# Coil formula

Discussion in 'Electronic Design' started by Dirk Bruere at Neopax, Jan 30, 2005.

1. ### Dirk Bruere at NeopaxGuest

Any got a pointer to the formula for inductance and field strength for a given
current for a large dia air core coil? Dia>>length or winding thickness

thanks
Dirk

The Consensus:-
The political party for the new millenium
http://www.theconsensus.org

3. ### Dirk Bruere at NeopaxGuest

Thanks, but I've already seen it.
I was hoping for a 'finished' formula so I wouldn't have to spend a few hours
messing around with stuff since I'll be juggling several other variables besides
the obvious ones.
Actually, a better version of the above is here:

--
Dirk

The Consensus:-
The political party for the new millenium
http://www.theconsensus.org

4. ### John WoodgateGuest

I read in sci.electronics.design that Dirk Bruere at Neopax
Inductance = 1.6 uH per metre of turn length, for one turn, if the
conductor diameter is much smaller than the coil diameter. For more
turns, if closely-coupled, multiply by the square of the number of
turns.

At what point do you want to know the field strength? At an arbitrary
point, it involves elliptic functions, but some points are degenerate
and give simple results.

5. ### John LarkinGuest

====================================================

' INDUCTANCE OF CIRCULAR RING

' REF DATA P 6-9

CLS

TOP: INPUT "RING RADIUS, INCHES ", A
IF A = 0 THEN GOTO EXX

PRINT

INPUT "WIRE DIA, INCHES ", D
IF D = 0 THEN GOTO EXX

PRINT

L = (A / 100) * (7.353 * LOG(16 * A / D) / LOG(10) - 6.386)

PRINT USING "L = #####.##### uH"; L

PRINT
PRINT
GOTO TOP

EXX: END

================================================================

' PROGRAM : MAGFIELD.BAS
' BY : JENNIFER HO
' HIGHLAND TECNHOLOGY, INC.
' FEBRUARY 2, 1995

DEFDBL A-Z

CLS

PRINT "GIVEN A CIRCULAR LOOP OF RADIUS (R) CARRYING CURRENT
(I),"
PRINT "THIS PROGRAM CALCULATES THE MAGNETIC FIELD (B) AT ALL"
PRINT "POINTS ON THE AXIS OF THIS LOOP, WHICH WE TAKE TO BE
THE"
PRINT "Z AXIS, WITH Z=0 AT THE LOOP CENTER."
PRINT
PRINT

INPUT "ENTER LOOP RADIUS (R) in Meters : ", R
IF R = 0 THEN GOTO EXXON

INPUT "ENTER LOOP CURRENT (I) in Amperes : ", I

INPUT "ENTER THE DISTANCE (Z) ALONG THE AXIS in Meters : ", Z

'Uo IS IN THE UNIT OF "GAUSS METER / AMPERE".

Uo = 12.57 * 10 ^ -3

B = (Uo * I * R ^ 2) / (2 * SQR((Z ^ 2 + R ^ 2) ^ 3))

PRINT
PRINT " ggg mmmuuunnn"
PRINT USING "FIELD (B) in Gauss IS : ###.#########"; B

EXXON:
END

=============================================================

' PROGRAM : MAGFIELD.BAS
' BY : JENNIFER HO
' HIGHLAND TECNHOLOGY, INC.
' FEBRUARY 2, 1995

DEFDBL A-Z

CLS

PRINT "GIVEN A CIRCULAR LOOP OF RADIUS (R) CARRYING CURRENT
(I),"
PRINT "THIS PROGRAM CALCULATES THE MAGNETIC FIELD (B) AT ALL"
PRINT "POINTS ON THE AXIS OF THIS LOOP, WHICH WE TAKE TO BE
THE"
PRINT "Z AXIS, WITH Z=0 AT THE LOOP CENTER."
PRINT
PRINT

INPUT "ENTER LOOP RADIUS (R) in Meters : ", R
IF R = 0 THEN GOTO EXXON

INPUT "ENTER LOOP CURRENT (I) in Amperes : ", I

INPUT "ENTER THE DISTANCE (Z) ALONG THE AXIS in Meters : ", Z

'Uo IS IN THE UNIT OF "GAUSS METER / AMPERE".

Uo = 12.57 * 10 ^ -3

B = (Uo * I * R ^ 2) / (2 * SQR((Z ^ 2 + R ^ 2) ^ 3))

PRINT
PRINT " ggg mmmuuunnn"
PRINT USING "FIELD (B) in Gauss IS : ###.#########"; B

EXXON:
END

====================================

John

6. ### John LarkinGuest

Oops, Jennifer's prog got pasted twice.

John

7. ### GenomeGuest

" Thanks, but I've already seen it.

I was hoping for a 'finished' formula.

You know, that one with the sum that don't include that there fancy math and
references to french people.

Just so I wouldn't have to spend a few hours fucking around with the locals.

I'll be juggling several other variables besides the obvious ones."

8. ### John LarkinGuest

As the conductor diameter trends towards zero, the inductance becomes
infinite.

