magnetics question...

[Leo Smith]

You can see if there is any transformer you are looking for https://www.easybom.com/c/transformers

 

[Mike Monett]

Lasse Langwadt Christensen <langwadt@fonz.dk> wrote:

[...]

Can\'t it be more or less simplified to:
if you take a suitable transformer and run it at 8 times the frequency
you can also increase the voltage 8 times, and thus get 8 times the
power

P = E^2 / R
8^2 = 64



--
MRM

 

[Jan Panteltje]

On a sunny day (Wed, 6 Apr 2022 11:17:32 -0700) it happened
dplatt@coop.radagast.org (Dave Platt) wrote in
<s221ii-pqmv2.ln1@coop.radagast.org>:

In article <t2ki95$afi$1@dont-email.me>,
Jan Panteltje <pNaonStpealmtje@yahoo.com> wrote:

Yes, that is how I make 60 Hz here in 50 Hz land,
100 W audio amp 60 Hz from PC signal generator
in 50 Hz mains transformer connected the other way around.
Not very efficient, but nice sinewave and no harmonics.
A simple raspberry followed by a low pass could drive that
(raspi audio out is some PWM I think, sure has RF on it).

It\'s pretty easy to connect a $10-or-so I2S audio DAC board to a Pi,
rather than using the on-board audio DAC. The ones I\'ve been using
(based on Ti/Burr-Brown PCM-series DAC chips) put out a pretty clean
waveform - one can add a very simple low-pass to block noise up
above a few hundred kHz if necessary.

I have a couple of those USB audio sticks,
adds a clean output and also a mike input.
Also has auto-gain for the mike
alsmixer -c 1
http://panteltje.com/pub/alsamixer_c_1.gif
show just an other USB device

Those sticks are about 3 USD on ebay with free shipping, something like this:
https://www.ebay.com/itm/144291219756
Sounds a bit like \'expanded\' audio....must be the \'3D\' part...

For the original Pi output I made a cable with a simple RC lowpass in it,
that goes to my audio amp for background music in the room.

 

[Jan Panteltje]

On a sunny day (Wed, 6 Apr 2022 23:00:32 +0200) it happened Piotr Wyderski
<bombald@protonmail.com> wrote in <t2kv1u$2c98k$1@portraits.wsisiz.edu.pl>:

Arie de Muijnck wrote:

Yes, which is exactly why switching PSU\'s are now the standard. The cost
saving in iron (ferrite) and copper and capacitors, and all transport
costs, far outweighs (pun intended) the cost of the semiconductors.

Their regulation capability is far better than that of the more
conventional PSUs.

And why airplanes use 400 Hz - the tiny transformers I had designed in
in the product were amusing, 8 times smaller than the usual 50 hz versions.

But why 400 then? A typical scaling factor would be 10, so 500Hz should
be expected. Instead, they have selected the odd value of 8. Backward
compatibility with an arbitrarily selected frequency back in the
medieval times?

Railroad here also uses 400 Hz.

 

[Phil Allison]

Mike Monett wrote:
================

Can\'t it be more or less simplified to:
if you take a suitable transformer and run it at 8 times the frequency
you can also increase the voltage 8 times, and thus get 8 times the
power

** That is too simple.

At 8 times the frequency, core losses go up by the same ratio dramatically increasing the heat that must be dissipated.
But more importantly, there are strict limits on the voltages that can be safely tolerated by insulation.
High voltage transformers groups windings into insulated sub sections consuming much available window space.
Destructive corona discharge becomes a big issue between layers and even turns.


....... Phil

 

[Piotr Wyderski]

Lasse Langwadt Christensen wrote:

can\'t it be more or less simplified to:
if you take a suitable transformer and run it at 8 times the frequency you can also
increase the voltage 8 times, and thus get 8 times the power

Core losses in ferrite/powder materials do not obey simple rules and the
exponents in the approximate equations have fancy values like f^2.8. So
these are not exactly equivalent.

