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transformer thermals...

P

Phil Allison

Guest
John Larkin wrote:

-------------------
BTW, what is the source of this and similar rules of thumb (e.g. equal
copper and core losses)? Logic says that one should always design for
minimal total losses, given the economic constraints.

Best regards, Piotr

I don\'t think transformers are usually designed for equal core and
copper losses.
** The condition for *max efficiency* IS when Cu and Fe losses are equal but this only affects the energy bill you have to pay.

For all other purposes, throughput or VA rating is what matters for a given size and cost. Filling the available winding space with copper and operating the core close to its saturation limit results in the most economical transformer.

Transformer \"efficiency\" is a variable, depending on load.

\"Rated efficiency\" is quoted at full load.


..... Phil
 
W

whit3rd

Guest
On Wednesday, August 5, 2020 at 6:36:17 PM UTC-7, Phil Allison wrote:
whit3rd ...

It is going to be hotter with AC.

Hardly any.

Iron lossses due to eddy currents and hysteresis aren\'t insignificant.


** They are with GOSS tape wound into a toroid.


It this for variable frequency use?
Those iron losses are frequency-dependent.
it might take a bunch of testing to characterize.

** No it wont.

JL\'s tranny is rated for 50/60Hz and will work fine with lower losses at any higher frequency. Core magnetisation goes DOWN with rising frequency for a given primary voltage.
Iron losses are zero with DC testing, and certainly not \'lower\' at all higher frequencies.
Core magnetization goes down with frequency, but losses go UP when the secondary
doesn\'t draw current. And, the core shape determines the magnetization profile,
at higher frequencies it\'s unclear whether the entire core shares the induction (so
the behavior at 4 kHz ought to be tested... at 4 kHz.
 
C

Cydrome Leader

Guest
Phil Allison <pallison49@gmail.com> wrote:
Cydrome Leader is Funny:

=======================

So I ran it for a few hours with 10 amps DC in the primary. Temp rise
was about 26C in free air. I think people design transformers for
equal copper loss in the primary and secondary, so temp rise would
double when loaded in the system.

What about the heat generated by losses in the secondary?


** Doubles the temp rise - as JL just claimed.
It sounded like the double the heat assumption was from the 50% of losses
being in the iron, when the transformer is used with AC. Even if you
double the primary resistive loses to account for the secondary, the core
is still being left out. That\'s how I read it.

https://www.dropbox.com/s/ylm8dc1e14dwv7y/P900_Xfmr_Thermal.jpg?raw=1

https://www.dropbox.com/s/5b55ybfoq2pkp9v/P900_Xfmr_Thermal_2.jpg?raw=1

You can even see on the label (looks sort of like a Noratel) the input is
266VA and output is rated 240VA. So depending on power factor at full
load, it could be upto 26 watts of loss, although I doubt a toroid that
size would have such a poor efficiency. The iron losses will surely be
less than 50% on a toroid. Maybe the maker can tell you the ratio?


** PF has no effect - VA is all that matters, effectively just the RMS
current. Iron losses are a watt or so per kg or iron. I mag is tiny.

So 20 watts copper loss, 6 watts for iron.
Could be- I have no references for core loss in small toroidal
tranformers handy. It should be fixed though and less than the losses
needed to magnetize the core with no load, so yeah, the 20 + 6 looks ok.

As for the PF has no effect statement, I\'ve never really understood the
point on the VA in and VA out ratings on some toroidal transformers.
Isolation transfomers are usually marked in a more sensible way like
\"input 120VAC 8.4A, output 120VAC 8.0A\". While these are safe use ratings,
it still doesn\'t answer the question about efficiency at no to full load.
You can only guess the worst case heat losses.


Regulation about 8%.

Toriods are very simple.


.... Phil
 
C

Cydrome Leader

Guest
jlarkin@highlandsniptechnology.com wrote:
On Wed, 5 Aug 2020 01:21:10 -0700 (PDT), Phil Allison
pallison49@gmail.com> wrote:

Cydrome Leader is Funny:

=======================

So I ran it for a few hours with 10 amps DC in the primary. Temp rise
was about 26C in free air. I think people design transformers for
equal copper loss in the primary and secondary, so temp rise would
double when loaded in the system.

What about the heat generated by losses in the secondary?


** Doubles the temp rise - as JL just claimed.


https://www.dropbox.com/s/ylm8dc1e14dwv7y/P900_Xfmr_Thermal.jpg?raw=1

https://www.dropbox.com/s/5b55ybfoq2pkp9v/P900_Xfmr_Thermal_2.jpg?raw=1

You can even see on the label (looks sort of like a Noratel) the input is
266VA and output is rated 240VA. So depending on power factor at full
load, it could be upto 26 watts of loss, although I doubt a toroid that
size would have such a poor efficiency. The iron losses will surely be
less than 50% on a toroid. Maybe the maker can tell you the ratio?


