Isolation transformer draws excessive current under no load condition

[JW]

Hi all,

Is there any reason that a 120VAC to 120VAC isolation transformer would
draw 2.54A on its primary when there is no load present on it's secondary?

Part reference:
http://www.temcoindustrialpower.com/products/Transformers/FT2036.html

datasheet:
http://attachments.temcoindustrialpower.com/product_info/Federal_FB_1Ph_120x240Pri.pdf

I finally got around to wiring this transformer, and I noticed something
that doesn't seem quite right to me. I have it wired for 120VAC (H1
connected to H3 and H2 connected to H4) and it seems to be working as I
get about 120VAC on the secondary, ( wired X1 to X3 and X2 to X4) but with
no load on the secondary, the transformer is drawing 2.54 Amps.

Looking for a sanity check I guess. I'm beginning to think the thing may
be defective... Email to the Temco has produced no response as of yet.

[nesesu]

On Feb 10, 8:17 am, JW <n...@dev.null> wrote:
> Hi all,
>
> Is there any reason that a 120VAC to 120VAC  isolation transformer would
> draw 2.54A on its primary when there is no load present on it's secondary?
>
> Part reference:http://www.temcoindustrialpower.com/products/Transformers/FT2036.html
>

> datasheet:http://attachments.temcoindustrialpower.com/product_info/Federal_FB_1...

>
> I finally got around to wiring this transformer, and I noticed something
> that doesn't seem quite right to me. I have it wired for 120VAC (H1
> connected to H3 and H2 connected to H4) and it seems to be working as I
> get about 120VAC on the secondary, ( wired X1 to X3 and X2 to X4) but with
> no load on the secondary, the transformer is drawing 2.54 Amps.
>
> Looking for a sanity check I guess. I'm beginning to think the thing may
> be defective... Email to the Temco has produced no response as of yet.

As a quick test, disconnect all the windings from each other and then
power up any ONE winding and see what the current draw is.
I see that it is a 15kVA rated, so it is not unreasonable that the
magnetizing curent is that high, but the actual power dissipation
would be much less than that current suggests. It is probably working
correctly, but a bit of an overkill for the average workbench.

Neil S.

[N_Cook]

JW <no...@dev.null> wrote in message
news:1dgaj7tpum8fe076c...@4ax.com...

If there are shorted turns then there would be a difference in DC ohms of
each coil, assuming they should be the same for 120/120

[mike]

It's not unusual for a transformer to draw some amps when unloaded.
That's what inductors do. The current should be out of phase with the
voltage.
What you care about is POWER. Measure the RMS power consumed by the
transformer. That's what counts.

If it's actually dissipating 300W, it will get very warm.

[Gareth Magennis]

> It's not unusual for a transformer to draw some amps when unloaded.
> That's what inductors do. The current should be out of phase with the
> voltage.
> What you care about is POWER. Measure the RMS power consumed by the
> transformer. That's what counts.
>

How might you do that?

(I don't have a power meter kicking around)


Gareth.

[William Sommerwerck]

2.5 amps seems like an awful lot of current, in-phase or not.

It sounds as if the unit is "defective" in some undefined. Or it might be
that the transformer's inductance is too low.

[mike]

Sure you do. It's on the outside of your house and goes
round and round...They send you a bill every month.
My base load is 200W, so an additional 300W would be
easy to see.
The newer ones simulate round and round
with an lcd display and have a flashing IR led that can
be used to measure actual power quite accurately.
If you have an old Palm III vintage PDA, I can send you
a program that lets you point the IR window at your power
meter and graph consumption...but a stopwatch counting
the display works as well.

It's best to turn off everything you can to reduce the base
load and improve the precision of your measurement with and
without the transformer connected.

If you wanna spend a few bucks, the P3 Kill A Watt meters
are very handy in this application.

As a go/no-go test, you can put an incandescent light bulb
in series with the transformer and see how bright it gets.

But at 300W, you shouldn't have any trouble sensing transformer
temperature rise with your hand.
OR
Wrap the transformer in insulation
and plot the temperature vs time...weigh the transformer to guess
at heat capacity and calculate the power from that.

So, several ways to "do that".
>
>
> Gareth.

[mike]

On 2/10/2012 10:38 AM, William Sommerwerck wrote:
> 2.5 amps seems like an awful lot of current, in-phase or not.

First guess, I'd have to agree. My Old Stancor 250W transformer
draws 9W 18VA .15A RMS unloaded.

>
> It sounds as if the unit is "defective" in some undefined. Or it might be
> that the transformer's inductance is too low.
>
>

One more thing to try.
Make sure you're not paralleling a primary and secondary winding.

Hook up one winding to the AC. Measure all 4 voltages very accurately.
How you connect the windings can make a difference. Small changes
in coupling due to the arrangement of the windings can produce
small differences in the output. When you start paralleling them,
you can get one winding fighting another. If that's the case,
energizing only one of the 4 windings with the others disconnected should
make the problem go away.
It's not impossible that a manufacturing defect screwed up the turns
count on one of the windings.

In a transformer this big, if you have a shorted turn, you should be
able to smell the result.

Depending on how close the transformer is to the box, the metal
box represents a shorted turn. All the flux is SUPPOSED to be inside
the core....supposed to be. I don't expect taking it out of the box
would make any significant difference, but I'd try it before scrapping
the device.

But the real diagnostic is to measure the real power consumed.
You can chase your tail trying to solve a problem that doesn't exist.
Try the series light bulb.

[Robert Macy]

Sounds VERY reasonable for a 15kVA transformer. 2.5 A suggests
coupling ratio on the order of 0.982, not bad for an AC mains
transformer that weighs that much.

If it bothers you, you can add a high quality AC cap in parallel
around 55 uF. That should 'resonate' out the reactive current assuming
120Vac, 60Hz yields around 127 mH.

Or, ignore it and let your house wiring dissipate a bit of power less
than 1W ?

[mike]

On 2/10/2012 12:36 PM, Robert Macy wrote:
> On Feb 10, 9:40 am, nesesu<neil_sutcli...@telus.net> wrote:
>> On Feb 10, 8:17 am, JW<n...@dev.null> wrote:
>>
>>
>>
>>
>>
>>> Hi all,
>>
>>> Is there any reason that a 120VAC to 120VAC isolation transformer would
>>> draw 2.54A on its primary when there is no load present on it's secondary?
>>
>>> Part reference:http://www.temcoindustrialpower.com/products/Transformers/FT2036.html
>>
>>> datasheet:http://attachments.temcoindustrialpower.com/product_info/Federal_FB_1...
>>
>>> I finally got around to wiring this transformer, and I noticed something
>>> that doesn't seem quite right to me. I have it wired for 120VAC (H1
>>> connected to H3 and H2 connected to H4) and it seems to be working as I
>>> get about 120VAC on the secondary, ( wired X1 to X3 and X2 to X4) but with
>>> no load on the secondary, the transformer is drawing 2.54 Amps.
>>
>>> Looking for a sanity check I guess. I'm beginning to think the thing may
>>> be defective... Email to the Temco has produced no response as of yet.
>>
>> As a quick test, disconnect all the windings from each other and then
>> power up any ONE winding and see what the current draw is.
>> I see that it is a 15kVA rated, so it is not unreasonable that the
>> magnetizing curent is that high, but the actual power dissipation
>> would be much less than that current suggests. It is probably working
>> correctly, but a bit of an overkill for the average workbench.
>>
>> Neil S.
>
> Sounds VERY reasonable for a 15kVA transformer.

Huh???
Federal Pacific SE120N1F FT2036 - Isolation Transformer 120 x 240
Primary 120/240V Secondary - 1 kVA 60Hz

[Gareth Magennis]

"mike" <spa...@gmail.com> wrote in message
news:jh3ruu$rfu$1...@dont-email.me...

[Gareth Magennis]

"mike" <spa...@gmail.com> wrote in message
news:jh3ruu$rfu$1...@dont-email.me...