Best regards, Piotr

 

[Piotr Wyderski]

whit3rd wrote:

Yes, that\'s correct. I was thinking, though, of resizing the core which would shorten
the wire length required, thus allow thinner wire with similar resistance; a redesign of
the transformer for the higher frequency is different from using the same transformer.
So, my scaling assumes a transformer reconfiguration in shape. It doesn\'t get into
the correct way to do that wire re-dimensioning, because that includes dissipation of heat
changing with size... and heat can be shed by conduction, or convection, with different
power laws.

I used to have a copy of an article from the ETH I believe, where they
ran global optimisation on power transformers and simulated them with
FEM solvers. The conclusion was that 200kHz is the optimal switching
frequency given the current state of the art. Switching faster to get
smaller size makes other parameters worse, switching slower makes things
unnecessarily bulky.

Best regards, Piotr

 

[Piotr Wyderski]

On 2022-04-07 08:25, Phil Allison wrote:

> At 8 times the frequency, core losses go up by the same ratio dramatically increasing the heat that must be dissipated.

One can see here how complex the formula is e.g. here:

https://www.tme.eu/Document/a26e91abd72e59c56f207dc94b9eb235/ARNOLD-MS-184026-2.pdf

Best regards, Piotr

 

[piglet]

On 06/04/2022 4:53 pm, jlarkin@highlandsniptechnology.com wrote:

https://www.dropbox.com/s/jnb3jmw8rcmdeir/XfmrScatter.JPG?raw=1

How does the mass of a transformer scale with frequency?

I want to make a 120v 400 Hz power supply. I might boost my 48v up to
200DC and use an isolated h-bridge out to the load, or we could put
the bridge down at 48v and boost with a biggish transformer.

I\'ll have lots of air flow, so maybe I can push things some too.

Your first option eliminates an output transformer and means you could
make AC out as low a frequency as you want, even DC. Only problem could
be if customer wants to see a DC winding resistance but perhaps even
that could be synthesiesed?

piglet

 

[Lasse Langwadt Christensen]

torsdag den 7. april 2022 kl. 07.46.39 UTC+2 skrev Mike Monett:

Lasse Langwadt Christensen <lang...@fonz.dk> wrote:

[...]

Can\'t it be more or less simplified to:
if you take a suitable transformer and run it at 8 times the frequency
you can also increase the voltage 8 times, and thus get 8 times the
power
P = E^2 / R
8^2 = 64

current must stay the same it is limited by the wire sizes

 

[server]

On Thu, 7 Apr 2022 08:46:43 +0100, piglet <erichpwagner@hotmail.com>
wrote:

On 06/04/2022 4:53 pm, jlarkin@highlandsniptechnology.com wrote:
https://www.dropbox.com/s/jnb3jmw8rcmdeir/XfmrScatter.JPG?raw=1

How does the mass of a transformer scale with frequency?

I want to make a 120v 400 Hz power supply. I might boost my 48v up to
200DC and use an isolated h-bridge out to the load, or we could put
the bridge down at 48v and boost with a biggish transformer.

I\'ll have lots of air flow, so maybe I can push things some too.




Your first option eliminates an output transformer and means you could
make AC out as low a frequency as you want, even DC. Only problem could
be if customer wants to see a DC winding resistance but perhaps even
that could be synthesiesed?

piglet

Yeah, I guess we\'ll do a high frequency inverter to 200 volts dc or
so, and then a floating h-bridge. That can output bipolar dc, ac,
anything. May as well have ferrite custom magnetics, than steel.

The Coilcraft PL300 transformers are fabulous, 300 watts in a
surface-mount package. Their Spice coupling coefficient is 0.9996.

I bet we could push some more watts if we blow some air through the
planar kapton windings.




--

I yam what I yam - Popeye

 

[server]

On Thu, 7 Apr 2022 05:46:32 -0000 (UTC), Mike Monett <spamme@not.com>
wrote:

Lasse Langwadt Christensen <langwadt@fonz.dk> wrote:

[...]

