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Bill Sloman
Guest

Thu Nov 19, 2009 1:08 am   



On Nov 18, 8:45 pm, John Fields <jfie...@austininstruments.com> wrote:
Quote:
On Wed, 18 Nov 2009 08:46:00 -0800 (PST),Bill Sloman





bill.slo...@ieee.org> wrote:
On Nov 17, 9:28 pm, John Fields <jfie...@austininstruments.com> wrote:
On Tue, 17 Nov 2009 10:59:38 -0800, "Joel Koltner"

zapwireDASHgro...@yahoo.com> wrote:
"John Fields" <jfie...@austininstruments.com> wrote in message
news:sir5g5h9h69vfurapjd9e2kn8efeod8qat_at_4ax.com...
news:7ar5g59hdrcdpu3icb3rlmdn31iqiqfa67_at_4ax.com

5uA... nice!

Seems that someone on eBay is selling a +/-5uA movement:
http://cgi.ebay.com/Weston-Bakelite-Glass-5ua-microamp-Panel-Meter-Hi....

Nope, it'll get you nothing. Smile
Know why?

Because the federales will toss your rear in jail quite rapidly?

---
Nope, because the magnetic field generated by the power line will never
cut the conductor wrapped around it since the conductor will be
essentially perpendicular to the varying field. :-)

Since the original claim was

" >Wrapping some turns around the power company's lines will get you
many, many
watts. Smile"

This isn't the reason - lines is plural and the nett current through
the lines as a bunch balances out to zero.

---
Since that's obvious to the most casual observer, the context of his
statement must have been about wrapping some turns around [one] of the
power company's lines, which I addressed by referring to it as "the
power line".
---

Nice try.

<snipped the rest>

--
Bill Sloman, Nijmegen

Bill Sloman
Guest

Thu Nov 19, 2009 1:25 am   



On Nov 18, 6:08 pm, Fester Bestertester <f...@fbt.net> wrote:
Quote:
On Tue, 17 Nov 2009 00:18:55 -0800, Fester Bestertester <f...@fbt.net
wrote:

I'm curious how the Fluke i200s current clamp probe can give mV output
without the use of batteries.

How is this done? If one is measuring 200A I can see how the magnetic field
could generate enough current in the probe to support some high-impedance,
low-draw circuitry.

But when measuring on the low scale, say, 2 or 3 amps, how could the probe
output a few hundred mV? (The clamp is spec'd to output 100mV / amp on the
20A low scale, 10mV on the 200A high scale.)

Can someone explain this to me? I'm fascinated to see it's possible &
curious
to know how.

---
OK.

A passive clamp-on ammeter is essentially the secondary of a transformer
wound on a core that can be opened or closed in order to get it around a
conductor so the current in that conductor can be measured without
cutting it and using a conventional ammeter.
[...]
JF

FINALLY an answer on-topic. Thank you.

You asked about the Fluke i200s current clamp probe. I've never used
one, and I'm not sure that I've even seen one, which discouraged me
from trying to improvise an explanation.

John Field's response - now that he has finally got around to making
the kind of useful post that he claims to represent the bulk of his
output - does seem to be plausible.

From time to time we get responses from the people who designed the
gear under discussion, but you don't seem to have been that lucky.

--
Bill Sloman, Nijmegen

John Nagle
Guest

Thu Nov 19, 2009 5:29 am   



Bill Sloman wrote:
Quote:
On Nov 18, 6:08 pm, Fester Bestertester <f...@fbt.net> wrote:
On Tue, 17 Nov 2009 00:18:55 -0800, Fester Bestertester <f...@fbt.net
wrote:
I'm curious how the Fluke i200s current clamp probe can give mV output
without the use of batteries.
How is this done? If one is measuring 200A I can see how the magnetic field
could generate enough current in the probe to support some high-impedance,
low-draw circuitry.
But when measuring on the low scale, say, 2 or 3 amps, how could the probe
output a few hundred mV? (The clamp is spec'd to output 100mV / amp on the
20A low scale, 10mV on the 200A high scale.)
Can someone explain this to me? I'm fascinated to see it's possible &
curious
to know how.
---
OK.
A passive clamp-on ammeter is essentially the secondary of a transformer
wound on a core that can be opened or closed in order to get it around a
conductor so the current in that conductor can be measured without
cutting it and using a conventional ammeter.
[...]
JF
FINALLY an answer on-topic. Thank you.

