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Author Topic: Measuring Amps on output coils  (Read 27627 times)

MarkE

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Re: Measuring Amps on output coils
« Reply #45 on: March 25, 2015, 06:19:30 PM »
Yes-bad wording on my behalf.
This is true some what.While it cant be switched off, an alnico's magnetic field can be flipped quite easly,and without much power to do so.
Do you know why the Ecore keepers will not stay together without the shorted coil?,the answer is quite interesting--odds and evens. ;)
The ferrite material has a very low remnant magnetization.
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The coil in that demonstration was not a good design. There is no need for two sepperate coil's. You need only one coil wound in a partiqular way. My PMH that was the same Ecore design(smaller Ecore),but with a coil wound this certain way,was able to maintain it's bonding for over 11 minutes. I believe a larger gauge wire would have seen this time increase,due to less resistance.
It is the ratio of resistance to inductance that matters.  It scales with the window area of the bobbin, AC and the fill factor, KFILL_FACTOR:

number of turns: n = KFILL_FACTOR*AC/AWIRE
L = K1*n2  = K1*KFILL_FACTOR2*AC2/AWIRE2
R = K2*n/AWIRE = K2*KFILL_FACTOR*AC/AWIRE2

L/R = K1/K2*KFILL_FACTOR*AC 

You can increase L/R by using a cores with the same length per turn but larger winding area, IE a longer bobbin, using wire with thinner insulation as a proportion of the wire cross-section area, or by going with square wire instead of circular wire.  So, large gauge, square magnet wire is the best choice, followed by large guage, round magnet wire.  But it only improves a percent or two per wire gauge step.
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I really think there is something that can be had from the PMH.
There is:  Stored energy actuators.  People have been building them for about 100 years that I know about. 

tinman

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Re: Measuring Amps on output coils
« Reply #46 on: March 26, 2015, 02:00:46 AM »

 
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The ferrite material has a very low remnant magnetization
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 No-thats not it. If you remove the center leg so as the core now has only one single loop,the two core halves will stay together for years. You need to look a little closer to the path that the magnetic currents can travel(if we can call them magnetic currents).

Remnant magnetism is also an incorrect term,as that is not what it is.

Remnant-1.a part or quantity that is left after the greater part has been used, removed, or destroyed.

MarkE

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Re: Measuring Amps on output coils
« Reply #47 on: March 26, 2015, 05:29:45 AM »
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 No-thats not it. If you remove the center leg so as the core now has only one single loop,the two core halves will stay together for years. You need to look a little closer to the path that the magnetic currents can travel(if we can call them magnetic currents).

Remnant magnetism is also an incorrect term,as that is not what it is.

Remnant-1.a part or quantity that is left after the greater part has been used, removed, or destroyed.
There is a field.  There is not a flow.  Low remanence material like ferrite will have very little force without a sustaining current.

tinman

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Re: Measuring Amps on output coils
« Reply #48 on: March 26, 2015, 10:52:20 AM »
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There is a field.  There is not a flow.

I disagree.I (like verpies) have done many test over many hours with the PMH. If there is no flow,then why will a U core retain this magnetic field,while an E core of the same ferrite will not?(both without the coil shorted)

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Low remanence material like ferrite will have very little force without a sustaining current.
Not what i found in my test. Useing a U core(ferrite),it takes the same force to sepperate the two halves of the core without current flowing through the coil as it dose with current still flowing through the coil that creates the field in the first place.
Is it the magnetic field that is creating the current flow through the coil,or is it the current flow through the coil that maintains the magnetic field?.

MarkE

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Re: Measuring Amps on output coils
« Reply #49 on: March 26, 2015, 11:20:09 AM »

I disagree.I (like verpies) have done many test over many hours with the PMH. If there is no flow,then why will a U core retain this magnetic field,while an E core of the same ferrite will not?(both without the coil shorted)
The flux distribution in the two shapes is different.  The mechanical force across a reluctance gap squares with the flux density.  An E-E combination reduces the flux density and therefore the mechanical force.
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Not what i found in my test. Useing a U core(ferrite),it takes the same force to sepperate the two halves of the core without current flowing through the coil as it dose with current still flowing through the coil that creates the field in the first place.
That would only make sense to me if you had a considerable gap, which would also make the force weak.
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Is it the magnetic field that is creating the current flow through the coil,or is it the current flow through the coil that maintains the magnetic field?.
A changing magnetic field is required to induce a voltage that then causes a current to flow.  The magnetic field is not changing, so you know you do not have electric current.  A current generates a static magnetic field.  But you know that your coils are not carrying current and by probing the surface of the magnetic material you can establish that it is not carrying a circulating current either.  All that you have is a soft magnetic structure that remains biased until you do something to break the alignment of the domains:  Heat above the Curie temperature, give it a whack with a hammer, apply opposing bias, or open the reluctance gap.