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

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

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

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

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

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

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

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?

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

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

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

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

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.

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.

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

jlarkin@highlandsniptechnology.com wrote:

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

And pretty cheap, as I can see. But the 1500 Vrms is a bit low.

Best regards, Piotr

On Thu, 7 Apr 2022 18:12:25 +0200, Arie de Muijnck
<eternal.september@ademu.com> wrote:

>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

I was refering to transport costs of matl. In the past, this
also encouraged local mfr of LF magnetics.

RL