Yes. Classic AC clamp-on ammeters are simply transformers. One
"turn" through the clamp, many turns in the fixed coil for output.
The output feeds into a voltmeter.

Those are AC-only devices. There are also Hall-effect clamp-on
ammeters, and those work for both AC and DC. These have been
available for a decade or so, and pricing is now down as low as
$60. I used to have one that could read down to about 500mA DC,
and it only cost $129. Very useful in robotics and controls work.

John Nagle

DaveC
Guest

Thu Nov 19, 2009 7:20 am   



[...]
Quote:
There are also Hall-effect clamp-on
ammeters, and those work for both AC and DC. These have been
available for a decade or so, and pricing is now down as low as
$60. I used to have one that could read down to about 500mA DC,
and it only cost $129. Very useful in robotics and controls work.

John Nagle

Which make & model would that $129 model be? It's always useful to know
someone else's favorite tools...

Dave

Tzortzakakis Dimitrios
Guest

Thu Nov 19, 2009 3:10 pm   



? "Fester Bestertester" <fbt_at_fbt.net> ?????? ??? ??????
news:0001HW.C7279C6F0007F514B08A39AF_at_news.eternal-september.org...
Quote:
I'm curious how the Fluke i200s current clamp probe can give mV output
without the use of batteries.

How is this done? If one is measuring 200A I can see how the magnetic
field
could generate enough current in the probe to support some high-impedance,
low-draw circuitry.

But when measuring on the low scale, say, 2 or 3 amps, how could the probe
output a few hundred mV? (The clamp is spec'd to output 100mV / amp on the
20A low scale, 10mV on the 200A high scale.)

Can someone explain this to me? I'm fascinated to see it's possible &
curious
to know how.

There's nothing fancy about that, the electricity meters of a medium-voltage

consumer (real and reactive energy) are powered from the two potential and
the two current transformers, without any other power supply (medium
voltage=15 kV in Crete).


--
Tzortzakakis Dimitrios
major in electrical engineering
mechanized infantry reservist
hordad AT otenet DOT gr

John Fields
Guest

Thu Nov 19, 2009 3:18 pm   



On Wed, 18 Nov 2009 15:08:46 -0800 (PST), Bill Sloman
<bill.sloman_at_ieee.org> wrote:

Quote:
On Nov 18, 8:45 pm, John Fields <jfie...@austininstruments.com> wrote:
On Wed, 18 Nov 2009 08:46:00 -0800 (PST),Bill Sloman





bill.slo...@ieee.org> wrote:
On Nov 17, 9:28 pm, John Fields <jfie...@austininstruments.com> wrote:
On Tue, 17 Nov 2009 10:59:38 -0800, "Joel Koltner"

zapwireDASHgro...@yahoo.com> wrote:
"John Fields" <jfie...@austininstruments.com> wrote in message
news:sir5g5h9h69vfurapjd9e2kn8efeod8qat_at_4ax.com...
news:7ar5g59hdrcdpu3icb3rlmdn31iqiqfa67_at_4ax.com

5uA... nice!

Seems that someone on eBay is selling a +/-5uA movement:
http://cgi.ebay.com/Weston-Bakelite-Glass-5ua-microamp-Panel-Meter-Hi...

Nope, it'll get you nothing. Smile
Know why?

Because the federales will toss your rear in jail quite rapidly?

---
Nope, because the magnetic field generated by the power line will never
cut the conductor wrapped around it since the conductor will be
essentially perpendicular to the varying field. :-)

Since the original claim was

" >Wrapping some turns around the power company's lines will get you
many, many
watts. Smile"

This isn't the reason - lines is plural and the nett current through
the lines as a bunch balances out to zero.