> On 2/10/2012 11:22 AM, Gareth Magennis wrote:
>>
>>
>>> It's not unusual for a transformer to draw some amps when unloaded.
>>> That's what inductors do. The current should be out of phase with the
>>> voltage.
>>> What you care about is POWER. Measure the RMS power consumed by the
>>> transformer. That's what counts.
>>>
>>
>>
>>
>> How might you do that?
>> (I don't have a power meter kicking around)
>
> Sure you do. It's on the outside of your house and goes
> round and round...They send you a bill every month.
> My base load is 200W, so an additional 300W would be
> easy to see.
> The newer ones simulate round and round
> with an lcd display and have a flashing IR led that can
> be used to measure actual power quite accurately.
> If you have an old Palm III vintage PDA, I can send you
> a program that lets you point the IR window at your power
> meter and graph consumption...but a stopwatch counting
> the display works as well.
>
> It's best to turn off everything you can to reduce the base
> load and improve the precision of your measurement with and
> without the transformer connected.
>
> If you wanna spend a few bucks, the P3 Kill A Watt meters
> are very handy in this application.
>

Er, not everyone lives in North America. I happen to live in the UK.

Tell me again how you might measure the power consumption of a transformer.


Gareth.

[Robert Macy]

ARRRGGG! That'll teach me NOT to do my own research. Now, I have to
reply to my OWN posting!
ok your transformer is the 1kVA version of that series, the smallest
transformer.

current of max load is 1kVA/120 or 8.3A.
reactive current is 2.5 A that implies the core reactive impedance
from its inductance is around 3.3 to 1 Seems a little low, but in
range for a super cheap transformer that will get hot while running. I
would have expected more like around 1A, or less.

Here are some 'good' rules of thumb:
The core inductance reactance is probably 5 to 10 times the load
impedance, I've seen as low as 3 times.
The winding resistance is usually split half in pri and half in sec.
actually more like 45% in primary and 55% in sec.and the total is less
than 1/10 of load impedance.

So the transformer is in 'range' but that current does seem pretty
high for what should be a high quality transfomer. Could be a short
somewhere. Depending on how the transformer is wound, you may or may
not learn much from measuring the DC resistance of each winding. You
could power each winding with 120Vac and measure the current of each
winding, but then again.

If you don't need much power through this thing, like less than 500W,
wire it for 240/240 and that'll lower the core current for you.

[David Lesher]

"Gareth Magennis" <sound....@btconnect.com> writes:

>> What you care about is POWER. Measure the RMS power consumed by the
>> transformer. That's what counts.


>How might you do that?

>(I don't have a power meter kicking around)

Buy a Kill-o-watt; a useful tool to have around.


--
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

[Ian Jackson]

In message
<41177fb9-3a45-4b99...@z31g2000vbt.googlegroups.com>,
Robert Macy <robert...@gmail.com> writes

The symptoms described sound very similar to using a 60Hz transformer on
a 50Hz supply (as might happen if you are using American equipment in
Europe), and the transformer hasn't got enough iron in it - so it's
saturating. However, that's not what you are doing.

If saturation IS the problem, you can usually confirm it (under no-load
conditions) by winding the supply voltage up on a variac, and measuring
the current the transformer draws. It will rise suddenly when the core
starts to saturate. Although the problem is much more likely to be
shorted turns, a quick test for saturation might be interesting.
--
Ian

[mike]

Sorry for your loss.

>
> Tell me again how you might measure the power consumption of a transformer.

Not sure how repeating myself helps, but here goes.
I'd plug it into a Kill A Watt meter. That's how I got the other
experimental
results I mentioned in this thread.

I also disclosed several other techniques.

If you would read the parts you snipped, I also gave you several other
ways to estimate the power consumption of a transformer.

If you don't have a readable utility meter or a stopwatch or a
light bulb or a voltmeter or a scale or a thermometer or a hand, you
probably
should look elsewhere for advice. I'm all out.

Wait.....
I think I figured out how to do it with a used tea bag, the chime
from Big Ben and a plate of fish and chips.
Nope, you're still gonna need the hand.
>
>
> Gareth.

[spamtrap1888]

On Feb 10, 1:57 pm, "Gareth Magennis" <sound.serv...@btconnect.com>
wrote:
> "mike" <spam...@gmail.com> wrote in message

http://www.reuk.co.uk/Buy-UK-Power-Meter.htm

[Robert Macy]

On Feb 10, 4:00 pm, mike <spam...@gmail.com> wrote:
> On 2/10/2012 1:57 PM, Gareth Magennis wrote:
>
>
>
>
>

> > "mike" <spam...@gmail.com> wrote in message

Thanks! I needed that after the sleep-induced blather I posted

[Phil Allison]

"Robert Macy"

If it bothers you, you can add a high quality AC cap in parallel
around 55 uF. That should 'resonate' out the reactive current assuming
120Vac, 60Hz yields around 127 mH.

** You are a total ignoramus about transformers.

FYI:

Magnetising current is not inductive - it is highly non linear with peaks
at each zero crossing.



.... Phil

[Phil Allison]

"JW"

>
> Is there any reason that a 120VAC to 120VAC isolation transformer would
> draw 2.54A on its primary when there is no load present on it's secondary?

** Is that 2.54 amps RMS or not ?

In any case, is it getting rather hot and making a humming noise ?

If not, then all is OK.

The magnetising current will drop significantly when a full load is
applied.

BTW:

Adding capacitance in parallel has no effect on the tranny whatsoever -
and it will make the PF worse.





.... Phil

[Robert Macy]

Phil makes a good point about the terms being thrown around here.
Magnetizing current is NOT core inductance current. It is magnetizing
current. The better the core material the less this current will be.


Back to the core' inductance...The core's inductance is usually 5 to
10 times the impedance of full load.

You use a pair of windings to get to 1kVA, therefore per winding is
500VA, so at full load each winding is capable of 120Vac at 4.17A into
a RESISTIVE load of 28.8 ohms.

Now, the core winding's inductive reactance is at least 3 times that
usually more than 5 times that or, 144j ohms [the j signifies reactive
impedance of the core and that the current through the inductor will
be out of phase with any load by 90 degrees.] At 60Hz that core's
inductance will be about 382 mH.

When wired in parallel to achieve the full 1kVA capability and NO LOAD
each winding will have approx 0.834A for a total of 1.67A current. Of
course this is reactive current and does not consume significant
power.

To get rid of such inductive reactive currents, which cause a
'lagging' power factor, it is possible to add a parallel capacitor
essentially in resonance taking it to near zero, thus 'correcting' the
power factor. Industrial consumers with lots of motors often have a
rack [building] full of such capacitors that are switched in and out
depending on the correction they need.

It is of note that the current is ALWAYS there, even at full load, in
parallel with your load. If the transformer is made properly, the
waveform will be fairly linear, if the core is starting to saturate,
the current at the peaks will increase due to that saturation

A reasonable model predicts lower current than you saw, but 2.5A is
still possible, just seems high.

Further the winding resistance is often less than 1/10 of load, which
implies less than 3 ohms, probably more like 1.5 ohms per winding.
since they're in series to the load.

The magnetizing current is not really the same as the core inductance
current with the core inductance current in parallel with the load,
albeit 90 degrees shifted. Magnetizing current is actually what it
takes to 'turn on' the magnetic material. Really shows up if you try
to measure the core's inductance with a little meter and only put
0.1Vac across a winding, you'll find the inductance you measure is
almost nil. All caused because you haven't supplied the required
'magnetizing current' to overcome the material's coercivity.

Hope this is more clear.

[Phil Allison]

"Robert Macy"
>
> If it bothers you, you can add a high quality AC cap in parallel
> around 55 uF. That should 'resonate' out the reactive current assuming
> 120Vac, 60Hz yields around 127 mH.
>
> ** You are a total ignoramus about transformers.
>
> FYI:
>
> Magnetising current is not inductive - it is highly non linear with peaks
> at each zero crossing.
>

Phil makes a good point about the terms being thrown around here.

** The one doing the chucking about is YOU - pal.

Magnetizing current is NOT core inductance current.

