I have a straightforward question: How can I determine the load capacity of a standard power transformer, like one going from 230V to 2x12V, if I want to use it in a reversed manner in an inverter circuit? There's a plethora of videos and written material available, but I haven't found a clear answer to this question. Is the process the same as using it conventionally? I doubt it, but I'm struggling to find relevant information. I have to know how many Amps I can load my inverter if I can finish one It would be an EL panel driver thing, running from 12V and the output will be 110V around 600Hz maximum 1800Hz. I want to use a normal power transformer, driven by IR2153 and 2 MOSFET. Something like this: https://danyk.cz/menic230_4_en.html just a herz would be higher. This circuit designer say: " For output above 600 watts is possible to combine multiple transistors IRF3205 in parallel. " It says to me, not the transformer but the MOSFETs are counts? How does it work? The transformer should play a part in this circuit, doesn't it?
Thank you for all the answers.

 

What are the winding details now?
i.e. voltage current of primary and/or secondary?
From this you can calculate the VA (wattage) , normally if you use a transformer in reverse connection, there is a 10% loss/de-rating of the known power rating of the unit.

 

normally, reversal will have little effect on VA rating. Your frequency is a different story. All bets are off, and only a field test will confirm, unless you have direct access to the design team.

 

normally, reversal will have little effect on VA rating.

That is not what I got from a large Transformer Manufacturer, i.e. Hammond Mfg.
Also to quote Maddox,
"When you reverse feed a step-down transformer, you lose the ability to adjust the primary voltage rating to accommodate for small discrepancies in the supply voltage. And if there is more than a 5% variance, the windings will over-excite causing excess heat and energy loss".

 

When used in its normal mode, the magnetisation current is provided by the primary, and the primary wire size is a little larger to allow for this. When reversed, the magnetisation current is provided by what is now the primary and used to be the secondary, but it doesn't have any allowance for it, so it has to be downrated to accommodate.

I don't quite get @MaxHeadRoom 's point about adjusting the primary voltage. Most transformers will be designed for an extra 10% on the primary voltage without saturating, but they will run warmer with more magnetisation current at higher voltages.

The main point is that the "regulation" works the opposite way round. Most transformers are specified "on load", so have the turns ratio adjusted for copper loss.

Used at a higher frequency than specified will mean that there is no danger of saturation, and core losses will be much reduced, but the leakage inductances won't have changed, so the voltage drops across them will be greater at higher frequencies.

Doubling the frequency (50Hz to 100Hz) would mean that you could operate a 120V winding on 230V with the same core losses.

Also watch out if you are driving with a square-wave that the voltage-time constant is not exceeded. A 12V peak to peak squarewave has π/2 times the voltage-time constant of a 12V peak-to-peak sinewave.

 

I don't quite get @MaxHeadRoom 's point about adjusting the primary voltage. Most transformers will be designed for an extra 10% on the primary voltage without saturating, but they will run warmer with more magnetisation current at higher voltages.

Not my words.
I am just quoting a couple of major players, Hammond & Maddox.
I got the initial info about the 10% power de-rating direct from Hammond.

 

Not my words.
I am just quoting a couple of major players, Hammond & Maddox.
I got the initial info about the 10% power de-rating direct from Hammond.

Not saying that they are wrong, I just didn't quite understand what they were referring to.
10% would be explained by the transfer of the magnetising current to the other winding.

 

The main limiting factor is the Wire-Gauge used in each winding.
Calculate the maximum-rated-Amperage for both the Primary and Secondary Windings,
and under no circumstances should You exceed those Amperage-Ratings,
actually, it would be a good plan to stay at least ~10% under those Amperage-Ratings
just to keep things cooler and casual.

Anytime You push the rated-limits on any Component,
You generally are shortening it's expected Service-Life, and compromising it's performance,
and possibly even the Service-Life of other connected or related Components.

Poop-Happens ............,
it's guaranteed,
will it destroy your Project when it does ?
.
.
.

 

That is not what I got from a large Transformer Manufacturer, i.e. Hammond Mfg.
Also to quote Maddox,
"When you reverse feed a step-down transformer, you lose the ability to adjust the primary voltage rating to accommodate for small discrepancies in the supply voltage. And if there is more than a 5% variance, the windings will over-excite causing excess heat and energy loss".