---
Since that's obvious to the most casual observer, the context of his
statement must have been about wrapping some turns around [one] of the
power company's lines, which I addressed by referring to it as "the
power line".
---

Nice try.

snipped the rest

---
Of course, you fraud, since by snipping the rest you sidestep the issue,
which is your ignorance in believing that a solenoid wound around an
alternating current carrying conductor can be used to extract power from
the varying magnetic field surrounding that conductor.

Nothing could be further from the truth, as demonstrated here:

news:26iag5hjpub42ookl0nk74vc3ffgs7316q_at_4ax.com

Since, conveniently, you don't have access to abse, I'll take the
liberty of emailing you the photos as soon as I post this.

Enjoy. :-)

JF

Fester Bestertester
Guest

Thu Nov 19, 2009 4:29 pm   



So, for a millivolt output probe, this might be as simple as 2 windings (or a
tapped single winding) with a range switch to select the winding?

John Larkin
Guest

Thu Nov 19, 2009 5:40 pm   



On Thu, 19 Nov 2009 07:29:26 -0800, Fester Bestertester <fbt_at_fbt.net>
wrote:

Quote:
So, for a millivolt output probe, this might be as simple as 2 windings (or a
tapped single winding) with a range switch to select the winding?

Current transformers are usually dumped into a load resistor aka
burden resistor, to convert their output current into voltage. I'm
sure the Fluke clamp-on has an internal burden resistor, and they may
switch that to change ranges.

Without a burden resistor, the output voltage will be proportional to
frequency and very dependent on core reluctance, which would be fatal
for a clamp-on meter with a hinge and a non-repeatable air gap.

Coreless Rogowsky coils are used unloaded, but need a downstream
integrator to accurately measure current.

http://en.wikipedia.org/wiki/Rogowski_coil

The coolest current transformer is a second-harmonic DCCT, accurate to
parts-per-million from DC to many kilohertz.

http://www.gmw.com/electric_current/Danfysik/866_867/867.html

John

George Herold
Guest

Thu Nov 19, 2009 8:27 pm   



On Nov 19, 11:40 am, John Larkin
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
Quote:
On Thu, 19 Nov 2009 07:29:26 -0800, Fester Bestertester <f...@fbt.net
wrote:

So, for a millivolt output probe, this might be as simple as 2 windings (or a
tapped single winding) with a range switch to select the winding?

Current transformers are usually dumped into a load resistor aka
burden resistor, to convert their output current into voltage. I'm
sure the Fluke clamp-on has an internal burden resistor, and they may
switch that to change ranges.

Without a burden resistor, the output voltage will be proportional to
frequency and very dependent on core reluctance, which would be fatal
for a clamp-on meter with a hinge and a non-repeatable air gap.

Coreless Rogowsky coils are used unloaded, but need a downstream
integrator to accurately measure current.

http://en.wikipedia.org/wiki/Rogowski_coil

The coolest current transformer is a second-harmonic DCCT, accurate to
parts-per-million from DC to many kilohertz.

http://www.gmw.com/electric_current/Danfysik/866_867/867.html

John


Wiki's great thanks John. That second link didn't have much info on
how the device works. Is the following the same thing?

http://adweb.desy.de/mdi/CARE/Lyon/Lyon%20DCCT_Technology_Review.pdf

(I googled second-harmonic DCCT)

George H.

Bill Sloman
Guest

Thu Nov 19, 2009 8:43 pm   



On Nov 19, 3:18 pm, John Fields <jfie...@austininstruments.com> wrote:
Quote:
On Wed, 18 Nov 2009 15:08:46 -0800 (PST),Bill Sloman





bill.slo...@ieee.org> wrote:
On Nov 18, 8:45 pm, John Fields <jfie...@austininstruments.com> wrote:
On Wed, 18 Nov 2009 08:46:00 -0800 (PST),Bill Sloman

bill.slo...@ieee.org> wrote:
On Nov 17, 9:28 pm, John Fields <jfie...@austininstruments.com> wrote:
On Tue, 17 Nov 2009 10:59:38 -0800, "Joel Koltner"

zapwireDASHgro...@yahoo.com> wrote:
"John Fields" <jfie...@austininstruments.com> wrote in message
news:sir5g5h9h69vfurapjd9e2kn8efeod8qat_at_4ax.com...
news:7ar5g59hdrcdpu3icb3rlmdn31iqiqfa67_at_4ax.com

5uA... nice!