John

9. ### Dirk Bruere at NeopaxGuest

How accurate is that?
Given, for example a coil with one metre dia and (say) 100 turns of #24?
Well, I suppose the centre might be a good starting point.
Typical coil dia would be around one metre.
Also two metres from centre in the plane of the coil.

--
Dirk

The Consensus:-
The political party for the new millenium
http://www.theconsensus.org

10. ### Donna and IanGuest

Sorry I'm not helping, except that, what is a millenium?

11. ### Dirk Bruere at NeopaxGuest

Thanks.
Interesting as I am going to write a Java applet to do something similar.

--
Dirk

The Consensus:-
The political party for the new millenium
http://www.theconsensus.org

12. ### Dirk Bruere at NeopaxGuest

True, its a real pain fucking around with the locals, or at least some of them.

--
Dirk

The Consensus:-
The political party for the new millenium
http://www.theconsensus.org

13. ### Dirk Bruere at NeopaxGuest

Its like 'millennium' but shorter.
A bit like 'It's' without an apostrophe.

--
Dirk

The Consensus:-
The political party for the new millenium
http://www.theconsensus.org

14. ### John LarkinGuest

It's 1/1000 of a lenium.

John

15. ### Donna and IanGuest

agreed, but what is a lenium?

16. ### GenomeGuest

Uo is 4piE-7.

That's in SI units.

Which have been established as being established by the French, I think.

take the piss out off Scotts speaking french people and had war with the
Americans, who are basically Irish......

What the **** you are doing calling your company Highland Technology for?
(and making me take care over the spelling) is another thing, perhaps you

Speff's Canadian (and he'd better not be fucking about with that one if I'm
not going to get overly disillusioned about the general state of things)

The Aylward appears to have claimed to be a nigger, but he's an export.....
so he's not an Indian. It's not that they write better software they are
just cheaper.... Sorry I read that Kevin has embedded something so deep in
his code that he would rather not be arsed getting it out again.

Which, taking Jennifer's sums, should be 12.57E-7.

Now, I know you Americans have had some problem in the past with the odd
factor of something like 4E8 or the odd erg slug foot cubit.

But!!!!!!!!! You now come along with your Power Penis.

DisFuckingGusting. Wot you want is one of these.

unit roundedit;

interface

uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
Grids, DBGrids, Db, DBTables, ToolWin, ComCtrls, Menus, DBActns,
ActnList, ImgList, ExtCtrls, DBCtrls, Math, Spin, StdCtrls, FileCtrl;

type
TRoundWireForm = class(TForm)
DataSource1: TDataSource;
Table1: TTable;
ToolBar1: TToolBar;
ImageList1: TImageList;
ActionList1: TActionList;
DataSetFirst1: TDataSetFirst;
DataSetLast1: TDataSetLast;
DataSetNext1: TDataSetNext;
DataSetPrior1: TDataSetPrior;
ToolButton1: TToolButton;
ToolButton2: TToolButton;
ToolButton3: TToolButton;
ToolButton4: TToolButton;
ToolButton5: TToolButton;
ToolButton6: TToolButton;
DataSetInsert1: TDataSetInsert;
ToolButton7: TToolButton;
DataSetCancel1: TDataSetCancel;
DataSetPost1: TDataSetPost;
ToolButton8: TToolButton;
ToolButton9: TToolButton;
DataSetDelete1: TDataSetDelete;
DBGrid1: TDBGrid;
Table1Standard: TStringField;
Table1CuDiamm: TFloatField;
Table1DiaLmm: TFloatField;
Table1DiaSmm: TFloatField;
Table1DiaHmm: TFloatField;
Table1DiaTmm: TFloatField;
GroupBox1: TGroupBox;
Label1: TLabel;
Label2: TLabel;
Label3: TLabel;
Flabel: TLabel;
Llabel: TLabel;
Tlabel: TLabel;
FUpDown: TUpDown;
LUpDown: TUpDown;
TUpDown: TUpDown;
GroupBox2: TGroupBox;
Label4: TLabel;
Label5: TLabel;
Label6: TLabel;
RdcLabel: TLabel;
RacLabel: TLabel;
RraLabel: TLabel;
Label7: TLabel;
Label8: TLabel;
Table1Guage: TFloatField;
procedure Exit1Click(Sender: TObject);
procedure FormCreate(Sender: TObject);
procedure DataSource1DataChange(Sender: TObject; Field: TField);
procedure FUpDownClick(Sender: TObject; Button: TUDBtnType);
procedure LUpDownClick(Sender: TObject; Button: TUDBtnType);
procedure TUpDownClick(Sender: TObject; Button: TUDBtnType);
private
{ Private declarations }
procedure Recalc;
public
{ Public declarations }
end;

var
RoundWireForm: TRoundWireForm;

