Can I use this for 220V input and 380V output?

https://www.ebay.com/itm/255681909221

This should give me around 400V to 450V full bridge rectified DC.

On a sunny day (Fri, 30 Jun 2023 20:55:08 -0700 (PDT)) it happened Eddy Lee
<eddy711lee@gmail.com> wrote in
<c944dcc8-8559-4276-bf78-b5e534061f1an@googlegroups.com>:

>Can I use this for 220V input and 380V output?
>
>https://www.ebay.com/itm/255681909221
>
>This should give me around 400V to 450V full bridge rectified DC.

450 / sqrt(2) = 318
318 - 220 = 98

Only 100 V extra needed!

So basically you can use a 220 to 100 V transformer in series with the 220 to get to 318
So less copper / money / weight needed.
In phase that is :-)

On Friday, June 30, 2023 at 9:39:22 PM UTC-7, Jan Panteltje wrote:
> On a sunny day (Fri, 30 Jun 2023 20:55:08 -0700 (PDT)) it happened Eddy Lee
> <eddy7...@gmail.com> wrote in
> <c944dcc8-8559-4276...@googlegroups.com>:
> >Can I use this for 220V input and 380V output?
> >
> >https://www.ebay.com/itm/255681909221
> >
> >This should give me around 400V to 450V full bridge rectified DC.
> 450 / sqrt(2) = 318
> 318 - 220 = 98
>
> Only 100 V extra needed!
>
> So basically you can use a 220 to 100 V transformer in series with the 220 to get to 318
> So less copper / money / weight needed.
> In phase that is :-)

Yes in theory, but ...

I get around 250V DC out of the 220V AC inverter.
Probably need high 300 AC to get 400 DC.

On a sunny day (Fri, 30 Jun 2023 21:46:53 -0700 (PDT)) it happened Eddy Lee
<eddy711lee@gmail.com> wrote in
<e9e3922c-3d4d-4459-95bd-40cad033df03n@googlegroups.com>:

>On Friday, June 30, 2023 at 9:39:22 PM UTC-7, Jan Panteltje wrote:
>> On a sunny day (Fri, 30 Jun 2023 20:55:08 -0700 (PDT)) it happened Eddy L=
>ee
>> <eddy7...@gmail.com> wrote in
>> <c944dcc8-8559-4276...@googlegroups.com>:
>> >Can I use this for 220V input and 380V output?
>> >
>> >https://www.ebay.com/itm/255681909221
>> >
>> >This should give me around 400V to 450V full bridge rectified DC.
>> 450 / sqrt(2) = 318
>> 318 - 220 = 98
>>
>> Only 100 V extra needed!
>>
>> So basically you can use a 220 to 100 V transformer in series with the 22=
>0 to get to 318
>> So less copper / money / weight needed.
>> In phase that is :-)
>
>Yes in theory, but ...
>
>I get around 250V DC out of the 220V AC inverter.
>Probably need high 300 AC to get 400 DC.

Ah, from an inverter, likely not a pure sinewave output one,
that likely has a square wave like output to approximate a 'sinewave', like this UPS one I have:
https://panteltje.nl/pub/APC_UPS_ES700_waveform_25W_edison_bulb_load_IMG_0270.JPG

The same math stays, but not sqrt(2) but 250 / 220
450 / (250 / 220) = 396 V
396 - 220 = 176 V

Then you need a 220 to 176 V transformer in series...
Not a standard thing.

So indeed then the ebay thing should work.. given the inverter can handle it.
For real work I have a 2000 Watt pure sinewave 12 V to 230 V one:
https://panteltje.nl/pub/250_Ah_12V_to_230V_sinewave_IXXIMG_0796.JPG
and a 250 Ah hour lifepo4 battery pack.
Sinewave is better ...

Also depends how many Watts / current yoy need for that 450 V DC.
Maybe simple switcher ?

Or you could use a voltage doubler circuit:

--|>|--------- +
| |
| ===
| ---
| | 500 V
|- -AC--|
| |
| ===
| ---
| |
--|<|-------- -

simplest solution!

Jan Panteltje wrote:
-----------------------------
> >
> >I get around 250V DC out of the 220V AC inverter.
> >Probably need high 300 AC to get 400 DC.
>
> Ah, from an inverter, likely not a pure sinewave output one,
> that likely has a square wave like output to approximate a 'sinewave',

** So the peak voltage is likely out of spec.

But does the OP have some filtering on that rectified DC ?
If not, average DC value applies rather than peak.

