Improvements in Electric Supply Meters.
Year: 1890

page_text: Date of Application, 17th Jan., 1890
Complete Specification Left, 17th Nov., 1890-Accepted, 10th Jan., 1891
PROVISIONAL SPECIFICATION.
Improvements in Electric Supply Meters.
JOHN PERRY. Professor of Engineering, Fellow of the Royal Society, of 10,
Penywern Road, Earl's Court, in the County of Middlesex, do hereby declare the
nature of this invention to be as follows:-
In the Provisional Specification of a supply meter, a Patent of which I have already
applied for, I described one way of carrying out a principle enunciated in my Patent
Specification, No 2642 of 1882.
This principle is that an electric motor either with permanent field magnets or
shunt electro-magnets resisted in its motion mainly by Foucault currents gives a good
supply meter.
When used with alternating currents I use choking coils or shunted condensers for
the purpose of causing the ratio of resistance to self induction to be the same in both
armature and field magnet circuits. It is possible to get this result by letting parts of
the shunt and series circuits be the two coils of a transformer. In the motor recently
described by me the armature is described as a surface of revolution; I have found
that this surface of revolution is most conveniently made conical in shape, as in this case
both the circular mercury cups can be made of small diameter, and that when I use the
cylindric form of armature which I described, not only do I make the upper lip small, but
I make the lower lip as small as possible, that is smaller in diameter than the cylindric
part of the armature which is passing through the magnetic field. I have also found that
the magnet pole pieces, one of which is placed inside and the other outside the armature,
ought not to be complete surfaces of revolution; that is the Foucault current resistance
to motion is very greatly increased if in its revolution a portion of the armature
passes through magnetic fields of very different intensities. Hence I introduce gaps
in the continuity of one or both of the pole pieces sufficiently broad and deep for these
portions of the field through which the armature passes to be comparatively weak,
but not so wide as those shown on the tubular magnet dynamo, Figure 4 of my
Specification No. 1178 of 1880. One good way of carrying out my invention is to
have the armature made that kind of surface of revolution which is formed of a
horizontal circular disc bounded by two cylindric lips which dip into two circular
mercury troughs. When magnetic induction takes place through the disc from
the upper to the under side, or from the under to the upper side, we have a
very good form of the motor described by me. The magnetic pole which is placed
underneath the disc part may be an iron expansion on the iron core of a tubular
magnet and the pole placed above the disc; the disc part may be a plate of iron
fastened to the outside or tubular part of the tubular magnet. As before the pole
pieces ought not to be continuous. In all cases a number of separate magnets may
be employed instead of one, whatever be the shape of my armature, all the north
poles being on one side and the south on the other. To reduce the solid friction of the
instrument I have found it good to surround a portion of the outer part of the
armature with paraffine oil or water or some other liquid which will partially lift it
from its bearings or diminish its weight on its bearings. To do away almost altogether
with the inaccuracy introduced in this and all other supply meters by solid friction I
have described the use of a little electro-anotor worked by constant currents, to act as
an auxiliary for the purpose of just overcoming whatever constant friction there may
be in the meter. When the armature of the electro-motor used in the supply meter
s of the Gramme or Siemens or any other ordinary type in which a commutator and
rushes are used, the auxiliary torque to overcome the constant or solid friction was
to be provided by merely winding the armature with a secondary circuit and a second
ommutator and brushes, this second circuit receiving nearly constant current from a
hunt circuit to the main supply leats, between which of course a nearly constant

