RESERVE CO are Applicable to Dynamo-electric Generators and Motors.
Year: 1887

page_text: Date of Application, 20th Dec., 1887
Complete Specification Left, 17th Sept., 1888
Complete Specification Accepted, 16th Nov., 1888
RESERVE CO
are Applicable to Dynamo-electric Generators and Motors.
1, GEORGE HOOкHAM of 7 & 8 New Bartholomew Street, Birmingham Manu-
facturer do hereby declare the nature of my invention for ELECTRICITY METERS
AND DYNAMO-ELECTRIC GENERATORS & MOTORS to be as follows:-
My improvements in Electricity Meters relate mainly to the construction of meters
designed to measure electric energy, whether in the shape of currents of constant
direction or alternating currents, some of the details, however, are also applicable to
meters designed to measure current only, and to Dynamo-electric generators and
motors.
I construct meters for measuring electric energy by causing the current to be
metered, or a portion of it to pass either through the armature or field-magnets of a
suitable electro-motor while the field-magnets or armature (as the case may be) are
placed upon a shunt circuit, in such a way as to give a field proportional to the
Electro-motive force. If the armature or field-magnets contain iron care must be
taken that they are far removed from saturation. If there is iron in the armature I
compensate for the magnetic drag produced either by giving a suitable amount of
positive lead to the brushes, or by compound-winding the armature or the field-
magnets.
The commutators used are preferably divided mercury commutators as they eliminate
the errors arising from the friction and the varying resistance at the commutator.
On the axis of this electro-motor is mounted a disc of copper or other suitable metal
which moves in a constant magnetic field, and offers resistance to the rotation of the
electro-motor by virtue of the eddy-currents generated in it. This constant field may
be made by perinanent magnets, or by electro-magnets which are practically saturated
when the meter is used for a system of the type for which it is designed; and they
are preferably arranged in series with that part of the electro-motor which carries the
shunt circuit. The pole-pieces of the magnets forming the magnetic field of the brake
may be grooved to increase the retarding effect.

page_text: The above may be made to measure electric energy when the currents are alterna-
ting, but in such cases the magnetic field acting upon the brake must be made by
permanent magnets or by electro-magnets of constant power either by reason of their
saturation or otherwise worked by some independent source of electricity.
In order to reduce friction in the above apparatus I may, when the spindle is hori-
zontal, support its reduced ends each on the edge of a horizontal or nearly horizontal
disc (the said edge or rim being turned up, if necessary, for the purpose) whose
vertical or slightly inclined axis rotates on a hardened point; the pointed ends of the
first spindle being kept in position by V slots as described in the complete specification
of Letters Patent granted to me on the 21st day of March 1887 No. 4225. If the
spindle is vertical, rotating on its lowest point, I may float the rotating part of the
meter in liquid by means of a bowl or hollow sphere through which the spindle
passes, and which is wholly or partially immersed in liquid.
When I wind the shunt circuit or part of the shunt circuit on the armature,
although the use of iron simplifies construction, I may dispense with it, and wind the
fine wire on the copper disc. In that case many turns are taken across each section,
and they are held in place, while winding, by being passed through slits in the edge
of the disc, and being carried along a trough formed on the back of the disc round its
periphery. The wire is finally held in place by a ring of ebonite or insulated metal
screwed to the face of the disc and pressing the wires between itself and the disc near
its periphery and by the edge of a cup-shaped attachment sliding on the spindle,
which with its rim is made to press the wires against the disc near its centre. The
arrangement is applicable to the main conductor for small currents. The connections
are similar to those described in full in my patent above referred to.
The last described part of my improvements, that is the method described of
repeated winding of the armature wire across the disc is applicable to dynamo-electric
generators and motors; in this case the disc is divided into sectors so as to minimise
Foucault currents; or the disc may be made of a non-metallic material.
Dated this 19th day of December 1887.

