reduce 125VAC to 120VAC, small form factor, and clean 60Hz s

[P E Schoen]

"John Fields" wrote in message
news:0saso81nc9fg38auieioe1uu5bqt963fkk@4ax.com...

On Fri, 10 May 2013 15:43:23 -0400, "P E Schoen" <paul@peschoen.com
wrote:

Hey, where is the test data promised by John Fields?

Just lazy, plus there doesn't seem to be a pressing need for it, and
posting the data will only lead to another pointless argument with Larkin,
so why even bother?

Well, since you made the assertion that variacs won't work "well" above
power line frequencies, even after having been shown the manufacturer's
specifications up to 2kHz, it is incumbent upon you to provide evidence
supporting your statements. Or, if you are lazy AND honest, you could simply
admit that you were wrong, and that should be the end of it. You could even
use some weasel-words to save face to some extent by quantifying your
statement, such as predicting a "probable" 5-10% reduction of efficiency
above 500 Hz to 2 KHz.

But my testing indicates that toroidal variac cores, at least those from
Superior and Staco, may work well up to 16 KHz and beyond, even with a
square wave. I predict that it is also possible to use these cores at a
constant V/Hz so that the 2 kVA cores might be able to produce at least 20
kVA as a DC-DC converter from 48-72 VDC batteries to 300-600 VDC for a VFD
motor controller. For my purposes, the smaller size and weight compared to
ferrite is not critical, and there should be lower switching losses at 16
KHz compared to 50-200 kHz for a ferrite converter, and such things as
wiring and PCB design should be much less critical.

So, for me, at least, some test data would be welcome.

Paul

 

[John Larkin]

On Sat, 11 May 2013 06:35:02 -0500, John Fields <jfields@austininstruments.com>
wrote:

On Fri, 10 May 2013 15:43:23 -0400, "P E Schoen" <paul@peschoen.com
wrote:


Hey, where is the test data promised by John Fields?

---
Just lazy, plus there doesn't seem to be a pressing need for it, and
posting the data will only lead to another pointless argument with
Larkin, so why even bother?

You certainly won't do it because it would be interesting. Electronics doesn't
seem to interest you.

Plus, you likely wouldn't know what to measure.


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

 

[Jim Thompson]

On Sat, 11 May 2013 18:38:06 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

On Sat, 11 May 2013 06:35:02 -0500, John Fields <jfields@austininstruments.com
wrote:

On Fri, 10 May 2013 15:43:23 -0400, "P E Schoen" <paul@peschoen.com
wrote:


Hey, where is the test data promised by John Fields?

---
Just lazy, plus there doesn't seem to be a pressing need for it, and
posting the data will only lead to another pointless argument with
Larkin, so why even bother?

You certainly won't do it because it would be interesting. Electronics doesn't
seem to interest you.

Plus, you likely wouldn't know what to measure.

Have you located your asshole yet ?>:-}

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

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

 

[P E Schoen]

"Jim Thompson" wrote in message
news:i93uo8tk8dhab2bffurcq6u7mrt8c9rrsr@4ax.com...

Have you located your asshole yet ?>:-}

Children! Please! Can't we act like adults here? We are relatively
superannuated, after all...

Perhaps that explains the reversion to childish behavior as a symptom of
dotage

Paul

 

[John Larkin]

On Sun, 12 May 2013 00:02:43 -0400, "P E Schoen" <paul@peschoen.com> wrote:

"Jim Thompson" wrote in message
news:i93uo8tk8dhab2bffurcq6u7mrt8c9rrsr@4ax.com...

Have you located your asshole yet ?>:-}

Children! Please! Can't we act like adults here? We are relatively
superannuated, after all...

Perhaps that explains the reversion to childish behavior as a symptom of
dotage

Paul

Thompson apparently isn't interested in Variacs either.


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

 

[John Fields]

On Sat, 11 May 2013 19:58:54 -0400, "P E Schoen" <paul@peschoen.com>
wrote:

"John Fields" wrote in message
news:0saso81nc9fg38auieioe1uu5bqt963fkk@4ax.com...