..... Phil

On Friday, June 30, 2023 at 11:55:14 PM UTC-4, Eddy Lee wrote:
> Can I use this for 220V input and 380V output?
>
> https://www.ebay.com/itm/255681909221
>
> This should give me around 400V to 450V full bridge rectified DC.

Where would you get 220V for the input? The US is 240V.

--

Rick C.

- Get 1,000 miles of free Supercharging
- Tesla referral code - https://ts.la/richard11209

On Saturday, July 1, 2023 at 2:24:04 AM UTC-7, Phil Allison wrote:
> Jan Panteltje wrote:
> -----------------------------
> > >
> > >I get around 250V DC out of the 220V AC inverter.
> > >Probably need high 300 AC to get 400 DC.
> >
> > Ah, from an inverter, likely not a pure sinewave output one,
> > that likely has a square wave like output to approximate a 'sinewave',
> ** So the peak voltage is likely out of spec.
>
> But does the OP have some filtering on that rectified DC ?
> If not, average DC value applies rather than peak.

47uF 400V cap.

On Saturday, July 1, 2023 at 2:45:14 AM UTC-7, Ricky wrote:
> On Friday, June 30, 2023 at 11:55:14 PM UTC-4, Eddy Lee wrote:
> > Can I use this for 220V input and 380V output?
> >
> > https://www.ebay.com/itm/255681909221
> >
> > This should give me around 400V to 450V full bridge rectified DC.
> Where would you get 220V for the input? The US is 240V.

48V DC to 220V AC inverter

On Saturday, July 1, 2023 at 1:36:15 AM UTC-7, Jan Panteltje wrote:
> On a sunny day (Fri, 30 Jun 2023 21:46:53 -0700 (PDT)) it happened Eddy Lee
> <eddy7...@gmail.com> wrote in
> <e9e3922c-3d4d-4459...@googlegroups.com>:
> >On Friday, June 30, 2023 at 9:39:22 PM UTC-7, Jan Panteltje wrote:
> >> On a sunny day (Fri, 30 Jun 2023 20:55:08 -0700 (PDT)) it happened Eddy L> >ee
> >> <eddy7...@gmail.com> wrote in
> >> <c944dcc8-8559-4276...@googlegroups.com>:
> >> >Can I use this for 220V input and 380V output?
> >> >
> >> >https://www.ebay.com/itm/255681909221
> >> >
> >> >This should give me around 400V to 450V full bridge rectified DC.
> >> 450 / sqrt(2) = 318
> >> 318 - 220 = 98
> >>
> >> Only 100 V extra needed!
> >>
> >> So basically you can use a 220 to 100 V transformer in series with the 22> >0 to get to 318
> >> So less copper / money / weight needed.
> >> In phase that is :-)
> >
> >Yes in theory, but ...
> >
> >I get around 250V DC out of the 220V AC inverter.
> >Probably need high 300 AC to get 400 DC.
> Ah, from an inverter, likely not a pure sinewave output one,
> that likely has a square wave like output to approximate a 'sinewave', like this UPS one I have:
> https://panteltje.nl/pub/APC_UPS_ES700_waveform_25W_edison_bulb_load_IMG_0270.JPG
>
> The same math stays, but not sqrt(2) but 250 / 220
> 450 / (250 / 220) = 396 V
> 396 - 220 = 176 V
>
> Then you need a 220 to 176 V transformer in series...
> Not a standard thing.
>
> So indeed then the ebay thing should work.. given the inverter can handle it.
> For real work I have a 2000 Watt pure sinewave 12 V to 230 V one:
> https://panteltje.nl/pub/250_Ah_12V_to_230V_sinewave_IXXIMG_0796.JPG
> and a 250 Ah hour lifepo4 battery pack.
> Sinewave is better ...
>
> Also depends how many Watts / current yoy need for that 450 V DC.
> Maybe simple switcher ?
>
> Or you could use a voltage doubler circuit:
>
> --|>|--------- +
> | |
> | ===
> | ---
> | | 500 V
> |- -AC--|
> | | ht
> | ===
> | ---
> | |
> --|<|-------- -
>
> simplest solution!

I might try a 3V/24V booster and a 24V/380V transformer. Would need additional switching circuit.