** But includes it.

Back to the core' inductance...The core's inductance is usually 5 to
10 times the impedance of full load.

** Wrong - it is way more than that.

The NON LINEAR magnetising current increases with applied voltage and rise
sharply as the max rating is approached.


Now, the core winding's inductive reactance .....

** Is so high the resulting current flow barely matters.

At 60Hz that core's inductance will be about 382 mH.

** It is far more likely to be many Henries.

To get rid of such inductive reactive currents, which cause a
'lagging' power factor, it is possible to add a parallel capacitor
essentially in resonance taking it to near zero, thus 'correcting' the
power factor.

** FFS - give up on this crap.

You cannot correct the PF of an unloaded AC supply tranny with a parallel
cap !!!

It is of note that the current is ALWAYS there, even at full load, in
parallel with your load. If the transformer is made properly, the
waveform will be fairly linear, if the core is starting to saturate,
the current at the peaks will increase due to that saturation

** In reality, the ONLY significant current flow occurs around each
voltage zero crossing.

BTW:

Toroidal AC supply transformers are different.

Inductance is way high and I mag is almost non existent up to the rated
input voltage at the rated frequency.


.... Phil

[Gareth Magennis]

> Wait.....
> I think I figured out how to do it with a used tea bag, the chime
> from Big Ben and a plate of fish and chips.
> Nope, you're still gonna need the hand.
>>
>>
>> Gareth.
>
>

I'll bet you don't have a Passport.

[mike]

I'm intrigued. How do you use a Passport to measure
transformer losses? If you don't have a hand, you can't
even pick it up.

[spamtrap1888]

I don't see how a radar detector is going to help him.

http://www.ukspeedtraps.co.uk/passport8500.htm

[Franc Zabkar]

On Fri, 10 Feb 2012 19:22:33 -0000, "Gareth Magennis"
<sound....@btconnect.com> put finger to keyboard and composed:

>> Measure the RMS power consumed by the transformer.
>

>How might you do that?
>
>(I don't have a power meter kicking around)

My local Aldi has these for AU$13:
http://aldi.com.au/au/html/offers/2827_20656.htm?WT.mc_id=2012-01-30-08-10

The meter also reports the power factor.

Same model number (GT-PM-04), probably made by Globaltronics:
http://www.teknihall.nl/index.php?id=1129&L=nl

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

[JW]

On Sun, 12 Feb 2012 01:05:04 +1100 "Phil Allison" <phi...@tpg.com.au>
wrote in Message id: <9pnasl...@mid.individual.net>:

>
>"JW"
>>
>> Is there any reason that a 120VAC to 120VAC isolation transformer would
>> draw 2.54A on its primary when there is no load present on it's secondary?
>
>
>** Is that 2.54 amps RMS or not ?

Yes. I've measured it with the same result using both a Watts Up meter and
a Fluke 87.

> In any case, is it getting rather hot and making a humming noise ?

Making a humming noise, yes. It's not getting hot, the external
temperature rise of the case is only about 10c.

> If not, then all is OK.
>
> The magnetising current will drop significantly when a full load is
>applied.

Nail. Head.

My test setup and how this all started:

120V in is being fed to a variac, then to the isolation transformer, then
the load. On the secondary of the transformer I added a toggle switch that
would connect the secondary in series or parallel depending whether I
wanted 120V or 240V out. When I first wired up everything as I stated in
my OP, being on the cautious side I placed a 1.5A fuse into the variac so
if I mis-wired something there'd be no damage. Well, on first power up I
slowly raised the voltage on the primary and at a little over 110V the
fuse blew.

The actual wattage when the primary is at 120V is only 42W as measured by
the Watt meter. Here's why - the power factor is really crappy at just
about .15. This would explain everything. I wonder if this is typical of a
1KVA transformer? I never thought to check the wattage being drawn...

> BTW:
>
>Adding capacitance in parallel has no effect on the tranny whatsoever -
>and it will make the PF worse.

Noted, and thanks.

Also, thanks to everyone else for their input - some very good thoughts.
It would appear that there's no problem after-all.

[JW]

On Fri, 10 Feb 2012 12:34:41 -0800 mike <spa...@gmail.com> wrote in
Message id: <jh3v48$emd$1...@dont-email.me>:

>
>Depending on how close the transformer is to the box, the metal
>box represents a shorted turn. All the flux is SUPPOSED to be inside
>the core....supposed to be. I don't expect taking it out of the box
>would make any significant difference, but I'd try it before scrapping
>the device.

It's potted inside the box, so that's not possible. In any case it would
seem that there's no problem (see my other post), thanks.

[William Sommerwerck]

Out of curiosity, I took out my Tenma 72-545 1.5A isolation transformer.

On my Kill A Watt, it draws 60 mA unloaded, 3W / 7VA, with a power factor of
0.48.

I assume the current without a load varies with the primary inductance, not
the rated capacity. So the 2.45A drawn by the OP's transformer seems to be
unnaturally high.

[Robert Macy]

On Feb 13, 5:45 am, JW <n...@dev.null> wrote:
>...snip...

>
> >Adding capacitance in parallel has no effect on the tranny whatsoever  -
> >and it will make the PF worse.
>
> Noted, and thanks.

> ...snip...

Adding caps will indeed have NO effect on the tranny, but WILL improve
the PF as seen by your AC mains, which means the amount of power you
drop in your wiring [and pay for] will be less.

Adding caps is a STANDARD way to adjust power factor to 1. Used by the
industrial power consumers that are heavily penalized for lagging
power factor. It is cheaper for them to add a building full of caps,
just to shift their PF and pay less for power.

If you do the analysis of power consumption throughout a standard AC
mains power distribution, you will find that a lagging power factor
[caused by motors, etc] INCREASES the power required to simply get
billable wattage to you. And, it's surprisingly large.

[Phil Allison]

"Robert Macy"


** Is there any way to shut fools like you up ??

Adding caps will indeed have NO effect on the tranny, but WILL improve
the PF as seen by your AC mains,

** Absolute BULLSHIT !!!!!!!!!

which means the amount of power you
drop in your wiring [and pay for] will be less.

** Absolute IDIOCY !!!!!!!

Adding caps is a STANDARD way to adjust power factor to 1.

** But never used with an off load transformer - because that idea is 100%
STUPID.

YOU are an obsessed IDIOT with a one track mind.

Piss off.



... Phil

[Phil Allison]

"JW"
"Phil Allison"

>>
>>> Is there any reason that a 120VAC to 120VAC isolation transformer would
>>> draw 2.54A on its primary when there is no load present on it's
>>> secondary?
>>
>>
>>** Is that 2.54 amps RMS or not ?
>
> Yes. I've measured it with the same result using both a Watts Up meter and
> a Fluke 87.

** Good.

>> In any case, is it getting rather hot and making a humming noise ?
>
> Making a humming noise, yes. It's not getting hot, the external
> temperature rise of the case is only about 10c.

** Sounds about normal for a large e-core tranny

> The actual wattage when the primary is at 120V is only 42W as measured by
> the Watt meter.

** That is pretty high actually - a typical 1KVA tranny has about 6 to 8 %
power loss at full load.

> Here's why - the power factor is really crappy at just
> about .15. This would explain everything.

** Not everything.

You have to know that the current waveform is distorted - THIS fact is
causing the poor PF when unloaded.


... Phil

[Robert Macy]

I stand by what I said as technically correct.

Many, many technical journals, text books, and supporting calculations
based upon terms of definition confirm what I said.

Quit spewing vitriole, making erroneous statements, *and* misleading.

CONTRIBUTE, EDUCATE, and LEARN!

[Phil Allison]

"Robert Macy"


** Is there any way to shut fools like you up ??

----------------------------------------------------

> Adding caps will indeed have NO effect on the tranny, but WILL improve
> the PF as seen by your AC mains,
>
> ** Absolute BULLSHIT !!!!!!!!!
>
> which means the amount of power you
> drop in your wiring [and pay for] will be less.
>
> ** Absolute IDIOCY !!!!!!!
>
> Adding caps is a STANDARD way to adjust power factor to 1.
>
> ** But never used with an off load transformer - because that idea is 100%
> STUPID.
>
> YOU are an obsessed IDIOT with a one track mind.
>
> Piss off.
>

I stand by what I said as technically correct.

