** Message to the PITA Stewart fool:


1. If you want to measure high frequency **core losses** then you MUST
measure a simple, single winding on a core - and not attempt to test a
whole bloody output transformer.

2. The primary winding, even though left unconnected in your test, is a
tuned circuit closely coupled to the secondary. Hence it will absorb power
at high frequencies due to self resonance. That absorbed power is dissipated
as heat in the copper wire of the primary as well as in the driven
secondary.






............. Phil

Phil Allison wrote:

** Message to the PITA Stewart fool:

1. If you want to measure high frequency **core losses** then you MUST
measure a simple, single winding on a core - and not attempt to test a
whole bloody output transformer.

2. The primary winding, even though left unconnected in your test, is a
tuned circuit closely coupled to the secondary. Hence it will absorb power
at high frequencies due to self resonance. That absorbed power is dissipated
as heat in the copper wire of the primary as well as in the driven
secondary.

In my OPTs, the primary is perhaps divided into
between 3 and 6 sections and the self capacitance of the whole winding
is thus quite low.

However, there is capacitance between layers of P and layers of S windings.
The resonance effects don't appear below about 80 kHz.
Exactly what are the inductances and capacitances involved with the
series or parallel resonant behaviour above 80 kHz are not always
able to be identified because the arrangement of stray L and C
quantities is so complex with an interleaved transformer.

Anyway, I agree with you that to measure for core losses at any F
its necessary to use a winding free of any capacitance effects at the
F where the measurement is taken.
The core losses in good OPTs below 20 kHz is negligible, as are resonance
effects.

The presence of resonances and core losses can indicated in an amp with an OPT
where the plate current flow is monitored by measuring the voltage across
a 10 ohm R between the OPV cathode and 0V.

Typically, with no load, the tube current will increase below
1 khz as the ZLp reduces in value, and above 1 kHz, the capacitance
will cause the anode signal to be increasingly shunted since there is a typical
500 pF of Cin looking into each end of the OPT primary with one end of the
secondary
grounded.

If the current witnessed is what one expects to see due to the measured C then
core losses must be utterly insignificant.

I would think the only way to fully reliably measure core losses of an OPT
at HF is to remove the core and test it using a coil made for the test.

Measurements of power trannies for losses and magnetizing currents using
a measure of current and voltage can be confusing.
I measured a Pt 1 Leak PT last night, and
the Im at 245v across the P at 50Hz and no load was 100 mA,
so you'd think there was 24 watts of magnetization core losses.
I left this suspect tranny on for 4 hrs on this warm evening,
and it only warmed slightly, and it seems impossible
that core losses amounted to 24 watts.

The no load primary current waveform had about 30% of 3H on the wave,
and thus this distorts the measurement with a meter.
The distorted wave has a pointy crest, rather than a flattened crest
seen on a clipped wave, so the 3H adds to the amplitude, rather than
subtract from the 50 Hz wave.
I concluded the core losses are maybe 10 watts at idle, and there is nothing
wrong with the transformer as 10% core loss was normal for 1955, and the Leak Pt
One
PT has to produce about 90 VA at its output.
So where the 3H wave is additive to the fundemental's amplitude there isn't as
much power
per cycle compared to where the 3H phase is the subtractive to the fundemental
F, and where
each distorted wave has the same max amplitude.

Put another way, the magnetizing currents at 150 Hz and 50 Hz
make up to a total current less than 100 mA indicated when measuring
the current with 10 ohms and with a Fluke DVM.

The old Leak PT also exhibited a very distorted current
wave form at all levels of applied AC from my variac.


The really good modern GOSS has far far less Im and distortion current flow.

The modern GOSS also performs a shirtload better than the
non oriented Si Fe, or any other lower grade material when used
in OPTs, and so much so that there is no need to take core losses
into account during the design process for a decent modern OPT.

Patrick Turner.

Phil Allison wrote:

** Message to the PITA Stewart fool:

1. If you want to measure high frequency **core losses** then you MUST
measure a simple, single winding on a core - and not attempt to test a
whole bloody output transformer.

2. The primary winding, even though left unconnected in your test, is a
tuned circuit closely coupled to the secondary. Hence it will absorb power
at high frequencies due to self resonance. That absorbed power is dissipated
as heat in the copper wire of the primary as well as in the driven
secondary.

............ Phil



Perhaps you didn't notice but the post is titled 'Transformer Loss
Measurements'.

JLS

"Patrick Turner"


The resonance effects don't appear below about 80 kHz.



