Amount of tape to manufacture form coils 1

[pirulo]

Dear All

We are trying to develop a good procedure to calculate the amount of tape (in length) necessary for one form coil, so if you have some good guide lines about it will be good.



Thanks for the Inputs and best regards

Pirulo

 

[electricpete]

Just thinking out loud, for half-lapped tape, it seems like it should be:

Tape Length per coil = 2*CP*NL / W
where
CP = Coil perimeter
NL = number of layers (half-lapped)
W = width of tape

(Sorry if this is obvious or you were looking for something more exact.)


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[electricpete]

Sorry, that is not even a good guess. One clue is the units don't work out. There are two different coil perimeters... one going all the way around the diamond, another going the short distance around the coil - both need to be accounted for.

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[electricpete]

Here’s a better guess, but still a guess
Tape Length per coil = 2*DP*NL * CP / W
where
DP = Diamond coil perimeter travelling all the way along both slots and both eendwindings
CP = Coil perimeter = 2*w*h of coil cross section
NL = number of layers (half-lapped)
W = width of tape

It seems like the CP/W term accounting for distance travelled along coil per wrap could be enhanced.

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[pirulo]

Thanks for the answer pete,

I will suggest add 10 % to allow for greater lapping around the the leads and knuckles

So the Pete´s formula is converted to :

Tape Length per coil = 2.2*DP*NL * CP / W

where DP = Diamond coil perimeter travelling all the way along both slots and both eendwindingsCP = Coil perimeter = 2*w*h of coil cross sectionNL = number of layers (half-lapped)

Pirulo

 

[electricpete]

Thanks. I agree with your correction.

Also I think with a little trig I can get closer to the ideal experession. Let me work on that some more.

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[electricpete]

I thought some more and I am happy with the equation as is (with your correction).

If instead of normal spiral half-lap wrap, you examine an idealized version it is simpler to see. The idealized version would be short strips of length CP wrapped around the cirfumference to form a loop. Then next loop overlaps the previous loop by a half tape width. It is easy to see the expression would apply to this ideal geometry. And you have two thicknesses of tape on the entire surface of the coil (neglecting gaps).

Now instead look at a real half lap with spiral, you still have two thickness of tape at all points on the coil, so you still have the same total volume of tape, so you must have the same length of tape and the equation above is correct.

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[Younsi]

Pirulo,
I am not sure what you are trying to achieve with this formula. If it is to assess your need for purchasing of tape, I think your formula and Pete's improved approach is ore than precise.
If it is for quality control and consistency in insulation build, I suggest you try on a test coil or two to reach your desired build and then figure out the mica tape weight applied. We used this in the past and mica+glass+resin weight seems to be the best indicator and predictor of coil insulation final compactness and consistency after bake and cure.
Good luck

 

[petronila]

Hi Pete and Pirulo

Only one Note: Coil Perimeter = 2*W*H I think is

Coil perimeter is : 2*(W + H)

Regards

Carlos

 

[electricpete]

You are absolutely correct Carlos. Thanks.

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