Improvements in Electricity Meters for Alternating Currents.
Year: 1896

page_text: Date of Application, 22nd Oct., 1896
Complete Specification Left, 22nd July, 1897--Accepted, 16th Oct., 1897
PROVISIONAL SPECIFICATION.
Improvements in Electricity Meters for Alternating Currents.
I, GEORGE HOOкHAM, of 7 and 8 New Bartholomew Street, in the City of
Birmingham, Manufacturer, do hereby declare the nature of this invention
to be as follows:-
My invention relates to electricity meters for alternating currents, and my
object is to improve the accuracy and range of the meters while retaining a
simple mechanical construction and arrangement.
My invention relates to alternating current meters in which the motor part
consists of a rotating disc or other body rotated by the interaction of currents
caused in the disc by an electro magnet operated by a shunt from the alternating
current to be metered, and series currents passing through coils placed close to
the disc. The brake action is obtained by means of a permanent magnet and
Foucault currents.
.
My invention consists in new arrangements of the magnets round which the
series coils are wound, and in new arrangement of the shunt and series magnetic
circuits and magnetic poles.
In constructing an alternating current meter by one method of carrying my
invention into effect I arrange a rotating disc rotating on a vertical spindle, that
is, the disc rotating in a horizontal plane. On one side I place an electro magnet
excited by a shunt wound bobbin and having a cast iron or other iron core which
bends over, terminating in pole pieces above and below the disc. Both pole
pieces I extend nearly across the radius of the disc, and I bring them as close to
the disc as possible. The pole pieces on the upper side of the disc I construct
narrow in proportion to its radial length. The pole piece below the disc I con-
struct narrow, so far as the part connecting to the back part of the core is
concerned, but I broaden the pole piece so as to extend over a surface three or
four times as wide as the surface covered by the upper pole piece. I preferably
curve the surface of the upper pole piece so as to present a convex surface to the
disc. Above the pole piece I mount a soft iron core with its polar ends parallel
in direction to the shunt magnet pole piece, and symmetrically disposed on each
side of the said pole piece. The polar ends of this electro-magnet I preferably
raise up from the disc both to a uniform distance, provided it be a distance
greater than the distance of the shunt magnet pole piece. I insulate the upper
part of this soft iron electra magnet from the cast iron core of the shunt electro-
magnet by means of a non-magnetic piece such as brass, and I wind the ends of
this electro magnet with series coils, which coils I dispose symmetrically and
equally both with regard to each other and with regard to the disc. The broad
cast iron pole piece below the disc serves at its two extremities to continue the
magnetic circuit of this series electro magnet, so that when in action two distinct
magnetic circuits are formed. As the two ends of the series electro magnet are

page_text: connected by the metal of the core, the winding is arranged to make them at
the same instant of opposite polarity. At the time when one pole of this series
wound electro magnet is north, tnen the opposed pole piece underneath the disc
will, by induction be south; the other end of it will be north, and the other pole
piece of the said series electro magnet will be south. The magnetic circuit thus
proceeds in a direction at right angles to the magnetic circuit of the shunt electro
magnet so far as the magnetic circuit is common to the two.
Instead of mounting my series electro magnet over the core of the shunt magnet,
I may form two separate series cores the poles of which extend above and below
the disc at either side. In this case I use a narrow central lower shunt pole, and
I wind the series windings upon the centre part of each core.
In another modification I preserve narrow upper and lower pole pieces for the
shunt electro magnet, and I mount a horse-shoe series magnet above the upper
pole as in the first instance described, and I also mount a semi-circular or horse-
shoe piece of soft iron below the lower shunt pole, and magnetically clear of it to
continue the magnetic circuit of the upper electra magnet. In some cases I form
a core casting which carries the shunt poles top and bottom, and also carries
projections from the shunt poles top and bottom, which projections serve for the
series circuit. These projections are in magnetic continuity with the shunt pole
pieces, and I so arrange them as to interfere with the magnetic circuit and the
shunt magnet as little as possible. This arrangement has the advantage of allow-
ing the whole of the cores for both shunt and series electro magnets to be cast
or formed in one piece.
In another arrangement, instead of making my series core of horseshoe shape.
with parallel sides, I increase the width of the cross connecting piece at the upper
end, and lend the poles inward and downward, and in this way I get my series
magnetic field more free from interference with the shunt magnet field.
In all these cases it will be seen that these arrangements cause the production of
three pole pieces above the rotating disc and approximately parallel and approxi-
mately radial to the disc axis.
In the instances I have given the lower pole piece is sometimes arranged as
one pole piece, sometimes divided into three separate pole pieces, and sometimes
provided with three projecting pole pieces in magnetic connection with each other.
To adjust the meter I sometimes provide a short circuit between the series coils
by means of a copper or silver wire of carefully regulated dimensions.
When an alternating current is passed through the series coils of this meter the
electro magnet is excited by the shunt current, and it produces currents in the
disc, which currents interact with the currents produced in the series coils, and
so drive the motor disc in the manner discovered by Professor Ferraris.
By my construction of meters I obtain the electro magnet poles very close to
the surface of the disc, and so I generate more intense induction currents in the
dise, and by my series magnet I obtain alternating current coils very close to the disc,
but capable of adjustment with regard to the disc independently of the adjustment
of the shunt magnet poles.
By the use of the short circuit wire I reduce the currrent passsing from the
series coils to a greater extent at low currents than at high currents, because the
high currents heat the short circuiting wire, and by increasing its resistance
reduce the proportional current passing at the higher eurents. I thus correct
for the braking effects which increase with the higher alternating currents.
Another part of my invention consists in a small addition to the end of the
permanent magnet pole piece, intended to allow adjustment with regard to a small
piece of iron placed upon the rotating disc intended to secure certainty of
stoppage. This improvement consists of a clamp piece clamping to the end of the
brake magnet pole, the said clamp piece being of soft iron, and carrying in a
projection a screwed iron pin passing through a screwed hole. This pin can be
adjusted to come within any desired distance from the disc, and the clamp may be
set so that the end of the pin occupies a position precisely over the piece of iro