page_text: are Applicable to Dynamo-electric Generators and Motors.
I GEORGE HOOK HAM of Nos. 7 and 8 New Bartholomew Street, Birmingham in the
County of Warwick, Manufacturer do hereby declare the nature of my invention
and in what manner the same is to be performed to be particularly described and
ascertained in and by the following statement:-
My improvements in electricity meters relate mainly to the construction of meters
designed to measure electric-energy whether in the shape of currents of constant
direction or alternating currents; some of the details however are also applicable to
meters designed to measure currents only and to dynamo-electric generators and
motors.
I construct meters for measuring electrical energy by causing the current to be
metered, or a portion of it, to pass either through the armature or field magnets of a
suitable electro-motor, while the field magnets or armature (as the case may be) are
placed upon a shunt circuit in such a way as to give a field proportional to the
electro motive force. If the armature or field magnets contain iron care must be taken
that they are far removed from saturation. If there is iron in the armature I com-
pensate the magnetic drag produced either by giving a suitable positive lead to the
brushes or by compound winding the armature or the field magnets.
The commutators used are preferably divided mercury commutators as they eliminate
the errors arising from friction or varying resistance at the commutators.
On the axis of the electro motor is mounted a disc of copper or other suitable metal
which moves in a constant magnetic field and offers resistance to the rotation of the
electro motor by virtue of the eddy currents generated in it. This constant field may
be made by permanent magnets or by electro magnets which are practically saturated
when the meter is used for a system of the type for which it is designed and they are
preferably arranged in series with that part of the electro motor which carries the
shunt circuit. The pole pieces of the magnets forming the magnetic field of the
brake may be grooved to increase the retarding effect.
The above may be made to measure electrical energy when the currents are
alternating but in such case the magnetic field acting upon the brake must be
made by permanent magnets or by electro magnets of constant power either by
reason of their saturation or otherwise worked by some independent source of
electricity.
Figure 1 of the accompanying Drawings represents in side elevation a meter
constructed according to my invention arranged for measuring the energy of currents
of constant direction and Figure 2 represents in front elevation and Figure 3 in edge
view the armature of the said meter separately.
The same letters of reference indicate the same parts in the several Figures of the
Drawings.

page_text: a is the armature; is the brake; c is the frictionless commutator with mercury
cups d. d arranged as described and represented in the specification of Letters Patent
granted to me dated 21st March 1887, No. 4225; e, e are electro magnets very far
removed from saturation so that the intensity of the field in which the armature a
moves varies as the electro motive force of the circuit, the said electro magnets being
placed on a shunt and the main current to he metered passing through the armature:
fare brass tubes containing steel magnets and giving a constant field in which the
brake rotates. The said steel magnets should be so proportioned that a being the
cross-section of the steel bars, L. their total length A the cross section of the pole
piece 7 the distance between the pole pieces then should be at least 70 times which
proportions are essentially the same as those contained in a proposed amendment of
the specification of the Letters Patent hereinbefore referred to which proposed
amendment was filed in the Patent Office on the 25th day of August 1888. When
these proportions are observed the field is very powerful and practically constant.
The part of the proposed amendment I refer to is in the following words-
*
#
*
A
11
"I prefer to make the ratio between the area of the pole pieces and the distance
apart of the said pole pieces at least seventy times as great as the ratio between the
"sectional area of the steel magnets and the length of the said magnets. For
example if the length of the steel magnet bars be six inches and their sectional
area four square inches the area of each of the pole pieces may be six square
"inches and their distance apart one eighth of an inch. Or the area of each of the
pole pieces may be three square inches and their distance apart one sixteenth of an
"inch. When these proportions are adopted a powerful and stable field is obtained."
The steel magnets are magnetised in position by a coil of wire coiled round the
brass tubes and carrying a powerful electric current which coil after the steel bars
have been magnetised is uncoiled from the tubes f. f.
In order to reduce the intensity of the magnetic field to the point below which
it will not fall during the use of the meter subject the magnets to a percussive
action as long as the magnetic intensity is diminished thereby. This I effect by
striking or hammering the magnets longitudinally by means of a mallet or hammer,
that is, by striking longitudinally the central or axial pins in the tubes ff is a worm
wheel driving the counter of the meter the said counter not being represented in the
drawing; h, are trains of anti-friction wheels of the kind described in the speci-
fication of the patent herein before referred to, on which wheels the axis of the
armature and brake & take a bearing.
as
I will now describe the armature. The sections of the armature instead of being
broad and in the form of sectors as described and represented in the specification of
the Patent before referred to are reduced in breadth and have the form of spokes
represented in the elevation of the armature Figure 2 where the spoke like sectors
are marked a². The said spoke like sectors a² may be made self supporting with the
aid of spiral connections which are soldered to them as also described in the
specification of the Patent before referred to. They are in that case screwed to a
central boss preferably made of ebonite and marked a³ in Figures 2 and 3. A
metallic boss may be employed in which case the sectors are insulated from the said
metallic boss. Or the spoke like sectors may have a metallic support but in this case
instead of using a continuous disc as described and represented in the specification of
the Patent before referred to, the disc is slit radially and is made preferably of a
metal or alloy such as German silver having a high specific resistance. The general
object of these arrangements is to make the Foucault currents generated in the
arinature negligible.
The general arrangement of the parts of the meter herein described and represented
is applicable to the measurement of alternating currents but in this case I use a
separate standard for the anti-friction train of supporting wheels at the electro
magnet end of the meter as described in the specification of the Patent before referred
to. The electro magnets are reduced to the smallest convenient dimensions, their cores
-being-formed-of-fine charcoal-wires and the magnets are fixed on insulating blocks.

