An Improved Alternating Current Meter.
Year: 1897

page_text: Date of Application, 11th June, 1897-Accepted, 4th Dec., 1897
COMPLETE SPECIFICATION.
An Improved Alternating Current Meter.
I, CARL RAAB of 18 Mainzerstrasse, Kaiserslautern in the Empire of Germany,
Engineer, 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:
This invention relates to alternating current meters in which the armature
is intersected at two places by the side-closing lines of force of two horse-shoe.
magnets, by which means at two places of the armature disc there is produced
each time a moment of rotation.
The improvement has for its object to increase the total moment of rotation
by bisecting the armature at four places by the flux of the lines of force of the
shunt circuit without the consumption of Watts in the shunt circuit and the
strength of the field and the magnetic field of the main current conductor being
necessarily increased in the slightest. Further the possibility of running loose or
to waste is entirely removed and the main current field is arranged in such a way
as regards the armature and the horse-shoe that as large a space of coil is obtained
for the solenoid as possible or so that the meter is available for the greatest
strengths of current.
Such a meter is shown in the accompanying drawings, in which:-
Figure 1 is an elevation;
Figure 2 a plan view; and
Figure 3 a side view of the meter;
Figure 4 is a diagrammatic elevation in which the horse-shoe E is reduced in
order to allow of the curve of the lines of force being better understood and is
shown as inserted in the horse-shoe D.
A main current solenoid C is arranged opposite a revolubly mounted disc
armature A, whilst two horse-shoe magnets D and E are arranged with their
pole ends del in turn respectively opposite the said solenoid. The horse-
shoe D carries two small tension coils WW2 both of which have an equally
large number of coils. As will be seen from Figure 2, the solenoid C is oval in
form and is arranged in such a way opposite the poles and e¹e that the
hollow and its extension lie between the arms of the two horse-shoes
There consequently result on both sides of the central line a-b two rotary
moments which all act in the same direction of rotation because the flux of the
lines of force passes through the poles in an opposite direction to that
through the poles e¹ es, as the poles are on the one and the poles el e² on
the other side of the central line a--b, and because the rotary moments of the
poles de act with a left hand and those of the poles with a right hand
leverage on the axis of the armature.
As is well known, magnetic lines of force of an iron closed magnetic conductor
travel with the least spreading if their course be free from bends or curves. The
lines of force of the coils W1 W2 must however be strongly bent at two places and
therefore a considerable number of the lines of force proceeding from the
coils W W must complete the circuit scatteringly after passing through the

page_text: armature disc, instead of all bending round to the horse-shoe E. Although then
these lines of force only cross the disc A at two places they still work to produce
a useful effect and they also act with a motor effect.
In the arrangement hereinbefore described, the lines of force must traverse a
very great air circuit, from which the special advantage results that the meter
can no longer operate without main current, whilst in the meters hitherto
employed the ends of the poles standing facing one another produced rotary
moments acting sometimes to the left sometimes to the right. These rotary
moments may indeed be compensated for, but they have the very dangerous
property of altering in course of time.
A further essential advantage of the arrangement of the horse shoes D and E
one behind the other consists in the fact that a greater space for the solenoid C
is obtained, and the solenoid C may be made available from the smallest up to
the greatest strengths of current without altering the model of the meter..
Any suitable counting or indicating mechanism may be connected with the
shaft of the meter as it is merely a question of registering the number of revolu-
tions of the motor armature. This may be effected most simply by providing
a worm on the motor shaft and allowing the worm wheel of a suitable counting
mechanism to engage therein. A brake is not necessary in the meter shown,
owing to the shunt fields having iron which naturally acts as a brake on the
metallic armature disc..
In using a bell armature in place of the disc armature the horse-shoes D and E
may be arranged both inside as well as outside the armature.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what I
claim is:
An alternating current motor meter, characterized by the arrangement of two
horse-shoe magnets one behind the other on one side of the armature and of a
single oval main current solenoid on the other side of the armature substantially
as herein before set forth.
ሰ
WM. P. THOMPSON & Co.,
Of 6 Lord Street, Liverpool, Agents for the Applicant.