inductance question

[Yzordderrex]

I have 50' of wire and I want to build an air core inductor and
maximize the inductance. Is 1 big turn going to give me the most
inductance?

regards,
Bob
N9NEO

Just say NEO!

 

[Fred Bartoli]

Yzordderrex a écrit :

I have 50' of wire and I want to build an air core inductor and
maximize the inductance. Is 1 big turn going to give me the most
inductance?

regards,
Bob
N9NEO

Just say NEO!

NEO! It isn't just one big turn

What you're after is called a Brook's coil.
The very nearly optimal coil has a square section (a x a), internal
diameter 2a (and consequently external diameter 4a ).
You'll have to solve this for your wire length and diameter.

Inductance value is L = 2.55E-9.a.N^2 (in H) with a given in mm.

 

[Harry Dellamano]

"Fred Bartoli"

Yzordderrex a écrit :

NEO! It isn't just one big turn

What you're after is called a Brook's coil.
The very nearly optimal coil has a square section (a x a), internal
diameter 2a (and consequently external diameter 4a ).
You'll have to solve this for your wire length and diameter.

Inductance value is L = 2.55E-9.a.N^2 (in H) with a given in mm.

Sweet!

 

[Tim Wescott]

Yzordderrex a écrit :

NEO! It isn't just one big turn

What you're after is called a Brook's coil.
The very nearly optimal coil has a square section (a x a), internal
diameter 2a (and consequently external diameter 4a ).
You'll have to solve this for your wire length and diameter.

Inductance value is L = 2.55E-9.a.N^2 (in H) with a given in mm.

Expect lots of interwinding capacitance.

A one-turn coil, by the way, makes a nice antenna when it gets to be one
wavelength in circumference -- think "loop antenna".

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html

 

[D from BC]

Yzordderrex a écrit :

NEO! It isn't just one big turn

What you're after is called a Brook's coil.
The very nearly optimal coil has a square section (a x a), internal
diameter 2a (and consequently external diameter 4a ).
You'll have to solve this for your wire length and diameter.

Inductance value is L = 2.55E-9.a.N^2 (in H) with a given in mm.

Square section?? Is that why those wallwart transformers have square
bobbins?


D from BC

 

[kell]

Square section?? Is that why those wallwart transformers have square
bobbins?

D from BC-

square in cross section. wound round.

 

[John Popelish]

square in cross section. wound round.

He'll get more inductance by tightly bundling those turns
than by winding them is a single layer solenoid of the same
diameter. The bundled form provides tighter coupling
between the turns, that most closely approaches the turns
squared effect on inductance.

The inter winding capacitance will be higher, also. I don't
know exactly what the optimum relationship between bundle
diameter and average turn diameter for optimum inductance
per wire length, but I am guessing that the bundle cross
section diameter needs to be quite a bit less than the
average turn diameter.

 

[The Phantom]

He'll get more inductance by tightly bundling those turns
than by winding them is a single layer solenoid of the same
diameter. The bundled form provides tighter coupling
between the turns, that most closely approaches the turns
squared effect on inductance.

The inter winding capacitance will be higher, also. I don't
know exactly what the optimum relationship between bundle
diameter and average turn diameter for optimum inductance
per wire length, but I am guessing that the bundle cross
section diameter needs to be quite a bit less than the
average turn diameter.

Just one of many web pages on the Brooks coil:

http://home.san.rr.com/nessengr/techdata/brooks/brooks.html

Making the cross section circular or hexagonal rather than square increases
the inductance by about 1%; hardly worth doing.

 

[LVMarc]

Just one of many web pages on the Brooks coil:

http://home.san.rr.com/nessengr/techdata/brooks/brooks.html

Making the cross section circular or hexagonal rather than square increases
the inductance by about 1%; hardly worth doing.

If you want to get the highest inductance and the highest "q" and at the
highest possible frequecny:

then you want a shape that incloses the maxium volume, with a minimium
shaped wire envelop I geomtery tis wold yield a sphere. not so goo for
coils.

the next shapoe woulb be apporx 2:1 right hand clynder shape,with
several turns, and the angle of wires about 42 degrees....

Marc

 

[John Popelish]

Just one of many web pages on the Brooks coil:

http://home.san.rr.com/nessengr/techdata/brooks/brooks.html

Making the cross section circular or hexagonal rather than square increases
the inductance by about 1%; hardly worth doing.

1% more is more. By the way, do you have a reference that
confirms this magnitude of improvement for a round copper
cross section? I would have guessed a couple more percent,
because it reduces the number of longest turns (that use the
most of the total wire length per turn) and the shortest
turns (that enclose the least area) and increases the number
of turns near the average length, Reducing the shortest flux
line that encircles all the turns, as well as reducing the
distance between each turn and its average neighbor,
improving their flux linkages. I would be a bit surprised
if all those slight but compounding factors added up to only
an additional percent.

 

[D from BC]

If you want to get the highest inductance and the highest "q" and at the
highest possible frequecny:

then you want a shape that incloses the maxium volume, with a minimium
shaped wire envelop I geomtery tis wold yield a sphere. not so goo for
coils.

the next shapoe woulb be apporx 2:1 right hand clynder shape,with
several turns, and the angle of wires about 42 degrees....

Marc

Right hand cylinder?

Is it like this

| ----/////////-
1 ---/////////-- 42deg angled windings
| --/////////---
<-----2---->
D from BC

 

[The Phantom]

1% more is more. By the way, do you have a reference that
confirms this magnitude of improvement for a round copper
cross section? I would have guessed a couple more percent,
because it reduces the number of longest turns (that use the
most of the total wire length per turn) and the shortest
turns (that enclose the least area) and increases the number
of turns near the average length, Reducing the shortest flux
line that encircles all the turns, as well as reducing the
distance between each turn and its average neighbor,
improving their flux linkages. I would be a bit surprised
if all those slight but compounding factors added up to only
an additional percent.

Courtesy of Google, I see that Brooks inductors were discussed on SED back
on August 25, 2004, where you asked Winfield about circular cross sections.

Winfield mentioned a "definitive" study of Brooks inductors, but apparently
nobody has ever posted it.

I'm going to take a chance that your email address is jpopelish at rica dot
net and send it to you.

 

[John Popelish]

Courtesy of Google, I see that Brooks inductors were discussed on SED back
on August 25, 2004, where you asked Winfield about circular cross sections.

Winfield mentioned a "definitive" study of Brooks inductors, but apparently
nobody has ever posted it.

I'm going to take a chance that your email address is jpopelish at rica dot
net and send it to you.

I put up with all the spam just to make it simple for nice
people like you to send me stuff. Thanks.