豐原原友液晶維修0935-721342 邱先生

coil.exe

This program computes the electrical self inductance of

various shapes and sizes of air core coils.

Usage:

On startup, the following initial menu is displayed:

Geometry of coil:

1 Circular solenoidal current sheet

2 Straight round wire

3 N-turn circular loop

4 Circular toroid, circular winding

5 Multi-layer square solenoid (low precision)

6 Circular torus ring, rectangular winding

7 Multi-layer circular solenoid

8 Single-layer circular solenoid of round wire

9 Single-layer square solenoid

10 Single-layer rectangular solenoid

11 Wire gauge calculation

12 Select dimensions in inches or centimeters

 Choose geometry (1) ?

Select the desired coil geometry from the menu. Enter mean

diameter, length, and thickness of winding, and total number of

turns, as prompted.  The program will display the inductance in

henrys, then loop back for more input.  "Mean diameter" is the

arithmetic average of the inner and outer diameters of the

winding; for a single layer coil it is measured to the center of

the wire.  "Thickness," for a single layer coil, is the

wire diameter (see below for the correction for empty space

in the winding).

For each item the previously entered value is displayed in

parentheses and will be kept if you just hit the carriage return

key.

Item 11, wire gauge calculation, prompts for the wire gauge

and the dimensions of a rectangular area to be filled.  It

displays the wire diameter and the number of turns that will

fit into the indicated space.

The formulas for a multi-layer circular solenoid were obtained

from National Bureau of Standards publications and are very

accurate. They work for arbitrary winding thickness and length.

A flat spiral disc coil is obtained by setting the length = 0.

Also very precise is the NBS formula for a helical solenoid of

round wire.  It models the size of the wire and the nonuniform

current density inside the wire. The only low precision formula

included is the one for a multi-layer square solenoid; it is an

approximation from the CRC handbook.

In the case of a single-turn loop or a straight piece of wire, a

skin effect correction is computed.  This requires that you enter

the frequency of operation.  The wire is then assumed to have the

conductivity of copper.

If the wire diameter or winding thickness is not explicitly

requested, the coil is modeled as a zero thickness current sheet.

Except for the circular solenoid of round wire, the formulas

assume uniform current density throughout the winding, modified

only when skin effect is included.

In the cases that assume uniform current density, there is no

correction for empty space in the winding.  An approximate

correction for close-wound coils is (Rosa, 1906)

     dL = 0.00097 d N

where d is the mean diameter of the winding, in centimeters, and

N is the total number of turns.  This correction, in microhenrys,

is added to the inductance.

All calculations assume both the core material and the wire are

non-magnetic.

Files:

coil.c         main program for coil calculator

coil.doc       this file

coil.mak       MSDOS makefile

coil.nmk       MS Visual C nmake file

coil.opt       VAX makefile

descrip.mms    VAX makefile

formulae.c     inductance formulas from NBS publications

lyle.h         approximations to Lyle's tables

makefile       Unix makefile

mathl.c        elliptic integrals and other math functions

tables.c       computes tables found in engineering handbooks

tables.ans     result of running tables.c

tables.opt     VAX makefile

References:

Butterworth 1915:

  S. Butterworth, "On the Coefficients of Self and Mutual Induction

  of Coaxial Coils," Philosophical Magazine, vol. 29 (1915), pp. 578-592

Grover 1918:

  Frederick W. Grover, "Additions to Inductance Formulas,"

  Sci. Pap. #320,  Bulletin of the Bureau of Standards 14, 555-570

Grover 1922a:

  Frederick W. Grover, "Tables for the calculation of the

  inductance of circular coils of rectangular cross section," Sci.

  Pap. #455, Scientific Papers of the Bureau of Standards 18,

  451-487 (1922)

Grover 1922b:

  Frederick W. Grover, "Formulas and tables for the calculation

  of the inductance of coils of polygonal form," Sci. Pap. #468,

  Scientific Papers of the Bureau of Standards 18, 737-762 (1922)

Grover 1946:

  Frederick W. Grover, _Inductance Calculations, Working Formulas

  and Tables_, Van Nostrand, 1946; Dover, 1962

Lyle 1914:

  T. R. Lyle, "On the self-inductance of circular coils of rectangular

  section." Philosophical Transactions of the Royal Society of London,

  Series A, Volume 213 (1914), 421-435.

Rosa 1906:

  Sci. Pap. #31,  Bulletin of the Bureau of Standards 2, 161

Skilling 1948:

  H. H. Skilling, _Fundamentals of Electric Waves_,

  Wiley, 1948, pp 99-101.

Snow 1952:

  Chester Snow, "Formulas for Computing Capacitance and Inductance,"

  National Bureau of Standards Circular #544

Niwa 1924:

  Formula for single-layer rectangular coil, quoted in Grover 1946.

Spielrein, 1915:

  Spielrein, Archiv fur Elektrotechnik 3, p. 182 (1915).

  Formula for wide disk coils.

See also the section "Radio Formulae" in _Handbook of

Chemistry and Physics_, Chemical Rubber Publishing Co.,

for toroidal and rectangular coils, loops, straight wire, etc.

Program by Steve Moshier

moshier@na-net.ornl.gov

coil00.zip: December, 1992

coil01.zip: February, 1996 (Menu item to choose inches or centimeters)

coil02.zip: January, 2002 (Use Lyle if b/r <= 0.2)