Improvements in Electricity Meters.
Year: 1899

page_text: Date of Application, 19th Dec., 1899
Complete Specification Left, 21st Aug., 1900-Accepted, 10th Nov., 1900
PROVISIONAL SPECIFICATION.
Improvements in Electricity Meters.
I, WILLIAM HENRY JOHNSON, of 26, Brandreth Road, Upper Tooting, in the
County of London, Electrical Engineer, do hereby declare the nature of this
invention to be as follows:-
This invention has reference to improvements in single phase alternating
current meters of the kind in which a rotary body, such as a disc of metal,
is caused to rotate by the inductive action thereon of two alternating electro-
magnetic fields produced respectively by shunt and series windings having a
phase displacement, the maximum emciency of such action being obtained when
the phase displacement is 90°. In such meters as heretofore constructed, there
has been provided in connection with the rotary body, which is connected to the
recording mechanism of the meter, a permanent magnetic brake for controlling
the speed of the said body (hereinafter called a disc).,
This construction of meter suffers from the disadvantage that its accuracy
depends upon the permanency or stability of the field of the so-called permanent
magnet. in practice, permanent magnets are very liable, through various causes,
to become weakened or strengthened, whereby the accuracy of the meter is
interfered with.
Now this invention has for object to obviate this disadvantage. For this
purpose an alternating current meter of the kind herein before referred to, is
constructed with an electro-magnetic brake that controls the motion of the
rotary disc and is excited by a shunt current. This electro-magnetic brake is
or may advantageously be arranged to act upon the disc at a point diametrically
opposite to that upon which the shunt electro-magnet used for rotating the
disc acts.
In one construction of meter according to this invention, a shunt electro-
magnet is used having two pairs of poles between which the disc rotates and
which are located opposite diametrically arranged parts of the disc so that only
that pair of poles which are adjacent to the series electro-magnet will exercise
any rotative action on the disc, and the other pair only a braking action. The
shunt electro-magnet in this case may comprise two horizontal bars arranged one
above and the other below the disc and having their ends bent towards the disc
so as to form two diametrically arranged pairs of poles between which the disc
is located, the two bars being wound with a shunt winding. The series coil or
electro-magnet may, as usual, consist of two parts arranged at opposite sides of
the disc and in proximity to one of the pair of poles of the shunt electro-
magnet.
When in use on circuits with standard pressure, the improved meter will
register true Watt-hours. On circuits with variable pressure, the meter will
register only current in phase with the pressure, since with increase or decrease
of pressure the strength of the brake poles will vary proportionately to the
strength of the motor poles of the shunt magnet and the speed of the disc will

page_text: only vary as the current varies. In this instance the improved meter will
record true ampére hours.
Dated thin 10th
1000
Improvements in Electricity Meters.
I, WILLIAM HENRY JOHNSON, of 26, Brandreth Road, Upper Tooting, in the
County of London, Electrical 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 has reference to improvements in single phase alternating
current meters of the kind in which a rotary body, such as a disc of metal,
is caused to rotate by the inductive action thereon of two alternating electro-
magnetic fields produced respectively by shunt and series windings having a
phase displacement, the maximum efficiency of such action being obtained when
the phase displacement is 90°. In such meters as heretofore constructed, there
has been provided in connection with the rotary body, which is connected to the
recording mechanism of the meter, a permanent magnetic brake for controlling
the speed of the said body (hereinafter called a disc).
This construction of meter suffers from the disadvantage that its accuracy
depends upon the permanency or stability of the field of the so-called permanent
magnet. In practice, permanent magnets are very liable, through various causes,
to become weakened or strengthened, whereby the accuracy of the meter is
interfered with.
Now this invention has for object to obviate this disadvantage. For this
purpose an alternating current meter of the kind hereinbefore referred to, is
constructed with an electro-magnetic brake that controls the motion of the
rotary disc and is excited by a shunt current. This electro-magnetic brake is
or may advantageously be arranged to act upon the disc at a point diametrically
opposite to that upon which the shunt electromagnet used for rotating the
disc acts.
In one construction of meter according to this invention, a shunt electro-
magnet is used having two pairs of poles between which the disc rotates and
which are located opposite diametrically arranged parts of the disc so that only
that pair of poles adjacent to the series electro-magnet will exercise
any rotative action on the disc, and the other pair only a braking action. The
shunt electro-magnet in this case may comprise two horizontal bars arranged one
above and the other below the disc and having their ends bent towards the disc
so as to form two diametrically arranged pairs of poles between which the disc
is located, the two bars being wound with a shunt winding. The series coil or
electro-magnet may, as usual, consist of two parts arranged at opposite sides of
the disc and in proximity to one of the pair of poles of the shunt electro-
magnet.
Referring to the accompanying illustrative drawings,
Figs. 1, 2 and 3 show in front elevation, side elevation and plan, respectively,
one construction of meter according to this invention, with the outer casing
removed.