On Fri, 10 May 2013 15:43:23 -0400, "P E Schoen" <paul@peschoen.com
wrote:

Hey, where is the test data promised by John Fields?

Just lazy, plus there doesn't seem to be a pressing need for it, and
posting the data will only lead to another pointless argument with Larkin,
so why even bother?

Well, since you made the assertion that variacs won't work "well" above
power line frequencies, even after having been shown the manufacturer's
specifications up to 2kHz, it is incumbent upon you to provide evidence
supporting your statements. Or, if you are lazy AND honest, you could simply
admit that you were wrong, and that should be the end of it. You could even
use some weasel-words to save face to some extent by quantifying your
statement, such as predicting a "probable" 5-10% reduction of efficiency
above 500 Hz to 2 KHz.

But my testing indicates that toroidal variac cores, at least those from
Superior and Staco, may work well up to 16 KHz and beyond, even with a
square wave. I predict that it is also possible to use these cores at a
constant V/Hz so that the 2 kVA cores might be able to produce at least 20
kVA as a DC-DC converter from 48-72 VDC batteries to 300-600 VDC for a VFD
motor controller. For my purposes, the smaller size and weight compared to
ferrite is not critical, and there should be lower switching losses at 16
KHz compared to 50-200 kHz for a ferrite converter, and such things as
wiring and PCB design should be much less critical.

So, for me, at least, some test data would be welcome.

---
You say you have a plethora of wound cores and finished variacs, plus
the ability and desire to test them, so would it not make more sense
for you to do that than trying to coerce me into doing my single unit?


--
JF

 

[John Fields]

On Sat, 11 May 2013 20:32:22 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

On Sat, 11 May 2013 18:38:06 -0700, John Larkin
jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

On Sat, 11 May 2013 06:35:02 -0500, John Fields <jfields@austininstruments.com
wrote:

On Fri, 10 May 2013 15:43:23 -0400, "P E Schoen" <paul@peschoen.com
wrote:


Hey, where is the test data promised by John Fields?

---
Just lazy, plus there doesn't seem to be a pressing need for it, and
posting the data will only lead to another pointless argument with
Larkin, so why even bother?

You certainly won't do it because it would be interesting. Electronics doesn't
seem to interest you.

Plus, you likely wouldn't know what to measure.

Have you located your asshole yet ?>:-}

...Jim Thompson

---
It seems to be just below his nose.

--
JF

 

[John Fields]

On Sat, 11 May 2013 18:38:06 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

On Sat, 11 May 2013 06:35:02 -0500, John Fields <jfields@austininstruments.com
wrote:

On Fri, 10 May 2013 15:43:23 -0400, "P E Schoen" <paul@peschoen.com
wrote:


Hey, where is the test data promised by John Fields?

---
Just lazy, plus there doesn't seem to be a pressing need for it, and
posting the data will only lead to another pointless argument with
Larkin, so why even bother?

You certainly won't do it because it would be interesting.

---
Interesting to you, perhaps, since it would present you with a
platform from which you could cast aspersions - as is your wont -
however unfounded.
---

Electronics doesn't seem to interest you.

---
You seem to have missed the "Transistors" thread, where I repaired
Uncle Steve's circuit, provided him with a nice ASCIImatic, as well as
with a nicely working simulation.

Nice thread without you; you should participate less more often.
---

Plus, you likely wouldn't know what to measure.

---
Well, then, Mister Knowitall, perhaps you'll grace us with the way
you'd do it?

Spare no detail, I'm sure we're all on tenterhooks just waiting for
your sage reply.

--
JF

 

[John Larkin]

On Sun, 12 May 2013 01:44:17 -0500, John Fields <jfields@austininstruments.com>
wrote:

On Sat, 11 May 2013 19:58:54 -0400, "P E Schoen" <paul@peschoen.com
wrote:

"John Fields" wrote in message
news:0saso81nc9fg38auieioe1uu5bqt963fkk@4ax.com...