Seems that someone on eBay is selling a +/-5uA movement:
http://cgi.ebay.com/Weston-Bakelite-Glass-5ua-microamp-Panel-Meter-Hi...

Nope, it'll get you nothing. Smile
Know why?

Because the federales will toss your rear in jail quite rapidly?

---
Nope, because the magnetic field generated by the power line will never
cut the conductor wrapped around it since the conductor will be
essentially perpendicular to the varying field. :-)

Since the original claim was

" >Wrapping some turns around the power company's lines will get you
many, many
watts. Smile"

This isn't the reason - lines is plural and the nett current through
the lines as a bunch balances out to zero.

---
Since that's obvious to the most casual observer, the context of his
statement must have been about wrapping some turns around [one] of the
power company's lines, which I addressed by referring to it as "the
power line".
---

Nice try.

snipped the rest

---
Of course, you fraud, since by snipping the rest you sidestep the issue,
which is your ignorance in believing that a solenoid wound around an
alternating current carrying conductor can be used to extract power from
the varying magnetic field surrounding that conductor.

Your enthusiasm for inventing implausible straw men knows no bounds. I
never made any such claim. My scepticism about you claim was purely
based on the fact that you were ignoring what Joel Koltner had
actually said.

Quote:
Nothing could be further from the truth, as demonstrated here:

news:26iag5hjpub42ookl0nk74vc3ffgs7316q_at_4ax.com

Since, conveniently, you don't have access to abse, I'll take the
liberty of emailing you the photos as soon as I post this.

Enjoy. Smile

The pictures were perfectly clear. It was less obvious what you were
actually doing, but since I couldn't care less, this isn't any great
loss.

The joke is that even if you do extract "many watts" from the power
company's power lines, you won't be stealing from them. In order to be
able to extract power you have to be drawing power for which you will
be billed, and any extra watts you extract by transformer action is
subtracted from the power you are already paying for - your paid for
load will be seeing a lower drive voltage.

Joel Koltner made a rather good joke, which you have totally failed to
get.

--
Bill Sloman, Nijmegen

John Larkin
Guest

Thu Nov 19, 2009 9:46 pm   



On Thu, 19 Nov 2009 10:27:34 -0800 (PST), George Herold
<ggherold_at_gmail.com> wrote:

Quote:
On Nov 19, 11:40 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Thu, 19 Nov 2009 07:29:26 -0800, Fester Bestertester <f...@fbt.net
wrote:

So, for a millivolt output probe, this might be as simple as 2 windings (or a
tapped single winding) with a range switch to select the winding?

Current transformers are usually dumped into a load resistor aka
burden resistor, to convert their output current into voltage. I'm
sure the Fluke clamp-on has an internal burden resistor, and they may
switch that to change ranges.

Without a burden resistor, the output voltage will be proportional to
frequency and very dependent on core reluctance, which would be fatal
for a clamp-on meter with a hinge and a non-repeatable air gap.

Coreless Rogowsky coils are used unloaded, but need a downstream
integrator to accurately measure current.

http://en.wikipedia.org/wiki/Rogowski_coil

The coolest current transformer is a second-harmonic DCCT, accurate to
parts-per-million from DC to many kilohertz.

http://www.gmw.com/electric_current/Danfysik/866_867/867.html

John


Wiki's great thanks John. That second link didn't have much info on
how the device works. Is the following the same thing?

http://adweb.desy.de/mdi/CARE/Lyon/Lyon%20DCCT_Technology_Review.pdf

(I googled second-harmonic DCCT)

George H.