page_text: in the disc. By this arrangement I am enabled to adjust the force with which the
disc is stopped to suit the required starting current.
Dated this 22nd day of October 1896.
MARKS & CLERK,
18, Southampton Buildings, London, W.C., and
13, Temple Street, Birmingham, Agents.
Improvements in Electricity Meters for Alternating Currents.
I, GEORGE HOOKHAM, of 7 and 8 New Bartholomew Street, in the City of
Birmingham, Manufacturer, 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:-
My invention relates to electricity meters for alternating currents, and my
object is to improve the accuracy and range of the meters while retaining a
simple mechanical construction and arrangement.
My invention relates to alternating current meters in which the motor part
consists of a rotating disc or other body rotated by the interaction of currents
caused in the disc by an electro magnet operated by a shunt from the alternating
current to be metered, and series currents passing through coils placed close to
the disc. The brake action is obtained by means of a permanent magnet and
Foucault currents.
My invention consists in new arrangements of the magnets round which the
series coils are wound, and in new arrangements of the shunt and series magnetic
circuits and magnetic poles.
Referring to the two accompanying sheets of drawings
Figure 1 is a side elevation of my improved meter with the covers of its case
removed.
Figure 2 is an end elevation with the cover in section.
Figure 3 is a plan with the case in section.
Figure 4 is a plan of the disc showing a groove carrying iron for the purpose
of stopping the disc.
Figure 5 is a side elevation of the shunt magnet core with the series magnet
core mounted on it.
Figure 6 is an end elevation of Figure 5, and Figure 7 is a plan.
In constructing an alternating current meter by one method of carrying my
invention into effect I arrange a rotating disc A rotating on a vertical spindle
that is, the disc rotating in a horizontal plane. On one side I place an electro
magnet B excited by a shunt wound bobbin and having a cast iron or other iron
core B which bends over, terminating in pole pieces B2 B3 above and below the
disc. Both poles I extend nearly across the radius of the disc, and I bring them
as close to the disc as possible. The pole piece 12 on the upper side of the disc
I construce narrow in proportion to its length radially. The pole piece B3 below
the disc I construct narrow, so far as the part connecting to the back part of the
core is concerned, but I broaden the pole piece so as to extend over a surface three
or four times as wide as the surface covered by the upper pole piece B2. Above the
pole piece I mount a cast or wrought iron core C with its polar ends either
parallel in direction to the shunt magnet pole piece or inclined as shown in
Figure 2 and symmetrically disposed on each side of the said pole piece. The
polar ends CC of this electro magnet I preferably raise up from the disc both to