On Fri, 10 May 2013 15:43:23 -0400, "P E Schoen" <paul@peschoen.com
wrote:

Hey, where is the test data promised by John Fields?

Just lazy, plus there doesn't seem to be a pressing need for it, and
posting the data will only lead to another pointless argument with Larkin,
so why even bother?

Well, since you made the assertion that variacs won't work "well" above
power line frequencies, even after having been shown the manufacturer's
specifications up to 2kHz, it is incumbent upon you to provide evidence
supporting your statements. Or, if you are lazy AND honest, you could simply
admit that you were wrong, and that should be the end of it. You could even
use some weasel-words to save face to some extent by quantifying your
statement, such as predicting a "probable" 5-10% reduction of efficiency
above 500 Hz to 2 KHz.

But my testing indicates that toroidal variac cores, at least those from
Superior and Staco, may work well up to 16 KHz and beyond, even with a
square wave. I predict that it is also possible to use these cores at a
constant V/Hz so that the 2 kVA cores might be able to produce at least 20
kVA as a DC-DC converter from 48-72 VDC batteries to 300-600 VDC for a VFD
motor controller. For my purposes, the smaller size and weight compared to
ferrite is not critical, and there should be lower switching losses at 16
KHz compared to 50-200 kHz for a ferrite converter, and such things as
wiring and PCB design should be much less critical.

So, for me, at least, some test data would be welcome.

---
You say you have a plethora of wound cores and finished variacs, plus
the ability and desire to test them, so would it not make more sense
for you to do that than trying to coerce me into doing my single unit?

Weasel! And a lazy weasel at that.

But coerce? You volunteered to do the measurements. You assured me that you had
the necessary equipment.

All hat, no horse.


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

 

[John Larkin]

On Sun, 12 May 2013 02:33:55 -0500, John Fields <jfields@austininstruments.com>
wrote:

On Sat, 11 May 2013 18:38:06 -0700, John Larkin
jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

On Sat, 11 May 2013 06:35:02 -0500, John Fields <jfields@austininstruments.com
wrote:

On Fri, 10 May 2013 15:43:23 -0400, "P E Schoen" <paul@peschoen.com
wrote:


Hey, where is the test data promised by John Fields?

---
Just lazy, plus there doesn't seem to be a pressing need for it, and
posting the data will only lead to another pointless argument with
Larkin, so why even bother?

You certainly won't do it because it would be interesting.

---
Interesting to you, perhaps, since it would present you with a
platform from which you could cast aspersions - as is your wont -
however unfounded.
---

Electronics doesn't seem to interest you.

---
You seem to have missed the "Transistors" thread, where I repaired
Uncle Steve's circuit, provided him with a nice ASCIImatic, as well as
with a nicely working simulation.

Nice thread without you; you should participate less more often.
---

Plus, you likely wouldn't know what to measure.

---
Well, then, Mister Knowitall, perhaps you'll grace us with the way
you'd do it?

OK, it's definite: you wouldn't know what to measure.


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

 

[Jim Thompson]

On Sun, 12 May 2013 02:33:55 -0500, John Fields
<jfields@austininstruments.com> wrote:

On Sat, 11 May 2013 18:38:06 -0700, John Larkin
jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

On Sat, 11 May 2013 06:35:02 -0500, John Fields <jfields@austininstruments.com
wrote:

On Fri, 10 May 2013 15:43:23 -0400, "P E Schoen" <paul@peschoen.com
wrote:


Hey, where is the test data promised by John Fields?

---
Just lazy, plus there doesn't seem to be a pressing need for it, and
posting the data will only lead to another pointless argument with
Larkin, so why even bother?

You certainly won't do it because it would be interesting.

---
Interesting to you, perhaps, since it would present you with a
platform from which you could cast aspersions - as is your wont -
however unfounded.
---

Electronics doesn't seem to interest you.

