Inductively coupled devices
The relationship between the physics and the small-signal electrical
behaviour of transformers
By David W Knight.
(version 0.10 provisional, 0.7 MiB)
This article introduces the theory required for the analysis and
modelling of inductively-coupled networks. The material presented is
applicable to electrical transformers of all types, but the examples
given relate primarily to high-frequency signal-processing
applications. Familiarity with circuit analysis technique is assumed;
but magnetism is discussed at an elementary level in order to ensure
that the fundamental concepts are understood.
with the basic
properties of ideal transformers is here assumed. A brief introduction
is given in AC Theory
, section 41.
are discussed in the RF
Mutual Inductance Apparatus
Intended for use as a teaching laboratory demonstration. Made
by C. F. Palmer Ltd., (Charles Fielding Palmer) Effra Road, London
S.W.2. Probably ca. 1950 (no date marking). Distance scale is in cm.
Screw threads are BA.
Despite the Victorian
appearance, the use of plasticised PVC sleeving (on the buzzer coil
indicates that manufacture of this particular coil cannot have taken
place until some time
after the invention of PVC (1926). PVC started to come
into widespread use in the late 1940s.
The primary of the Palmer Induction
coil (and other Ruhmkorff-type coils in general) is packed with lengths
of varmished iron wide disposed in the axial direction (see right). The
varnish insulation increases efficiency by preventing eddy currents
from flowing in the radial (winding) direction.
Click the picture to
Palmer induction coil
lighting a Ferranti
NSP2 neon strobotron
tube. Power supply is 1.5 V
Precision Variable Mutual Inductor
, 1 μH to 11.1 mH.
Variometer using stranded silk-covered wire wound on marble formers.
centre-tapped to enable use in Heaviside-Campbell and Carey-Foster
Features very low capacitance between
secondary windings to give negligible capacitance error, resulting in
high accuracy. Consists of a primary coil and three secondary coils
having mutual inductances with the primary of 1, 3, and 6 units. Other
values are given by +ve and -ve combinations of the three basic units.
Eg., 2 is given by 3-1, 5 by 6-1, and 10 by 1+3+6. These combinations
are given by a special type of 6-pole dual contact switch. In this way,
a variable mutual inductance standard is built up.
Info originally obtained from the
Tinsley 2002 catalogue / Product
Range / Specialist Standards Equipment.
Top panel demensions are 42 cm × 36 cm. Overall height: 159
mm. Weight: 15.6 kg.
Widely used in magnetic susceptometry.
© D W Knight 2009 - 2013 - 2021.
David Knight asserts the right to be
as the author of this work.