Can\'t it be more or less simplified to:
if you take a suitable transformer and run it at 8 times the frequency
you can also increase the voltage 8 times, and thus get 8 times the
power

P = E^2 / R
8^2 = 64

Transformer power is usually limited by heating from copper loss. 64x
power implies 8x current, which won\'t work.

It might be worse than 8x power at 8x frequency, if skin and proximity
effects increase copper loss.



--

I yam what I yam - Popeye

 

[Jan Panteltje]

On a sunny day (Thu, 07 Apr 2022 07:50:22 -0700) it happened
jlarkin@highlandsniptechnology.com wrote in
<50ut4hlsh2r8u2ev6b4n8ja1gm1icf4k9p@4ax.com>:

On Thu, 7 Apr 2022 08:46:43 +0100, piglet <erichpwagner@hotmail.com
wrote:

On 06/04/2022 4:53 pm, jlarkin@highlandsniptechnology.com wrote:
https://www.dropbox.com/s/jnb3jmw8rcmdeir/XfmrScatter.JPG?raw=1

How does the mass of a transformer scale with frequency?

I want to make a 120v 400 Hz power supply. I might boost my 48v up to
200DC and use an isolated h-bridge out to the load, or we could put
the bridge down at 48v and boost with a biggish transformer.

I\'ll have lots of air flow, so maybe I can push things some too.




Your first option eliminates an output transformer and means you could
make AC out as low a frequency as you want, even DC. Only problem could
be if customer wants to see a DC winding resistance but perhaps even
that could be synthesiesed?

piglet

Yeah, I guess we\'ll do a high frequency inverter to 200 volts dc or
so, and then a floating h-bridge. That can output bipolar dc, ac,
anything. May as well have ferrite custom magnetics, than steel.

The Coilcraft PL300 transformers are fabulous, 300 watts in a
surface-mount package. Their Spice coupling coefficient is 0.9996.

I bet we could push some more watts if we blow some air through the
planar kapton windings.

How will a H bridge like that without transformers react to inductive peaks
from loads?

 

[Arie de Muijnck]

On 2022-04-06 23:00, legg wrote:

On Wed, 6 Apr 2022 18:45:43 +0200, Arie de Muijnck
eternal.september@ademu.com> wrote:
Yes, which is exactly why switching PSU\'s are now the standard. The cost
saving in iron (ferrite) and copper and capacitors, and all transport
costs, far outweighs (pun intended) the cost of the semiconductors.

And why airplanes use 400 Hz - the tiny transformers I had designed in
in the product were amusing, 8 times smaller than the usual 50 hz versions.

Arie

I think you\'re living in the past. 60-400Hz magnetics are
routinely shipped around the world for local cost reduction,
making \'iron\' transport costs irrelevant.

Only end-use weight and volume remain significant.

RL

In the past? Could be, I designed it more than 30 years ago.

But airplane equipment should still be as light-weight as possible.
Nowadays of course even those 400 Hz transformers will have been
replaced by switchers.

Arie

 

[server]

On Thu, 07 Apr 2022 16:01:12 GMT, Jan Panteltje
<pNaonStpealmtje@yahoo.com> wrote:

On a sunny day (Thu, 07 Apr 2022 07:50:22 -0700) it happened
jlarkin@highlandsniptechnology.com wrote in
50ut4hlsh2r8u2ev6b4n8ja1gm1icf4k9p@4ax.com>:

On Thu, 7 Apr 2022 08:46:43 +0100, piglet <erichpwagner@hotmail.com
wrote:

On 06/04/2022 4:53 pm, jlarkin@highlandsniptechnology.com wrote:
https://www.dropbox.com/s/jnb3jmw8rcmdeir/XfmrScatter.JPG?raw=1

How does the mass of a transformer scale with frequency?

I want to make a 120v 400 Hz power supply. I might boost my 48v up to
200DC and use an isolated h-bridge out to the load, or we could put
the bridge down at 48v and boost with a biggish transformer.

