Hi Thanks for reading.
Just saw a video where a woman claimed to raise the va of a transformer by removing the secondary windings of the transformer and replaced with much thicker enamled copper cable.
Is it that simple to raise transformer va? Simply count the number of secondary windings, replace with thicker cable, measure with voltmeter to make sure the voltage is correct?
Thanks
Just saw a video where a woman claimed to raise the va of a transformer by removing the secondary windings of the transformer and replaced with much thicker enamled copper cable.
Is it that simple to raise transformer va? Simply count the number of secondary windings, replace with thicker cable, measure with voltmeter to make sure the voltage is correct?
Thanks
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Like the old saying goes, no such thing as a free lunch. Maybe you could get a bit more power if the core was conservatively rated... But the core size is what sets the VA.
As the previous poster said, TANSTAAFL...Increasing the secondary wire size might help eke out some more power, but the primary wire size stays the same size, and will dissipate more power as a result of the increased load. Proceed cautiously. One of my colleagues at work tried to draw 1kW from a 500VA transformer, and was rewarded with the characteristic smell of overheated kraft paper and transformer varnish. Think burning paper bags dipped in varnish, and you get the general idea.
True, very much, but i love free lunches and also massive transformers are expensive and this is diy audio after all.
Woild love some comments, is it the thickness of the primary that is of importance.
The transorformer i want is 8 volts secondary and they are difficult to purchase in high va, trying to mod a 15volt transformer.
I have the norateel ta225/15, labelled as 15v 7.5a dual secondary. Does this mean if i parallel both secondaries i get 15v 15a.
Also, if i remove some of the windings to get down to 8v the current should go up, will it double since the voltage has halved.
Sorry, i know it sounds like i am not listening but i genuinely am, would love some more information.
Thanks
Woild love some comments, is it the thickness of the primary that is of importance.
The transorformer i want is 8 volts secondary and they are difficult to purchase in high va, trying to mod a 15volt transformer.
I have the norateel ta225/15, labelled as 15v 7.5a dual secondary. Does this mean if i parallel both secondaries i get 15v 15a.
Also, if i remove some of the windings to get down to 8v the current should go up, will it double since the voltage has halved.
Sorry, i know it sounds like i am not listening but i genuinely am, would love some more information.
Thanks
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Yes.
In theory you could get 225VA / 8V = 28A. But in practice you would need larger wire size on the secondary. Or split the current secondary into four parallel windings and keep same wire size.
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Thanks.
Not sure what stock gauge the wire is, what gauge would you recommend to get the current up to 28A.
I only need a single secondary, if i were to rewind the secondary with thicker wire would you recommend winding dual windings or more, is there an advantage to paralleling multiple secondaries.
Not sure what stock gauge the wire is, what gauge would you recommend to get the current up to 28A.
I only need a single secondary, if i were to rewind the secondary with thicker wire would you recommend winding dual windings or more, is there an advantage to paralleling multiple secondaries.
One advantage to parallel windings could be that you don't have to use very thick wire (easier to wind). I would measure stock gauge first. It is recommended to keep copper losses about the same on primary vs secondary, so it's not good to deviate much from original design. I.e. you need to calculate how many A/mm^2 the original secondary winding is and approximate when changing to larger gauge.
You will keep VA, so lowering voltage will increase current prportionately, V*I product will stay the same.
Obviously, to be able to use added current capability you will need proportionately increased wire area/section.
And as said above, commercial winders are no fools and know their business, so they even all 3 table legs: core capability, primary and seconday resistive loss.
You can´t increase "just one" on its own.
Now on "you tube designers", forget them.
28A @ 3A/mm^2 (I wouldn´t go above that) means 9.33 sq mm area so 3.44 mm diameter. Call it 3.5mm .
It will be VERY hard to wind so choose 2 x 2.50mm diameter wires (about as thick as can be wound by hand) or better 4 x 1.75mm wires , later connected in parallel.
Be careful to wind **exact** number of turns, just 1 more or less will become a nasty shorted turn, your transformer will buzz and overheat for no visible reason..
EDIT: simulposted with johan 🙂
Obviously, to be able to use added current capability you will need proportionately increased wire area/section.
And as said above, commercial winders are no fools and know their business, so they even all 3 table legs: core capability, primary and seconday resistive loss.
You can´t increase "just one" on its own.
Now on "you tube designers", forget them.
only advantage is practicity, 28A is a lot of current, will require VERY THICK wire which will be hardto wind, specially since you have no commercial/professional winding equipment.
28A @ 3A/mm^2 (I wouldn´t go above that) means 9.33 sq mm area so 3.44 mm diameter. Call it 3.5mm .
It will be VERY hard to wind so choose 2 x 2.50mm diameter wires (about as thick as can be wound by hand) or better 4 x 1.75mm wires , later connected in parallel.
Be careful to wind **exact** number of turns, just 1 more or less will become a nasty shorted turn, your transformer will buzz and overheat for no visible reason..
EDIT: simulposted with johan 🙂
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No doubt transformers are optimized, there is no VA gain to expect from a mod.