Right, but your taps fall to the secondary, with appropriate ratio. Asked an electrician to adjust taps on an auto step up arrangement, which he did. A week later I saw globs of metal dripping out from the enclosure. Turned out he hadn’t cleaned the varnish off the tap before making the connection.

A variance across phases in a multi phase will give you issues.

 

What are the winding details now?
i.e. voltage current of primary and/or secondary?
From this you can calculate the VA (wattage) , normally if you use a transformer in reverse connection, there is a 10% loss/de-rating of the known power rating of the unit.

Thanks, but at this moment there are no details, I am just looking for the "knowledge" to understand what happens with the power rating if a transformer used in reversed. Let's say a transformer like this: (example only) https://www.conrad.com/en/p/block-v...v-ac-50-va-2-08-a-710933.html#productTechData
It says the Output Current is 2A . OK. Now, what if I use this transformer in my inverter? How many amps I can get it out?
I have to understand this because I do not have time to create transformers by myself. That would be too much. But I have to make an inverter (more actually) where the inverter can operate at min. 2amps. So I can add an "EL panel" that would work and not burn down the whole unit. etc. You have my point here.
The second question (again): How does the MOSFET play a part in an inverter? As I watch a tonne of videos where people make inverters or spot welders, and what I see, is they add a lot of MOSFET, they make some "questionable" transformers. But the point is on the MOSFETs as far as I see. So why is that?
I have to understand this guys. Why do I see that, the current mostly depends on MOSFET in such circuits and the transformers are kind of "secondary"? I mean, I do not want to go so deeply into this, as I am not an electrical engineer, I just love to play with it. But, at this time it is even not a hobby, this will be part of my earnings!
I am painting cars and fixing cars at the moment, but I want to spray now something more interesting, called LUMILOR. This is a paint system and very cool. Basically, it is an EL panel, that you can spray onto any surface. I love art, and design and love everything that is NOT original and factory-based. I love creating. I cannot stop myself. They are selling not just the paint system but inverters too. But expensive and I really want to do it myself, as I have to add some extra as well. I am going to add a sequencer driven by an Arduino or ESP-32 etc. And I want to add all this in one unit. Make it very usable, and as small as possible. (I will have another question but that would be a different thread in this forum.)

So how do I know what transformers would be good for my project, if I build something like this: https://danyk.cz/menic230_4_en.html ? or should "just" I duplicate or even add more MOSFETs in parallel to get out more amps? (But with the 2 original MOSFETs I think 2Amps is OK, isn't it?)
I need really practical advice not so much theoretical and ordinary information. LoL
THANK YOU GUYS! I highly appreciate all your help!

Ps.
TEST:
Yesterday I tested out a simple inverter, with a 555 IC around on 600Hz, using a 230V to 2x16V transformer in reverse, and it worked well! Of course, I couldn't add LOAD on the output I have just used my multimeter. I have used 12V instead of 16V and I have got 113V on the output that was perfect on 600Hz for LUMILOR. I am KIND of HAPPY with this but also afraid
of what happens if I paint a 1x1 meter logo on a car that would consume 1.6Amps and I use this test inverter. Would it hold? I read about - as much as I found - the normal iron-cored power transformers that plan to use on 50Hz or 60Hz, are not so good on 600Hz or even a little bit more frequency. But as I see it, it works at the moment, even without any "noise".

 

The main limiting factor is the Wire-Gauge used in each winding.
Calculate the maximum-rated-Amperage for both the Primary and Secondary Windings,
and under no circumstances should You exceed those Amperage-Ratings,
actually, it would be a good plan to stay at least ~10% under those Amperage-Ratings
just to keep things cooler and casual.

Anytime You push the rated-limits on any Component,
You generally are shortening it's expected Service-Life, and compromising it's performance,
and possibly even the Service-Life of other connected or related Components.

Poop-Happens ............,
it's guaranteed,
will it destroy your Project when it does ?
.
.
.

This is basic, and of course, it should be like that. But the point is, I don't want to create a transformer, and "calculating" I wish to use something available on the market. However, there is no such transformer that you can buy to use in a DIY inverter from 2x12V to 110V or 230V. All is 230V to 2x12V! That's what causes me "a little problem" as the power rating is "uncurtain" for me. I hope someone can help to understand this, as I do not wish to "sell" something that I am not 100% sure is good!