** Bet that measurable effects *START* much lower when the OT is driven
in reverse.

The maxima may well be at 80 kHz.





................ Phil

"John Stewart"
"Phil Allison"


** Message to the PITA Stewart fool:

1. If you want to measure high frequency **core losses** then you MUST
measure a simple, single winding on a core - and not attempt to test a
whole bloody output transformer.

2. The primary winding, even though left unconnected in your test, is a
tuned circuit closely coupled to the secondary. Hence it will absorb power
at high frequencies due to self resonance. That absorbed power is dissipated
as heat in the copper wire of the primary as well as in the driven
secondary.


Perhaps you didn't notice but the post is titled 'Transformer Loss
Measurements'.



** Perhaps you forgot what you bloody wrote - ****WIT !!!

EG: " Was it core losses or was it something else? "


Like any other trolling, criminal POS you now want to re-define the topic
to save face.

Or is it to save your bleeding arse ???????






............. Phil

Phil Allison wrote:

"Patrick Turner"

The resonance effects don't appear below about 80 kHz.

** Bet that measurable effects *START* much lower when the OT is driven
in reverse.

The maxima may well be at 80 kHz.

The reverse case could be where the tranny is used as a step up say for ES
speakers.

This may mean that a 100:1 step up tranny may be connected to
a 1 ohm output resistance of an amplifier, but that Rout is
10,000 ohms at the secondary.
Small L and C quantities will therefore have a large effect.

The same tranny turned around and used with triodes
for a step down tranny will have its primary shunted by the low Ra of the
triodes,
even without and RL connected.
But that don't mean resonance effects won't play havoc in a triode amplifier
with global NFB.
Meanwhile a pentode amp has Ra-a very high, so usually the open loop response
is a large arch,
since Lp and Csh reduce the high mid F gain without any RL.
So RL *is* the main damping resistance with pentode amps.
Trouble is speakers don't conveniently always provide a resistive load.
Only some do, while many don't, and in fact RL can be a high impedance,
and often inductive, so pentode amps need careful attention for stability
and should have zobel networks across each 1/2 primary of the OPT
to provide R damping of the resonances at HF, and some restriction of HF gain
when npo load is connected.

The winding geometry still determines the nature of the HF response, and a
well
interleaved tranny will give less resonance problems at HF than one
less interleaved, and with less PS insulation thickness.

The more interleaving, and with prudent thicknesses of insulation,
the higher the resonant F and the problems they cause because they are further

away from the AF band.

I have seen a few ****ty trannies with series resonances below 50 kHz...not
good,
because they are harder to damp, and global FB application can be difficult
if unconditional stability is the design aim.


Patrick Turner.







............... Phil

Well, at least my post got a debate going!!

Anyway, I believe the information as measured is useful. That is because it
measures the transformer as it will be used in a real live circuit with all of
it's problems associated with core, coils & insulation all in place as it would
be when installed. It gives one an idea of what the parasitic loads are. It also
shows them to be somewhat non-linear, probably of a magnitude similar to the
tubes we drive them with.

There has been some discussion of Skin Effect as it is related to the copper
conductors & the laminations. I've posted over at ABSE an interesting short
article from Electronics World magazine authored by Nick Wheeler. He gives as an
example of Skin Effect a plot made on a 2mm conductor, showing what to expect up
to one MHz. At 10 KHz the effects are all but negligible. A 2mm conductor is
about #12 Gauge, something we run 20 amps legally thru a house here. You might
find that on some OPT secondaries. Not likely on a primary. Skin Effect is even
less of a problem on smaller gage conductors.

The author goes on to explain why Litz wire is used at RF in order to reduce
losses due to Skin Effect. In a way the cross section of the many conductors
wound around the core of a transformer are like the Litz wire arrangement. As a
result the effect of Skin Effect at 10 KHz in a transformer should not be
excessive, unless some other factor is at work. That may be the 'proximity
effect' as mentioned by Doug Bannard. I assume he is referring to the proximity
of the conductor pack to the iron core, but not sure.

It would be a great help if others here who have access to the 'finer' OPT's
took some time to make some careful measurements as I have. The 3-voltmeter
method is simple & strait forward. All the measurements at each point do not
need to be made simultaneously so one VM will do. You will need to be sure your
VM has enough bandwidth & is RMS responding. An HP3400A could be used for that.
Many of the low cost DMM's on the market are useless above one KHz.