---
You seem to have missed the "Transistors" thread, where I repaired
Uncle Steve's circuit, provided him with a nice ASCIImatic, as well as
with a nicely working simulation.

Nice thread without you; you should participate less more often.
---

Plus, you likely wouldn't know what to measure.

---
Well, then, Mister Knowitall, perhaps you'll grace us with the way
you'd do it?

Spare no detail, I'm sure we're all on tenterhooks just waiting for
your sage reply.

It'll never happen. Remember back when Larkin said, "It's not
"Larkin's" uni-shot. It was widely used in model airplane r/c
transmitters before ICs replaced it. And sure, you can make it not
work if you really want to, and that's your skill set."

And I replied, "Perhaps, with your "skill set", you'll provide us with
component values that make it work?"

Note the silence. But he sent his butt buddy, Jason Betts, around to
behave like a horsefly. Time to get out the fly swatter >:-}

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

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

 

[John Fields]

On Sun, 12 May 2013 07:50:09 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

On Sun, 12 May 2013 02:33:55 -0500, John Fields <jfields@austininstruments.com
wrote:

On Sat, 11 May 2013 18:38:06 -0700, John Larkin
jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

On Sat, 11 May 2013 06:35:02 -0500, John Fields <jfields@austininstruments.com
wrote:

On Fri, 10 May 2013 15:43:23 -0400, "P E Schoen" <paul@peschoen.com
wrote:


Hey, where is the test data promised by John Fields?

---
Just lazy, plus there doesn't seem to be a pressing need for it, and
posting the data will only lead to another pointless argument with
Larkin, so why even bother?

You certainly won't do it because it would be interesting.

---
Interesting to you, perhaps, since it would present you with a
platform from which you could cast aspersions - as is your wont -
however unfounded.
---

Electronics doesn't seem to interest you.

---
You seem to have missed the "Transistors" thread, where I repaired
Uncle Steve's circuit, provided him with a nice ASCIImatic, as well as
with a nicely working simulation.

Nice thread without you; you should participate less more often.
---

Plus, you likely wouldn't know what to measure.

---
Well, then, Mister Knowitall, perhaps you'll grace us with the way
you'd do it?

OK, it's definite: you wouldn't know what to measure.

---
Well, your sidestepping the question makes me think that you're afraid
to answer it because you might be found wrong yet again.

Now _that's_ a weasel!

--
JF

 

[John Fields]

On Fri, 10 May 2013 15:43:23 -0400, "P E Schoen" <paul@peschoen.com>
wrote:

"John Larkin" wrote in message
news:md4sm891hivhkujpvvr7sjk65gm4nkphuo@4ax.com...

Not really old. Calrad mostly rebrands Asian stuff.

http://www.calradstore.com/calrad.html

Wiki says that "Variac" dates from 1934. I can't imagine that there is a
lot of variation among Variac clones any more.

Hey, where is the test data promised by John Fields? Once I recover from hip
replacement surgery**

---
Wow, that's amazing!

I didn't think that medical science could make you hip again once
you'd lost it!
---

**JF, what's your excuse?

---
No excuses, just equipment problems.

I've got a DENON POA 800 from which I can get 190 watts into a 2 ohm
resistive load, but it hates inductance and shuts itself down if it
feels the least bit threatened.

Pretty smart.

My plan was this:

+--[AMP]--+ +-----+--------+
| | | | |
| P||S | [VARIAC]<--+------+
[GEN] R||E [DVM] | | |
| I||C | | [LOAD] [DVM}
| | | | | | |
+---------+ +-----+--------+-------+------+

But I've got to work out the impedances so the amp is looking into
something it won't mind driving.

Once I get that done I'll probably go ahead and run the test, just for
fun, this coming week.

--
JF

 

[P E Schoen]

"John Fields" wrote in message
news:05ivo8lq5k8t11k3jd6jt045077hj38t60@4ax.com...

On Fri, 10 May 2013 15:43:23 -0400, "P E Schoen" <paul@peschoen.com
wrote:

Hey, where is the test data promised by John Fields? Once I recover from
hip replacement surgery**

Wow, that's amazing!