page_text: The object of reducing the magnets to the small size described is to diminish the
loss of energy caused by the magnetization and demagnetization of the wires.
In place of iron wire thin horse shoe shaped plates of iron may be used the said
plates being insulated from one another by varnish or paper.
The main current as before described passes through the armature whose sections
are made as narrow as possible and if it is supported on metal the radial slits in the
metal must be as close together as possible the metal itself having a very high specific
resistance. Owing to the difference of phase in the main and shunt currents there
may be a loss of driving force to the extent possibly of seventy per centum but
nevertheless the rotating parts being made very light and as small as practicable this
is aimply sufficient and the meter can be made to work with very small currents.
The rotations of the armature will be a measure of energy or current according as
the field of the electro magnet does or does not vary with the electro motive force.
Practically in the case of alternating currents this field will always vary with the
electro motive force to a greater or less extent and consequently the meter will never
measure current simply.
By giving a positive lead to the brushes I mean setting them forward beyond the
neutral line of commutation in the direction of rotation. When this is done with an
armature containing iron, it magnetises the cores of the magnets by induction and
the motor will start or tend to start without any current passing round the magnets
as is well understood.
That portion of the alternating current ineter hereinbefore described and illustrated
in the accompanying drawings constituting the motor, namely the armature and
magnets may be employed as an alternating generator and motor for general
purposes and that portion of the electric brake constituting the permanent magnet
circuit is applicable to continuous current generators and motors.
Having now particularly described and ascertained the nature of my Inven-
tion and the manner in which the same is to be performed I declare that I claim
as my invention :-
First In an electricity meter the combination of the parts of electro motors of the
kinds hereinbefore described and illustrated in the accompanying drawings, whereby
the driving force acting on its armature is proportional both to the quantity of the
current to be metered and to its electro motive force, with an electric brake moving
in a constant field as herein before described and illustrated in the accompanying
Drawings.
Secondly-In an electricity meter where the constant field of the brake is obtained
by electro magnets, the placing of these electro magnets in series with those of the
electro motor as herein before described.
Thirdly-In an electricity meter in which iron is used in the armature, com-
pensating for magnetic drag and friction by giving a positive lead to the brushes
as herein before described.
Fourthly In an electricity meter for alternating currents, the combination of an
alternating current electro motor with an electric brake moving in a constant field and
the use of the said motor generally as a generator and motor as hereinbefore described
and in part illustrated in the accompanying Drawings.
Dated the 17th day of Santamban 1000
W. T. WHITEMAN,
Agent for the Applicant.