Improvements in Electricity Meters.
Year: 1891

page_text: Date of Application, 27th Feb., 1891-Accepted, 28th Mar., 1891
COMI LEIM DE MULTICATION.
Improvements in Electricity Meters.
STEA
We, EUGEN HARTMANN and WUNIBALD BRAUN, both of Bockenheim, Frank-
fort-on-the-Maine, in the Empire of Germany, 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:
In the electric meter forming the object of the present invention a unipolar
machine or apparatus on the principle of Barlow's wheel is employed through the
dise of which preferably of copper the current to be measured or metered is led
the magnetic field being formed by a powerful electro magnet magnetized by a
constant current.
The revolutions of the said dise under these conditions are proportional to the
quantity of electricity passing through it when with a constant field the current to
be metered is proportional to the local or Foucault currents. In order to comply
with these conditions care must be taken that there is nothing to interfere with the
formation of these local or eddy currents. In case the magnetic field presents the
same form and extent as the path of the current passed through the said disc for
example, an electro motive force also results from the rotation of the said dise in
the magnetic field which acts in opposition to and weakens the current to be
measured. In this case the local or eddy currents are not produced in full so that
a special brake magnet is necessary. In order to obviate this the magnetic field
of the electro magnets in the apparatus arranged according to our invention is
enlarged or extended beyond the path of the current by means of lateral enlarge-
ments or projections on the pole pieces so that the local or Foucault currents are
enabled to form close up to the passing current. This arrangement gives most
advantageous results with regard to the aforesaid proportion or ratio of the
currents.
.
Figures 1 and 2 are views at right angles to each other of apparatus arranged or
constructed according to our invention.
A is a copper disc. It is secured to a shaft a mounted so as to turn upon pivots
at a² and provided with a toothed wheel driving indicating or registering mechanism
showing the number of revolutions of the shaft and whereby the quantity of electricity
can be directly ascertained. The current' to be measured passes through the disc A
by the leading wires being connected to arms and e which are in electric contact with
the shaft and disc respectively by the contact pieces 63 and and springs &² and e.
Mercury cups or troughs may be employed in place of the spring contacts for
the purpose of causing the current to be measured to pass radially through
the disc.
This arrangement is represented in Figure 4 in which represents a mercury cup
making contact with a flange on the central part of the disc and C is another cup
making contact with the peripheral part. D is the electro magnet through the
coils of which a constant current passes. The pole pieces of the magnet have
the aforesaid enlargements or projections d³.
The driving power of the disc A increases in proportion to the intensity of the
magnetic field. The arrangement hereinafter described is employed for the purpose
of increasing the magnetic induction and especially for obtaining a uniform closeness
of the lines of force between the whole of the surface of the pole pieces () that
is to say obtaining uniformity in the magnetic resistance with regard to all the lines
of force produced. With this object also the copper disc A is perforated with a
number of holes which are filled up with plugs of soft iron a³ (see Figure 3). At
the parts where the greatest resistance is presented to the lines of force these

page_text: holes are more numerous or set closer together as shewn so that a perfectly
uniform closeness of the lines of force over the entire surface of the pole pieces
is obtained.
Having now particularly described and ascertained the nature of our said inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is
1. In electricity meters in which the current to be measured is caused to pass
radially through a conductive disc rotating in a constant magnetic field, enlarge-
ments or projections such as d³ on the pole pieces of the magnet giving the said field
substantially as herein before described with reference to Figures 12 and 4 of the
accompanying drawings.
2. For the purpose of obtaining uniformity in or equalising the magnetic
resistance in an electricity meter such as that herein before referred to the introduc-
tion of pieces of iron into the conductive disc substantially as hereinbefore described
with reference to Figure 3 of the accompanying drawings.
Dated this 27th day of February 1891.
J. H. JOHNSON & Co.