page_text: a uniform distance, preferably a distance greater than, the distance, of the shunt
magnet pole piece. I insulate the upper part of this soft iron electro magnet from
the cast iron core of the shunt electro magnet by means of a non-magnetic piece D
such as brass, and I wind the ends of this electro magnet with series coils D¹ D
which coils I dispose symmetrically and equally both with regard to each other
and with regard to the disc. Upon the pole piece D I arrange a copper screen
slotted attachment D³ to assist in, starting. The broad cast iron pole piece B³
below the disc serves at its two extremities to continue the magnetic circuit of
this series electro magnet so that when in action two distinct inagnetic circuits
are formed. As the two ends of the series electro magnet are connected by the
metal of the core, the winding is arranged to make them at the same instant of
opposite polarity. At the time when one pole of this series wound electro magnet
is north, then the opposed pole piece underneath the disc will, by induction, be
south the other end of it will be north, and the other pole piece of the said
series electro magnet will be south. The magnetic circuit thus proceeds in a
direction at right angles to the magnetic circuit of the shunt electro-magnet so
far as the magnetic circuit is common to the two.
In another modification I preserve narrow upper and lower pole pieces for the
shunt elec.ra magnet, and I mount a horse-shoe series magnet above the upper
pole as in the first instance described, and I also mount a semi-circular or horse-
shoe piece of soft iron below the lower shunt pole, and magnetically clear of it to
continue the magnetic circuit of the upper electro magnet. In some cases I form
a core casting which carries the shunt poles top and bottom, which projections
serve for the series circuit. These projections are in magnetic continuity with the
shunt pole pieces, and I so arrange them as to interfere with the magnetic circuit
and the shunt magnet as little as possible. This arrangement has the advantage
of allowing the whole of the cores for both shunt and series electro magnets to be
cast or formed in one piece.
In all cases it will be seen that my arrangements cause the production of
three pole pieces above the rotating disc all approximately parallel and approxi-
mately radial to the disc axis.
In the instances I have given the lower pole piece is sometimes arranged as
one pole piece, sometimes divided into three separate pole pieces, and sometimes
provided with three projecting pole pieces in magnetic connection with each other.
When an alternating current is passed through the series coils of this meter the
electro magnet is excited by the shunt current, and it produces currents in the
dise, which currents interact with the currents produced in the series coils, and
so drive the motor disc in the manner discovered by Professor Ferraris.
By my construction of meters I obtain the electro magnet poles very close to
the surface of the disc, and so I generate more intense induction currents in the
dise, and by my series magnet I obtain alternating current coils very close to the
dise, but capable of adjustment with regard to the disc independently of adjustment
of the shunt magnet poles.
Another part of my invention consists in a small addition to the end of the
manent magnet pole piece G intended to allow adjustment with regard to a
small pieces of iron placed upon the rotating disc intended to secure certainty of
sterpage. This improvement consists of a clamp piece clamping to the end of the
bake magnet pole the said clamp piece being of soft iron, and carrying in a
gretion a screwed iron pin E passing through a screwed hole. This pin E
can be adjusted to come within any desired distance from the dise, and the clamp
may be set so that the end of the pin occupies a position precisely over the piece of
is in the dise. The iron in the dise may be a small piece of circular shape or
other shape but I prefer to arrange it in a circular groove as at F so as to allow
of the prolonged action of the iron in the dise on the magnet pole. In one form
I fill a quadrant F of the groove Figure 4 with iron filings, but I may use soft iron
wire let into the groove.
This arrangement has the advantage that the acceleration of the disc due to the

page_text: pull of the magnet on the iron is spent before the iron quadrant completely passes
and so the magnetic pull tending to stop the disc has only the normal velocity of
the disc to contend against.
Without this arc of iron the pull of the magnet has a tendency to increase the
disc velocity sufficiently to carry the iron past the magnet.
By this arrangement I am enabled to adjust the force with which the disc is
stopped to suit the required starting current.
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:
1. In an electricity meter for alternating currents a shunt excited electro magnet
with a narrow pole piece on one side of a disc or cylinder and a broad pole piece
or a divided pole piece on the other side, together with a series excited electro
magnet mounted one side with its poles faced by the broad pole or divided pole
piece on the other side, substantially as described.
2. In an electricity meter for alternating currents the arrangement of two
magnet circuits respectively shunt and series at or near right angles to each other
for the purposes herein before described.
3. In electricity meters the device for stopping the disc with certainty consisting
of iron on the disc and an adjustable piece on the brake magnet, substantially
as described.
4. In an electricity meter constructed as claimed in Claim 1 the device for
stopping with certainty consisting of an iron arc or extended piece on the disc
and a magnet substantially as described.
001
T.... 1907
MARKS & CLERK,
18, Southampton Buildings, London, W.C., and
13, Temple Street, Birmingham, Agents.
MARKS & CLERK,
18, Southampton Buildings, London, W.C., and
13, Temple Street, Birmingham, Agents.