Fig 3 is about right. The green feedback path is usually an N-turn
winding to net an N-to-1 current transformer.

There are usually two physical toroids. Ib, If, and T3 are wound on
both, as if they were a single core. T1 and T2 are each wound on one
of the cores, in opposite directions so that there's no net coupling
of the carrier frequency into T3 or the customer's Ib circuit.

The AC path (sense winding T3 and its amplifier, driving If) fight to
keep the flux zero at higher frequencies. The second-harmonic system
works at low frequencies, again to keep net core flux zero, which
happens when Ib = N * If.

I designed one of these once. It was fun, and not all that easy.

John

daestrom
Guest

Fri Nov 20, 2009 3:29 am   



Bill Sloman wrote:
Quote:
On Nov 19, 3:18 pm, John Fields <jfie...@austininstruments.com> wrote:
On Wed, 18 Nov 2009 15:08:46 -0800 (PST),Bill Sloman





bill.slo...@ieee.org> wrote:
On Nov 18, 8:45 pm, John Fields <jfie...@austininstruments.com> wrote:
On Wed, 18 Nov 2009 08:46:00 -0800 (PST),Bill Sloman
bill.slo...@ieee.org> wrote:
On Nov 17, 9:28 pm, John Fields <jfie...@austininstruments.com> wrote:
On Tue, 17 Nov 2009 10:59:38 -0800, "Joel Koltner"
zapwireDASHgro...@yahoo.com> wrote:
"John Fields" <jfie...@austininstruments.com> wrote in message
news:sir5g5h9h69vfurapjd9e2kn8efeod8qat_at_4ax.com...
news:7ar5g59hdrcdpu3icb3rlmdn31iqiqfa67_at_4ax.com
5uA... nice!
Seems that someone on eBay is selling a +/-5uA movement:
http://cgi.ebay.com/Weston-Bakelite-Glass-5ua-microamp-Panel-Meter-Hi...
Nope, it'll get you nothing. Smile
Know why?
Because the federales will toss your rear in jail quite rapidly?
---
Nope, because the magnetic field generated by the power line will never
cut the conductor wrapped around it since the conductor will be
essentially perpendicular to the varying field. Smile
Since the original claim was
" >Wrapping some turns around the power company's lines will get you
many, many
watts. Smile"
This isn't the reason - lines is plural and the nett current through
the lines as a bunch balances out to zero.
---
Since that's obvious to the most casual observer, the context of his
statement must have been about wrapping some turns around [one] of the
power company's lines, which I addressed by referring to it as "the
power line".
---
Nice try.
snipped the rest
---
Of course, you fraud, since by snipping the rest you sidestep the issue,
which is your ignorance in believing that a solenoid wound around an
alternating current carrying conductor can be used to extract power from
the varying magnetic field surrounding that conductor.

Your enthusiasm for inventing implausible straw men knows no bounds. I
never made any such claim. My scepticism about you claim was purely
based on the fact that you were ignoring what Joel Koltner had
actually said.

Nothing could be further from the truth, as demonstrated here:

news:26iag5hjpub42ookl0nk74vc3ffgs7316q_at_4ax.com

Since, conveniently, you don't have access to abse, I'll take the
liberty of emailing you the photos as soon as I post this.

Enjoy. :-)

The pictures were perfectly clear. It was less obvious what you were
actually doing, but since I couldn't care less, this isn't any great
loss.

The joke is that even if you do extract "many watts" from the power
company's power lines, you won't be stealing from them. In order to be
able to extract power you have to be drawing power for which you will
be billed, and any extra watts you extract by transformer action is
subtracted from the power you are already paying for - your paid for
load will be seeing a lower drive voltage.

Joel Koltner made a rather good joke, which you have totally failed to
get.


If you make a 'tap' upstream of the revenue meter, even with just
transformer action, you're stealing. Revenue meters (kilowatt-hour
meters) have always had terminal voltage as one of their inputs. An
illegal tap upstream may affect the voltage at the service entrance some
small amount, but the metering will reduce the billed kWh accordingly.
So regardless of the exact voltage supplied by the utility (it often
varies slightly throughout the day), the amount of energy delivered at
the service entrance is what is billed for. Power drawn off before the
meter isn't measured and is 'stolen'.