On Sat, 01 Jul 2023 04:39:14 GMT, Jan Panteltje <alien@comet.invalid>
wrote:

>On a sunny day (Fri, 30 Jun 2023 20:55:08 -0700 (PDT)) it happened Eddy Lee
><eddy711lee@gmail.com> wrote in
><c944dcc8-8559-4276-bf78-b5e534061f1an@googlegroups.com>:
>
>>Can I use this for 220V input and 380V output?
>>
>>https://www.ebay.com/itm/255681909221
>>
>>This should give me around 400V to 450V full bridge rectified DC.
>
>450 / sqrt(2) = 318
>318 - 220 = 98
>
>Only 100 V extra needed!
>
>So basically you can use a 220 to 100 V transformer in series with the 220 to get to 318
>So less copper / money / weight needed.
>In phase that is :-)

Autotransformer mode, but no isolation.

One concern about cheapish transformers is copper loss. Some people
design transformers with minimal copper and assume a high temperature
rise. Signal Transformer used to be famous for selling "soft"
transformers; I think they used high temperature varnish.

If such a transformer is used to rectify to DC, one may see an
unexpected high DC voltage at low loads and bad regulation after that.
And figure it might get hot at full load. Rectifying into a capacitor
makes all that worse.

On Friday, June 30, 2023 at 11:55:14 PM UTC-4, Eddy Lee wrote:
> Can I use this for 220V input and 380V output?
>
> https://www.ebay.com/itm/255681909221
>
> This should give me around 400V to 450V full bridge rectified DC.

You'll never know from that fantasy, fake advertisement. What is the load you're putting on the 400-450 VDC in Amps?

On Sat, 1 Jul 2023 05:07:53 -0700 (PDT), Eddy Lee
<eddy711lee@gmail.com> wrote:

>47uF 400V cap.

If you feed the 220/380 V transformer with something that even
remotely looks like 220 Vrms and rectify the output with a bridge
rectifier, the idle (no load) voltage will be the peak voltage or
about 530 V.

I would suggest using a capacitor rated for 600 V.

On Saturday, July 1, 2023 at 9:53:36 AM UTC-4, John Larkin wrote:
> On Sat, 01 Jul 2023 04:39:14 GMT, Jan Panteltje <al...@comet.invalid>
> wrote:
> >On a sunny day (Fri, 30 Jun 2023 20:55:08 -0700 (PDT)) it happened Eddy Lee
> ><eddy7...@gmail.com> wrote in
> ><c944dcc8-8559-4276...@googlegroups.com>:
> >
> >>Can I use this for 220V input and 380V output?
> >>
> >>https://www.ebay.com/itm/255681909221
> >>
> >>This should give me around 400V to 450V full bridge rectified DC.
> >
> >450 / sqrt(2) = 318
> >318 - 220 = 98
> >
> >Only 100 V extra needed!
> >
> >So basically you can use a 220 to 100 V transformer in series with the 220 to get to 318
> >So less copper / money / weight needed.
> >In phase that is :-)
> Autotransformer mode, but no isolation.
>
> One concern about cheapish transformers is copper loss. Some people
> design transformers with minimal copper and assume a high temperature
> rise. Signal Transformer used to be famous for selling "soft"
> transformers; I think they used high temperature varnish.
>
> If such a transformer is used to rectify to DC, one may see an
> unexpected high DC voltage at low loads and bad regulation after that.
> And figure it might get hot at full load. Rectifying into a capacitor
> makes all that worse.

Signal had a separate line of "rectifier" transformers designed to support current peaks in rectification. Standard regulation was 10% and core temperature rise was something like 40oC at rated. My experience with them is everything always worked to specification. For excellent isolation in addition to only a few p's coupling capacitance, their split bobbin design is unbeatable.

On Saturday, July 1, 2023 at 8:24:59 AM UTC-7, Fred Bloggs wrote:
> On Friday, June 30, 2023 at 11:55:14 PM UTC-4, Eddy Lee wrote:
> > Can I use this for 220V input and 380V output?
> >
> > https://www.ebay.com/itm/255681909221
> >
> > This should give me around 400V to 450V full bridge rectified DC.
> You'll never know from that fantasy, fake advertisement. What is the load you're putting on the 400-450 VDC in Amps?

0.5A to 2A. I can put in multiple 100W Ts.