page_text: Fig. 4 shows (without casing) the meter in cross section on the line A, A of
Fig. 1, and
Fig. 5 indicates diagrammatically, the meter connected to the line wires of an
electrical circuit.
a is a disc of suitable metal fixed on a spindle a¹ mounted in suitable bearings
so as to rotate freely and, through appropriate gear, to actuate the recording
mechanism.
In the example, teeth on the spindle a¹ gear with a toothed wheel d¹ fast on
a spindle on which is a fast pinion which drives a toothed wheel d¹ fast
on another spindle do on which is a fixed pinion do which drives a toothed wheel d
fast on another spindle 8 on which is fast a worm d, which drives a worm
wheel do on a spindle on which is fixed a pinion d" that drives the first wheel e¹
of the recording mechanism e. The shunt electro-magnet f, f, comprises two
bent bars or series of juxtaposed plates f f, the ends forming two pairs of
poles g, and h, h between which the disc a rotates. I have represented the
cores of these electro-magnets as composed each of a series of juxtaposed plates,
clamped together by hook-like extensions k of a bracket which is secured by
screws m to the back plate c of the meter.
The series electro-magnet, consists of two parts n, n, arranged at opposite sides
of the disc a, each part comprising a strip of copper wound in a coil, the two
parts being carried by a bracket o secured to, but insulated from, the base plate c.
It will be seen that the portion of the disc a for the time being between the
shunt-magnet poles g g is diametrically opposite the portion that is between
the poles h h, so that only that pair of poles g, g, adjacent to the series electro-
magnet n exercises any rotative action on the disc, whereas the poles h h have
braking action.
One end of the series coil n is connected to a screw clamp and its other end
is connected to a screw-clamp r to which is also connected one end of the shunt
winding f, the other end of said shunt winding being connected to a screw
clamp s.
The method of connecting the meter to the main wires of an electrical circuit
is illustrated diagrammatically in Fig. 5. The line wire is severed as at y,
the severed end being connected, one to the terminals q, the other to the
terminal r; the line wire u is connected to the terminals, so that the current
passes in series through the winding n and in shunt through the winding fl of
the shunt electro-magnets f.
When in use on circuits with standard pressure the improved meter will
register true Watt-hours. On circuits with variable pressure, the meter will
register only current in phase with the pressure, since with increase or decrease
of pressure the strength of the brake poles will vary proportionately to the
strength of the motor poles of the shunt-magnet and the speed of the disc will
only vary as the current varies. In this instance, the improved meter will record
true ampere hours.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed I declare that what
I claim is:-
1. In an alternating current meter of the kind in which a rotary body, such
as a disc of suitable metal, is caused to rotate by the inductive action thereon
of two alternating electro magnetic fields produced respectively by shunt and
series windings having a phase displacement, controlling the speed of the said
rotary body by means of an electro magnetic brake that is excited by a shunt
current.
2. An alternating current meter of the kind referred to comprising a rotary
body, such as a disc of suitable metal, a series coil or electro magnet, and a
shunt electro magnet having two pairs of poles between which the said rotary
body can rotate, the series coil or electro magnet being arranged in proximity

page_text: to one pair of poles of the shunt electro magnet, whose other pair of poles
occupies a diametrically opposite position in relation to the rotary body and
acts as a brake only, substantially as described.
3. The improved alternating current electricity meter constructed arranged
and operating substantially as hereinabove described with reference to, and
illustrated by, the accompanying drawings.
Dated this 21st day of August 1900.
For the Applicant,
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C.,
Chartered Patent Agent.