This transformer was made for us by Amgis. I specified it so I know
the ratios: 1 : 1.4 : 1.4 : 1.4 : 1.4. We have a relay board that
switches the secondaries to get four output voltage ranges.
Are these ratios exact or is there a fudge factor for losses at rated
load? Just curious. Retired transformer designer friend seemed to spend a
bit of his time trying to get \"the facts\" from customers to make designs
that would actually work under load. The stubborn customers would get full
production runs of stuff that met specs, but didn\'t work for the
application.

** PF has no effect - VA is all that matters, effectively just the RMS current. Iron losses are a watt or so per kg or iron. I mag is tiny.

So 20 watts copper loss, 6 watts for iron.

Regulation about 8%.

Toriods are very simple.


.... Phil

Unloaded, the AC operating primary current is essentially zero, so I
don\'t think core loss is significant.

As an alternator simulator, voltage increases with frequency, which
keeps Imag low on the low end.

It\'s a weird application. We specialize in weird.
Was amgis friendly about making samples?
 
C

Cydrome Leader

Guest
Phil Allison <pallison49@gmail.com> wrote:
Piotr Wyderski wrote:

===============================

I think people design transformers for
equal copper loss in the primary and secondary

BTW, what is the source of this and similar rules of thumb (e.g. equal
copper and core losses)? Logic says that one should always design for
minimal total losses, given the economic constraints.


** The source is simple calculus that finds the minimum or maximum in a curve. It\'s also kinda obvious that if the primary and secondary run at different temps then you have one heating the other. Same goes for core and windings.

The issue with tape wound toriodals is their very sharp saturation
curves - forcing the designer to keep away from that condition. Hence
their low contribution to heat from the core.

Commercial toroidals are made using a clever machine passing wire
through the centre hole - this sets a limit on the amount of copper that
can be used.
It looks like they could dump more copper on the typical toroidal
transfomer. The diameters for large ones get huge, with
gigantic empty holes in the middle. The stacking factor, if that\'s the
right term is terrible on most toroids. Not sure why this is though. They
seems to scale the wide and thin vs. taller with more copper stuffed in
the hole and around the rest of it.

I know of one amplifier designer who at my suggestion had the winder use
his machine for the primary and wind the secondary by hand in order to
fill the hole almost completely. This almost doubled the amount of
copper used.

Along with a bit of fan cooling, the result was a 3kW rated amplfier
that used a 1kW size transformer core.
Was the core really more than 3x oversize?
 
S

server

Guest
On Thu, 6 Aug 2020 06:57:07 +0000 (UTC), Cydrome Leader
<presence@MUNGEpanix.com> wrote:

jlarkin@highlandsniptechnology.com wrote:
On Wed, 5 Aug 2020 01:21:10 -0700 (PDT), Phil Allison
pallison49@gmail.com> wrote:

Cydrome Leader is Funny:

=======================

So I ran it for a few hours with 10 amps DC in the primary. Temp rise
was about 26C in free air. I think people design transformers for
equal copper loss in the primary and secondary, so temp rise would
double when loaded in the system.

What about the heat generated by losses in the secondary?


** Doubles the temp rise - as JL just claimed.


https://www.dropbox.com/s/ylm8dc1e14dwv7y/P900_Xfmr_Thermal.jpg?raw=1

https://www.dropbox.com/s/5b55ybfoq2pkp9v/P900_Xfmr_Thermal_2.jpg?raw=1

You can even see on the label (looks sort of like a Noratel) the input is
266VA and output is rated 240VA. So depending on power factor at full
load, it could be upto 26 watts of loss, although I doubt a toroid that
size would have such a poor efficiency. The iron losses will surely be
less than 50% on a toroid. Maybe the maker can tell you the ratio?


This transformer was made for us by Amgis. I specified it so I know
the ratios: 1 : 1.4 : 1.4 : 1.4 : 1.4. We have a relay board that
switches the secondaries to get four output voltage ranges.

Are these ratios exact or is there a fudge factor for losses at rated
load?
Exact turns ratio. We know the other parameters: wire resistance, mag
inductance, leakage inductance, SRF, saturation. We plug all that into
the system Spice model.

Just curious. Retired transformer designer friend seemed to spend a
bit of his time trying to get \"the facts\" from customers to make designs
that would actually work under load. The stubborn customers would get full
production runs of stuff that met specs, but didn\'t work for the
application.