Cheers, John Stewart

Patrick Turner wrote:

Phil Allison wrote:

** Message to the PITA Stewart fool:

1. If you want to measure high frequency **core losses** then you MUST
measure a simple, single winding on a core - and not attempt to test a
whole bloody output transformer.

2. The primary winding, even though left unconnected in your test, is a
tuned circuit closely coupled to the secondary. Hence it will absorb power
at high frequencies due to self resonance. That absorbed power is dissipated
as heat in the copper wire of the primary as well as in the driven
secondary.

In my OPTs, the primary is perhaps divided into
between 3 and 6 sections and the self capacitance of the whole winding
is thus quite low.

However, there is capacitance between layers of P and layers of S windings.
The resonance effects don't appear below about 80 kHz.
Exactly what are the inductances and capacitances involved with the
series or parallel resonant behaviour above 80 kHz are not always
able to be identified because the arrangement of stray L and C
quantities is so complex with an interleaved transformer.

Anyway, I agree with you that to measure for core losses at any F
its necessary to use a winding free of any capacitance effects at the
F where the measurement is taken.
The core losses in good OPTs below 20 kHz is negligible, as are resonance
effects.

The presence of resonances and core losses can indicated in an amp with an OPT
where the plate current flow is monitored by measuring the voltage across
a 10 ohm R between the OPV cathode and 0V.

Typically, with no load, the tube current will increase below
1 khz as the ZLp reduces in value, and above 1 kHz, the capacitance
will cause the anode signal to be increasingly shunted since there is a typical
500 pF of Cin looking into each end of the OPT primary with one end of the
secondary
grounded.

If the current witnessed is what one expects to see due to the measured C then
core losses must be utterly insignificant.

I would think the only way to fully reliably measure core losses of an OPT
at HF is to remove the core and test it using a coil made for the test.

Measurements of power trannies for losses and magnetizing currents using
a measure of current and voltage can be confusing.
I measured a Pt 1 Leak PT last night, and
the Im at 245v across the P at 50Hz and no load was 100 mA,
so you'd think there was 24 watts of magnetization core losses.

Not really since power is EI*Cos Theta, where Theta is the angle between current &
voltage. JLS


I left this suspect tranny on for 4 hrs on this warm evening,
and it only warmed slightly, and it seems impossible
that core losses amounted to 24 watts.

The no load primary current waveform had about 30% of 3H on the wave,
and thus this distorts the measurement with a meter.
The distorted wave has a pointy crest, rather than a flattened crest
seen on a clipped wave, so the 3H adds to the amplitude, rather than
subtract from the 50 Hz wave.
I concluded the core losses are maybe 10 watts at idle, and there is nothing
wrong with the transformer as 10% core loss was normal for 1955, and the Leak Pt
One
PT has to produce about 90 VA at its output.
So where the 3H wave is additive to the fundemental's amplitude there isn't as
much power
per cycle compared to where the 3H phase is the subtractive to the fundemental
F, and where
each distorted wave has the same max amplitude.

Put another way, the magnetizing currents at 150 Hz and 50 Hz
make up to a total current less than 100 mA indicated when measuring
the current with 10 ohms and with a Fluke DVM.

The old Leak PT also exhibited a very distorted current
wave form at all levels of applied AC from my variac.

The really good modern GOSS has far far less Im and distortion current flow.

The modern GOSS also performs a shirtload better than the
non oriented Si Fe, or any other lower grade material when used
in OPTs, and so much so that there is no need to take core losses
into account during the design process for a decent modern OPT.

Patrick Turner.

"John Stewart"
Pat Turner

I measured a Pt 1 Leak PT last night, and
the Im at 245v across the P at 50Hz and no load was 100 mA,
so you'd think there was 24 watts of magnetization core losses.


Not really since power is EI*Cos Theta, where Theta is the angle between
current &
voltage. JLS



** WRONG !!!!

Magnetising current is non sine wave.

Copper loss can be found from: I rms squared times R primary.

Power consumption can be measured with a *wattmeter*.

The iron loss is the difference.






............. Phil

"John Stewart"

Well, at least my post got a debate going!!


** Only about just how big a ****wit, troll and time waster John Stewart
is.

Anyway, I believe the information as measured is useful.


** Misleading data is worse than useless.

And JS's dumb misinterpretations and ambiguous comments and it becomes
purest evil.



That is because it
measures the transformer as it will be used in a real live circuit with
all of
it's problems associated with core, coils & insulation all in place as it
would
be when installed. It gives one an idea of what the parasitic loads are.
It also
shows them to be somewhat non-linear, probably of a magnitude similar to
the
tubes we drive them with.