 

Has anyone brought up the problems with operating a 60 Hz, steel core transformer at 0.6 kHz to 1.8 kHz?

ak

 

Has anyone brought up the problems with operating a 60 Hz, steel core transformer at 0.6 kHz to 1.8 kHz?

ak

Yes, briefly - middle of post #5
"Used at a higher frequency than specified will mean that there is no danger of saturation, and core losses will be much reduced, but the leakage inductances won't have changed, so the voltage drops across them will be greater at higher frequencies."

 

Thanks, but at this moment there are no details, I am just looking for the "knowledge" to understand what happens with the power rating if a transformer used in reversed. Let's say a transformer like this: (example only) https://www.conrad.com/en/p/block-v...v-ac-50-va-2-08-a-710933.html#productTechData
It says the Output Current is 2A . OK. Now, what if I use this transformer in my inverter? How many amps I can get it out?
I have to understand this because I do not have time to create transformers by myself. That would be too much. But I have to make an inverter (more actually) where the inverter can operate at min. 2amps. So I can add an "EL panel" that would work and not burn down the whole unit. etc. You have my point here.
The second question (again): How does the MOSFET play a part in an inverter? As I watch a tonne of videos where people make inverters or spot welders, and what I see, is they add a lot of MOSFET, they make some "questionable" transformers. But the point is on the MOSFETs as far as I see. So why is that?
I have to understand this guys. Why do I see that, the current mostly depends on MOSFET in such circuits and the transformers are kind of "secondary"? I mean, I do not want to go so deeply into this, as I am not an electrical engineer, I just love to play with it. But, at this time it is even not a hobby, this will be part of my earnings!
I am painting cars and fixing cars at the moment, but I want to spray now something more interesting, called LUMILOR. This is a paint system and very cool. Basically, it is an EL panel, that you can spray onto any surface. I love art, and design and love everything that is NOT original and factory-based. I love creating. I cannot stop myself. They are selling not just the paint system but inverters too. But expensive and I really want to do it myself, as I have to add some extra as well. I am going to add a sequencer driven by an Arduino or ESP-32 etc. And I want to add all this in one unit. Make it very usable, and as small as possible. (I will have another question but that would be a different thread in this forum.)

So how do I know what transformers would be good for my project, if I build something like this: https://danyk.cz/menic230_4_en.html ? or should "just" I duplicate or even add more MOSFETs in parallel to get out more amps? (But with the 2 original MOSFETs I think 2Amps is OK, isn't it?)
I need really practical advice not so much theoretical and ordinary information. LoL
THANK YOU GUYS! I highly appreciate all your help!

Ps.
TEST:
Yesterday I tested out a simple inverter, with a 555 IC around on 600Hz, using a 230V to 2x16V transformer in reverse, and it worked well! Of course, I couldn't add LOAD on the output I have just used my multimeter. I have used 12V instead of 16V and I have got 113V on the output that was perfect on 600Hz for LUMILOR. I am KIND of HAPPY with this but also afraid
of what happens if I paint a 1x1 meter logo on a car that would consume 1.6Amps and I use this test inverter. Would it hold? I read about - as much as I found - the normal iron-cored power transformers that plan to use on 50Hz or 60Hz, are not so good on 600Hz or even a little bit more frequency. But as I see it, it works at the moment, even without any "noise".

The current ratings of the windings remain the same. You have to derate it slightly as the magnetising current is provided by the "other" winding, say 10%.
The biggest problem is the operating frequency. Three times as much as rated you will get away with, but more than ten times, and the inductance will start to cause a problem. The impedance of the leakage inductance, which is in series with the load will now be ten times the original value. Measured off-load, you will not see the effect of the inductance. Connect the load, and the voltage will drop by 10 times the design amount, because the impedance of the series inductance is proportional to frequency.

If you know the leakage inductances, you may be able to use them to your advantage, to limit the output current.

The MOSFET just acts as a switch, and switches the supply voltage in alternate directions across the windings to create the AC.

 

OK ........
Now we find out a little more about what You are trying to do, but only a tiny bit.

If You purchase a standard Toroidal-Core Transformer from someone like Hammond in Canada,
there will be very little, if any, difference in performance regardless of the Frequency used,
( there are limits and trends of course ).

What is actually being done with the high-Voltage being generated ?
Is this for "Electro-Static-Paint-Deposition" ????
In that case, the Currents and Power involved are quite low, and things will be easier, and cost less.

