs are much heavier for a given wattage.


[snip]

Helluva good idea! Maybe automotive headlamps? They're quite rugged.

Very rugged indeed, but at the expense of efficiency, since they don't run
as hot as other halogens. They also will be difficult to adapt to normal
fixtures.

Commercially available low voltage halogens should be available all over the
place, at hardware stores and lighting centers - just look at the fixture to
see if it has a designed in, vented box or hump to hide a SMPS, or look at
the bulb spec's. Low voltage bulbs are generally always 12V.

A quick google search for halogen fixtures found this site:

http://www.pegasusassociates.com/products/HalogenFixtures/HalogenFixtures.ht
ml

Most fixtures that are labeled "low voltage" should have a SMPS to convert
line voltage to 12V. Watch out for the ones labled with magnetic
transformers, since they won't help much. Line voltage fixtures don't use
step down techniques. An added advantage of the 12V lights, with good
quality bulbs, gives a nicer white light, at least IMHO.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[Watson A.Name - \"Watt Su]

"John Woodgate" <jmw@jmwa.demon.contraspam.yuk> wrote in message
news:$BMK2EE94C2BFwpv@jmwa.demon.co.uk...

I read in sci.electronics.design that Watson A.Name - "Watt Sun, the
Dark Remover" <NOSPAM@dslextreme.com> wrote (in
10tg7i5n51j6gbd@corp.su
pernews.com&gt about 'Constant Voltage Transformer Question', on Sun, 2
Jan 2005:
which led me to the conclusion
that all the microwave was doing was switching the magnetron on and
off,
and not 'dimming' it on a per cycle basis.

Yes. I don't think you can phase-control a magnetron. DON'T TRY!

Yeah, maggies like to have their voltage constant. So they need a nice
flat topped pulse. But the pulse width can be varied to get diffetent
power levels. It's just that the microwave oven doesn't care much about
the freq, just as long as it's microwaves. So just feed it 60 Hz pulses
(or 50) and let it do its thing. Like the makers treat the transformer,
magnetron, HV rectifier and the capacitor as a unit. It wouldn't be
cost effective to try to gate the HV, so just use a SSR and turn the AC
to the transformer on and off.

--
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

 

[John Stewart]

"Watson A.Name - \"Watt Sun, the Dark Remover\"" wrote:

"John Woodgate" <jmw@jmwa.demon.contraspam.yuk> wrote in message
news:$BMK2EE94C2BFwpv@jmwa.demon.co.uk...
I read in sci.electronics.design that Watson A.Name - "Watt Sun, the
Dark Remover" <NOSPAM@dslextreme.com> wrote (in
10tg7i5n51j6gbd@corp.su
pernews.com&gt about 'Constant Voltage Transformer Question', on Sun, 2
Jan 2005:
which led me to the conclusion
that all the microwave was doing was switching the magnetron on and
off,
and not 'dimming' it on a per cycle basis.

Yes. I don't think you can phase-control a magnetron. DON'T TRY!

Yeah, maggies like to have their voltage constant.

CW Magnetrons as used for cooking need a CC supply. I managed to destroy a
very expensive Philips cooking magnetron rated at 2500 watts, 2.5 GHZ around
1960 running it from a CV, 4500 vdc, one amp regulated supply. Changed that
to a CC supply & the next magnetron lasted a long time. The application was
a research project where we needed a lot of RF in in small volume.

Far as I know you will find the PS in a Microwave Oven to be CC by virtue of
the transformer having lots of leakage inductance. The microwave frequency
is determined by the physical dimensions inside the magnetron. The power
delivered to the load depends on the PS duty cycle selected.

The magnetrons Watson has referred to are for pulsed Radar applications. The
amplitude of the output is controlled by the voltage stored in the
transmission line (usually lumped constant), while the length of the pulse
depends on the electrical length of the transmission line.

Cheers, John Stewart

So they need a nice
flat topped pulse. But the pulse width can be varied to get diffetent
power levels. It's just that the microwave oven doesn't care much about
the freq, just as long as it's microwaves. So just feed it 60 Hz pulses
(or 50) and let it do its thing. Like the makers treat the transformer,
magnetron, HV rectifier and the capacitor as a unit. It wouldn't be
cost effective to try to gate the HV, so just use a SSR and turn the AC
to the transformer on and off.

--
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

 

[Watson A.Name - \"Watt Su]

"Tam/WB2TT" <t-tammaru@c0mca$t.net> wrote in message
news:ndGdnc9QdPvArkXcRVn-iw@comcast.com...

"Watson A.Name - "Watt Sun, the Dark Remover"" <NOSPAM@dslextreme.com
wrote
in message news:10tg7i5n51j6gbd@corp.supernews.com...
.....................................
At work I've found this happens with three phase, and I've seen the
neutral wire carrying substantial current, especially when I measure
the
current near areas where there is one or more copiers. They seem to
have a very high current draw at times, when the fuser comes on.
I've
seen several volts diff between the neutral and ground. Check to
see if
you nave a situation where the neutral and ground are not close to
the
same voltage. Run appliances to see if that makes a diff. And if
you
find that there is, it can be fixed with some rearrangement of the
loads
on the breaker panel.

Power Co fixed it. There was a bad splice in the feed coming off the
pole
into the house. You have a point about copiers and printers. I had to
run a
separate feed to the color laser printer.