** Rot.

Good OTs are virtually distortion free.

Tubes never are.



It would be a great help if others here who have access to the 'finer'
OPT's
took some time to make some careful measurements as I have.


** Help to what exactly ????????

You misleading and sidetracking everyone in a desperate attempt to big note
yourself ???

Vying for the " Turneroid PITA Wind Bag " award are you ??





............. Phil

I see that you are still your placid internally contained self Phil

How's the medicine going?

why are several of you guys down under seething with pent up rage?

I thought Australia was an unspoiled paradise, with beautiful girls and
plenty of wide open space?

just because salvia is illegal is no reason to be this angry with life!

On Thu, 24 Feb 2005 01:25:24 -0500, "cowboy"
cacheoverflow@yahooDOTcom wrote:

why are several of you guys down under seething with pent up rage?

Hey, if you woke up this morning and discovered that you were
Australian, you'd be mad as hell too!

I thought Australia was an unspoiled paradise, with beautiful girls and
plenty of wide open space?

Unfortunately, it's also full of Australians...........
--

Stewart Pinkerton | Music is Art - Audio is Engineering

cowboy wrote:

why are several of you guys down under seething with pent up rage?

Gee, that many. I'd have hardly noticed.


I thought Australia was an unspoiled paradise, with beautiful girls and
plenty of wide open space?

Its absolutely true what you say of our wonderful country.



just because salvia is illegal is no reason to be this angry with life!

Well, you ain't met silvia. She's dangerous, and can wreck most blokes
in 30 minutes, so that's why she's been declared illegal.

She's very expensive as well.

Useless at mowing the lawns.

Patrick Turner.

Stewart Pinkerton wrote:

On Thu, 24 Feb 2005 01:25:24 -0500, "cowboy"
cacheoverflow@yahooDOTcom wrote:

why are several of you guys down under seething with pent up rage?

Hey, if you woke up this morning and discovered that you were
Australian, you'd be mad as hell too!

I thought Australia was an unspoiled paradise, with beautiful girls and
plenty of wide open space?

Unfortunately, it's also full of Australians...........

Yeah, but the way pomme land is fuct up with so many poms
is a shame....

Maybe I'd prefer Ireland...

Patrick Turner.


--

Stewart Pinkerton | Music is Art - Audio is Engineering

On Thu, 24 Feb 2005 01:25:24 -0500, "cowboy"
cacheoverflow@yahooDOTcom wrote:
Well, I suppose it's because they live way down under and the blood
just all, like rushes to their heads. That's my theory on why.

Sorry Shane C., i couldn't resist...

http://www.cardsbycarolyn.com/buttons/hug.jpg

Just for you.


Adam

albundy wrote:

On Thu, 24 Feb 2005 01:25:24 -0500, "cowboy"
cacheoverflow@yahooDOTcom wrote:
Well, I suppose it's because they live way down under and the blood
just all, like rushes to their heads. That's my theory on why.

So ppl in the US have all the blood in their feet, so they can't think,
and ppl at the equator think about nothing else apart from having sex.

Patrick Turner.



Sorry Shane C., i couldn't resist...

Why not? They're allowed. Also Koreans, Chinese,
Japanese Europeans, name it....

cowboy wrote:
why are several of you guys down under seething with pent up rage?

This NG is a tea party compared to some NGs I've seen.
soc.culture.india and similar makes us look like
pretenders.....

I thought Australia was an unspoiled paradise, with beautiful girls and
plenty of wide open space?

I took a vacation there years ago and it is a nice place.
Most even liked Americans. (Though many were in the
tourist trade, where they need to like us :-) )

I saw a few kangaroos (at the city zoo, the wild ones tend
to avoid mankind). No, they don't make a springy noise
as they hop around, not like in Warner Brothers' cartoons. :-)

On Fri, 25 Feb 2005 23:48:25 +1100, Patrick Turner
wrote:



albundy wrote:

On Thu, 24 Feb 2005 01:25:24 -0500, "cowboy"
cacheoverflow@yahooDOTcom wrote:
Well, I suppose it's because they live way down under and the blood
just all, like rushes to their heads. That's my theory on why.

So ppl in the US have all the blood in their feet, so they can't think,
and ppl at the equator think about nothing else apart from having sex.

Patrick Turner.



Sorry Shane C., i couldn't resist...
Hey Patrick, it fits with the theory