I didn't think that medical science could make you hip again once you'd
lost it!

Heh. Good one!

**JF, what's your excuse?

No excuses, just equipment problems.

I've got a DENON POA 800 from which I can get 190 watts into a 2 ohm
resistive load, but it hates inductance and shuts itself down if it feels
the least bit threatened.

Pretty smart.

My plan was this:

+--[AMP]--+ +-----+--------+
| | | | |
| P||S | [VARIAC]<--+------+
[GEN] R||E [DVM] | | |
| I||C | | [LOAD] [DVM}
| | | | | | |
+---------+ +-----+--------+-------+------+

But I've got to work out the impedances so the amp is looking into
something it won't mind driving.

Once I get that done I'll probably go ahead and run the test, just for
fun, this coming week.

I suppose that's a reasonable test. I have no doubt that the output voltage
ratio will stay constant over any reasonable range of frequency (including
DC, in fact), but the question may be if the inductance of the transformer
limits the current as a function of frequency. I admit that my understanding
of magnetics is a bit weak, but I have had a lot of experience with
inductors and transformers, particularly large high current types and
toroids as well as E-I and C-cores.

What I plan to do is wind a few turns on one of the 2 kVA cores I have, and
use a center tap push-pull switching circuit to drive it from 12 to 24 VDC.
Then I will load the secondary with power resistors and measure the
peak-to-peak voltage to determine the power. Thus I can read the input DC
voltage and current accurately and determine the overall efficiency.

I may have a hard time with even a 2 kVA load, as that is 83 amps at 24
volts, which is a heavy current draw for even a large automotive battery,
and I'd need two of them.

What do you expect to find with your setup? 190 watts is barely enough for
even the smallest variacs which are like 0-140V at 2A.

Paul

 

[John Larkin]

On Sun, 12 May 2013 21:16:19 -0400, "P E Schoen" <paul@peschoen.com> wrote:

"John Fields" wrote in message
news:05ivo8lq5k8t11k3jd6jt045077hj38t60@4ax.com...

On Fri, 10 May 2013 15:43:23 -0400, "P E Schoen" <paul@peschoen.com
wrote:

Hey, where is the test data promised by John Fields? Once I recover from
hip replacement surgery**

Wow, that's amazing!

I didn't think that medical science could make you hip again once you'd
lost it!

Heh. Good one!

**JF, what's your excuse?

No excuses, just equipment problems.

I've got a DENON POA 800 from which I can get 190 watts into a 2 ohm
resistive load, but it hates inductance and shuts itself down if it feels
the least bit threatened.

Pretty smart.

My plan was this:

+--[AMP]--+ +-----+--------+
| | | | |
| P||S | [VARIAC]<--+------+
[GEN] R||E [DVM] | | |
| I||C | | [LOAD] [DVM}
| | | | | | |
+---------+ +-----+--------+-------+------+

But I've got to work out the impedances so the amp is looking into
something it won't mind driving.

Once I get that done I'll probably go ahead and run the test, just for
fun, this coming week.

I suppose that's a reasonable test. I have no doubt that the output voltage
ratio will stay constant over any reasonable range of frequency (including
DC, in fact),

Not above 1.00 out/in ratio!


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

 

[John Fields]

On Sun, 12 May 2013 21:16:19 -0400, "P E Schoen" <paul@peschoen.com>
wrote:

"John Fields" wrote in message
news:05ivo8lq5k8t11k3jd6jt045077hj38t60@4ax.com...

On Fri, 10 May 2013 15:43:23 -0400, "P E Schoen" <paul@peschoen.com
wrote:

Hey, where is the test data promised by John Fields? Once I recover from
hip replacement surgery**

Wow, that's amazing!

I didn't think that medical science could make you hip again once you'd
lost it!

Heh. Good one!

**JF, what's your excuse?

No excuses, just equipment problems.

