Related to coil winding basics question

[milind.a.kulkarni]

Hello To all,

I have one fundamental doubt - In case of AC winding used in machine like transformer coils used in primary or secondary winding ..... if there is a multi-turn coil need to be used ( most practical scenario) ..... What is the proper method of winding ?..... I had seen lot of videos on this but .....I have following doubt....

- In the videos - In the winding of the coil...... the winding of the first layer, turns are wound from bottom to top..... and then in next layer of the winding....the turns of the winding are wound from top to bottom.....Is this is right way ?

- Or do we need to maintain the direction of winding same .... I mean if we wound the first layer Let say from bottom to top direction...... then for next layer..... every time take a single cross winding thread down to bottom...... and wind the next layer of winding from bottom to top again....

Please share your valuable review on this...

Thanking you in advance....

With regards,

Milind

 

[FvM]

Winding back and forth, no cross-windings as far as possible.

 

[milind.a.kulkarni]

Hi FvM,

You mean to say if we are winding turns for layer-1 from say bottom to top then layer-2 of winding turns should come from top to bottom and process continues....did I catch u correctly ?

I am attaching one image - can you tell me what is right Case-1 or Case-2.



with regards,

Milind

 

[BradtheRad]

The articles I have seen recommend that you pack the turns closely together (as Case 1). The idea is to not allow room for wires to shift and vibrate, etc.

If you use Case 2, then that creates regions of empty space throughout the layers. This is undesirable because it reduces efficiency.

Furthermore with Case 2, you have one wire crossing perpendicular to many wires. Eventually, if vibrations cause rubbing of wires against each other, this could result in varnish wearing through at a point of contact. The result will be a short circuit between windings. Just one shorted winding can make the transformer useless.

Helpful info is at this link:

https://ludens.cl/Electron/trafos/trafos.html

 

[kripacharya]

Two criteria are affected with the different styles of winding :

The interwinding voltage difference can become quite large with bottom-top/ top-bottom style. I.e. once you reach the bottom again, the p.d. between the windings at this point is the highest. However with bottom-top/ bottom-top this p.d. remains constant, and lesser than the max of the other method. This is important where high voltages & insulation is a concern.

Next, it has also been shown that the inter-layer capacitance charge is lesser with bottom-top/ bottom-top method. Leading to a better 'ideal' transformer.

 

[Venkadesh_M]

ya may be there is a small change in capacitance but I think crossing a line could make a winding size a little bit more because a single wire crosses more times....

 

[kripacharya]

ya may be there is a small change in capacitance but I think crossing a line could make a winding size a little bit more because a single wire crosses more times....

Yes it would make it marginally thicker. But for a given application, functionality might be more important than size.

 

[Venkadesh_M]

Yes it would make it marginally thicker. But for a given application, functionality might be more important than size.

These are very tiny factors, and also the winding machine design is some more complicated in both manual and automatic and there may be breakage of conductors while winding in jerky movements these are also can be considered..........

 

[kripacharya]

Like i said, it depends on the application. For a power transformer working at 50Hz this may be a non-issue. But for a broadband signal transformer working in the VHF/ UHF region it might be a very important consideration and not a tiny factor at all.

Secondly, for power applications which are also by nature higher voltage applications, the method also reduces the interwinding p.d. This implies that a lesser/ thinner insulation can be used, and hence mitigates the effect of the extra cross-over winding.

 

[Venkadesh_M]

Ya it depends application also.........

 

[kripacharya]

These are very tiny factors, and also the winding machine design is some more complicated in both manual and automatic and there may be breakage of conductors while winding in jerky movements these are also can be considered..........

Practical manufacturing issues & economic consideration of course must always be weighed when doing a complete design.
But it's not clear to me why there would be a jerky movement or breakage ? Surely a properly designed system would not do this ?

 

[FvM]

The interwinding voltage difference can become quite large with bottom-top/ top-bottom style. I.e. once you reach the bottom again, the p.d. between the windings at this point is the highest. However with bottom-top/ bottom-top this p.d. remains constant, and lesser than the max of the other method. This is important where high voltages & insulation is a concern.

Next, it has also been shown that the inter-layer capacitance charge is lesser with bottom-top/ bottom-top method. Leading to a better 'ideal' transformer.

Sounds good, but only in theory. I presume the question is about general transformers, not special devices like RF transformers. For RF transformers, a number of special winding techniques is in use. Snellings "Soft ferrites" has a complete chapter about the "properties of windings" discussing this stuff.

But do you know transformer handbooks that suggest the said "ideal" technique for standard transformer?

Regarding voltage strength, layer insulation is the usual method for windings above a certain voltage limit.

 

[Venkadesh_M]

Practical manufacturing issues & economic consideration of course must always be weighed when doing a complete design.
But it's not clear to me why there would be a jerky movement or breakage ? Surely a properly designed system would not do this ?

No machine is perfect and I mean It increases the chance of failure when machine in operation...

If the coil size increases the size of transformer also increases so the leakage reactance and eddy current loss will also increases and also which affect the size of the compact sized equipments (If you considered about application)...

 

[milind.a.kulkarni]

Two criteria are affected with the different styles of winding :

The interwinding voltage difference can become quite large with bottom-top/ top-bottom style. I.e. once you reach the bottom again, the p.d. between the windings at this point is the highest. However with bottom-top/ bottom-top this p.d. remains constant, and lesser than the max of the other method. This is important where high voltages & insulation is a concern.

Next, it has also been shown that the inter-layer capacitance charge is lesser with bottom-top/ bottom-top method. Leading to a better 'ideal' transformer.

Hi kripacharya;

First of all many many thanks for such a knowledgeable response.....

So in my picture your thought is case-2 meaning bottom-top / bottom-top should be better design ..... If I catch you correctly.....

Now...... Let me phrase here the purpose of asking this question - I went to the winder who dose the winding of the Induction motor ......Now in that case of induction motor winding the way that he was doing for the coils expected to be put across the poles of the induction motor ....he was taking one thread down and winding once again for bottom to up layer wise..... I ask him the reason.... he was not able to answer .....except telling two things....
1) if they do not follow this method of winding then motor become hot and even winding get burned in some cases.....especially true with higher HP of motor....
2) The gauge of wire that they get for winding are many times different from the market than the original gauge of wire used for winding....because of vendor problems and even the insulation on wire also changes ......
However this look really non-technical reason but may be works in particle scenarios.....I was trying to co-relate his views on method that he is following.... then I went and saw some videos of how the transformer and induction motor winding machine works.. .... and they follows bottom-to-top and top-to-bottom method.... where my understanding was it is because of simplicity of the mechanism used in winding machine .....I also read some material on winding techniques too ..... but I was not able to get any clear answer....

Please share your views on this will help me ( all of us) for better understanding of reason and proper methods....

with regards,

Milind