** LOL - that only makes you a BIGGER fucking idiot.

Many, many technical journals, text books, and supporting calculations
based upon terms of definition confirm what I said.

** Shame you cannot supply one that backs up your idiotic comments about
unloaded transformers.

Listen PAL !!!!!!!!

YOU are nothing but a lying, bullshitting NUT CASE !!

Clueless to the core.

FOAD.




... Phil

[spamtrap1888]

What are your PFC capacitors doing when the transformer supplies a
load? And if you were to switch them out when there was a load on the
secondary, wouldn't it make more sense just to open the primary when
there was no load? Then you wouldn't get any idle current draw at all.

[Robert Macy]

There is a difference between
CANNOT supply reference material,
DID NOT supply reference material, and
WILL NOT supply reference material.

I simply DID NOT for several reasons. Takes a lot of time. Your
attitude appears closed, thus, I did not expect you to take the time
to read what I took the time to research for you; and not sure anyone
else is interested.

However, I AM INTERESTED, and upon searching, found over 15,000
related articles. The artricles either dismiss the small effects/
distortions and then describe linear transformer models, or support
the models I use/modified/developed. However, after one of the most
promising articles also misused the term 'magnetizing current' as I
had; I decided to rederive my transformer model from basics. I already
have distrust for information in printed sources. I'm going to
specifically look into whether the nonlinearity of the magnetizing
current does lessen with load. I suspect that in an isolation
transformer it does NOT, because the full voltage pretty much remains
constant across the core. However, in an audio matching transformer,
going from no load to full load drops the voltage across the core
approx. in half and indeed the magnetizing current would then change,
with less voltage across the core, the magnetizing current would also
lessen.

If the core material of an isolation transformer is extremely high
quality with low coercivity, whether the transformer is loaded, or
unloaded, will make small difference to the inductive current flowing
through the core, BECAUSE the voltage the core must sustain stays
pretty constant, whether unloaded or fully loaded. The inductive
current through the core appears in parralell to the load and is
pretty much constant. Being summed in quadrature just makes it appear
that it is getting smaller.

For example consider an isolation transformer that has 1A core current
(assume linear) with NO LOAD, one would measure 1A of current flowing.
Now load the transformer with a relatively small 5A load, now one
would measure only 5.1A, which makes the core current APPEAR to be
less as load increases, when in actuality, the core current has stayed
the same 1A inductive current.
= sqrt( 5*5 + 1*1 ) = 5.1 Is your comment that the core's current
decreases with load based upon such observation?

Your personal attack is unwarranted. I'm not a "...lying, bullshitting
NUT CASE !!" But this discussion is not about how you perceive my
character, rather this discussion is about explaining whether the OP's
transformer is broken or not, based upon his observation that the
transformer's leakage current is 2.5A. From that question the
discussion has become a positive LEARNING experience! so, STICK to
the SUBJECT.

However, thanks for the pricelss comment:
"Clueless to the core." LOL!
What did I do to deserve such PUNishment?

[Robert Macy]

The cap in parallel will continue to 'remove' the inductive current -
as far as the AC mains sees it. The inductive current remains whether
the transformer is loaded or not.

Completely disconnecting everything from the AC mains will always save
power.

As far as I know, no industrial power consumer adds caps just for
transformer core currents, only for large motors that are extremely
inductive loads.

[Phil Allison]

"Robert Macy = Troll "


** Is there any way to this MORON up ??

( Load of totally absurd crap deleted )



... Phil

[Phil Allison]

"Robert Macy"

** Is there any way to shut fools like you up ??
----------------------------------------------------

Shame you cannot supply one that backs up your idiotic comments about
unloaded transformers.

Listen PAL !!!!!!!!

YOU are nothing but a lying, bullshitting NUT CASE !!

Clueless to the core - pun intended.

FOAD.



... Phil

[Sylvia Else]

But, except for the extra power dissipated in the household wiring, is
not measured by the meter, and not included in the billed energy units.

Sylvia.

[Robert Macy]

Although you are wrong, you say with such conviction that people
believe. I would not have bothered replying and supplying references
supporting my statements, except your claims/comments are proving a
disservice to people seeking information. As an example of the effects
of your incorrect statements, see reply posted by spamtrap1888, whose
question appears to be based upon having accepted your erroneous claim
that as a transformer is loaded, the inductive core current decreases.
Not true. As an isolation transformer is loaded, the inductive core
current DOES NOT decrease. rather stays fairly constant.

Stop misleading people. You do NOT contribute, rather distract/
distort. Stop it.

To prevent/undo the damage you cause, I post the following references:

using advanced google search with the following words
"magnetizing current" transformer distortion
yields 38,200 results, starting at the first, they are worthwhile
reading, such as...

this shows how saturation causes a spike in current as the voltage
waveform crosses zero:
<http://www.allaboutcircuits.com/vol_2/chpt_9/1.html>
section "Transformer Principles" describes constant voltage across the
core, thereby constant inductive current, etc.
<http://lehmanengineering.com/quiz/quiz6sol.html>
also, these two pdf files are a decent background reference:
<http://classicaudio.ru/articles/Output_Transformer_a57.pdf>
<http://www.classicaudio.ru/articles/ot_distortion_p2_a57.pdf>

etc, etc, etc.

These references supported my statements.

.
.
.
However, you did not supply any reference refuting my statements.

[Phil Allison]

" Robert Macy = fuckwit TROLL "


( snip piles of the idiot's steaming great turds )


Listen here PAL !!!!!!!!

YOU are nothing but a lying, bullshitting, tenth witted NUT CASE !!

Clueless right to the core.

Fuck OFF !!!!!!!!!!!!!!!!



... Phil

[Robert Macy]

True!

Today, the only way that utilities companies can bill for this lost
energy is by assigning a 'penalty' for bad PF.

I'll bet with today's smarter metering, they'll figure a way to
measure it real-time and bill for it.

[William Sommerwerck]

God knows, we've tried... but you keep posting.

[Robert Macy]

On Feb 15, 3:37 pm, "William Sommerwerck" <grizzledgee...@comcast.net>
wrote:

> God knows, we've tried... but you keep posting.

I use google access so the thread line is NOT preserved.

William,

Is this email for me?

Is there an error(s) in what I posted?

[Sylvia Else]

And if we correct our power factor, our bills will be lower than they
are now.

Oh, wait a minute, what was I thinking?

Sylvia.

[Robert Macy]

On Feb 13, 4:42 pm, "Phil Allison" <phi...@tpg.com.au> wrote:
>...snip...

> **  That is pretty high actually -  a typical 1KVA tranny has about 6 to 8 %
> power loss at full load.

>...snip...

Agree with that range.

Assume for this transformer the power loss is 8%, 80W.
Further assume this is a 'well designed' transformer where the
designer allowed half the dissipation in the windings and half in the
core.
That means 40W in the core and 40W in the windings, at full load.
Four windings with each carrying half the full load current, 4.167A,
implies 0.576 ohms/winding
two in series would be 1.15 ohm and since most pri/sec are 45%/55%
that would mean
each pri winding 0.52 ohm
each sec winding 0.63 ohm

Now unloaded the two pri windings are passing 1.27A each, dissipating
almost 2 W and the core is dissipating around 40W, so JW would have
measured power for the unloaded transformer at around 42W, which he
said he measured.

JW,
Did you ever measure the winding impedance?
It would be interesting to compare prediction to actual values. [of
course, preaching to the choir, for better accuracy put the two pri in
series and the two sec in series]

[Robert Macy]

On Feb 13, 5:45 am, JW <n...@dev.null> wrote:

> On Sun, 12 Feb 2012 01:05:04 +1100 "Phil Allison" <phi...@tpg.com.au>

> wrote in Message id: <9pnaslF48...@mid.individual.net>:
>
> >...snip...