I've got a DENON POA 800 from which I can get 190 watts into a 2 ohm
resistive load, but it hates inductance and shuts itself down if it feels
the least bit threatened.

Pretty smart.

My plan was this:

+--[AMP]--+ +-----+--------+
| | | | |
| P||S | [VARIAC]<--+------+
[GEN] R||E [DVM] | | |
| I||C | | [LOAD] [DVM}
| | | | | | |
+---------+ +-----+--------+-------+------+

But I've got to work out the impedances so the amp is looking into
something it won't mind driving.

Once I get that done I'll probably go ahead and run the test, just for
fun, this coming week.

I suppose that's a reasonable test. I have no doubt that the output voltage
ratio will stay constant over any reasonable range of frequency (including
DC, in fact), but the question may be if the inductance of the transformer
limits the current as a function of frequency. I admit that my understanding
of magnetics is a bit weak, but I have had a lot of experience with
inductors and transformers, particularly large high current types and
toroids as well as E-I and C-cores.

What I plan to do is wind a few turns on one of the 2 kVA cores I have, and
use a center tap push-pull switching circuit to drive it from 12 to 24 VDC.
Then I will load the secondary with power resistors and measure the
peak-to-peak voltage to determine the power. Thus I can read the input DC
voltage and current accurately and determine the overall efficiency.

I may have a hard time with even a 2 kVA load, as that is 83 amps at 24
volts, which is a heavy current draw for even a large automotive battery,
and I'd need two of them.

What do you expect to find with your setup? 190 watts is barely enough for
even the smallest variacs which are like 0-140V at 2A.

Paul

---
Whether, with a fixed input level and a fixed load, the output level
will change as frequency is varied.

--
JF

 

[P E Schoen]

"John Fields" wrote in message
news:aj41p8dd4b7b0snn97d5shofintb055jvc@4ax.com...

On Sun, 12 May 2013 21:16:19 -0400, "P E Schoen" <paul@peschoen.com
wrote:

What do you expect to find with your setup? 190 watts is barely enough
for
even the smallest variacs which are like 0-140V at 2A.

Whether, with a fixed input level and a fixed load, the output level
will change as frequency is varied.

I ran a simulation. The results depend on the inductance of the transformer
and the coupling factor K. I used 500 mH for the two coupled inductors, and
K of 0.995, which I think may be reasonable for toroids. The result is a
flat Vout/Vin up to 2.5 kHz at which point the output drops by 0.5 dB. This
is small signal analysis, however:

http://enginuitysystems.com/pix/Variac.png

So I did a transient analysis with the input at 240 VAC (which required
346.6V rather than 339 as expected for sqrt(2) ). With a total of 0.2 ohms
ESR at 60 Hz I got 120 VRMS into a 70 ohm load (200W), and 118.9V into 7
ohms (2.02 kW).

At 2 kHz I got 48.6 VRMS. That is surprisingly low. Setting the coupling
factor K=1 gives 119V. Hard to say what it really is. K=0.998 gives 87.2V.
If I change the inductance of the two halves to 50 mH, I get 118.6V. So,
what is the inductance of a variac coil?

I changed the load resistance to 7 meg to find out the magnetizing current,
and it is about 100 mA at 2 kHz. This corresponds to 3.5 amps at 60 Hz,
which is pretty obviously too high. I would expect more like 500 mA. So I
change the inductances to 500 mH, which gives 480 mA at 60 Hz.

OK, so I'll try K=0.999 for the coupling factor. I get 119V at 60 Hz, 118.6V
at 400 Hz, 108.6V at 2 kHz. This "seems" about right. It's about 10%
reduction of output at 2 kHz, which is a reasonable cut-off point for
practical usage.

For my purposes, however, I plan to use a fixed V/Hz to get higher power
from the coil. It seems to reason that if I apply ten times the voltage at
ten times the frequency, I should get ten times the power into ten times the
resistance. Sure enough, with a 70 ohm load at 600 Hz and an input of 2400
V, I get 1198V output and 20.5 kW.

