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Stiff Wire and Tight Toroids

D

D from BC

Does my post title seem a little perverted? :)
......anyways..
I'd like to lower the copper loss in an inductor design.
So, I'm lowering the wire gauge to reduce the resistance.
However...
(I never get something for nothing in electronics.. :)
Aside from running out of room for turns, could the wire be too stiff
to wind?

Some core info:
100 turns
Across: 1.1cm^2
OD: 1.6"

At what gauge does it generally get too difficult to hand wind a
tightly wound toroid??

What's the gauge of the fattest wire that can be found in typical
switchmode power supply magnetics?

What's the gauge limit on a typical toroid winding machine?
D from BC
 
J

John Popelish

D said:
On Mon, 02 Apr 2007 17:56:45 -0700, Joerg


I'll need a thin insulator around the stranded wire..
Seems like one of those PITA items to find.

I would wind a chunk of 3 strand wire made of enameled
strands. This also increases the utilization of the copper
(AC resistance closer to the DC resistance) by decreasing
the fraction of the copper that is inside the skin depth.
 
J

John Popelish

D said:
Would those wires need twisting?

I'm not sure but I think twisted wire occupies more cross section area
than untwisted.
How about no twisting?

They don't need twisting, from a magnetic standpoint. It
just makes the wire easier to handle. Magnetically
speaking, you could make 3 separate windings that each cover
a third of the core, and then parallel them, But you had
better get the turns count right.

The trick to twisting wires is to spin the individual
strands and let then rotate around each other. The Boy
Scouts showed me the tool, made of two pieces of plank and 3
bent sections of coat hanger wire, that they use to make
rope, this way, from 3 strands of twine. But I have
approximated the effect by turning the three strands,
together, at one end, while letting the other ends rotate,
individually. But it is hard to keep much of a length from
tangling with three ends spinning around.
 
D

D from BC

When them fingers still hurt the next morning despite a good dose of
aloe vera?



I have seen up to garden hose diameter. The drums came in via a railroad
connector line and were unloaded by a huge crane.

Wow! Particle accelerator???
Don't know the machine limits versus core diameter but why don't you use
stranded wire?

I'll need a thin insulator around the stranded wire..
Seems like one of those PITA items to find.
D from BC
 
M

MassiveProng

Depends on the hole size, and the wire type. Solid mag wire gets
pretty stiff below 16 Ga. (relatively). Fingers get sore fairly
quickly if large quantities of finished product is needed, and
uniformity is retained throughout.
When them fingers still hurt the next morning despite a good dose of
aloe vera?

Depends on the number of turns you need.
I have seen up to garden hose diameter. The drums came in via a railroad
connector line and were unloaded by a huge crane.

Depends on the turns needed, and the fact that final operating
temperature must be controlled.
Don't know the machine limits versus core diameter but why don't you use
stranded wire?

The hole diameter is what matters for winding. Hand "winding
machines" use a poke through dolly/caddy. It has to be very narrow if
more than one layer of windings is required.
 
P

Paul Hovnanian P.E.

D said:
Does my post title seem a little perverted? :)
.....anyways..
I'd like to lower the copper loss in an inductor design.
So, I'm lowering the wire gauge to reduce the resistance.
However...
(I never get something for nothing in electronics.. :)
Aside from running out of room for turns, could the wire be too stiff
to wind?

Some core info:
100 turns
Across: 1.1cm^2
OD: 1.6"

I.D. and wire gauge might be of interest as well. If its too small,
large wire might not fit.
At what gauge does it generally get too difficult to hand wind a
tightly wound toroid??

What's the gauge of the fattest wire that can be found in typical
switchmode power supply magnetics?

What's the gauge limit on a typical toroid winding machine?
D from BC

Use Chinese prison labor.
 
J

Joerg

D said:
Does my post title seem a little perverted? :)
.....anyways..
I'd like to lower the copper loss in an inductor design.
So, I'm lowering the wire gauge to reduce the resistance.
However...
(I never get something for nothing in electronics.. :)
Aside from running out of room for turns, could the wire be too stiff
to wind?

Some core info:
100 turns
Across: 1.1cm^2
OD: 1.6"

At what gauge does it generally get too difficult to hand wind a
tightly wound toroid??

When them fingers still hurt the next morning despite a good dose of
aloe vera?

What's the gauge of the fattest wire that can be found in typical
switchmode power supply magnetics?

I have seen up to garden hose diameter. The drums came in via a railroad
connector line and were unloaded by a huge crane.

What's the gauge limit on a typical toroid winding machine?


Don't know the machine limits versus core diameter but why don't you use
stranded wire?
 
D

D from BC

I would wind a chunk of 3 strand wire made of enameled
strands. This also increases the utilization of the copper
(AC resistance closer to the DC resistance) by decreasing
the fraction of the copper that is inside the skin depth.

Would those wires need twisting?

I'm not sure but I think twisted wire occupies more cross section area
than untwisted.
How about no twisting?
D from BC
 
J

Joerg

D said:
Wow! Particle accelerator???

Nope. IIRC it was for locomotives for a Brazilian railroad.
I'll need a thin insulator around the stranded wire..
Seems like one of those PITA items to find.


Thin but lots of breakdown voltage? Check this company out:
http://www.rubadue.com/products.html

A client uses their litz wire and I had to make some experimental pulse
transformers with it. Very smooth. No cracked nails and not a single
callus at the end of the week.
 
