Segmented Coil?

[Vietti]

I have wound a number of small, 1"x1", ignition coils for my magnetos with spotty success. I wonder if anyone has experience with winding segmented Coils in this application and would be willing to share their knowledge?

I realize this may not be of interest to very many members here, so if you like respond with a personal message.

Thanks

 

[petertha]

I'm not sure if this is relevant or even close to what you are after, but Ken has done some coil work. I emailed him on occasion & although English is not is first language, he did reply.

http://modelicengine.la.coocan.jp/kinner index.htm

 

[dsage]

Segmented coils are abound on Ali Express. Search for what you see below. At that price for sure it's not worth winding you own. I just bought several to experiment with a CDI design I'm working on.

Or if you want more info on winding your own:
Find a copy of "Model ignition coils and magnetos in miniature" by Bob Shores. A real wealth of information on winding your own coils. I wound ONE from the book (Only one). It's a real problem winding 20,000 turns of something like #38 wire on a bobbin. So I won't do it again. But good luck. I just use Ford COP coils now.
Green twin made mention of the book here. It may still be available from Village Press.
https://www.homemodelenginemachinist.com/threads/bob-shores-model-engine-ignition-book.35714/
A really good book.

 

[mrehmus]

Segmented coils are abound on Ali Express. Search for what you see below. At that price for sure it's not worth winding you own. I just bought several to experiment with a CDI design I'm working on.
View attachment 163607
Or if you want more info on winding your own:
Find a copy of "Model ignition coils and magnetos in miniature" by Bob Shores. A real wealth of information on winding your own coils. I wound ONE from the book (Only one). It's a real problem winding 20,000 turns of something like #38 wire on a bobbin. So I won't do it again. But good luck. I just use Ford COP coils now.
Green twin made mention of the book here. It may still be available from Village Press.
https://www.homemodelenginemachinist.com/threads/bob-shores-model-engine-ignition-book.35714/
A really good book.

Yes, the Ford coils are cheap and good.

 

[Ken I]

The logic behind segmented coils is to keep down the potential difference between windings.

Let's say we want 20kV off 20000 turns over ten layers - so that's 2kV per layer - if we wind one layer perfectly (good luck with that) over the other by the time we get back to the beginning of the first layer then we have a 4000V difference - wire lacquer isn't going to cut it.

In above example the anypoint difference between two layers will be 4000V. And that's if you wind it perfectly - if you hand wind on a lathe, you might end up with two wires crossing from as far as 5 layers apart - 10000V difference (or worse) ARRGGHHHH !

You can add inter-layer insulation sheets or use DCC (Double Coated Cotton) wire to increase the anypoint interlayer insulation resistance and / or by segmenting the coils into a series of short in series coils.

So if we only wind one tenth of the length per segment as a series of 10 segmented coils of 200V per layer giving an anypoint difference between layers of 400V vs 4000V = more segments less voltage needs insulating.

It doesn't use any more wire but does occupy a slightly greater length in the inter segment divider insulation.

Apologies if I'm teaching you to suck eggs - but others might like to know the logic behind it.

Double coated cotton provides more gap between windings and is usually vacuum impregnated with lacquer - such as GE Glyptal - and cured before use - the cotton (usually Dacron) merely provides the latticework for the lacquer rather than insulation per-se.

Example:

My drawing for a 120kVA 200kHz induction heater feedback choke.

Regards, Ken I

 

[SmithDoor]

I have wound a number of small, 1"x1", ignition coils for my magnetos with spotty success. I wonder if anyone has experience with winding segmented Coils in this application and would be willing to share their knowledge?

I realize this may not be of interest to very many members here, so if you like respond with a personal message.

Thanks

I have look at Microwave transformer s.
Then outside is about 9,000 volts . The takeout low voltage side and rewind it for new voltage.

Dave