Obviously it will now require some actual measurements on a toroid variac
core to determine the magnetizing current and leakage inductance, and also
the core losses as a function of frequency.

Let's see what you got!

Paul

 

[Steve Gonedes]

"ScottWW" <spamtrap@dcorp.com> writes:

< Two occasional (electrical) causes of hum in electric motors (specifically
< ceiling fans) are overvoltage and a noisy sine-wave.

If a US home is measured over 127VAC the local power utility will often

< install a line conditioner. If a home is measured at 125VAC, in most cases
< the power utility states that it is "within tolerances".

Tracking the source of line noise on 120VAC is often trial and error and

< cannot always identify a single culprit. O'scopes are not commonly carried
< by the installers. But I have documented a few overvoltage situations where
< the line noise was also present; and I suspect creating some of the measured
< overrvoltage.

I would like a device, that can reduce 125VAC voltage by 10% while

< maintaining a smooth sine waveform. The last time I researched 120V
< transformers for a 10% voltage reduction, they were too large (4"x 4" x 4")
< for my purposes. Optimally I would like to this device to fit within a
< "pancake box" outlet box, but even a 4" octagon outlet box.

Are there any new developments in small sized transformers capable of doing

< this?
< Does anybody have any ideas how else this could be accomplished?

Thanks!

< Scott
< Dunedin FL



Have you tried using Tetrafluoroethane and mineral oil on the ball
bearings? Seems to help (?) - but then again I just like to squirt stuff
with cans.

 

[John Fields]

On Mon, 13 May 2013 16:28:09 -0400, "P E Schoen" <paul@peschoen.com>
wrote:

"John Fields" wrote in message
news:aj41p8dd4b7b0snn97d5shofintb055jvc@4ax.com...

On Sun, 12 May 2013 21:16:19 -0400, "P E Schoen" <paul@peschoen.com
wrote:

What do you expect to find with your setup? 190 watts is barely enough
for
even the smallest variacs which are like 0-140V at 2A.

Whether, with a fixed input level and a fixed load, the output level
will change as frequency is varied.

I ran a simulation. The results depend on the inductance of the transformer
and the coupling factor K. I used 500 mH for the two coupled inductors,

---
I don't think a variac is like two magnetically coupled inductors -
except, maybe, for the case where the winding is extended in order to
get 140V out 120V in - otherwise it's more like an inductive voltage
divider.
---

and
K of 0.995, which I think may be reasonable for toroids. The result is a
flat Vout/Vin up to 2.5 kHz at which point the output drops by 0.5 dB. This
is small signal analysis, however:

http://enginuitysystems.com/pix/Variac.png

So I did a transient analysis with the input at 240 VAC (which required
346.6V rather than 339 as expected for sqrt(2) ).

---
I don't understand...

If you did a transient analysis with a stiff 240VRMS source, why would
you lower its peak to 346.6V?
---

With a total of 0.2 ohms
ESR at 60 Hz I got 120 VRMS into a 70 ohm load (200W), and 118.9V into 7
ohms (2.02 kW).

At 2 kHz I got 48.6 VRMS. That is surprisingly low. Setting the coupling
factor K=1 gives 119V. Hard to say what it really is. K=0.998 gives 87.2V.
If I change the inductance of the two halves to 50 mH, I get 118.6V.

---
That's the nice thing about simulation; you get to change what's
keeping your predictions from being accurate, regardless of whether
those changes are real in the real world.
---

So, what is the inductance of a variac coil?

---
Mine, a Thordarson Meissner VAR104, exhibits a measured 311mH with the
output switch in the 120V position and 227mH with the output switch in
the 140V position
---

I changed the load resistance to 7 meg to find out the magnetizing current,
and it is about 100 mA at 2 kHz. This corresponds to 3.5 amps at 60 Hz,
which is pretty obviously too high. I would expect more like 500 mA. So I
change the inductances to 500 mH, which gives 480 mA at 60 Hz.