implementation

{\$R *.DFM}

procedure TRoundWireForm.Recalc;
var
Resistivity : double;
SkinDepth : double;
CuDiametre : double;
InsDiametre : double;
Height : double;
LayFact : double;
Quality : double;
Mac : double;
Dac : double;
Fratio : double;
DCResistance : double;
ACResistance : double;
begin
InsDiametre := Table1.FieldByName('Dia (L) / mm').AsFloat/1000;
InsDiametre := Table1.FieldByName('Dia (S) / mm').AsFloat/1000;
InsDiametre := Table1.FieldByName('Dia (H) / mm').AsFloat/1000;
InsDiametre := Table1.FieldByName('Dia (T) / mm').AsFloat/1000;
CuDiametre := Table1.FieldByName('Cu Dia / mm').AsFloat/1000;
If (InsDiametre>0) and (CuDiametre>0) then
begin
Resistivity := 1.72417E-8*(1+0.00393*(TUpDown.Position-20));
SkinDepth := Sqrt(Resistivity/(pi*4*pi*1E-7*1000*FUpDown.Position));
Height := CuDiametre*Sqrt(pi/4);
LayFact := CuDiametre/InsDiametre;
Quality := Sqrt(LayFact)*Height/SkinDepth;
Mac :=
Quality*(sinh(2*Quality)+sin(2*Quality))/(cosh(2*Quality)-cos(2*Quality));
Dac := 2*Quality*(sinh(Quality)-sin(Quality))/(cosh(Quality)+cos(Quality));
Fratio := Mac+Dac*(Sqr(LUpDown.Position)-1)/3;
DCResistance := Resistivity/(Sqr(CuDiametre/2)*pi);
ACResistance := Fratio*DCResistance;
RdcLabel.Caption := FloatToStrf(DCResistance,ffGeneral,5,0);
RacLabel.Caption := FloatToStrf(ACResistance,ffGeneral,5,0);
RraLabel.Caption := FloatToStrf(Fratio,ffGeneral,5,0);
end
else
begin
RdcLabel.Caption := 'Not Available';
RacLabel.Caption := 'Not Available';
RraLabel.Caption := 'Not Available';
end;
end;

procedure TRoundWireForm.Exit1Click(Sender: TObject);
begin
close;
end;

procedure TRoundWireForm.DataSource1DataChange(Sender: TObject;Field:
TField);
begin
Recalc;
end;

procedure TRoundWireForm.FUpDownClick(Sender: TObject;
Button: TUDBtnType);
begin
Flabel.Caption := IntToStr(FUpDown.Position);
Recalc;
end;

procedure TRoundWireForm.LUpDownClick(Sender: TObject;
Button: TUDBtnType);
begin
Llabel.Caption := IntToStr(LUpDown.Position);
Recalc;
end;

procedure TRoundWireForm.TUpDownClick(Sender: TObject;
Button: TUDBtnType);
begin
Tlabel.Caption := IntToStr(TUpDown.Position);
Recalc;
end;

begin
Recalc;
end;

begin
Recalc;
end;

begin
Recalc;
end;

begin
Recalc;
end;

procedure TRoundWireForm.FormCreate(Sender: TObject);
begin
Label1.Caption := 'Frequency KHz';
Label2.Caption := 'Layers';
Label3.Caption := 'Temperature C';
Label4.Caption := 'DC Resistance/m';
Label5.Caption := 'AC Resistance/m';
Label6.Caption := 'Rac/Rdc Ratio';
Flabel.Caption := IntToStr(FUpDown.Position);
Llabel.Caption := IntToStr(LUpDown.Position);
Tlabel.Caption := IntToStr(TUpDown.Position);
end;
end.

17. ### GenomeGuest

In case you missed it we had a New One.

Like you think a Millenium has something to do with a Million things.

It was probably something invented by Greeks and adopted by the Romans so it
got divided by a thousand, you know, like towards the end.

Like in modern times.... third fourth and fifth reich. Cherry blossoms of

Yup, this ones going to last a 'mill' oo0ps thousand years. Oh bugger we got
fucked over, shit.

Hey! folks. It's a new Millenium.......

And, just in case your thinking we're going to tell you that we sure aint
going to **** you over again... just don't forget that it's all worth 9.99
in the new currency.

DNA

18. ### Spehro PefhanyGuest

LENIUM ES is a binary azeotrope of n-Propyl Bromide (nPB) and
isopropanol expressly formulated to remove both polar and non-polar
soils from circuit assemblies and components.

http://www.petroferm.com/PTF-053/clean/eprod_len_content.html

Best regards,
Spehro Pefhany

19. ### John LarkinGuest

Irish, German, dark rumors of a trace of French and possibly even a
bit of converted Jew somewhere.

I used to live on Highland Avenue and decided to incorporate and my
expensive lawyer called me and asked for the company name to file the
papers, so I said you-know-what. Never paid him, come to think of it.

Our company logo depicts the view looking at Mount Tamalpias as seen
from the toll plaza of the Bay Bridge. The moon thing is Artistic

If you want the field in Tesla, which she apparently didn't.

John

20. ### GenomeGuest

Gauss.....

Just like a Texan.

DNA