> >Adding capacitance in parallel has no effect on the tranny whatsoever  -
> >and it will make the PF worse.
>
> Noted, and thanks.
>

A cap does improve PF...

To answer the question whether an external capacitor placed in
parallel with the input of a transformer improves power factor or not,
for both loaded and unloaded conditions; I started the following
analyses and share with others who may be interested.

First, use a Linear Model to represent the isolation transformer.
Simulate the iso transformer and circuitry by using LINEAR SIMULATION,
that is, only using linear components to represent observed data.

Second, simulate using nonlinear components, specifically the chan
model, which simulates BOTH hysteresis (coercivity) and saturation.
TO BE DONE LATER.

(Model of the 1kVA ISO-Transformer wound for 120/120 operation)

LINEAR SIMULATION
The following transformer model is accepted for low frequency
operation. The transformer is approximated by representing the
transformer as primary and secondary winding resistances connected to
a core which has a parallel resistance to represent the core losses.
The transformer's coupling coefficient was arbitrarily set to one,
more likely to be as low as 0.98. But modifying coupling coefficient
does not appreciably change results.

Values for core inductance and parallel resistor were determined from
data provided by JW and winding resistance values were estimated based
upon experience:

Core Inductance:
Lcore = 0.128 H, based upon JW's measurement of current with NO LOAD
Core Losses:
Rcore = 360 ohms, based upon JW's measurement using Watts Up meter
with NO LOAD
Winding Resistances:
Rpri = 0.26 ohms, Rsec = 0.315 ohms estimated from experience

The measurements that one would obtain with this linear model are
Current NO LOAD = 2.54 Arms
Power NO LOAD = 41.7 W
PF = 0.137

All fairly close.

As a sanity check, what happens at FULL load with 14.4 ohms?
Vout = 115V, Power = 922W, PF = 0.960, which is reasonable.

Load regulation is not that good in this model. The output voltage
with NO LOAD is 120V, but when loaded with 14.4 ohms to get the
expected 1kW output, the output voltage drops to 115V. This
manufacturer probably did what everyone else does and not wind the
transformer EXACTLY 1:1, but add a few extra turns on the secondary to
compensate for this expected drop, more like 100:105 or such. JW could
verify the winding ratio by running the transformer 'backwards'. He
would then see he'd probably only get 110 out the pri with 120 into
the sec. Anybody who has used two doorbell transformers, one down and
one back up just to make an isolation transformer has discovered this
'feature'.

For simplicity, I leave the winding ratio as 1:1, which will not
appreciably change results.


In a previous post I said add a parallel capacitor, 55uF, to adjust
the PF closer to 1.

When 55uF cap is added in parallel to the input of the transformer,
the PF does indeed change.
NO LOAD: PF = 0.997
FULL LOAD: PF = 1.00
And, as I claimed adding a cap improved for both NO Load and FULL
Load.


I've included a copy of the simulation model below, watch out for word
wrap, but feel free to try it in FREE LTspice and see for yourself.

CONCLUSION:
Adding a parallel capacitor to the input of a transformer does help
power factor both loaded and unloaded.


Now, this was LINEAR simulation. I will now more accurately model the
non-linear characteristics of a real transformer and compare to see if
my assertion is still true.





LINEAR SIMULATION:

Version 4
SHEET 1 3060 1012
WIRE 1216 752 1184 752
WIRE 1344 752 1296 752
WIRE 1456 752 1344 752
WIRE 1584 752 1456 752
WIRE 1728 752 1664 752
WIRE 1808 752 1728 752
WIRE 1904 752 1808 752
WIRE 2080 752 1984 752
WIRE 2384 752 2160 752
WIRE 2432 752 2384 752
WIRE 1728 768 1728 752
WIRE 1808 768 1808 752
WIRE 1904 768 1904 752
WIRE 1984 768 1984 752
WIRE 2432 768 2432 752
WIRE 1456 784 1456 752
WIRE 1184 800 1184 752
WIRE 1728 880 1728 848
WIRE 1808 880 1808 848
WIRE 1904 880 1904 848
WIRE 1984 880 1984 848
WIRE 2432 880 2432 848
WIRE 1184 896 1184 880
WIRE 1456 896 1456 848
FLAG 1184 896 0
FLAG 1808 880 0
FLAG 1904 880 0
FLAG 1984 880 0
FLAG 2432 880 0
FLAG 2384 752 OUT
FLAG 1344 752 IN
FLAG 1728 880 0
FLAG 1456 896 0
SYMBOL voltage 1184 784 R0
WINDOW 0 48 52 Left 0
WINDOW 3 47 113 Left 0
WINDOW 123 49 82 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName Vac
SYMATTR Value SINE(0 170 60)
SYMATTR Value2 AC 120
SYMBOL res 1200 768 R270
WINDOW 0 32 56 VTop 0
WINDOW 3 0 56 VBottom 0
SYMATTR InstName Racmains
SYMATTR Value 0.01
SYMBOL ind 1792 752 R0
SYMATTR InstName Lcore
SYMATTR Value 0.128
SYMBOL ind2 1888 752 R0
SYMATTR InstName Lpri
SYMATTR Value 10
SYMATTR Type ind
SYMBOL ind2 1968 752 R0
SYMATTR InstName Lsec
SYMATTR Value 10
SYMATTR Type ind
SYMBOL res 1568 768 R270
WINDOW 0 32 56 VTop 0
WINDOW 3 0 56 VBottom 0
SYMATTR InstName Rpri
SYMATTR Value 0.26
SYMBOL res 2064 768 R270
WINDOW 0 32 56 VTop 0
WINDOW 3 0 56 VBottom 0
SYMATTR InstName Rsec
SYMATTR Value 0.315
SYMBOL res 2416 752 R0
SYMATTR InstName Rload
SYMATTR Value 10MEG
SYMBOL res 1712 752 R0
SYMATTR InstName Rcore
SYMATTR Value 360
SYMBOL cap 1440 784 R0
SYMATTR InstName Cc
SYMATTR Value 55µF
TEXT 1808 936 Left 0 !K1 Lpri Lsec 1
TEXT 1152 624 Left 0 !.ac LIN 201 50 70
TEXT 1152 552 Left 0 ;.ac LIN 201 50 70
TEXT 2672 800 Left 0 ;NO Load Rload = 10MEG\nFULL Load Rload =
14.4 ohms
TEXT 1648 624 Left 0 ;PF = RE(V(in)*I(Racmains))/(V(in)*I(Racmains))
TEXT 1400 936 Left 0 ;NO PF Correction Cc = 55pF\nWITH PF
Correction Cc = 55uF

[Phil Allison]

"Robert Macy" = one stubborn fucker

>A cap does improve PF...

** But only with theoretical transformers - NOT real ones.

> First, use a Linear Model to represent the isolation transformer.

** Waste of fucking time and effort - as it only repeats the same FUCKWIT
error you have been sprouting here all along.

The primaries of REAL commercially made E-core transformers are NOT
linear inductors !!!!!!!!!!!

The off load primary current at rated voltage is *dominated by the third
harmonic * of the AC supply frequency.

The laminated iron core is then saturating, quite heavily.

JW's 1kVA iso tranny is a very typical example of this fact.

You will NOT find this information on webs sites that merely discuss
transformer basics.

You WILL find this if you test a cross section of commercial E-core
transformers with the aid of a variac, RMS current meter and a scope
monitoring the current waveform.

This has NOTHING do with badly or well made transformers - all makers do it
to save weight and cost.

BTW:

I happen to own a 1kVA transformer very similar to that described by the OP.

Tested as above, these are the figures:

VAC A rms I peak

30 0.08 0.11
50 0.11 0.14
70 0.20 0.35

90 0.45 1.0
110 1.0 2.0
120 1.4 2.9
130 2.2 4.6


Up to 70 volts AC, the tranny is approximately linear with an effective
inductance of about 1.1 H.