I\'ll have lots of air flow, so maybe I can push things some too.




Your first option eliminates an output transformer and means you could
make AC out as low a frequency as you want, even DC. Only problem could
be if customer wants to see a DC winding resistance but perhaps even
that could be synthesiesed?

piglet

Yeah, I guess we\'ll do a high frequency inverter to 200 volts dc or
so, and then a floating h-bridge. That can output bipolar dc, ac,
anything. May as well have ferrite custom magnetics, than steel.

The Coilcraft PL300 transformers are fabulous, 300 watts in a
surface-mount package. Their Spice coupling coefficient is 0.9996.

I bet we could push some more watts if we blow some air through the
planar kapton windings.

How will a H bridge like that without transformers react to inductive peaks
from loads?

Inductive peaks? Like saturation? It would current limit.

Our PM alternator simulator is similar, uses a full-bridge output
stage, and can drive a dead short. Regulators for PM alternators
usually short the alternator to limit voltage. That blew up our
first-gen design that used a TI audio output chip.



--

I yam what I yam - Popeye

 

[Lasse Langwadt Christensen]

torsdag den 7. april 2022 kl. 16.50.35 UTC+2 skrev jla...@highlandsniptechnology.com:

On Thu, 7 Apr 2022 08:46:43 +0100, piglet <erichp...@hotmail.com
wrote:
On 06/04/2022 4:53 pm, jla...@highlandsniptechnology.com wrote:
https://www.dropbox.com/s/jnb3jmw8rcmdeir/XfmrScatter.JPG?raw=1

How does the mass of a transformer scale with frequency?

I want to make a 120v 400 Hz power supply. I might boost my 48v up to
200DC and use an isolated h-bridge out to the load, or we could put
the bridge down at 48v and boost with a biggish transformer.

I\'ll have lots of air flow, so maybe I can push things some too.




Your first option eliminates an output transformer and means you could
make AC out as low a frequency as you want, even DC. Only problem could
be if customer wants to see a DC winding resistance but perhaps even
that could be synthesiesed?

piglet
Yeah, I guess we\'ll do a high frequency inverter to 200 volts dc or
so, and then a floating h-bridge.

https://www.hobbielektronika.hu/forum/getfile.php?id=125378

 

[Lasse Langwadt Christensen]

torsdag den 7. april 2022 kl. 01.22.48 UTC+2 skrev John Larkin:

On Wed, 6 Apr 2022 21:19:49 -0000 (UTC), Mike Monett <spa...@not.com
wrote:
Piotr Wyderski <bom...@protonmail.com> wrote:

Arie de Muijnck wrote:

Yes, which is exactly why switching PSU\'s are now the standard. The
cost saving in iron (ferrite) and copper and capacitors, and all
transport costs, far outweighs (pun intended) the cost of the
semiconductors.

Their regulation capability is far better than that of the more
conventional PSUs.

And why airplanes use 400 Hz - the tiny transformers I had designed in
in the product were amusing, 8 times smaller than the usual 50 hz
versions.

But why 400 then? A typical scaling factor would be 10, so 500Hz should
be expected. Instead, they have selected the odd value of 8. Backward
compatibility with an arbitrarily selected frequency back in the
medieval times?

Best regards, Piotr

Aircraft are moving away from the fixed 400Hz frequency to variable
360-800Hz.

\"On the other hand, the innovation of power supply system in aircraft
performance in the system of power supply: 360~800Hz large capacity
variable frequency AC power system is using gradually instead of the
constant frequency of 400Hz power supply on most of the aircraft[3,4]\"

https://www.atlantis-press.com/article/25862618.pdf
There are constant-frequency generators that always make 400 Hz. I
don\'t know how they work.

https://en.wikipedia.org/wiki/Doubly-fed_electric_machine#Double_fed_induction_generator ?