** PF has no effect - VA is all that matters, effectively just the RMS current. Iron losses are a watt or so per kg or iron. I mag is tiny.

So 20 watts copper loss, 6 watts for iron.

Regulation about 8%.

Toriods are very simple.


.... Phil

Unloaded, the AC operating primary current is essentially zero, so I
don\'t think core loss is significant.

As an alternator simulator, voltage increases with frequency, which
keeps Imag low on the low end.

It\'s a weird application. We specialize in weird.

Was amgis friendly about making samples?
Not free samples, but I didn\'t ask for that. We placed a PO that
included a few first-articles for verification, with the rest shipped
on approval.



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard
 
S

server

Guest
On Thu, 6 Aug 2020 06:41:36 +0000 (UTC), Cydrome Leader
<presence@MUNGEpanix.com> wrote:

Phil Allison <pallison49@gmail.com> wrote:
Cydrome Leader is Funny:

=======================

So I ran it for a few hours with 10 amps DC in the primary. Temp rise
was about 26C in free air. I think people design transformers for
equal copper loss in the primary and secondary, so temp rise would
double when loaded in the system.

What about the heat generated by losses in the secondary?


** Doubles the temp rise - as JL just claimed.

It sounded like the double the heat assumption was from the 50% of losses
being in the iron, when the transformer is used with AC. Even if you
double the primary resistive loses to account for the secondary, the core
is still being left out. That\'s how I read it.
No, I\'m assuming zero core losses, but figure the copper loss will
double if I have 10 amps RMS AC into the primary and load the
secondary to get there. That\'s probably close.

Any decent power transformer runs cold at rated voltage and no load.
Core losses can be ignored.



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard
 
S

server

Guest
On Thu, 6 Aug 2020 07:08:33 +0000 (UTC), Cydrome Leader
<presence@MUNGEpanix.com> wrote:

Phil Allison <pallison49@gmail.com> wrote:
Piotr Wyderski wrote:

===============================

I think people design transformers for
equal copper loss in the primary and secondary

BTW, what is the source of this and similar rules of thumb (e.g. equal
copper and core losses)? Logic says that one should always design for
minimal total losses, given the economic constraints.


** The source is simple calculus that finds the minimum or maximum in a curve. It\'s also kinda obvious that if the primary and secondary run at different temps then you have one heating the other. Same goes for core and windings.

The issue with tape wound toriodals is their very sharp saturation
curves - forcing the designer to keep away from that condition. Hence
their low contribution to heat from the core.

Commercial toroidals are made using a clever machine passing wire
through the centre hole - this sets a limit on the amount of copper that
can be used.

It looks like they could dump more copper on the typical toroidal
transfomer. The diameters for large ones get huge, with
gigantic empty holes in the middle. The stacking factor, if that\'s the
right term is terrible on most toroids. Not sure why this is though. They
seems to scale the wide and thin vs. taller with more copper stuffed in
the hole and around the rest of it.
Iron is cheaper than copper.



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard
 
P

Phil Allison

Guest
whit3rd is a Fuckwit wrote:

================================

Phil Allison wrote:


It this for variable frequency use?
Those iron losses are frequency-dependent.
it might take a bunch of testing to characterize.

** No it wont.

JL\'s tranny is rated for 50/60Hz and will work fine with lower losses at any higher frequency. Core magnetisation goes DOWN with rising frequency for a given primary voltage.

Iron losses are zero with DC testing,
** Huuuuh ???

Massive stupid red herring, from a desperate LIAR !!


> Core magnetization goes down with frequency, but losses go UP when the secondary doesn\'t draw current.

** Complete BOLLOCKS !!!!


> And, the core shape determines the magnetization profile,

** On which planet is that faintly relevant here ?

What a LYING pile of shit you are.

Fucking oxygen thief


.... Phil
 
P

Phil Allison

Guest
Cydrome Leader is an IDIOT wrote:

================================


So I ran it for a few hours with 10 amps DC in the primary. Temp rise
was about 26C in free air. I think people design transformers for
equal copper loss in the primary and secondary, so temp rise would
double when loaded in the system.

What about the heat generated by losses in the secondary?


** Doubles the temp rise - as JL just claimed.

It sounded like the double the heat assumption was from the 50% of losses
being in the iron, when the transformer is used with AC.
** You on drugs ??


Even if you
double the primary resistive loses to account for the secondary, the core
is still being left out. That\'s how I read it.
** JL neglected it as he knows it is trivial.