At and above 90 volts AC it suddenly changes - current starts to increase
exponentially and the wave becomes very peaky with a 1:2 ratio between rms
and peak values.

At 130 VAC input, effective primary inductance ( based on simplistic
calculations) has dropped to less than 0.2H due to core saturation.

I must have tested hundreds of E-core trannys this way in the last 20 years
or so and ALL do much the same thing.

Toroidal and C- core types are different.


.... Phil

[Robert Macy]

Thank you for the explanation and the data.

I did see that in my non-linear models the third harmonic peaks
started 'popping' up as the voltage increased.

Obviously, the concept of inductance loses something with that much
distortion.

Will try to curve fit that data to the chan model and see if the
simulations match your measurements. It would be great to have a model
one can trust to at least somewhat 'look' like reality.

[Cydrome Leader]

yes it is. the problem with low power factors is the power loss before the
meter, which isn't measured and can be huge for large customers.

If at home, I toss a giant capacitor or huge inductor across the line, my
meter will pick up all the wiring and heating losses from the capacitors
or inductor.

It will not measure the losses to the power company for me circulating 100
amps to and from the power grid. the power companies losses on that will
be larger than mine, plus it wastes capacity of the grid itself.

For residential customers in the US, it's just assumed we're not idling
huge motors or testing capacitor banks in the dining room, so the
utilities don't pay attention to us.

[Cydrome Leader]

JW <no...@dev.null> wrote:
> Hi all,

>
> Is there any reason that a 120VAC to 120VAC isolation transformer would
> draw 2.54A on its primary when there is no load present on it's secondary?
>

> Part reference:
> http://www.temcoindustrialpower.com/products/Transformers/FT2036.html
>
> datasheet:
> http://attachments.temcoindustrialpower.com/product_info/Federal_FB_1Ph_120x240Pri.pdf
>
> I finally got around to wiring this transformer, and I noticed something
> that doesn't seem quite right to me. I have it wired for 120VAC (H1
> connected to H3 and H2 connected to H4) and it seems to be working as I
> get about 120VAC on the secondary, ( wired X1 to X3 and X2 to X4) but with
> no load on the secondary, the transformer is drawing 2.54 Amps.
>
> Looking for a sanity check I guess. I'm beginning to think the thing may
> be defective... Email to the Temco has produced no response as of yet.

I just ran a test I have on a similar transformer. Mine is a cutler hammer
1.5kVA unit in the same type of metal box and potted in expoxy and sand -
nothing special.

it's actually a 240/480 to 240/120 unit, but you can switch the H and X
leads with no no big deal.

Anyways, running 125 VAC (line voltage is high around here) across "half"
the secondary (X1 and X2 instead of X1+x3 and X2+x4) resulted in 24 watts
of loss and a current of 0.5A according to the kilowatt meter. The thing
even buzzes somehow.

I'd say your transformer is bad or somehow connected wrong. My transformer
is rated 115C rise, so it's probably no winner when it comes to energy
efficiency. %Z isn't even listed on the nameplate.

[Phil Allison]

"Cydrome Leader"

> I'd say your transformer is bad or somehow connected wrong.

** No way.

The OP's data shows it is operating normally and correctly.

10 degrees temp rise and a PF of 0.15 is A-OK.



.... Phil

[Cydrome Leader]

that's a pretty horrible transformer if those parameters are A-OK.

[Phil Allison]

"Cydrome Lunatic"

>>
>>> I'd say your transformer is bad or somehow connected wrong.
>>
>>
>> ** No way.
>>
>> The OP's data shows it is operating normally and correctly.
>>
>> 10 degrees temp rise and a PF of 0.15 is A-OK.
>>
>>
>

> that's a pretty horrible transformer if those parameters are A-OK.
>

** ROTFL - you are one colossal, know nothing bloody fool.



.... Phil

[spamtrap1888]

Why doesn't the transformer data sheet include idle current, power
factor, etc.? Or is it embedded in some transformer standard I have to
spend 2000 swiss francs to get?

[Phil Allison]

"spamtrap1888"
"Phil Allison"

>
> > I'd say your transformer is bad or somehow connected wrong.
>
> ** No way.
>
> The OP's data shows it is operating normally and correctly.
>
> 10 degrees temp rise and a PF of 0.15 is A-OK.
>

Why doesn't the transformer data sheet include idle current, power
factor, etc.?

** Why should it ?

They are easily measured parameters and of little interest to most users.

If the safety ratings, VA rating, temp rise, dimensions, weight and mounting
details are all described - that is enough.



... Phil

[William Sommerwerck]

"Phil Allison" <phi...@tpg.com.au> wrote in message
news:9qb4mg...@mid.individual.net...

> "Cydrome Lunatic"

>>>> I'd say your transformer is bad or somehow connected wrong.

>>> ** No way.
>>> The OP's data shows it is operating normally and correctly.
>>> 10 degrees temp rise and a PF of 0.15 is A-OK.

>> That's a pretty horrible transformer if those parameters are A-OK.

> ** ROTFL -- you are one colossal, know[-]nothing bloody fool.


Phil, do you know the word "empirical"? If not, you should learn it.
Empirical data are knowledge, as assuredly as theoretical considerations.

Last week I measured the no-load drain of a 1.5A isolation transformer. * My
Kill A Watt read 0.06 amperes, which could be anywhere between 0.055 and
0.065 amps. (The display doesn't have enough resolution.) That's 4% of the
rated load. Not bad.

The OP's transformer seems way out of line. It should definitely be placed
off-line. (Ar, ar.)

* I was about to specify 125V, when I realized that, in theory, an isolation
transformer should "work" at any voltage -- short (joke intended) of a
voltage high enough to break down the insulation, etc, etc, etc.

[Cydrome Leader]

spamtrap1888 <spamtr...@gmail.com> wrote:

> On Feb 18, 4:22?pm, "Phil Allison" <phi...@tpg.com.au> wrote:
>> "Cydrome Leader"
>>
>> > I'd say your transformer is bad or somehow connected wrong.
>>
>> ** No way.
>>
>> The OP's data shows it is operating normally and correctly.
>>
>> 10 degrees temp rise and a PF of 0.15 is A-OK.
>>

>> .... ?Phil

>
> Why doesn't the transformer data sheet include idle current, power
> factor, etc.? Or is it embedded in some transformer standard I have to
> spend 2000 swiss francs to get?

The only transformers I've seen specs for idle power consumption listed
(but not on the nameplate) are for distribution transformers the power
company would own. They seem to care about how much money it costs to keep
a transformer running for 30 years or until it finally explodes, so every
watt counts.

For loose reference, I recall some 1kVA oil filled poole mount
distribution tranformers with the real step-lap core idling at 14 watts,
or something close to that. They really make 1kVA units for stuff like
streetlights and running switchgear. At the 10kVA oil filled ones with the
typical step-lap cores, something like 45 watts is normal for some brands.

These monsters aren't really rated the same as smaller EI core potted unit
which are only meant to be cheap to produce in mexico or china or wherever
they come from these days.

[rrus...@hotmail.com]

On Feb 10, 4:42 pm, Ian Jackson
<ianREMOVETHISjack...@g3ohx.demon.co.uk> wrote:
> In message
> <41177fb9-3a45-4b99-b150-285f289a5...@z31g2000vbt.googlegroups.com>,
> Robert Macy <robert.a.m...@gmail.com> writes
>
>
>
>
>
>
>
>
>
> >On Feb 10, 1:36 pm, Robert Macy <robert.a.m...@gmail.com> wrote:
> >> On Feb 10, 9:40 am, nesesu <neil_sutcli...@telus.net> wrote:

>
> >> > On Feb 10, 8:17 am, JW <n...@dev.null> wrote:
>
> >> > > Hi all,
>
> >> > > Is there any reason that a 120VAC to 120VAC  isolation transformer would
> >> > > draw 2.54A on its primary when there is no load present on it's
> >> > >secondary?
>
> >> > > Part
>
> >> > >>>reference:http://www.temcoindustrialpower.com/products/Transformers/FT2036.html
>

> >> > >>>datasheet:http://attachments.temcoindustrialpower.com/product_info/Federal_FB_1...

