Plenty of single-layer
coil (inductor) winding calculators, charts, and nomographs can be found on the
World Wide Web, but finding one for multi-layer coils is a bit harder - until
now. Actually, this Multi-Layer Coil Calculator Nomograph appeared in a 1955 issue
of Radio & Television News magazine. It was an era long before personal
calculators, computers, and smartphones, when long-hand written-out problem solving
was the norm, and slide rules made such tasks easier for those fortunate enough
to know how to work one. I did a little head scratching upon encountering the
term "no. 27 d.c.c. wire," not being familiar with the "d.c.c." part. A little research
turned up that it means "double cotton covered" for insulation, and there was also
"s.c.c." for single cotton covered. Belden and Alpha used to make it. Enamel-covered
wire is now used for winding coils and transformers. As you might expect, some companies
who specialize in replicating vintage components still make the
(here's another), or at least something
that looks like it but is better quality.
Multi-Layer Coil Calculator Nomograph
By S. Yamasita
A nomograph for determining multi-layer coil inductance on the basis of the H.
A. Wheeler inductance equation.
An example will serve to illustrate the use of this nomograph. Assume a coil
of one inch mean diameter (2a) and a width and thickness of one-half inch (b and
c), wound with 500 turns of no. 27 d.c.c. wire. A line is drawn through the "mean
diameter" and "width" scales to the reflect axis, then back to the "mean diameter"
scale through the "thickness" scale. A line is then drawn vertically until it intercepts
the curve, and then horizontally to the right-hand side of the graph. From this
point, a line is drawn to the proper point on the "mean dia." scale, thus locating
a point on the "cross axis." A straight line through this point and the proper point
on "total no. of turns" scale locates the inductance. By proper manipulation, the
nomograph can assist greatly in designing a coil of a specified inductance.
Posted September 30, 2021