Of course if you just 'wrap some turns around the power line' without
orienting the coil properly in relation to the line, you're not going to
get any power because transformer action won't work when your turns of
wire are parallel to the power line's magnetic field (i.e. 'wrapped
around' the power line). And I think that was John Field's point.

daestrom

John Fields
Guest

Fri Nov 20, 2009 1:31 pm   



On Thu, 19 Nov 2009 10:43:58 -0800 (PST), Bill Sloman
<bill.sloman_at_ieee.org> wrote:

Quote:
On Nov 19, 3:18 pm, John Fields <jfie...@austininstruments.com> wrote:
On Wed, 18 Nov 2009 15:08:46 -0800 (PST),Bill Sloman





bill.slo...@ieee.org> wrote:
On Nov 18, 8:45 pm, John Fields <jfie...@austininstruments.com> wrote:
On Wed, 18 Nov 2009 08:46:00 -0800 (PST),Bill Sloman

bill.slo...@ieee.org> wrote:
On Nov 17, 9:28 pm, John Fields <jfie...@austininstruments.com> wrote:
On Tue, 17 Nov 2009 10:59:38 -0800, "Joel Koltner"

zapwireDASHgro...@yahoo.com> wrote:
"John Fields" <jfie...@austininstruments.com> wrote in message
news:sir5g5h9h69vfurapjd9e2kn8efeod8qat_at_4ax.com...
news:7ar5g59hdrcdpu3icb3rlmdn31iqiqfa67_at_4ax.com

5uA... nice!

Seems that someone on eBay is selling a +/-5uA movement:
http://cgi.ebay.com/Weston-Bakelite-Glass-5ua-microamp-Panel-Meter-Hi...

Nope, it'll get you nothing. Smile
Know why?

Because the federales will toss your rear in jail quite rapidly?

---
Nope, because the magnetic field generated by the power line will never
cut the conductor wrapped around it since the conductor will be
essentially perpendicular to the varying field. :-)

Since the original claim was

" >Wrapping some turns around the power company's lines will get you
many, many
watts. Smile"

This isn't the reason - lines is plural and the nett current through
the lines as a bunch balances out to zero.

---
Since that's obvious to the most casual observer, the context of his
statement must have been about wrapping some turns around [one] of the
power company's lines, which I addressed by referring to it as "the
power line".
---

Nice try.

snipped the rest

---
Of course, you fraud, since by snipping the rest you sidestep the issue,
which is your ignorance in believing that a solenoid wound around an
alternating current carrying conductor can be used to extract power from
the varying magnetic field surrounding that conductor.

Your enthusiasm for inventing implausible straw men knows no bounds. I
never made any such claim. My scepticism about you claim was purely
based on the fact that you were ignoring what Joel Koltner had
actually said.

---
What Joel _actually_ said was that energy could be extracted from the
varying magnetic field surrounding a power line by wrapping turns around
it.

Since you pointed out that energy can't be had by wrapping turns around
bundled conductors carrying charge flowing in opposite directions,
that's something that, obviously, every dunce realizes.

Knowing that, my take on Koltner's lighthearted comment was that he was
referring to a single conductor, such as the ones used in high voltage
distribution systems which are called, by the way, "power lines".
---

Quote:
Nothing could be further from the truth, as demonstrated here:

news:26iag5hjpub42ookl0nk74vc3ffgs7316q_at_4ax.com

Since, conveniently, you don't have access to abse, I'll take the
liberty of emailing you the photos as soon as I post this.

Enjoy. :-)

The pictures were perfectly clear. It was less obvious what you were
actually doing, but since I couldn't care less, this isn't any great
loss.

---
You're really not much of an objective, honest, truth-seeking scientist,
are you?

