As part of an experiment, I need to wind two enamel wire coils on a ferrite rod. One is to be CW and the other CCW. They need to be interlaced somehow to create the most unform interaction of their respective fields.
In other words, not just winding one on top of the other, or side-by-side.
What would be the best method for doing this, or the next best thing?
Presumably to be done by hand, although I do have a mechanical winder.
No hurtful comments please.
Glen Lewis
Interesting. Can you disclose what you're trying to accomplish?
Sounds like a geometry problem where you've disallowed the two possibilities?
The devil is in the details. Most uniform might be to use two separate rods and separate them as far as possible. Won't be tightly coupled, but might be very uniform interaction...but that's not what you want, I expect. Then there's the whole issue of your definition of "uniform" in time? Space? In the ferrite? external field? End effects? Radiation?
Why is CW/CCW important? You can get good coupling with bifilar winding. Swap the wire ends to reverse the field.
What frequencies are involved, and how big the rod? Many kinds of ferrites don't work well at high frequencies. You get transmission line effects at high frequencies with bifilar that may be beneficial or harmful...which brings us right back to what you're trying to accomplish.
Use bifilar enamel wire and reverse the phase of one winding. Can't see the practical difference in reality from what you have specified.
A variation on the Ayrton-Perry winding:
...except the windings exchange "outer" and "inner" at the cross overs?
I see no particular advantage in doing so, but there you go.
If you drive the windings as shown, their fields cancel. If you drive them independently and oppositely, their fields will add.
What are you trying to do?
Mark L. Fergerson
This is a low-inductance, high-pulse-power, manganin-wire resistor.
Of course, I wanted the magnetic fields to cancel. I don't know what you want the windings to do to the ferrite rod. You could wind a twisted pair, or micro-coax, or something.
What are you trying to do?
-- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
On Sat, 16 Nov 2013 12:50:30 -0000, "Andy Bartlett" Gave us:
He seems to think that placing the second winding on top of the first is somehow a lossy condition from the coupling POV or some such. Folks just getting into transformers think that there are proximity inefficiencies all over the place.
With HV, it would be"which winding is on top", etc.
It makes not much difference, which the exception being that the HV winding goes on a LOT smoother onto the spool hub, than being placed over far larger diameter primary windings. Electrically though, they should operate practically identically.
SO, I would stack them with any smaller gauge choice going on first. I would also place or make a "bobbin" on the rod. In other words, a pair of cheek plates like one would see on a plastic molded bobbin to keep the wire stacks confined and allow tape separators to be used.
Wow! TRUE/FALSE exams must have driven you nuts!
Don't get me wrong. I IMMEDIATELY made a bunch of assumptions to answer this question without the 'step back and review' what was ACTUALLY required.
Bifilar won't suffice? (wrap, twist, wrap, twist..) Then, swap the ends?
Not sure where you are going, here... (sorry)
WOW! I think you are confusing a true/false exam with a brain teaser.
True/false exams attempt to determine your knowledge in a manner that requires no effort by the instructor. They're complete descriptions of a situation with sufficient context.
Brain teasers are purposely obfuscated to elicit novel approaches to problem solution.
Yes, many true/false exams end up being brain teasers because of incompetent test writers.
Most questions asked on the interweb are more like brain teasers.
Yes, that knee-jerk reaction is a major failing of society...multiplied here on the internet by isolation and lack of accountability. Very smart people, more interested in proving the other guy's inference to be wrong/stupid than in solving the OP's ill-defined problem. Goes far down hill from there.
My first mentor taught me that there are two parts to problem solving. The first is defining the problem. The second is solving the problem. Many people skip the first part. And if you press for the definition, you're stupid or worse.
Back in the day, I left an organization because they had decided to send ALL the engineers into the field to ask customers true/false questions. In the end, they got what they asked for...the premise was FALSE. A better question might have been, "what are you doing and how do you do it and how do you envision doing it in the future?" Problem with that is that it requires pre-planning and understanding and analysis and competence...all of which are in short supply.
Common mode chokes have the best mutual coupling when one winding ends are reversed they cancel. A tertiary winding can measure the imbalance such as in ground fault interrupters.
Winding with twisted pairs might get uniform results. The start of a CW winding pair would get the dots. Then you can choose to connect them as required.
When more than one choke is present on a board in close proximity, stray coupling polarity will depend on the phase or winding direction, so the Dots or CW direction becomes important.
I will have to try winding one of these by hand.
The "spider web" coil below might be a bit quicker than a cylindical former and have the same effect. Wind from two spools and alternate direction.
Ferite rod through the center??
Can anyone think of an easier way?
Glen Lewis
I can't see from the photo howt this would result in both CW and CCW winidngs.
Is there some kind of twist were the "lumps" are?
Glen Lewis
Den søndag den 17. november 2013 22.18.30 UTC+1 skrev snipped-for-privacy@alphaquest.c om:
doesn't get much easier than: make a twisted pair from two pieces of wire, wind the coil and swap the ends on one of them
-Lasse
On Sun, 17 Nov 2013 13:46:07 -0800 (PST), Lasse Langwadt Christensen Gave us:
The only way to do what he wants is to hand wind both together at the same time, turn for turn. And stagger the 'stack-bumps' which would result.
No gains. If anything it might lose a slight amount of coupling efficiency.
No, the currents just flow in opposite directions.
What are you trying to accomplish?
-- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
So, wind a twisted wire pair. Connect your current source to the CCW end of strand 1, and the CW end of strand 2.
CW and CCW do not imply different helicity (for that, you'd say right-hand and left-hand).
It's fairly common for large motors or generators to use a spare winding or two as a copper resistor (for temperature moitoring), this kind of non-inductive winding on a magnetic core is not unheard-of, though it seems rather... odd.
..or take the (insulated) wire, fold it in half, twist together,and wind the composite in normal fashion.
OK, then I will say it. One winding right-hand (CW) and one left-hand (CCW) winding, superimposed in the same direction on the same cylindrical former. That is what I am after.
I know about non-inductive coils, twisted pairs, etc. This is something different for a lab exp.
Thought I might find a way other than hand winding. Electronics has made me phyiscally unfit.
Glenn Lewis
Still not understand Most automatic winders will handle bifilar wire.
You could also use flexible PCB materials like polyamide and simply 'wrap' that around some core.
snipped-for-privacy@alphaquest.com schrieb:
Hello,
I would try to start with one winding only first. Between the windings there should be a gap of the same width as the diameter of the wire. When the first winding layer is finished, the second wire is wound into the gaps in opposite direction. There are two wire crossings for each turn, for a uniform look these crossings should be on opposite sides of the ferrite rod. If you want to wind several layers in this way, it is even more tricky. The problem is what to do with the second wire while winding the second layer with the first wire and what to do with first wire while winding the second layer with the second wire.
Good luck, you will need it.
Winding bifilar with to wires in the same winding direction and reversing only the start and end of one wire within the circuit is much easier.
Bye
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