On Saturday, July 1, 2023 at 6:53:36 AM UTC-7, John Larkin wrote:
> On Sat, 01 Jul 2023 04:39:14 GMT, Jan Panteltje <al...@comet.invalid>
> wrote:
> >On a sunny day (Fri, 30 Jun 2023 20:55:08 -0700 (PDT)) it happened Eddy Lee
> ><eddy7...@gmail.com> wrote in
> ><c944dcc8-8559-4276...@googlegroups.com>:
> >
> >>Can I use this for 220V input and 380V output?
> >>
> >>https://www.ebay.com/itm/255681909221
> >>
> >>This should give me around 400V to 450V full bridge rectified DC.
> >
> >450 / sqrt(2) = 318
> >318 - 220 = 98
> >
> >Only 100 V extra needed!
> >
> >So basically you can use a 220 to 100 V transformer in series with the 220 to get to 318
> >So less copper / money / weight needed.
> >In phase that is :-)
> Autotransformer mode, but no isolation.
>
> One concern about cheapish transformers is copper loss. Some people
> design transformers with minimal copper and assume a high temperature
> rise. Signal Transformer used to be famous for selling "soft"
> transformers; I think they used high temperature varnish.
>
> If such a transformer is used to rectify to DC, one may see an
> unexpected high DC voltage at low loads and bad regulation after that.
> And figure it might get hot at full load. Rectifying into a capacitor
> makes all that worse.

Question is whether they are symmetrical from either side (primary/secondary) in efficiency and load capacity. I will be driving it from both sides, but not at the same time.

On Sat, 1 Jul 2023 10:39:25 -0700 (PDT), Eddy Lee
<eddy711lee@gmail.com> wrote:

>On Saturday, July 1, 2023 at 6:53:36?AM UTC-7, John Larkin wrote:
>> On Sat, 01 Jul 2023 04:39:14 GMT, Jan Panteltje <al...@comet.invalid>
>> wrote:
>> >On a sunny day (Fri, 30 Jun 2023 20:55:08 -0700 (PDT)) it happened Eddy Lee
>> ><eddy7...@gmail.com> wrote in
>> ><c944dcc8-8559-4276...@googlegroups.com>:
>> >
>> >>Can I use this for 220V input and 380V output?
>> >>
>> >>https://www.ebay.com/itm/255681909221
>> >>
>> >>This should give me around 400V to 450V full bridge rectified DC.
>> >
>> >450 / sqrt(2) = 318
>> >318 - 220 = 98
>> >
>> >Only 100 V extra needed!
>> >
>> >So basically you can use a 220 to 100 V transformer in series with the 220 to get to 318
>> >So less copper / money / weight needed.
>> >In phase that is :-)
>> Autotransformer mode, but no isolation.
>>
>> One concern about cheapish transformers is copper loss. Some people
>> design transformers with minimal copper and assume a high temperature
>> rise. Signal Transformer used to be famous for selling "soft"
>> transformers; I think they used high temperature varnish.
>>
>> If such a transformer is used to rectify to DC, one may see an
>> unexpected high DC voltage at low loads and bad regulation after that.
>> And figure it might get hot at full load. Rectifying into a capacitor
>> makes all that worse.
>
>Question is whether they are symmetrical from either side (primary/secondary) in efficiency and load capacity. I will be driving it from both sides, but not at the same time.

Sure, a transformer works either way.

On Saturday, July 1, 2023 at 1:35:53 PM UTC-4, Eddy Lee wrote:
> On Saturday, July 1, 2023 at 8:24:59 AM UTC-7, Fred Bloggs wrote:
> > On Friday, June 30, 2023 at 11:55:14 PM UTC-4, Eddy Lee wrote:
> > > Can I use this for 220V input and 380V output?
> > >
> > > https://www.ebay.com/itm/255681909221
> > >
> > > This should give me around 400V to 450V full bridge rectified DC.
> > You'll never know from that fantasy, fake advertisement. What is the load you're putting on the 400-450 VDC in Amps?
> 0.5A to 2A. I can put in multiple 100W Ts.

When you correct for magnetics regulation and filter (capacitor) losses, Vsecondary,RMS= 0.71 x 450 VDC / 0.95 = 340 VAC RMS, and the I secondary,RMS= 3 x 2 A= 6A. So that's a 340 x 6 =2 kVA transformer.
Those corrections are based on a middling w x C x RL = 20, where w=377 line radian frequency, C= filter capacitor, RL= load resistor 400 VDC/2A= 200 Ohm, and an assumption of 10% transformer regulation with an approximate 340 VRMS, making for an equivalent series output impedance of Rs= 34 V/6A= 6 Ohm. Ripple factor, ratio of RMS ripple to DC output will be about 4% or 14VRMS. wCRL too small and it gets sloppy, ripply, and less predictable, too large and you get excessive diode current peaks and surges. Your call. This is an iterative process based on a process and associated curves published in 1943 by O.H. Shade and pretty much used ever since.