If you're as smart as you unabashedly keep on proclaiming you are, you
should know very well what the pictures show; that energy cannot be
extracted from the varying magnetic field surrounding a conductor with a
solenoid-wound coil, but can be readily extracted using a
toroidally-wound coil.

Of course you have to feign ignorance and invoke indifference because
your position, from a technical point of view is untenable and you know
it, so in order to save face, instead of simply admitting error, you
resort to subterfuge.
---

Quote:
The joke is that even if you do extract "many watts" from the power
company's power lines, you won't be stealing from them. In order to be
able to extract power you have to be drawing power for which you will
be billed, and any extra watts you extract by transformer action is
subtracted from the power you are already paying for - your paid for
load will be seeing a lower drive voltage.

---
Geez, Dr. Sloman, even for you that's pretty stupid.

Have you never even considered that getting "free" power involves
tapping into the lines on the energy company's side of the meter?
---

Quote:
Joel Koltner made a rather good joke, which you have totally failed to
get.

---
Trying to make trouble, huh?

I have no quarrel with Joel and I don't think he has one with me since
all I did was apprise him, with no rancor, (with a little humor, even)
of the reason why one can't use a solenoid oriented coaxially with a
conductor carrying AC to extract energy from the varying field.

You, on the other hand, do nothing _but_ try to foment discord when your
errors are exposed, in an effort to diffuse the focus and allow you to
exit, without brickbats, from the melee you created in the first place.
JF

John Fields
Guest

Fri Nov 20, 2009 2:09 pm   



On Thu, 19 Nov 2009 21:29:10 -0500, daestrom <daestrom_at_twcny.rr.com>
wrote:


Quote:
If you make a 'tap' upstream of the revenue meter, even with just
transformer action, you're stealing. Revenue meters (kilowatt-hour
meters) have always had terminal voltage as one of their inputs. An
illegal tap upstream may affect the voltage at the service entrance some
small amount, but the metering will reduce the billed kWh accordingly.
So regardless of the exact voltage supplied by the utility (it often
varies slightly throughout the day), the amount of energy delivered at
the service entrance is what is billed for. Power drawn off before the
meter isn't measured and is 'stolen'.

Of course if you just 'wrap some turns around the power line' without
orienting the coil properly in relation to the line, you're not going to
get any power because transformer action won't work when your turns of
wire are parallel to the power line's magnetic field (i.e. 'wrapped
around' the power line). And I think that was John Field's point.

---
Indeed.

Thank you. :-)

JF

Tzortzakakis Dimitrios
Guest

Fri Nov 20, 2009 4:28 pm   



? "John Larkin" <jjlarkin_at_highNOTlandTHIStechnologyPART.com> ?????? ???
?????? news:dnsag51jfmub8nppj2kfj3nt07l3jv6djg_at_4ax.com...
Quote:
On Thu, 19 Nov 2009 07:29:26 -0800, Fester Bestertester <fbt_at_fbt.net
wrote:

So, for a millivolt output probe, this might be as simple as 2 windings
(or a
tapped single winding) with a range switch to select the winding?

Current transformers are usually dumped into a load resistor aka
burden resistor, to convert their output current into voltage. I'm
sure the Fluke clamp-on has an internal burden resistor, and they may
switch that to change ranges.

Without a burden resistor, the output voltage will be proportional to
frequency and very dependent on core reluctance, which would be fatal
for a clamp-on meter with a hinge and a non-repeatable air gap.

Coreless Rogowsky coils are used unloaded, but need a downstream
integrator to accurately measure current.

http://en.wikipedia.org/wiki/Rogowski_coil

The coolest current transformer is a second-harmonic DCCT, accurate to
parts-per-million from DC to many kilohertz.

http://www.gmw.com/electric_current/Danfysik/866_867/867.html
Anyway, current transformers must always be operated with the secondary

shorted. In the generating facilities in Kozani, West Macedonia, where 400
kV current transformers were involved, the operators of the plant had a
special indicator whether the secondary was shorted.


--
Tzortzakakis Dimitrios
major in electrical engineering
mechanized infantry reservist
hordad AT otenet DOT gr

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