# How do I find Mutual Inductance of 2 parallel coils with fields aiding each other?

Discussion in 'The Projects Forum' started by electronice123, Jul 6, 2009.

1. ### electronice123 Thread Starter AAC Fanatic!

Oct 10, 2008
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I am trying to learn how to figure out the mutual inductance of the following but do not know how to do so.

2 Inductors in parallel with fields aiding?

2 Inductors in series with fields aiding?

Can mutual inductance be measured? Or does it have to be calculated?

If it has to be calculated how does one find the coupling coefficient to be able to calculate it. (I have no information on the inductors as I made them myself)

Any help will be appreciated!!! Thanks!

2. ### studiot AAC Fanatic!

Nov 9, 2007
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If you have two physically separate inductors

This could be a rope trick question.

In other words how will you allow for the degree of coupling?
This is why you are probably finding a shortage of information.

3. ### electronice123 Thread Starter AAC Fanatic!

Oct 10, 2008
311
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The mutual Inductances I am trying to figure out are as follows:

The first is a primary and secondary of a transformer (parallel with fields aiding)

The second is just 2 inductors wound together on the same core (and connected in series with fields aiding)

I just can't seem to find any good information that can tell me how to figure out what the coupling coefficient (k) is.

4. ### studiot AAC Fanatic!

Nov 9, 2007
5,003
523
Hopefully you don't actually mean this?

Is this a power transformer or an RF transformer?

We don't usually work in terms of inductance for transformers, but work instead directly in terms of the Fluxes, currents and EMFs.

The mutual Inductance M = (L1-L2)/4

5. ### beenthere Retired Moderator

Apr 20, 2004
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This is Stan Meiyer's voltage intensifier circuit. The theory is a bit odd...

Last edited by a moderator: Sep 27, 2009
6. ### DickCappels Moderator

Aug 21, 2008
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1,798
The inductance will be a strong function of the leakage inductance between the two widnings. The only reliable method of determining the inductance would be to measure it.

Simulations might get you pretty close, but it would take a lot of work to develop the correct input for the simulator.

Generally, people tend to avoid connecting the primary to the secondary of a transformer.

The voltage intensifier looks like very strange flyback converter.

7. ### studiot AAC Fanatic!

Nov 9, 2007
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Overunity

I'm out of here.

Last edited by a moderator: Sep 27, 2009
8. ### electronice123 Thread Starter AAC Fanatic!

Oct 10, 2008
311
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Funny that people think this transformer is overunity, it is no such thing.

I personally don't believe in overunity devices.

I think this can be built, the problem is it's the exact opposite of everything taught in electrical engineering so it's very hard to understand.

In the end, if the transformer is built right the output is a constant (not pulsed) high voltage.

It's tricky, very tricky, but I know first hand people who have built them successfully.

Seems like I'm on my own on this one.

Thank you all for the comments though!

9. ### beenthere Retired Moderator

Apr 20, 2004
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295
I seem to recall that the core and winding directions are reasonably complete, so you have some guide. The stuff about using stainless wire is just horse pucky. If it works, it will work with copper wire.

For experimental purposes, you might want to use a capacitor to develop the voltage on. I think the theory is pretty shaky, so I would use an AC rated cap, or two DC capacitors in series with two terminals of the same polarity connected to one another. This makes the pair of capacitors able to handle AC, or DC of either polarity.