Tam
.....................

What really used to bother me was when I connected the thin ethernet T
connector to a PC in the classroom. There were a dozen or more PCs
daisychained to each other and to the network. I could see a spark when
I touched the T connector to the jack in the back. Shocking.

 

[John Woodgate]

I read in sci.electronics.design that Watson A.Name - "Watt Sun, the
Dark Remover" <NOSPAM@dslextreme.com> wrote (in <10tiipltk1d31be@corp.su
pernews.com&gt about 'Constant Voltage Transformer Question', on Mon, 3
Jan 2005:

What really used to bother me was when I connected the thin ethernet T
connector to a PC in the classroom. There were a dozen or more PCs
daisychained to each other and to the network. I could see a spark when
I touched the T connector to the jack in the back. Shocking.

I doubt that the voltage was literally shocking. The PCs are all
connected together by the safety earth conductor, and current from
filter capacitors from line to earth in each PC flows in the earth
conductor. Contrary to popular belief, this conductor has finite
resistance, so a voltage is developed across it. When you connect the
parallel path formed by the net cable shield, you cause a proportion of
the current to divert and flow in the shield. The voltage is very low,
but so is the impedance, so the current can be appreciable.

--
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

 

[Nicholas O. Lindan]

Various wrote:

'Constant Voltage Transformer Question' .... microwave ....
CW Magnetrons as used for cooking need a CC supply.

FWIW: Panasonic uWave ovens use solid-state power supplies. Very light
weight. The variable power feature on mine went bust pretty quick and
now it is 100% power 100% of the time.

http://www.panasonic.com/consumer_electronics/microwave/inverter_story.asp

More that this I do not know.

--
Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer: Electronics; Informatics; Photonics.
Remove spaces etc. to reply: n o lindan at net com dot com
psst.. want to buy an f-stop timer? nolindan.com/da/fstop/

 

[Zak]

Chuck Harris wrote:

Back in the early '80s, a company I worked with made a "precision"
microwave that did the power adjustment on a per cycle basis. It was
a simple thing that could go from 10 to 100% power by dropping full
cycles from the transformer's input.

The nice thing about that microwave was it didn't burn small things
when you were running at reduced power. One demonstration they
used was filling a watch glass with saline and running at 10% power
using a conventional microwave, and then the "precision" microwave.
The conventional microwave would spit and spatter as it blew up the
water around the edges of the puddle, the "precision" microwave heated
everything nice and evenly.

I just checked a new Bosch 'InnoWave' microwave with a switching power
supply. At the 90 watts setting it is 6 seconds on 16 seconds off
approximately.

This would scale up to 330 watts. Indeed, at the 360 watts level, my CFL
'test tube' doesn't switch off.

Strangely enough at the 1000 watts setting it doesn't shine much brighter.

Obviously I also put some containers with water in the oven.


Thomas

 

[Chuck Harris]

Zak wrote:

Chuck Harris wrote:

Back in the early '80s, a company I worked with made a "precision"
microwave that did the power adjustment on a per cycle basis. It was
a simple thing that could go from 10 to 100% power by dropping full
cycles from the transformer's input.

The nice thing about that microwave was it didn't burn small things
when you were running at reduced power. One demonstration they
used was filling a watch glass with saline and running at 10% power
using a conventional microwave, and then the "precision" microwave.
The conventional microwave would spit and spatter as it blew up the
water around the edges of the puddle, the "precision" microwave heated
everything nice and evenly.


I just checked a new Bosch 'InnoWave' microwave with a switching power
supply. At the 90 watts setting it is 6 seconds on 16 seconds off
approximately.

This would scale up to 330 watts. Indeed, at the 360 watts level, my CFL
'test tube' doesn't switch off.

Strangely enough at the 1000 watts setting it doesn't shine much brighter.

Your "CFL test tube" has a capacitor filtered DC power supply, and adjusts
its inverter to regulate the current going into the bulb. As long as the
converter can make the 60 (or so) volt drop the plasma requires to stay
lit, the bulb will stay lit.

-Chuck

 

[Zak]

Chuck Harris wrote:

This would scale up to 330 watts. Indeed, at the 360 watts level, my
CFL 'test tube' doesn't switch off.

Strangely enough at the 1000 watts setting it doesn't shine much
brighter.



Your "CFL test tube" has a capacitor filtered DC power supply, and adjusts
its inverter to regulate the current going into the bulb. As long as the
converter can make the 60 (or so) volt drop the plasma requires to stay
lit, the bulb will stay lit.

Well... I checked the microwave by placing the CFL tube (sans
electronics) in the oven.... the DC power suppy - if it would be
inclined to rectify 2.4 GHz - was not there to do its job


Thomas

 

[Chuck Harris]

Zak wrote:

Chuck Harris wrote:


Well... I checked the microwave by placing the CFL tube (sans
electronics) in the oven.... the DC power suppy - if it would be
inclined to rectify 2.4 GHz - was not there to do its job


Thomas

Hi Thomas,

That's an interesting use of technology ;-)

The same phenomon applies though: The plasma is lit by the E field
of the 2.4GHz E-M wave. Once the E field gets to be large enough
to make the plasma light off, further increases in E field have no
great effect.

-Chuck