Improvements in Apparatus for Measuring the Expenditure of Electrical Energy.
Year: 1891

page_text: Date of Application, 12th Dec., 1891
Complete Specification Left, 6th Sept., 1892-Accepted, 10th Dec., 1892
TRUVIDIONAL DILULTICATION.
Improvements in Apparatus for Measuring the Expenditure of
Electrical Energy.
We, SIGMUND SCHUCKERT and ALEXANDER WACKER of the firm of
"Schuckert & Co., Commandit-Gesellschaft," of Nuremberg, in the Empire of
Germany, Manufacturers, do hereby declare the nature of this invention to be as
follows:-
This invention relates to improvements in the apparatus hitherto known for
measuring the expenditure of electrical energy. For this purpose different con-
structions have been devised in which the electro-motor and a damping device are
so combined that the torque of the motor is proportional to the energy effect, and
that of the damping device to the speed of the motor.
In the improved apparatus the field windings of the electromotor are passed
through by the current to be measured, while the armature is connected to points
of constant potential. The damping device consists of a pair of electromagnets in
the vicinity of which rotates a copper disc, so that eddy currents are produced
therein which damp the disc.
In such electric meters,-which are supposed as known,--the work done by
the electromotor can be divided into two parts, first the overcoming of the
mechanical resistances and second of the damping action effected by the copper
disc. While the counting is based on the use of said action, the frictional work
has only a disturbing effect and produces inaccuracies in the indications of the
instrument. This led to the use of a supplementary coil in order to climinate the
frictional resistances by creating a constant additional magnetic field and to effect
easy starting of the instrument. The constant magnetic additional field, which is
destined to produce a momentum of revolution equal to the frictional resistances
may however also be attained in a different manner. The additional coil can be
replaced by a piece of iron, which when approached to the armature becomes
magnetic and produces the requisite torque. Also the magnetic action at a
distance of the damping of the electromagnets may be employed in a corresponding
manner direct for the said purpose.
To render the armature of the motor as light as possible, a construction is
preferred in which the armature of the electric meter is formed as a drum,
preferably of spherical shape, in order to attain the least possible weight with
economy in space. The wire layers of said drum are connected to two small plates,
opposite each other. In order to prevent the formation of a bulging or knot at
the places of crossing, the wire layers are made as flat as possible. Said plates
may however also be dispensed with and the wire layers merely cemented together.
It is essential in the improved arrangement, that the core, which as dead weight
would only increase the total weight is completely avoided and consequently the
frictional resistances are reduced by the small weight to a minimum.
A further improvement consists in the application of a temperature correction,
which is necessary for very exact indications, as the resistance of the copper disc,
and consequently the damping action by the eddy currents, depends upon the
temperature. The temperature correction which we prefer to employ, essentially
consists of a metal thermometer so disposed as to switch, by establishing contacts,
in a more or less number of windings of the damping magnets, thereby diminishing
or increasing the power of the damping electromagnet and therefore the damping
action corresponding to the temperature.
Dated this 10th dox of December 1891
HUELSER & Co.,
Agents for the Applicants.

page_text: COMPLETE SPECIFICATION.
Improvements in Apparatus for Measuring the Expenditure of
Electrical Energy.
We, SIGMUND SCHUCKERT and ALEXANDER WACKER, of the firm of
Schuckert & Co., Electrical Engineers, of Nuremberg, in the German Empire,
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 :-
For recording the consumption of electrical energy, various meters have been
designed, in which an electromotor and a brake device are so combined, that the
torque of the motor is proportional to the energy supplied, and that of the brake
device to the speed of the motor.
In the accompanying drawing, Fig. illustrates such an instrument. The
field windings of the electromotor a carry the current to be measured, while the
armature 6 is connected to points of constant potential. The brake device
consists of a pair of electromagnets c, e, in the vicinity of which rotates a copper
disc d, so that eddy currents are produced therein, which damp or retard the motion
of the disc.
In this well known class of electric supply-meters, the work done by the electro-
motor may be divided into two parts, namely, that which is necessary for over-
coming the mechanical resistances, and that which is due to the damping action of
the copper disc. While the counting is based on the use of said action, the frictional
work has only a disturbing effect, and produces errors in the indications of the
instrument. This led to the use of a supplemental coil, e, Fig. 1, in order to com-
pensate for the frictional resistances by creating a constant supplemental magnetic
field, which also facilitates the starting of the instrument.
The supplemental and constant magnetic field, which is destined to produce a
torque equal to the frictional resistances, may, however, be produced in a different
manner. In our improved supply meter, we replace the supplemental coil by a
piece of iron, e, Fig. 3, which, when placed close to the revolving armature,
becomes magnetic and produces the requisite torque. For the same purpose, we
may directly employ the magnetic action at a distance of the damping electro-
magnets or electro-magnet brake, as indicated in Figs. 2 and 3 by dotted lines,
that is by forming on one of the poles of the electro-magnet c c a lateral
extension f.
To render the armature of the motor as light as possible, we adopt by preference
the construction, which is shown by Fig. 2 in elevation and by Fig. 3
in cross section, all parts except the armature, the damping electro-magnets,
and the copper disc, being omitted for the sake of clearness. The armature of the
electric motor is formed as a drum, preferably of spherical shape, in order to com-
bine lightness with economy of space. The armature shaft carries a pair of small
discs a, a', to which the wires bare cemented in groups or layers. In order to
prevent the formation of a bump or knot, where the layers cross each other, the
latter are made as flat as possible.
The plates a may, however, be dispensed with, and the layers of wire merely
cemented together. It is essential in the improved arrangement, that the core,
which would only increase the dead weight, is completely avoided and consequently
the frictional resistances are reduced to a minimum.
A further improvement consists in the use of a temperature correction, which is
necessary for very exact indications, as the resistance of the copper disc, and con-
sequently the brake action by the eddy currents, depends upon the temperature.
The temperature correcting device, which we prefer to employ, chiefly comprises a
metal thermometer, so arranged, as to switch in, by establishing suitable contacts,
a greater or less number of windings of the magnetic brake, thereby diminishing

page_text: or increasing the power of the brake magnet and therefore the damping or
retarding action, in accordance with the temperature.
In Fig. 4, A designates a spiral-shaped metallic thermometer, or Bourdon tube,
which by its expansion assumes the position shewn by dotted lines, and takes along
the contact lever B, which slides over the contact pieces C.
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-
In electric supply meters or apparatus for measuring the expenditure of
electrical energy:
1. For producing a constant supplemental magnetic field adapted to compensate
for the errors caused by frictional resistances and to facilitate the starting of the
apparatus, the use, in lieu of a supplemental coil, of a separate piece of iron
influenced by the armature, or the utilization of the magnetic distance effect of the
electro-magnetic brake, substantially as described.
2. A drum armature without iron, having coils formed as flat strips which are
rigidly connected with the shaft, so that a core is dispensed with, for the purpose
of reducing the weight of the armature, and consequently the frictional resistances,
substantially as set forth.
3. A temperature correcting device, chiefly comprising a metallic thermometer
adapted to establish suitable contacts, and thereby to switch in and out of circuit a
greater or less number of windings of the electro-magnetic brake, substantially as
described.
Dated Ch 200
S. SCHUCKERT,
A. WACKER,
By Fairfax & Wetter,
433, Strand, London, Agents.