How can wire leakage inductance be controlled?

Thread Starter

russwr

Joined Aug 29, 2017
66
Need ideas for methods of making adjustments to cross leakage inductance VOLTS from higher voltage side to lower side from adjacent wires. Adding sleeving as shrink wrap tubing, or reducing the second wire number of turns, so as less induction effect for less voltage transference.? Example- electromagnet with steel core instills magnetic field and amps onto separate bare copper wire EXITING electromagnet. Wire has previous higher voltage and is 90 degrees wrapped with 7 turns insulated wire. (no steel core) Voltage is transferred- instilled in the outer 7 turn coil. Initial voltage in insulated turns is then increased. Suggestions of adjusting this DESIRED transfer voltage is needed , such as number of turns, initial change of volts on copper wire, wider spacing or with thicker insulation, etc.?
 
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Papabravo

Joined Feb 24, 2006
21,264
I think he means parallel wires. I'm not sure that that is even a problem that sleeving or shrink wrap tubing will solve. The magnetic field lines will go right through those materials.
 

ronsimpson

Joined Oct 7, 2019
3,156
cross leakage inductance
Please define. What is the problem. It is probably a vocabulary problem.
Is this a primary to secondary problem?

There are a number of ways I have used transformer shielding but I don't know your problem yet and don't want to just add information that is not what you want. There are shields that go around the primary to protect the secondary. There are shields that go around the entire transformer.

You say leakage inductance but that is a very different problem. Almost the reverse of shielding.
 
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MrAl

Joined Jun 17, 2014
11,593
Need ideas for methods of controlling cross leakage inductance VOLTS from higher voltage side to lower side from adjacent wires. Adding sleeving as shrink wrap tubing?
I would think shielded wire with shield connected to ground.
 

BobTPH

Joined Jun 5, 2013
9,189
Haven't I seen transformers with a band of copper around them? IDK this, but isn't the copper band blocking the electromagnetic field from affecting other components?
Try placing magnets on either side of a thin sheet of copper. Do they stick together?

If the copper shielded out the magnetic field, the transformer would not work, would it?
 

nsaspook

Joined Aug 27, 2009
13,446
Haven't I seen transformers with a band of copper around them? IDK this, but isn't the copper band blocking the electromagnetic field from affecting other components?
It's a Flux Band for "leakage flux", shielding by shunting energy from the electromagnetic to thermal (short circuit). It's also (or can be) an electrostatic shield.
https://piexpertonline.power.com/help/piexpert/en/topics/shields.htm
https://www.ti.com/seclit/ml/slup394/slup394.pdf?ts=1603871011457

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Thread Starter

russwr

Joined Aug 29, 2017
66
Don’t run the wires near each other?
I believe that wire inductance decreases with distance. A larger spacing between 2 wires may solve problem of voltage transference. Old style car engines of high mileage have worn out ignition cables. At night time they spark all over with cross misfiring. Enclosing wire in thick rubber hose my allow less voltage transference. - (Due to the further spacing insulation thickness )
 
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Tonyr1084

Joined Sep 24, 2015
7,968
Try placing magnets on either side of a thin sheet of copper. Do they stick together?
Logically, yes, they do. But I've seen transformers banded with copper. I admittedly don't know much about transformers, only that I've seen it. And it must serve some purpose.
It's a Flux Band for "leakage flux", shielding by shunting energy from the electromagnetic to thermal (short circuit). It's also (or can be) an electrostatic shield.
Thought something similar. Yes, this makes a lot of sense. Thanks.

So I guess copper shielding around wires will do nothing. So forget what I suggested.
What about ferrite beads?
Yes, what about ferrite beads? I see them all the time on power cables and other type/purpose cables. Maybe that's to prevent RF interference coming from the wires themselves. But now I'm wondering if FB's would be a plausible solution. (Pete - this is not directed at you)
 

MrAl

Joined Jun 17, 2014
11,593
Depending on the shield material, there may be no effect on magnetic coupling.
Hi,

Well this usually helps maybe because the shield partly cancels out the fields due to the current in the shield running in the opposite direction to the signal wire current.
I guess a simple test would be in order.
 

MrAl

Joined Jun 17, 2014
11,593
Logically, yes, they do. But I've seen transformers banded with copper. I admittedly don't know much about transformers, only that I've seen it. And it must serve some purpose.

Thought something similar. Yes, this makes a lot of sense. Thanks.

So I guess copper shielding around wires will do nothing. So forget what I suggested.

Yes, what about ferrite beads? I see them all the time on power cables and other type/purpose cables. Maybe that's to prevent RF interference coming from the wires themselves. But now I'm wondering if FB's would be a plausible solution. (Pete - this is not directed at you)
In this case a wire with a copper shield may work to some degree if the shield is used for the ground return wire. The current will run opposite to the signal wire current so would partially cancel out the magnetic field. How much of an effect it will have would have to be tested in real life.
 

MisterBill2

Joined Jan 23, 2018
19,093
Inductive coupling is only possible when a conductor carrying current is generating a magnetic field. If there is coupling without current than it is probably capacitance coupling.
So a more detailed description of what the actual problem is will help with discovering a solution.

AND, note the comment about from a higher voltage wire to a lower voltage wire. THAT is the description of capacitance coupling.
 

nsaspook

Joined Aug 27, 2009
13,446
Inductive coupling is only possible when a conductor carrying current is generating a magnetic field. If there is coupling without current than it is probably capacitance coupling.
So a more detailed description of what the actual problem is will help with discovering a solution.

AND, note the comment about from a higher voltage wire to a lower voltage wire. THAT is the description of capacitance coupling.
Translate this:
Need ideas for methods of controlling cross leakage inductance VOLTS from higher voltage side to lower side from adjacent wires. Adding sleeving as shrink wrap tubing, or reducing the second wire number of turns, so as less induction effect for less voltage transference.? (no steel core)
 

MisterBill2

Joined Jan 23, 2018
19,093
OK, here is the solution, very commonly used in a successful commercial product: Use a twisted pair, similar to what is done in "CAT5" data cable four data pairs in tight proximity with only thin insulation between them.And no interference problems. I realize that usually only two pairs are used. BUT STILL, this is the solution. Precision twisting together of the high voltage wire and the high voltage return wire, likewise with the lower voltage wire.
No need to invent a new solution, just copy one that works.
 
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