None of this precise.

That would be Figures 7.4 thru 7.7 in this handbook:

https://frank.pocnet.net/other/sos/TexasInstruments_TheVoltageRegulatorHandbook_1977.pdf

None of the above addresses line variation which can be pretty bad worst case.

On Saturday, July 1, 2023 at 1:35:53 PM UTC-4, Eddy Lee wrote:
> On Saturday, July 1, 2023 at 8:24:59 AM UTC-7, Fred Bloggs wrote:
> > On Friday, June 30, 2023 at 11:55:14 PM UTC-4, Eddy Lee wrote:
> > > Can I use this for 220V input and 380V output?
> > >
> > > https://www.ebay.com/itm/255681909221
> > >
> > > This should give me around 400V to 450V full bridge rectified DC.
> > You'll never know from that fantasy, fake advertisement. What is the load you're putting on the 400-450 VDC in Amps?
> 0.5A to 2A. I can put in multiple 100W Ts.

The foregoing was meant to show that a 60 Hz magnetics approach is kinda absurd.

Buy a high efficiency switcher.

On Sat, 1 Jul 2023 14:06:23 -0700 (PDT), Fred Bloggs
<bloggs.fredbloggs.fred@gmail.com> wrote:

>On Saturday, July 1, 2023 at 1:35:53?PM UTC-4, Eddy Lee wrote:
>> On Saturday, July 1, 2023 at 8:24:59?AM UTC-7, Fred Bloggs wrote:
>> > On Friday, June 30, 2023 at 11:55:14?PM UTC-4, Eddy Lee wrote:
>> > > Can I use this for 220V input and 380V output?
>> > >
>> > > https://www.ebay.com/itm/255681909221
>> > >
>> > > This should give me around 400V to 450V full bridge rectified DC.
>> > You'll never know from that fantasy, fake advertisement. What is the load you're putting on the 400-450 VDC in Amps?
>> 0.5A to 2A. I can put in multiple 100W Ts.
>
>The foregoing was meant to show that a 60 Hz magnetics approach is kinda absurd.
>
>Buy a high efficiency switcher.

High voltage output switchers are rare.

PFC modules output around 400 DC and lots of power, but aren't
isolated.

On Saturday, July 1, 2023 at 5:35:56 PM UTC-4, John Larkin wrote:
> On Sat, 1 Jul 2023 14:06:23 -0700 (PDT), Fred Bloggs
> <bloggs.fred...@gmail.com> wrote:
>
> >On Saturday, July 1, 2023 at 1:35:53?PM UTC-4, Eddy Lee wrote:
> >> On Saturday, July 1, 2023 at 8:24:59?AM UTC-7, Fred Bloggs wrote:
> >> > On Friday, June 30, 2023 at 11:55:14?PM UTC-4, Eddy Lee wrote:
> >> > > Can I use this for 220V input and 380V output?
> >> > >
> >> > > https://www.ebay.com/itm/255681909221
> >> > >
> >> > > This should give me around 400V to 450V full bridge rectified DC.
> >> > You'll never know from that fantasy, fake advertisement. What is the load you're putting on the 400-450 VDC in Amps?
> >> 0.5A to 2A. I can put in multiple 100W Ts.
> >
> >The foregoing was meant to show that a 60 Hz magnetics approach is kinda absurd.
> >
> >Buy a high efficiency switcher.
> High voltage output switchers are rare.

Not anymore. China makes them a commodity:

https://idealplusing.en.made-in-china.com/product/EdjGBQbxgzkH/China-Hot-Sale-220V-110V-AC-to-400V-500V-600V-700V-DC-1000W-Switching-Power-Supply.html

Pointless to read the specs, but it sounds right.

>
> PFC modules output around 400 DC and lots of power, but aren't
> isolated.

lørdag den 1. juli 2023 kl. 23.35.56 UTC+2 skrev John Larkin:
> On Sat, 1 Jul 2023 14:06:23 -0700 (PDT), Fred Bloggs
> <bloggs.fred...@gmail.com> wrote:
>
> >On Saturday, July 1, 2023 at 1:35:53?PM UTC-4, Eddy Lee wrote:
> >> On Saturday, July 1, 2023 at 8:24:59?AM UTC-7, Fred Bloggs wrote:
> >> > On Friday, June 30, 2023 at 11:55:14?PM UTC-4, Eddy Lee wrote:
> >> > > Can I use this for 220V input and 380V output?
> >> > >
> >> > > https://www.ebay.com/itm/255681909221
> >> > >
> >> > > This should give me around 400V to 450V full bridge rectified DC.
> >> > You'll never know from that fantasy, fake advertisement. What is the load you're putting on the 400-450 VDC in Amps?
> >> 0.5A to 2A. I can put in multiple 100W Ts.
> >
> >The foregoing was meant to show that a 60 Hz magnetics approach is kinda absurd.
> >
> >Buy a high efficiency switcher.
> High voltage output switchers are rare.