>
> >> > > I finally got around to wiring this transformer, and I noticed something
> >> > > that doesn't seem quite right to me. I have it wired for 120VAC (H1
> >> > > connected to H3 and H2 connected to H4) and it seems to be working as I
> >> > > get about 120VAC on the secondary, ( wired X1 to X3 and X2 to X4)
> >> > >but with
> >> > > no load on the secondary, the transformer is drawing 2.54 Amps.
>
> >> > > Looking for a sanity check I guess. I'm beginning to think the thing may

> >> > > be defective... Email to the Temco has produced no response as of yet.
>
> >> > As a quick test, disconnect all the windings from each other and then
> >> > power up any ONE winding and see what the current draw is.
> >> > I see that it is a 15kVA rated, so it is not unreasonable that the
> >> > magnetizing curent is that high, but the actual power dissipation
> >> > would be much less than that current suggests. It is probably working
> >> > correctly, but a bit of an overkill for the average workbench.
>
> >> > Neil S.
>
> >> Sounds VERY reasonable for a 15kVA transformer. 2.5 A suggests
> >> coupling ratio on the order of 0.982, not bad for an AC mains
> >> transformer that weighs that much.
>
> >> If it bothers you, you can add  a high quality AC cap in parallel
> >> around 55 uF. That should 'resonate' out the reactive current assuming
> >> 120Vac, 60Hz yields around 127 mH.
>
> >> Or, ignore it and let your house wiring dissipate a bit of power less
> >> than 1W ?
>
> >ARRRGGG!  That'll teach me NOT to do my own research.  Now, I have to
> >reply to my OWN posting!
> >ok your transformer is the  1kVA version of that series, the smallest
> >transformer.
>
> >current of max load is 1kVA/120 or 8.3A.
> >reactive current is 2.5 A that implies the core reactive impedance
> >from its inductance is around 3.3 to 1  Seems a little low, but in
> >range for a super cheap transformer that will get hot while running. I
> >would have expected more like around 1A, or less.
>
> >Here are some 'good' rules of thumb:
> >The core inductance reactance is probably 5 to 10 times the load
> >impedance, I've seen as low as 3 times.
> >The winding resistance is usually split half in pri and half in sec.
> >actually more like 45% in primary and 55% in sec.and the total is less
> >than 1/10 of load impedance.
>
> >So the transformer is in 'range' but that current does seem pretty
> >high for what should be a high quality transfomer.  Could be a short
> >somewhere. Depending on how the transformer is wound, you may or may
> >not learn much from measuring the DC resistance of each winding.  You
> >could power each winding with 120Vac and measure the current of each
> >winding, but then again.
>
> >If you don't need much power through this thing, like less than 500W,
> >wire it for 240/240 and that'll lower the core current for you.
>
> The symptoms described sound very similar to using a 60Hz transformer on
> a 50Hz supply (as might happen if you are using American equipment in
> Europe), and the transformer hasn't got enough iron in it - so it's
> saturating. However, that's not what you are doing.
>
> If saturation IS the problem, you can usually confirm it (under no-load
> conditions) by winding the supply voltage up on a variac, and measuring
> the current the transformer draws. It will rise suddenly when the core
> starts to saturate. Although the problem is much more likely to be
> shorted turns, a quick test for saturation might be interesting.
> --
> Ian

When I buy transformers I always buy ones rated for 50 Hz, that way
on 60 Hz they run cooler. That does not apply to ferroresonant
transformers of course, but I have never bought one so it doesn't
matter.

[rrus...@hotmail.com]

On Feb 13, 10:15 pm, "Phil Allison" <phi...@tpg.com.au> wrote:
> "Robert Macy"
>
> ** Is there any way to shut fools like you up ??
>    ----------------------------------------------------
>
>
>
>
>
>
>
>
>

> > Adding caps will indeed have NO effect on the tranny, but WILL improve
> > the PF as seen by your AC mains,
>

> > ** Absolute BULLSHIT !!!!!!!!!

>
> > which means the amount of power you
> > drop in your wiring [and pay for] will be less.
>

> > ** Absolute IDIOCY !!!!!!!

>
> > Adding caps is a STANDARD way to adjust power factor to 1.
>

> > ** But never used with an off load transformer - because that idea is 100%
> > STUPID.
>
> > YOU are an obsessed IDIOT with a one track mind.
>
> > Piss off.
>

> I stand by what I said as technically correct.
>

> ** LOL -  that only makes you a BIGGER fucking idiot.
>

> Many, many technical journals, text books, and supporting calculations
> based upon terms of definition confirm what I said.
>

> ** Shame you cannot supply one that backs up your idiotic comments about

> unloaded transformers.
>
> Listen PAL  !!!!!!!!
>
> YOU  are nothing but a lying, bullshitting  NUT CASE !!
>

> Clueless to the core.
>
> FOAD.
>
> ...  Phil

Phil is mentally disturbed, probably autistic, although he is
technically knowledgeable. He'd be okay but for his illness.

[Ian Jackson]

In message
<03332c05-5f3e-4f02...@s13g2000yqe.googlegroups.com>,
rrus...@hotmail.com writes

FWIW (and from what I remember), ferro-resonant (constant voltage)
transformers usually DO get pretty hot on no load. Regardless of the
load current, the input power is fairly constant. What doesn't come out
heats up the transformer.
--
Ian

[Phil Allison]

"William Sommerwanker TROLL"


** Big shame narcissistic fucking idiots like you still roam the earth.

FOAD now !!

[William Sommerwerck]

"Phil Allison" <phi...@tpg.com.au> wrote in message

news:9qdfqc...@mid.individual.net...

> "William Sommerwanker TROLL"
> ** Big shame narcissistic fucking idiots like you still roam the earth.
> FOAD now !!

ROAR!
I am a tyrannosaur! I will rip off your limbs with my silly two-fingered
arms, and greedily scarf them down.
If you are still alive after all your limbs have been consumed, I will bite
through your skull and savor the crunching sound.
ROAR!

[William Sommerwerck]

It should have read...

ROAR!

I am a tyrannosaur! I will rip off your limbs with my silly two-fingered
arms, and greedily scarf them down.

If you remain alive after all your limbs have been consumed, I will
bite through your skull and savor your agonized screams of fear
and excruciating pain, before you pass forever from this world.

ROAR!

[Phil Allison]

[josephkk]

If it is covered under a IEEE standard it would be about uS$100 to $200.
I have several of them already, but maybe not the one for your
transformer. Nor is the IEEE standard a mandatory one, check local
regulation for what is mandatory.

Speaking of, i need to go buy some more standards right now.

?-)

[Robert Macy]

For various reasons, it took MUCH longer than I anticipated to post
back here!

After more accurately modeling a REAL transformer based upon PA's
data, I am convinced that adding a cap in parallel will NOT improve
the PF.

The best intuitive way to explain is to simply say: in order to reduce
PF, a resonating cap is added in parallel to cancel the effect of the
inductance. The effect relies upon the inductance to be a CONSTANT
value, the core of a typical isolation transfomer during its operation
is NOT constant {reducing dramatically as the peak current flows. With
this changing value of inductance all the 'goodness' of adding the cap
completely disappears. Using the following simple model, I could not
even change the cap to some 'optimum' value. PF just stayed bad, did
not get worse, just stayed bad, and the cost of adding any cap was
wasted. .

Small discussion about the dataset. The slight increase in apparent
inductance going from 30 to 50 can be explained as being due to the
coercivity of the core material. At low currents, the BH curve loop
being followed is more horizontal than the BH curve being followed as
the voltage increases and current increases, the inductance then
starts dropping due to the saturation of the core. If you plot the
data set as Apk/(sqrt(2)*Arms) vs Vac, you'll see a strange shape to
the curve. plot as 20*log10(Apk/Apkcalc) vs Vac and it is VERY
interesting to notice a 'step' and then constant value. see the
undershoot, overshoot, and ringing of the data as Vac increases. Note:
The following model does NOT display this type of performance. I
wonder if it was caused by a 'two-step' saturation? In other words,
material saturated leaving another material that saturates at a higher
current value, like regions in the core?. I'm going to go back and
try 3 inductors in series, to see if I can get a 'better' fit - air
core inductor, inductor 1 saturating first, inductor 2 saturating 2nd.
Only mentioned as interesting, do not think a finer model will result
in a different conclusion, though.]