360 (sometimes 250) to 800 Hz is \"Wild power\", what you can get from
anywhere to stay alive. A ram air turbine is \"the thing you never want
to see used.\"

afaiu some newer airplanes have power that varies in frequency
because it is simpler and lighter to do than a fixed output frequency
as engine rpm varies from idle to takeoff

 

[server]

Piotr Wyderski <bombald@protonmail.com> wrote in
news:t2m3g2$38tt4$1@portraits.wsisiz.edu.pl:

whit3rd wrote:

Yes, that\'s correct. I was thinking, though, of resizing the
core which would shorten the wire length required, thus allow
thinner wire with similar resistance; a redesign of the
transformer for the higher frequency is different from using the
same transformer. So, my scaling assumes a transformer
reconfiguration in shape. It doesn\'t get into the correct way to
do that wire re-dimensioning, because that includes dissipation
of heat changing with size... and heat can be shed by conduction,
or convection, with different power laws.

I used to have a copy of an article from the ETH I believe, where
they ran global optimisation on power transformers and simulated
them with FEM solvers. The conclusion was that 200kHz is the
optimal switching frequency given the current state of the art.
Switching faster to get smaller size makes other parameters worse,
switching slower makes things unnecessarily bulky.

Best regards, Piotr

Ferrite core miniature transformers we used for HVPS design ran best
at around 56kHz. It varies too depending on the ferrite formulation
and finished product functional characteristics. But you should know
that.

Essentially, you are off the mark on this too.

 

[Jan Panteltje]

On a sunny day (Thu, 07 Apr 2022 09:12:47 -0700) it happened
jlarkin@highlandsniptechnology.com wrote in
<v23u4hhn9o712gkobu1nenkf63k6i28s3v@4ax.com>:

On Thu, 07 Apr 2022 16:01:12 GMT, Jan Panteltje
pNaonStpealmtje@yahoo.com> wrote:
How will a H bridge like that without transformers react to inductive peaks
from loads?

Inductive peaks? Like saturation? It would current limit.

I actually meant flyback pulses

Our PM alternator simulator is similar, uses a full-bridge output
stage, and can drive a dead short. Regulators for PM alternators
usually short the alternator to limit voltage. That blew up our
first-gen design that used a TI audio output chip.

I have this one:
https://www.bol.com/nl/nl/p/green-cell-12v-voltage-auto-omvormer-12v-naar-220v-230v-2000w-zuivere-sinus-golf/9200000122523930/#product_specifications
12 V DC to 230V AC 50 Hz
It is heavy, 4.7 kg

Works great so far, so have not opened it yet
was 200 Euro
No idea of the circuit.

 

[John Larkin]

On Thu, 7 Apr 2022 09:18:49 -0700 (PDT), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:

torsdag den 7. april 2022 kl. 16.50.35 UTC+2 skrev jla...@highlandsniptechnology.com:
On Thu, 7 Apr 2022 08:46:43 +0100, piglet <erichp...@hotmail.com
wrote:
On 06/04/2022 4:53 pm, jla...@highlandsniptechnology.com wrote:
https://www.dropbox.com/s/jnb3jmw8rcmdeir/XfmrScatter.JPG?raw=1

How does the mass of a transformer scale with frequency?

I want to make a 120v 400 Hz power supply. I might boost my 48v up to
200DC and use an isolated h-bridge out to the load, or we could put
the bridge down at 48v and boost with a biggish transformer.

I\'ll have lots of air flow, so maybe I can push things some too.




Your first option eliminates an output transformer and means you could
make AC out as low a frequency as you want, even DC. Only problem could
be if customer wants to see a DC winding resistance but perhaps even
that could be synthesiesed?

piglet
Yeah, I guess we\'ll do a high frequency inverter to 200 volts dc or
so, and then a floating h-bridge.

https://www.hobbielektronika.hu/forum/getfile.php?id=125378

I\'m leaning towards a full h-bridge in the first stage. It uses the
copper better and doesn\'t need snubbing.

--

If a man will begin with certainties, he shall end with doubts,
but if he will be content to begin with doubts he shall end in certainties.
Francis Bacon