---
Again, change the model to suit your expectations, regardless of the
constraints dictated by the real world.
---

OK, so I'll try K=0.999 for the coupling factor. I get 119V at 60 Hz, 118.6V
at 400 Hz, 108.6V at 2 kHz. This "seems" about right.

---
Well, perhaps because that's what you want to see, but what is it in
the real world?
---

For my purposes, however, I plan to use a fixed V/Hz to get higher power
from the coil. It seems to reason that if I apply ten times the voltage at
ten times the frequency, I should get ten times the power into ten times the
resistance. Sure enough, with a 70 ohm load at 600 Hz and an input of 2400
V, I get 1198V output and 20.5 kW.

Obviously it will now require some actual measurements on a toroid variac
core to determine the magnetizing current and leakage inductance, and also
the core losses as a function of frequency.

---
So do the work and post what you find in the real world, instead of
just posting conjecture.
---

Let's see what you got!

Paul

---
Using this setup: Vin
/
.. +--[AMP]--+ +-----+--------+ Vout
.. | | | | | /
.. | S||P | [VARIAC]<--+------+
.. [GEN] E||R [DVM1] | | |
.. | C||I | | [LOAD] [DVM2]
.. | | | | | | |
.. +---------+ +-----+--------+-------+------+

Where the transformer primary is rated at 120VAC 60Hz and the
secondary is rated at 12V 35A, is used backwards, and:

GEN Goldstar FG8002
AMP Denon POA800
DVM1 Fluke 8060A
VARIAC Thordarson Meissner VAR 104
LOAD 100 ohms 300 watts
DVM2 Wavetek 27XT

The Variac's spec's:

120V 60Hz in, 0 to 120V or 0 to 140V out at 12 amperes.

Empirical data taken with the output voltage switch in the position
shown and the variac's output unloaded:

OUT Rs L I(mag)
VOLTS ohms H A

120 1.59 0.311 0.0325

140 1.48 0.227 0.0561

With the variac's output switch in the 120V position and the output
cranked to 50% we have:

freq Vin Vout Vout/Vin
Hz volts volts
-----+--------+-------+----------
60 120 60 0.5
100 121 60.3 0.498
1000 120.15 58.8 0.489
2000 119.37 57.7 0.483
4000 120.11 58.4 0.486
6000 121.49 60.5 0.498
10k 119.65 65.5 0.547

Vin changed as the frequency was varied, so it was leveled by changing
the output voltage of the generator to get Vin close to 120V.

--
JF

 

[John Fields]

On Sun, 26 May 2013 17:06:04 -0500, John Fields
<jfields@austininstruments.com> wrote:

On Mon, 13 May 2013 16:28:09 -0400, "P E Schoen" <paul@peschoen.com
wrote:

"John Fields" wrote in message
news:aj41p8dd4b7b0snn97d5shofintb055jvc@4ax.com...

On Sun, 12 May 2013 21:16:19 -0400, "P E Schoen" <paul@peschoen.com
wrote:

What do you expect to find with your setup? 190 watts is barely enough
for
even the smallest variacs which are like 0-140V at 2A.

Whether, with a fixed input level and a fixed load, the output level
will change as frequency is varied.

I ran a simulation. The results depend on the inductance of the transformer
and the coupling factor K. I used 500 mH for the two coupled inductors,

---
I don't think a variac is like two magnetically coupled inductors -
except, maybe, for the case where the winding is extended in order to
get 140V out 120V in - otherwise it's more like an inductive voltage
divider.
---

and
K of 0.995, which I think may be reasonable for toroids. The result is a
flat Vout/Vin up to 2.5 kHz at which point the output drops by 0.5 dB. This
is small signal analysis, however:

http://enginuitysystems.com/pix/Variac.png

So I did a transient analysis with the input at 240 VAC (which required
346.6V rather than 339 as expected for sqrt(2) ).

---
I don't understand...

If you did a transient analysis with a stiff 240VRMS source, why would
you lower its peak to 346.6V?

---
Oops...

Why would you _raise_ its peak to 346.6V?

--
JF