there's one in the inverter, likely something like this: https://www.tehnomagazin.com/Power-supply/24v-to-220v-inverter-1000W-schematic-diagram.jpg

On Sat, 1 Jul 2023 15:06:47 -0700 (PDT), Fred Bloggs
<bloggs.fredbloggs.fred@gmail.com> wrote:

>On Saturday, July 1, 2023 at 5:35:56?PM UTC-4, John Larkin wrote:
>> On Sat, 1 Jul 2023 14:06:23 -0700 (PDT), Fred Bloggs
>> <bloggs.fred...@gmail.com> wrote:
>>
>> >On Saturday, July 1, 2023 at 1:35:53?PM UTC-4, Eddy Lee wrote:
>> >> On Saturday, July 1, 2023 at 8:24:59?AM UTC-7, Fred Bloggs wrote:
>> >> > On Friday, June 30, 2023 at 11:55:14?PM UTC-4, Eddy Lee wrote:
>> >> > > Can I use this for 220V input and 380V output?
>> >> > >
>> >> > > https://www.ebay.com/itm/255681909221
>> >> > >
>> >> > > This should give me around 400V to 450V full bridge rectified DC.
>> >> > You'll never know from that fantasy, fake advertisement. What is the load you're putting on the 400-450 VDC in Amps?
>> >> 0.5A to 2A. I can put in multiple 100W Ts.
>> >
>> >The foregoing was meant to show that a 60 Hz magnetics approach is kinda absurd.
>> >
>> >Buy a high efficiency switcher.
>> High voltage output switchers are rare.
>
>Not anymore. China makes them a commodity:
>
>https://idealplusing.en.made-in-china.com/product/EdjGBQbxgzkH/China-Hot-Sale-220V-110V-AC-to-400V-500V-600V-700V-DC-1000W-Switching-Power-Supply.html
>
>Pointless to read the specs, but it sounds right.

At least it's CE!

upsidedown@downunder.com wrote:

> On Sat, 1 Jul 2023 05:07:53 -0700 (PDT), Eddy Lee
> <eddy711lee@gmail.com> wrote:
>
>>47uF 400V cap.
>
> If you feed the 220/380 V transformer with something that even
> remotely looks like 220 Vrms and rectify the output with a bridge
> rectifier, the idle (no load) voltage will be the peak voltage or
> about 530 V.
>
> I would suggest using a capacitor rated for 600 V.

That hardly provides any margin.

Use two 450 volt caps in series with equalizing resistors in parallel.

--
MRM

John Larkin wrote:
----------------------------
> Eddy Lee
>
> >Question is whether they are symmetrical from either side (primary/secondary) in efficiency and load capacity.
> > I will be driving it from both sides, but not at the same time.
>
> Sure, a transformer works either way.
>

** But makers nominate the primary and secondary for good reasons.

The primary supplies the magnetising current, which can be significant, plus is wound to allow for voltage drop at the secondary under full load. If the roles are swapped, there are several changes that can catch the unwary.

....... Phil

On Sat, 1 Jul 2023 19:32:12 -0700 (PDT), Phil Allison
<pallison49@gmail.com> wrote:

>John Larkin wrote:
>----------------------------
>> Eddy Lee
>>
>> >Question is whether they are symmetrical from either side (primary/secondary) in efficiency and load capacity.
>> > I will be driving it from both sides, but not at the same time.
>>
>> Sure, a transformer works either way.
>>
>
>** But makers nominate the primary and secondary for good reasons.
>
>The primary supplies the magnetising current, which can be significant, plus is wound to allow for voltage drop at the secondary under full load. If the roles are swapped, there are several changes that can catch the unwary.
>
>
>
>
>...... Phil

Any winding can magnetize the core. The primary is the one you decide
to put power into and the secondary is the one you elect to take power
out of.

2-winding power transformers are usually designed for equal copper
loss on both windings. So are thermally symmetric.

Sometimes some windings are insulated better than others.

What other catches might there be?