Improvements in Reactance Coils."
Year: 1897

page_text: Date of Application, 5th Nov., 1897-Accepted, 11th Dec., 1897
COMPLETE SPECIFICATION.
"Improvements in Reactance Coils."
We, THE BRITISH THOMSON-HOUSTON COMPANY, LIMITED, and HENRY METCALF
HOBART, all of 83, Cannon Street, in the City of London, Electrical Engineers, do
hereby declare the nature of this invention and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement:
a
This invention relates to reactance coils and has for its object to secure
structure more analogous to those met with in transformer design with their
attendant advantages, and to so arrange the structure as to secure a total magnetic
reluctance which can at any time be adjusted to the requisite value. This latter
object we effect by arranging the cross section of part of the closed magnetic circuit
so as to be capable of variation at some portion or portions of it, which is or are,
arranged to be readily accessible for the purpose. Hitherto in apparatus of this
kind the necessary proportions of volts to amperes has been secured by providing
and incorporating an air path in the magnetic circuit of the coil, but experience
has shown that the latter method entails various difficulties and defects and these
are avoided in reactance coils constructed in accordance with the present invention.
We will describe our invention in reference to the accompanying drawings in
which we have illustrated for example a reactance coil designed to absorb about 50
amperes at 3 volts and 100 cycles. In the drawing Fig. I is a sectional view on
line 1-2 of Fig. 2, and Fig. 2 a plan, partly in section, of our improved reactance
coil. It consists of two laminated iron legs L L upon which are wound coils C C
composed of a suitable number of turns of copper.
The mechanical structure as
well as the magnetic circuit is completed by the insertion between the ends of the
stampings forming the legs L L of ends pieces E E mainly composed of non-
magnetic strips, but having interspersed amongst them such a number of strips
of magnetic material as is requisite for giving the necessary relation between volts
and amperes. Such non-magnetic strips, may be made of zinc or other non-
magnetic material, and the remainder of magnetic strips of iron, or 'other magnetic
material.
It will be seen that the essential feature of the invention is the provision of
means admitting of the adjusting at any time of the reluctance of the magnetic
circuit to the required value by varying the magnetic cross section at certain parts
such as E E of the magnetic circuit, such parts carrying no coils and projecting
beyond the main structure so as to be readily accessible."
Although the specific rate of generation of heat may be high in the magnetic
material in the portion E E of the circuit, it can still, by suitably proportioning
the parts to be kept within suitable limits relative to the available radiating surface.
The proportion would of course depend upon the periodicity, and other conditions
of the design, and the non-magnetic portion of the members E E could be chosen
from a wide range of materials.

page_text: Having now particularly described and ascertained the nature of our said
invention, and in what manner the same is to be performed, we declare that what
we claim is: -
1. A reactance coil having a closed magnetic circuit so constructed that portions
thereof may be adjusted in regard to their magnetic length and cross-section so as 5
to obtain a magnetic reluctance of any required amount, substantially as set forth.
2. In a reactance coil having a closed magnetic circuit with coils, forming an
accessible part or parts of same of laminated stampings composed partly of magnetio
and partly of non-magnetic material, the magnetic reluctance being adjusted by
the proportion used of magnetic material substantially as set forth.
3. A reactance coil constructed and arranged substantially as described with
reference to and shown in the drawings, for the purposes set forth.
Da ed the 5th day
L
For the Applicants.
J. C. CHAPMAN.
Chartered Patent Agent, 70 Chancery Lane, London, W.C.