P

Paul Probert

D said:
Does my post title seem a little perverted? :)
.....anyways..
I'd like to lower the copper loss in an inductor design.
So, I'm lowering the wire gauge to reduce the resistance.
However... ....

What's the gauge of the fattest wire that can be found in typical
switchmode power supply magnetics?

What's the gauge limit on a typical toroid winding machine?
D from BC

Look into Litz wire. Individually insulated strands braided together.
Gives you the lowest resistance at high frequency.

Paul Probert
University of Wisconsin
 
J

Joerg

D said:
Would those wires need twisting?

I'm not sure but I think twisted wire occupies more cross section area
than untwisted.
How about no twisting?


If it's not RF then you don't need twisting. Even for a big switcher
doing a few hundred kHz you might get away without.
 
D

D from BC

On Mon, 02 Apr 2007 17:41:39 -0700, MassiveProng

[snip]
Depends on the hole size, and the wire type. Solid mag wire gets
pretty stiff below 16 Ga. (relatively). Fingers get sore fairly
quickly if large quantities of finished product is needed, and
uniformity is retained throughout.

Yup... Sounds good..I'll go for that... 16AWG @1.29mm..
(My rough guess was 15AWG.)
Any further DC conductivity required and I'll switch to multiconductor
for easy winding.
[snip]
D from BC
 
B

Barry Lennox

Does my post title seem a little perverted? :)
.....anyways..
I'd like to lower the copper loss in an inductor design.
So, I'm lowering the wire gauge to reduce the resistance.
However...
(I never get something for nothing in electronics.. :)
Aside from running out of room for turns, could the wire be too stiff
to wind?

Some core info:
100 turns
Across: 1.1cm^2
OD: 1.6"

At what gauge does it generally get too difficult to hand wind a
tightly wound toroid??

My personal limit is around 16g, and I'm not even sure I'd want to
wind 100 turns with that. A 1-off might be OK, but not 10 !!
What's the gauge of the fattest wire that can be found in typical
switchmode power supply magnetics?

They can go a lot thicker, but Litz wire is more normal.

Barry
 
D

D from BC

I.D. and wire gauge might be of interest as well. If its too small,
large wire might not fit.

The ID is 0.95"...A very rough calculation: (pie*[(0.95"/2)]^2)/100 ~
= 0.007sq in...taken as squares.. root 0.007 = 0.08"...So something
bigger (thinner) than #12 wire will fill the ID...
I'm guessing a more accurate calc would yield #15. Still probably too
painful to wind a tight 100 turn toroid by hand..
Use Chinese prison labor.

Wow...that's cheaper than those chinese sweat shop kids.
More crime for cheaper inductors!! :p
D from BC
 
D

D from BC

D from BC wrote:
[snip]
I'll need a thin insulator around the stranded wire..
Seems like one of those PITA items to find.


Thin but lots of breakdown voltage? Check this company out:
http://www.rubadue.com/products.html

A client uses their litz wire and I had to make some experimental pulse
transformers with it. Very smooth. No cracked nails and not a single
callus at the end of the week.

Cool ...thin insulation...
I couldn't find the Litz wire on the site..
Nor did I see:
"To order trainload of Litz wire...press here.."
I'll poke at the site again later...

By the way...I mentioned a thin insulator covering the stranded wire
(bare stranded wire,not Litzy) to take up less space. I was comparing
to plastic coated stranded hook up wire.

My app has negligible losses due to skin effect. Mostly core and
copper loss.
Kinda ironic to use Litz wire to control copper loss due to low guage
wire being too stiff..
D from BC
 
J

John Larkin

Does my post title seem a little perverted? :)
.....anyways..
I'd like to lower the copper loss in an inductor design.
So, I'm lowering the wire gauge to reduce the resistance.
However...
(I never get something for nothing in electronics.. :)
Aside from running out of room for turns, could the wire be too stiff
to wind?

Some core info:
100 turns
Across: 1.1cm^2
OD: 1.6"

At what gauge does it generally get too difficult to hand wind a
tightly wound toroid??

What's the gauge of the fattest wire that can be found in typical
switchmode power supply magnetics?

What's the gauge limit on a typical toroid winding machine?
D from BC

I knew a guy who wound solid #8 on toroids. He built a machine with a
flat steel-plate table with a hole in the middle. There was a sort of
huge crochet hook that came through the hole from below, through the
toroid, and hooked the wire. Then the operator hit a foot pedal and a
pneumatic cylinder pulled the hook down, doing the tough part of the
winding. The rest of each turn was pretty much manual labor.

John
 
D

D from BC

My personal limit is around 16g, and I'm not even sure I'd want to
wind 100 turns with that. A 1-off might be OK, but not 10 !!


They can go a lot thicker, but Litz wire is more normal.

Barry

Thanks..
I'll be staying away from 16AWG or lower..
I imagined a nightmare project like winding a coat hanger on a toroid
:)
But that's steel and harder to bend than copper, IIRC from the last
time I locked my keys in the car...
D from BC
 
R

Robert Baer

Joerg said:
When them fingers still hurt the next morning despite a good dose of
aloe vera?



I have seen up to garden hose diameter. The drums came in via a railroad
connector line and were unloaded by a huge crane.





Don't know the machine limits versus core diameter but why don't you use
stranded wire?
Better yet, "pseudo-litz" by using a number of small (insulated)
wires in a bundle.
That way, less space gets wasted during winding due to the smaller
size as well as thinner insulation (use "enamel" instead of plastic).
 
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