As said, and details are given. Among optimization rules, copper loss is made equal to iron loss.
60Hz versus 50Hz certainly matters, at least for large transformers.
Moding one for the other, makes sense but you really must know what you are doing.
I remember some of those tedious transformer computations, but rather forget about it and would buy the right gear.
As said, and details are given. Among optimization rules, copper loss is made equal to iron loss.
60Hz versus 50Hz certainly matters, at least for large transformers.
Moding one for the other, makes sense but you really must know what you are doing.
I remember some of those tedious transformer computations, but rather forget about it and would buy the right gear.
The transformer VA rating is given for some particular conditions, for example when used in still air at 20C. It's all about how much heat will build up inside it, and what the max temp rating is for the insulation, etc. There is a simple "solution": put it in a a much colder environment.
Buy yourself a cooler, drop in some dry ice, add your transformer, let it cool off for a while, and you are good to go. For greater effect, use liquid nitrogen to "cryo cool" the transformer.
I think that buying a new and higher VA transformer will be the most judicial route to the goal you seek!
Buy yourself a cooler, drop in some dry ice, add your transformer, let it cool off for a while, and you are good to go. For greater effect, use liquid nitrogen to "cryo cool" the transformer.
I think that buying a new and higher VA transformer will be the most judicial route to the goal you seek!
Transformers are optimised for price of production, not power density.
While good E-cores have the winding window completely filled with copper (+ insulation), many toroids have lots of open space in the middle. The winding machines have to fit a loaded spool inside, then unwind it before removal.
With hand winding you can completely fill that window and get more power out. This is lots of work and only done for special use cases, with audio probably none of them.
Some toroids have so much space left, you could fit another primary + secondary on, for maybe 150% VA. Not 200% because heat transfer from the inner windings is hampered by the outer.
While good E-cores have the winding window completely filled with copper (+ insulation), many toroids have lots of open space in the middle. The winding machines have to fit a loaded spool inside, then unwind it before removal.
With hand winding you can completely fill that window and get more power out. This is lots of work and only done for special use cases, with audio probably none of them.
Some toroids have so much space left, you could fit another primary + secondary on, for maybe 150% VA. Not 200% because heat transfer from the inner windings is hampered by the outer.
Thanks!
Had an idea.
Since the stock value is dual 15v secondaries and i want about half that which is 8v, how about cutting the secondary at the half way point and making four secondaries next to each other, this doubles the wire thickness as well.
Is this okay, and what is the best way it should be done.
Had an idea.
Since the stock value is dual 15v secondaries and i want about half that which is 8v, how about cutting the secondary at the half way point and making four secondaries next to each other, this doubles the wire thickness as well.
Is this okay, and what is the best way it should be done.
It works if you are able to split them in four windings with equal amount of turns. Best way? I imagine there can't be many ways to do it. Count very carefully, cut very carefully so you don't scratch isolation on other turns, solder wires on and Bob's your uncle.
Possible in theory, hard in practice.
1) You need to find the*exact* center of the winding, with not even 1 turn error allowed, easier said than done.
2) that point will usually be buried deep inside the winding.
3) IF you want to go that route, *fully* unwind secondary and carefully rewind counting turns.
Even that has a problem: if you extend unwound wire, you´ll get, say, 16 meters of wire.
If you cut it in half, *internal* 8 meters will give you "about" 20% more turns than outer one, because as you wind length-per-turn becomes longer, because turn diameter increases in and one, by 1 "wire diameter" each layer.
No big deal for a commercial winder (like me) who has a large spoool of fresh wire by the winding machine, but how will you wind 2 exact same turns and voltage windings when you do not know beforehand where to cut already available wire?
Trick of the trade:
a) fully unwind secondary.
b) extend wire (maybe on the street)
c) bend it in half
d) wind bifilar , holding both wires side by side in your hand. Not too difficult to do neatly and practice makes perfect.
Only GUARANTEE that both windings will have exact same length and , more important, exact same turns.
Good luck and post results.
Thanks for the replies, much appreciated
Got some enameled wire now.
So far: the toroid transformer has two 15volt secondaries. I have taken turns off each secondary to give me the required 8 volts.
Now with so much wire removed the toroid is half empty. Since it is good practice, should I spread out the secondary turnings to cover the empty surface.
I want to keep the voltage at 8volts but raise the current by making another secondary, can I wind it over the two secondaries already present. Just this post here states winding more secondaries will not raise current.
https://www.diyaudio.com/forums/power-supplies/299824-toroidal-transformer-rewind.html
What should i do.
Thanks.
Got some enameled wire now.
So far: the toroid transformer has two 15volt secondaries. I have taken turns off each secondary to give me the required 8 volts.
Now with so much wire removed the toroid is half empty. Since it is good practice, should I spread out the secondary turnings to cover the empty surface.
I want to keep the voltage at 8volts but raise the current by making another secondary, can I wind it over the two secondaries already present. Just this post here states winding more secondaries will not raise current.
https://www.diyaudio.com/forums/power-supplies/299824-toroidal-transformer-rewind.html
What should i do.
Thanks.