As for the PF has no effect statement, I\'ve never really understood the
point on the VA in and VA out ratings on some toroidal transformers.
Isolation transfomers are usually marked in a more sensible way like
\"input 120VAC 8.4A, output 120VAC 8.0A\". While these are safe use ratings,
it still doesn\'t answer the question about efficiency at no to full load.
You can only guess the worst case heat losses.
** My god you are stupid.

Max heat loss happens at max load, always.

Maybe on on planet Claire where know nothing jerks like you come from.




...... Phil
 
L

legg

Guest
On Thu, 6 Aug 2020 07:08:33 +0000 (UTC), Cydrome Leader
<presence@MUNGEpanix.com> wrote:

Phil Allison <pallison49@gmail.com> wrote:
Piotr Wyderski wrote:

===============================

I think people design transformers for
equal copper loss in the primary and secondary

BTW, what is the source of this and similar rules of thumb (e.g. equal
copper and core losses)? Logic says that one should always design for
minimal total losses, given the economic constraints.


** The source is simple calculus that finds the minimum or maximum in a curve. It\'s also kinda obvious that if the primary and secondary run at different temps then you have one heating the other. Same goes for core and windings.

The issue with tape wound toriodals is their very sharp saturation
curves - forcing the designer to keep away from that condition. Hence
their low contribution to heat from the core.

Commercial toroidals are made using a clever machine passing wire
through the centre hole - this sets a limit on the amount of copper that
can be used.

It looks like they could dump more copper on the typical toroidal
transfomer. The diameters for large ones get huge, with
gigantic empty holes in the middle. The stacking factor, if that\'s the
right term is terrible on most toroids. Not sure why this is though. They
seems to scale the wide and thin vs. taller with more copper stuffed in
the hole and around the rest of it.
snip
For windings, it\'s a \'fill factor\'.

If you check the ratio of copper vs air in the inner
diameter of a toroid, as the fill approaches a certain
percentage, you\'ll see a diminishing return for agravated
difficulty in fabrication.

Any time manual winding methods enter the equation, costs
traditionally skyrocket. There may be different considerations
in today\'s off-shore sourcing.

Forty years ago, you would be considered foolish to ship
anything with a high density - resulting in relatively local
magnetics fab.

RL
 
P

Piotr Wyderski

Guest
Phil Allison wrote:

> ** The source is simple calculus that finds the minimum or maximum in a curve.

Ultimately yes, but the curve is multidimensional and non-linear,
especially when the frequency is high. I wonder if there is some FEM
simulation evidence actually supporting this rule.

> It\'s also kinda obvious that if the primary and secondary run at different temps then you have one heating the other. Same goes for core and windings.

Sure, but it is a local optimisation. Globally one may get 8W of losses
instead of 10 by disturbing this balance.

> I know of one amplifier designer who at my suggestion had the winder use his machine for the primary and wind the secondary by hand in order to fill the hole almost completely. This almost doubled the amount of copper used.

Yes, this is a good idea in low volume.

Best regards, Piotr
 
J

John Larkin

Guest
On Wed, 5 Aug 2020 18:36:12 -0700 (PDT), Phil Allison
<pallison49@gmail.com> wrote:

whit3rd is Witless wrote:

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

It is going to be hotter with AC.

Hardly any.

Iron lossses due to eddy currents and hysteresis aren\'t insignificant.


** They are with GOSS tape wound into a toroid.


It this for variable frequency use?
Those iron losses are frequency-dependent.
it might take a bunch of testing to characterize.

** No it wont.

JL\'s tranny is rated for 50/60Hz and will work fine with lower losses at any higher frequency. Core magnetisation goes DOWN with rising frequency for a given primary voltage.
We rated the tranny for 100 Hz to 4K, but the box currently works from
200 to 4K. We got a bunch more VAs by raising the low frequency limit.
 
B

boB

Guest
On Wed, 5 Aug 2020 22:02:16 -0700 (PDT), whit3rd <whit3rd@gmail.com>
wrote:

On Wednesday, August 5, 2020 at 6:36:17 PM UTC-7, Phil Allison wrote:
whit3rd ...

It is going to be hotter with AC.

Hardly any.

Iron lossses due to eddy currents and hysteresis aren\'t insignificant.


** They are with GOSS tape wound into a toroid.


It this for variable frequency use?
Those iron losses are frequency-dependent.
it might take a bunch of testing to characterize.

** No it wont.

JL\'s tranny is rated for 50/60Hz and will work fine with lower losses at any higher frequency. Core magnetisation goes DOWN with rising frequency for a given primary voltage.

