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How to modify a toroidal transformer windings?

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J_Nichols

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I have a toroidal transformer which has one input of 220 Volts AC, and 2 secondary outputs of 40 volts AC each one.

I want to modify it to have two 220 volts outputs instead the two 40 volts outputs that it has at the moment.

I would assume that it's a very easy task and I have just to modify the windings, but I have no prior experience. How do I should modify it?
 

Nigel Goodwin

Super Moderator
Most Helpful Member
I have a toroidal transformer which has one input of 220 Volts AC, and 2 secondary outputs of 40 volts AC each one.

I want to modify it to have two 220 volts outputs instead the two 40 volts outputs that it has at the moment.

I would assume that it's a very easy task and I have just to modify the windings, but I have no prior experience. How do I should modify it?
You would assume wrong :D
 

MaxHeadRoom78

Well-Known Member
You first need to wind a test wind of say 10 turns, this will tell you the turns/volt.
But other that a small addition/reduction or small overwind, once you get into many scores of turns it becomes Very difficult on a Toroidal.
For complete/major rewind, the EI is easier if you can remove the laminations and rewind the Bobbin.
Max.
 

J_Nichols

Member
You first need to wind a test wind of say 10 turns, this will tell you the turns/volt.
But other that a small addition/reduction or small overwind, once you get into many scores of turns it becomes Very difficult on a Toroidal.
For complete/major rewind, the EI is easier if you can remove the laminations and rewind the Bobbin.
Max.
So you suggest that I use the EI transformer type.
I have a tiny E E transformer at home. It's not EI, but it's very similar. It has only E laminations, but each one is in opposite direction, so at the end you have like an EI core.

Just one question... If I have an opened transfomer... Imagine an E (without I). The transformer will work or not? Do I need to close the path?
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Well, so.. now I know it's difficult. Can you explain me how to do it?
Sorry for the brief reply, but I was in the process of leaving work :p

As for how to do it - I would say it's near impossible.

Assume 10 turns per volt, then you need 2200 turns per winding, and two windings.

Go to the grocery shop and buy a bagel - now try and wind 4400 turns of wire through and round the bagel :banghead:

It's a job for a specialist machine, and I can't even understand how they work?.

As already suggested, a conventional transformer is far easier to do - but still pretty tricky due to the high voltages and resulting high number of turns required.

What are you wanting to do with the transformer?, what power do you require?, and why can't you buy one?.

Another option is 'DIY transformers' - these come with a pre-wound mains primary, and you wind the secondary yourself.
 

J_Nichols

Member
Sorry for the brief reply, but I was in the process of leaving work :p

As for how to do it - I would say it's near impossible.

Assume 10 turns per volt, then you need 2200 turns per winding, and two windings.

Go to the grocery shop and buy a bagel - now try and wind 4400 turns of wire through and round the bagel :banghead:

It's a job for a specialist machine, and I can't even understand how they work?.

As already suggested, a conventional transformer is far easier to do - but still pretty tricky due to the high voltages and resulting high number of turns required.

What are you wanting to do with the transformer?, what power do you require?, and why can't you buy one?.

Another option is 'DIY transformers' - these come with a pre-wound mains primary, and you wind the secondary yourself.
Thanks for the reply.
Of course, after reading the comments I think toroid transformers are difficult to modify.

I'm just experimenting, like a hobby. Nothing special. I have bought the step down toroid I have.

What about 'DIY transformer'? There is a kit or something like a kit that I can assemble myself?

I need around 100 watts.
 

MaxHeadRoom78

Well-Known Member
I have found when adding small overwinds on Toroids it runs from anywhere from 1.5turns/volt to a max of 4 or 5.
5 is usually more prevalent on EI type.
AFAIK the machine uses a bobbin principle for winding Toroids.
Max.
 

KeepItSimpleStupid

Well-Known Member
Most Helpful Member
The most I wound was 80 turns. You can measure the primary resistance using the Kelvin technique. Using the resitance, cross-sectional area, resistivity and get the length. So you could figure out what a 220-40 volt winding is.

Your winding wouldbe bi-filar or two together.

A long flat "stick" with the wires wound initially on it is then passwd through the core.

There are some calculators that can help. You want a uniform wind spacing at least per layer.

Its much easier to have a custom transformer made. I did it once.

Torroidal transformers are easy to customize.
 

JimB

Super Moderator
Most Helpful Member
To see toroid winding machines in action, look here:



JimB
 
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