LTspice has a simple nonlinear model, called "Behavioural Model", for
an inductor. The inductor's flux is: Flux = tanh(x), where x is the
current through the inductor.

The model is supposed to follow the saturation curve fairly well, but
assumes ZERO coercivity, in other words, zero hysteresis. The model is
like following the 'centerline' of the hysteresis curve.

Several observations, I could NEVER get the model to fit the data
provided by Phil Allison, [which translates to still don't have a good
model]. However, after some 'adjustments'. the characteristics of the
model did fit the characteristics of the data [No time to EXACTLY
create/present the tables of comparison, will do later]

Suffice to say, as the input voltage increased; the rms current went
up faster than if the transformer's core were a constant inductor, the
peak current for the rms current went up at about the same ratio as
PA's data. At higher voltage, the peak current noticeably distorted
the current waveform into appearing to have severe 3rd harmonic
distortion. Actually, instead of sinusoidal, looks triangular.

Using this model, I calculated an appropriate cap, added it to the
circuit, and found NO EFFECT on PF !!!

I then started changing the cap's value, looking for some optimum, and
found none.

CONCLUSION: For "real" isolation transformers, it is NOT POSSIBLE to
add a cap to 'adjust' the PF for the load.

I defer to PA's experience with a multitude of manufactured
transformers, in defense of my comments, my experience was limited to
custom transformers [whose performance was always better than
commercially available] and my own transformers, which perform a bit
better. Example, 100 turns to get 1 Henry. No DC current is allowed,
but you do measure 1H inductance with only 100 turns. Coercivity is
about 1/100th silicon steel, which my understanding is usually used in
commercial transformers. So what I'm used to working with does
approach 'ideal' inductance.


The simple model is here for any interested:
name the file something ending with .cir LTspice will run the
simulation. You're on your own for changing values.
Note the Rcore value was added to represent the unloaded 40+W
dissipation, you will find its absence/presence does not affect the
conclusions.

TEST_ModelBehaviour - nonlinear inductor using behavioural Model
* for use on LTspice
*
.tran .1 20 19.95 .1m
.param k0=sqrt(2)
.param k1=120
Vac 1 0 AC={k1} SIN(0 {k0*k1} 60)
Racmains 1 IN 0.01
*Cc IN 0 30uF
Rpri IN 3 0.26
.param kk0=1
.param kk1=1.2/{kk0}
.param kk2=0.412
Lcore 3 0 Flux={kk2*kk1}*tanh(x/{kk2})
Rcore 3 0 350
.end

[Robert Macy]

>,,,snip...!!!

What a WRONG STATEMENT! Adding a cap in parallel to the isolation
transformer 'should' improve PF, but not as much as one would like.,
but does improve it, without makinganything worse, except cost.

The error was caused by monitoring the current through Rpri, not
through Racmains, so OF COURSE PF never changed!!!

Didn't discover the error until went to a three inductor model which
matches the data fairly closely.

Note: the behavioural model should be fairly accurate, because the
transformer has a constant voltage across it, so it is possible to
approximate the hysteresis loss with a fixed resistor. The transformer
has enough voltage that each cycle the same amount of power is lost.
I would NOT use this model tor represent an audio transformer, where
the drive can vary a great deal.

The 'three' inductor model starts very closely matching the data,
results and data are at the end of this posting. Same conclusion,
adding a cap helps PF.


For the single inductor model, I added a residual amount of AIR
inductance [about 30mH] and got the following:

The model very closely models observation, at low voltages current is
fairly sinusoidal, near 70+ Vac, the thrid harmonic starts to dominate
the wave shape, DRAMATICALLY. We're talking major 'pointy' waveforms.
I can't post the plot, but you can copy the model below and see for
yourself.

Checking the model's match to the data:
LTspice PA's Data
Vac Arms Apk Arms Apk
30 0.068 0.098 0.08 0.11
50 0.118 0.172 0.11 0.14
70 0.180 0.270 0.20 0.35
90 0.275 0.447 0.45 1.0
110 0.744 1.68 1.00 2.0
120 1.38 2.96 1.4 2.9
130 2.08 4.22 2.2 4.6

simulating the circuit with the model:
NO LOAD [add Rcore = 350]
120Vac Arms Vinrms Pwr(Rcore) PF
no cap 1.408 119.9 41.54 0.25
28uF 0.762 120 41.57 0.45
56uF 1.542 120 41.61 0.22

FULL LOAD 14.4 ohm [add Rcore = 350]
120Vac Arms Vinrms Pwr(Rcore) PF
no cap 8.594 119.9 1,020 0.99
29uF 8.533 119.9 1,020 1.00

CONCLUSION: adding a cap in parallel to an isolation transformer,
whether loaded or unloaded, is expected to improve PF

copy and name something ending in .cir:

TEST_ModelBehaviour - nonlinear inductor using behavioural Model

* Voltage is V(in), current is I(Racmains)
* Real power is average of V(in)*I(Racmains)
* apparent power is V(in)rms times I(Racmains)rms
* Plot these three: I(Racmains), V(in), V(in)*I(Racmains)
.tran .1 10 9.95 .1m

.param k0=sqrt(2)
.param k1=120
Vac 1 0 AC={k1} SIN(0 {k0*k1} 60)
Racmains 1 IN 0.01

*Cpf IN 0 28uF
Rpri IN 3 0.26
*
.param kAIR=.03 ;set to 'residual' inductance in Henries
.param kk0=1.2 ;set to 'initial' inductance very low current
.param A0=0.274 ;set to current where var. ind. drops to half
.param kk=1.13
.param kk1={A0*kk} ;set to current for half saturation
.param kk2={kk0-kAIR}
*
Lcore 3 0 Flux={ {kk2*kk1}*tanh(x/{kk1})+{kAIR}*x }
*
*Rcore 3 0 350
*Rload 3 0 14.4
.end



= = = =
The three inductor model:

LTspice PA's Data
Vac Arms Apk Arms Apk
30 0.071 0.114 0.08 0.11
50 0.130 0.210 0.11 0.14
70 0.231 0.383 0.20 0.35
90 0.464 0.830 0.45 1.0
110 0.922 1.74 1.00 2.0
120 1.40 2.83 1.4 2.9
130 2.21 4.58 2.2 4.6

NO LOAD
120Vac Arms Vinrms Pwr(Rcore) PF
no cap 1.441 119.9 41.30 0.24
29uF 0.642 120 41.31 0.54
64uF 1.728 120 41.32 0.20

FULL LOAD 14.4 ohm
120Vac Arms Vinrms Pwr(Rcore) PF
no cap 8.708 1,032 119.9 0.99
29uF 8.622 1,032 119.9 1.00


TEST_MB three - nonlinear inductors using behavioural Model

* for use on LTspice
*
.tran .1 20 19.95 .1m
.param k0=sqrt(2)
.param k1=120
Vac 1 0 AC={k1} SIN(0 {k0*k1} 60)
Racmains 1 IN 0.01

Cpf IN 0 29uF
*
Rpri IN 3 0.1
*
* first inductor
.param kk0=1.2
.param kk1={kk0-mm0}
.param kk2=.2
Lcore01 3 4 Flux={kk2*kk1}*tanh(x/{kk2})
* second inductor
.param mm0=0.185
.param mm1={mm0-nn0}
.param mm2=1.17
Lcore02 4 5 Flux={mm2*mm1}*tanh(x/{mm2})
* third inductor == air core
.param nn0=.02
Lcore03 5 0 {nn0}
*
Rcore 3 0 350
*Rload 3 0 14.4
.end