# Design for replacement of windings of a transformer for reducing the thickness

Discussion in 'The Projects Forum' started by ancilcleetuschirayath, Jan 3, 2014.

1. ### ancilcleetuschirayath Thread Starter New Member

Jan 2, 2014
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For using a different gauge wire in a transformer winding(by using parallel windings of less thickness), is there any design equations or methods?
Do we need to match the resistance and inductance of the designed winding with the equivalent windings in parallel?
How can we measure the inductance if transformer is working at 100kHz frequency with a ferrite core?

2. ### bountyhunter Well-Known Member

Sep 7, 2009
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508
It depends on a lot of things. I designed switching power supplies for about 25 years: even though I knew how to design transformers, we still used an outside house to do them for us. If the winding you are asking about is the primary winding, it has to have enough winds to have a specific amount of inductance but it must not create too much flux density in the core (max for ferrite is around 3k gauss). The secondary windings have to go on after the primary.

There are a lot of physical considerations in designing a transformer, to maximize coupling between windings and reduce leakage inductance. You also need insulation between layers.

Selecting the best core, winding thickness, layout etc is something that experience teaches.

3. ### bountyhunter Well-Known Member

Sep 7, 2009
2,498
508
If you mean the primary inductance, it's done by setting up a tester that switches a FET to put a voltage across the winding. Then look at the current ramp up through the winding, and the inductance is given by:

V = L di/dt

Since you know the applied voltage and are measuring the current ramp rate, that gives the inductance.

4. ### DickCappels Moderator

Aug 21, 2008
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A small question about the premise: How much space to think you will save? The ratio of copper area to winding area is constant because of the shape, so I would not expect any advantage. It might even be a disadvantage because you would have two sets of enamel insulation.

They make flat wire for the advantage you are looking for, but even moving to that you might not be able to change the core size because unless you have very deep pockets, you will have to use a standard core size. To maximize efficiency, cores come with fixed ratios of core area to copper area, so reducing the copper are, your efficiency will go down.

There are other reasons for using finer wired, but I wonder whether this is one of them.

Please Don't take this as criticism, please understand that I am just concerned that you might go all through this and not obtain the desired benefit.

By the way, what is the circuit topology that you are working with?
There might be other ways to reduce the core size.