You need to know ALL THE DETAILS of exactly what is actually occurring in the complete process.

If You cannot obtain these details, You are wasting your time, and everyone else's too.

Why are You starting-out with ~12-Volts in the first place ?

You can easily double the Mains-Voltage and turn it into
any Frequency desired, Pulsating-DC or AC, or steady DC, for relatively little expense, ( at low Currents ),
( You can also easily kill yourself in the process ).
.
.
.

 

Just to tie up my point in Post #14 with @LowQCab 's in post #15: A toroidal transformer would have very low value of leakage inductance, making it usable to about 1kHz. An EI-laminated transformer that is concentrically wound would have a much lower leakage inductance than a transformer wound on a two-section bobbin, but would still be more than a toroid. You can measure the leakage inductance by measuring the primary inductance with the secondary shorted out.

 

It says the Output Current is 2A . OK. Now, what if I use this transformer in my inverter? How many amps I can get it out?

At the very most, you could get:

Iout = Iin Vin / Vout

For 12V, 2A in and 120V out you will get 200mA out. But, as others have said you should derate that, so maybe 180mA.

 

OK ........
Now we find out a little more about what You are trying to do, but only a tiny bit.

If You purchase a standard Toroidal-Core Transformer from someone like Hammond in Canada,
there will be very little, if any, difference in performance regardless of the Frequency used,
( there are limits and trends of course ).

What is actually being done with the high-Voltage being generated ?
Is this for "Electro-Static-Paint-Deposition" ????
In that case, the Currents and Power involved are quite low, and things will be easier, and cost less.

You need to know ALL THE DETAILS of exactly what is actually occurring in the complete process.

If You cannot obtain these details, You are wasting your time, and everyone else's too.

Why are You starting-out with ~12-Volts in the first place ?

You can easily double the Mains-Voltage and turn it into
any Frequency desired, Pulsating-DC or AC, or steady DC, for relatively little expense, ( at low Currents ),
( You can also easily kill yourself in the process ).
.
.
.

Thank you for your and anyone else time.
I have shared everything I know and what I need.
This "paint system" requires almost the same voltage and frequency as EL wire/panel. Same technology.
Which could be between 50Hz till 1800Hz but 600Hz is recommended and on 110V AC.
So this is what I need to achieve. Power consumption for 1inch³ lighted area is 1mA.

I see now, why the normal transformers are not sufficient or even unusable. Toroidal could be the solution, I understand.
They are even more expensive like a fully workable "cheaper" type of EL inverter

I am starting with 12V as mostly I will apply this paint onto bikes and cars
I understand, there are boost converters, DC-DC I have been using them for years in my other projects. So basically, using 12V is not that important. Only important because creating something with fewer parts always could be, hm.. better?

There is something else that I do not understand. Here is this EL panel chip: HV823 for instance. It is 4x5mm only, and itself capable of creating not just a frequency but the 70-80V AC that is enough for EL panels. Not to mention it, works from 1.5V to 12V easily. It can lit up a EL panel about 3-12inch³ area by itself! Well, almost itself. Some parts need, not much next to the chip.
So, if that is so, why do I need transformers at all in my inverter, if that can be achieved another way? Like this chip? Someone created this chip, didn't it?
Would it be possible to make such a circuit that would be able to drive the EL panel in my case the Lumilor paint system without a transformer?

Summary: I need to create 110V AC from 12V DC on 600Hz (maybe adjustable way till 1800Hz) at min. 2Amps loadability.
Like this: https://el-technik.de/Leuchtfolie/El-inverters.html They are just a bit expensive. But I think I buy the 95 euros one and check it out inside and see how they achieved it! It seems to impossible me, I am not able to find a circuit diagram on the whole internet I cannot believe this

Note: Maybe I don't understand fully transformers, but I have done some 100 projects during the last 30 years, and I know what I am doing otherwise. Thank you for your concern for my health Mostly I made light effects, some Arduino projects, cars, etc. I am not so good in AC

 

At the very most, you could get:

Iout = Iin Vin / Vout

For 12V, 2A in and 120V out you will get 200mA out. But, as others have said you should derate that, so maybe 180mA.

Thank you I totally see it now. Iron core transformers are not the solution.

 

Thank you I totally see it now. Iron core transformers are not the solution.

Air-cored transformers are definitely not the solution.
All ferromagnetic material will behave the same.