page_text: potential difference exists or any other two points between which a nearly constant
potential difference exists. I find, however, that in all cases I can dispense with this
secondary winding in the following way, whether the current through the supply
meter is the whole current or only a shunted part of the whole current which is being
measured. Let A and B be the brushes or mercury cups which receive and give out
the current for and from the armature. Let C and D be the supply leads between
which there is nearly a constant potential difference. As already described the current
to be measured goes from C to A, then through the armature to B, and then to the
lamps or other contrivances which are being used, and a shunt circuit between C
and D, works the field magnet. Now my improvement consists in letting the shunt
circuit be between B and D, so that the current through the armature is not merely
the current to be measured, but, in addition, a nearly constant current due to this
shunt circuit. When this current is so great that there would be much waste of
energy in this shunt circuit, I connect B not to D but to an auxiliary wire E, whose
potential difference from Cis nearly constant but not as great as the potential difference
between C and D. It can be arranged that some customers take current from E by
the shunt circuits of their supply meters, and some give current to the same auxiliary
wire E, so that in such cases it is very easy to keep it at a nearly constant potential
difference from B without the use of an auxiliary generator or transformer of
electricity. When a house is wired on the "three wire" system E would be the
intermediate cable. I find that it is usually better to let the motor receive only a
shunted part of the whole current. Thus let the terminal of the meter receiving
current be A, and that which gives out current be M. In the instrument or attached
to it I sometimes have a conductor between A and M as well as the armature circuit.
I find that the back electromotive force of the motor acts causing at higher speeds
more of the current to pass through the direct branch from A to M, and hence this
contrivance produces to some extent the same sort of resistance as a Foucault current
resistance.
F
1000
Bated
15th day of January 1890.
1100T 23
COMPLETE SPECIFICATION.
Improvements in Electric Supply Meters.
1, JOHN PERRY, of 31 Brunswick Square, London W.C., Fellow of the Royal
Society, 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 a Patent Specification No. 2642 of 1882 I described an instrument for recording,
as a gas meter does for gas, the total quantity of electric energy (i.e. the integral of
current multiplied by potential difference) given during any time to a house or
machine. This instrument is called an Ergmeter. It was an electro motor through
whose armature the current passed, and the field magnet was an electro magnet coiled
with wire whose ends were kept at the potential difference of the electric supply to
the house or machine. All solid friction was diminished as much as possible and the
resistance to motion of the motor was either fluid friction or the magnetic friction
produced when a conducting body is moved in a constant magnetic field. Such an
instrument really measures the total quantity of electricity, instead of the electric
energy, when the potential difference of the electric supply is kept constant, or
when the field magnet is a permanent magnet. The instrument is then called a
Coulomb-meter.
1 have for eight years endeavoured to apply the above principle, but, there were
great difficulties due to the fact that the solid friction both at the brushes and bearings
of a motor was always considerable. This I got over by using roller bearings and
vessels of mercury as brushes, but the mercury surfaces altered with time and the
mercury brushes had to be given up. Now I have got over this difficulty in the
following way. I arrange as an adjunct to any Coulomb-meter or Ergmeter, in which

page_text: solid friction introduces errors, an auxiliary motor having a constant turning moment
(say an electromotor worked by a constant current) which is just not quite sufficient
to overcome the solid friction. Such a motor may be one like a little dynamo machine,
with either permanent magnets or electromagnets, or it may be a windmill or turbine
actuated by currents of air or other fluids produced by the heating of a wire conveying
a constant current. When the armature of the electromotor used in the supply meter
is of the Gramme or Siemens or any other ordinary type in which a commutator and
brushes are used, the auxiliary torque to overcome the constant or solid friction may
be provided by merely winding the armature with a secondary circuit and using a
second commutator and brushes, this secondary circuit receiving nearly constant current
from a shunt circuit to the main supply leads, between which a nearly constant potential
difference may be supposed to exist, or any other two points between which a nearly
constant potential difference exists, or in any other way receiving nearly constant
current. I find, however, that in many cases I can dispense with this secondary
winding in the following way, whether the current through the supply meter is the
whole current that is to be measured, or only a shunted part of the whole current.
Let A & B (Fig. 3) be the electrodes or brushes which receive and give out the
current for and from the armature. Let C and D be the supply leads between which
there is a nearly constant potential difference. The current goes from C to A then
through the armature to B and then to the lainps or other contrivances that are being
used, and a shunt circuit between C and D works the field magnet. Now my improve-
ment consists in letting the shunt circuit be between B and D so that the current
through the armature is not merely the current to be measured, but in addition a nearly
constant current due to this shunt circuit. When this current is so great that there
would be much waste of energy in this shunt circuit I connect B not to D but to an
auxiliary wire E or any electrode whose potential difference from C is nearly constant
but not so great as the potential difference between C and D.
My present improvement is also peculiar in the shape of the electromotor. My
armature consists of metal forming a hollow surface of revolution, capable of rotating
about its axis, which is vertical, bounded by two horizontal circular lips which dip
all the way round into two circular ring mercury troughs so that current passing from
one trough to the other through the armature passes in the direction of generating
lines in the surface of revolution. Thus there is the same kind of current all the way
round. If, however, the armature has holes in it or is not quite uniform it will still
work. The armature is attached to a vertical spindle in any rigid way and trains of
wheels or other well known devices may be used to record its number of revolutions
from one date to another. My armature is sometimes of a thin cylindric shape with a
disc closing one end, a smaller thicker cylinder forming the second lip. Sometimes
I not only make the upper lip small in diameter but I make the lower lip also smaller
than the cylindric part of the armature which passes through the magnetic field. I
sometimes make the armature conical in shape as in this case both the mercury cups
may be of smaller diameter.
Now such an armature as I have described will rotate if there is a magnetic flux or
induction from the inside to the outside or from the outside to the inside. The flux
may be produced, as all electricians know, by mere fixed coils of wire with currents
flowing in them. But an instrument with less error due to solid friction is produce.
when we have iron to increase the flux so that there is one kind of magnetic pole on the
one side and the other kind on the other side of my rotating armature. The flux may
also be produced by steel magnets. If the magnetic flux is permanent or constint or
produced by constant currents the instrument is a Coulomb meter. The most suitable
form of magnet is that which is called a tubular magnet, the wire being wound in a
hollow space between an iron centre M and an iron tube N₁, one pair of the ends
of M and N, being connected by iron so that the other ends of M and N, are opposite
magnetic poles. Pole pieces of iron may be attached outside M and inside N, so that
the surfaces or poles opposed to one another may be surfaces of revolution having
common axis, the axis of the magnet, and between these surfaces the part of the
armature which is to be acted upon may rotate. Thus the magnetic flux will be
it