Iron losses are zero with DC testing, and certainly not \'lower\' at all higher frequencies.
Core magnetization goes down with frequency, but losses go UP when the secondary
doesn\'t draw current. And, the core shape determines the magnetization profile,
at higher frequencies it\'s unclear whether the entire core shares the induction (so
the behavior at 4 kHz ought to be tested... at 4 kHz.
Yes, and copper losses go up with frequency, typically, too.
 
W

whit3rd

Guest
On Thursday, August 6, 2020 at 3:51:07 AM UTC-7, Phil Allison wrote:
whit3rd is a physicist wrote:

Core magnetization goes down with frequency, but losses go UP when the secondary doesn\'t draw current.

** Complete BOLLOCKS !!!!
But not untrue; secondary current lessens the core magnetization because it is in the opposite
sense as primary current.
And, the core shape determines the magnetization profile,

** On which planet is that faintly relevant here ?
On any magnetization by AC, there\'s a skin depth that depends on the frequency, and
that determines how much of the core actually polarizes during the cycle. That affects
the saturation and the resultant hysteresis loss in the core.

It\'s just physics.
 
P

Phil Allison

Guest
whit3rd = context shitfing LUNATIC TROLL


========================================

** FOAD you ridiculous pile of dung
 
P

Phil Allison

Guest
legg wrote:

==========


For windings, it\'s a \'fill factor\'.

If you check the ratio of copper vs air in the inner
diameter of a toroid, as the fill approaches a certain
percentage, you\'ll see a diminishing return for agravated
difficulty in fabrication.
** Cost is everything in manufacture.

But as here like to consider what physics allows, it is clearly a fact that filling a toroidal with as much copper as possible maximises the VA for a given core.

This IS the practice for all other types of core shape.

Most toroidals are low and flat - again not optimum but liked by many customers. Same goes for R-cores and U cores which result in low height products.



..... Phil
 
P

Phil Allison

Guest
booB the bullshitter wrote:

============================

Yes, and copper losses go up with frequency, typically, too.
** Really - in a mains or audio frequency tranny ??

GOSS tape wound toroidal cores are not used at higher frequencies.

But you just HAD to be a smartarse - didn\'t you ?


...... Phil
 
B

boB

Guest
On Thu, 6 Aug 2020 15:01:10 -0700 (PDT), whit3rd <whit3rd@gmail.com>
wrote:

On Thursday, August 6, 2020 at 3:51:07 AM UTC-7, Phil Allison wrote:
whit3rd is a physicist wrote:

Core magnetization goes down with frequency, but losses go UP when the secondary doesn\'t draw current.

** Complete BOLLOCKS !!!!

But not untrue; secondary current lessens the core magnetization because it is in the opposite
sense as primary current.

And, the core shape determines the magnetization profile,

** On which planet is that faintly relevant here ?

On any magnetization by AC, there\'s a skin depth that depends on the frequency, and
that determines how much of the core actually polarizes during the cycle. That affects
the saturation and the resultant hysteresis loss in the core.

It\'s just physics.
Yep. Core flux is Volt-Seconds. the lower the frequency, given the
same voltage, the volt-seconds go up and further towards saturation.

Worse case losses on the core is no load for a given frequency and
amplitude of H.
 
L

legg

Guest
On Thu, 6 Aug 2020 16:41:03 -0700 (PDT), Phil Allison
<pallison49@gmail.com> wrote:

legg wrote:

==========


For windings, it\'s a \'fill factor\'.

If you check the ratio of copper vs air in the inner
diameter of a toroid, as the fill approaches a certain
percentage, you\'ll see a diminishing return for agravated
difficulty in fabrication.

** Cost is everything in manufacture.

But as here like to consider what physics allows, it is clearly a fact that filling a toroidal with as much copper as possible maximises the VA for a given core.

This IS the practice for all other types of core shape.

Most toroidals are low and flat - again not optimum but liked by many customers. Same goes for R-cores and U cores which result in low height products.



.... Phil
Those last few turns also have the longest length
per turn, further diminishing their \'return\'.

The \'practice\' is to assume a fill factor of less
than 80%, to allow for insulation, wire shape and
cover. For mains voltage wall thickness, creepage
spacing, and bobbin tolerancing, it\'s even worse.

Toroids depend upon 3xlayer film overlapping weave for
reinforced layering and core or outer wrap, though
some cores use fitted caps at the expense of efficiency.

Low and flat toroids are a \'style\' (at the expense of
efficiency) - the most efficient physical ratio being
roughly 2.2:1 / OD:H.

High frequency stuff . . . .

RL
 
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