page_text: produced as I have described. In this case one of the circular mercury troughs will
lie inside the tubular space of the magnet. If instead of iron we use magnet steel, a
magnetization of the magnet when it is made will be sufficient; but 1 prefer it to be of
iron, and whether of iron or steel to let the current which magnetizes it be such a
current as produces saturation, so that small changes in this current shall not produce
much change in the magnetization, and this current may now be derived from the
potential difference of the supply leads.
The part of the armature which dips into the mercury troughs may be of iron or
aluminium or nickel or any other metal which does not readily get amalgamated, or
the whole of the armature may be of such a metal; or it may be of copper or other
metal plated with nickel or some other metal that is not affected by mercury. Of course
a number of wires dipping into these mercury troughs will serve equally well with lips
which are quite continuous.
To produce my Foucault current resistance I place upon the main spindle or any
spindie gearing with it a mass of conducting material,-preferably a disc of copper-
moving in a permanent magnetic field; that is a magnetic field, howsoever produced,
whose strength does not alter with time. But not a uniform magnetic field, for a
portion of the moving conductor must in its motion find itself in places of very
different strengths. I prefer, however, to let the Foucault current resistance act in
the moving armature itself. That is, the magnetic polar surfaces one of which is
placed on the one side and the other on the other side of the armature ought not to be
complete surfaces of revolution. I introduce gaps in the continuity of one or both
of the polar surfaces sufficiently broad and deep for these portions of the field through
which the armature passes to be comparatively weak, but not so wide as those shewn
on the tubular magnet dynamo Fig. 4 of my Specification No. 1178 of 1880.
One way of carrying out my invention is to have my armature made that kind of
surface of revolution which is formed of a horizontal circular disc bounded by two
cylindric lips which dip into two circular mercury troughs. Magnetic induction
ought in this case to take place through the disc from the upper to the under side or
from the under to the upper side. One of the magnetic poles may be an iron
expansion on the iron core of a tubular magnet and the other may be a plate of iron
fastened to the outside or tubular part of a tubular magnet, but obviously there are
many ways of producing the flux. As before the polar surfaces ought not to be
continuous plane surfaces; they ought to have such gaps in them as will enable
Foucault currents to be formed in the armature as it rotates. In this and all other
cases a number of separate magnets may be employed instead of one, whatever be the
shape of my armature, to produce a permanent but discontinuous magnetic flux
(permanent as to time but discontinuous as to space).
As an example of one form of my invention the magnet (Figs. 1 and 2) is made a
tubular magnet whose polar surfaces N S are arranged in coaxial cylindric surfaces;
W is the wire winding through which the magnetizing current passes. A coaxial
hollow cylindric or cup shaped vessel of copper C (the armature) rotates in the spaces
between the magnetic polar surfaces N S, being attached to the spindle D. A copper
ring A insulated from the iron of the magnet forms one of the mercury troughs, being
connected to one of the supply conductors. The upper mercury trough is merely a
hollow space B in the top of the magnet. Into this mercury trough the cylindric
boss C₁ (taking the place of an inner lip in this case) of the copper vessel dips.
Current is taken away at B' from the mercury cup B. Fig. 2 is a horizontal section
through the poles of the magnet, shewing the gaps or projections, arranged so that
the strength of the magnetic field is great between opposite projections, and nearly
zero between the gaps, and hence the resistance to motion due to Foucault currents is
very great. A train of wheels, not shewn in the figure, gears with the upper part of
the spindle D and records the total number of the revolutions made by the arinature
from one date to another.
When in my claims I speak of a motor-supply-meter I want it to be understood
that I mean a supply meter using a motor constructed like any dynamo machine in its
arrangement of field magnets and armature, but not such an electromotor as one which

page_text: acts through the agency of heat or electrolysis; for indeed strictly speaking even such
electric meters as volummeters and ammeters are electromotors.
Having now particularly ascertained and described the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. To gear with supply meters, the use of a motor of such nearly constant turning
moment, as will nearly overcome the resistance to motion due to solid friction.
2. In ordinary electromotors used in supply meters, the use of a secondary circuit
or winding on the armature, arranged as described, to procure such a nearly constant
turning moment as will nearly overcome the resistance due to solid friction."
3. In using electromotors in supply meters, the arrangement described, by means
of which the current in the armature is always by a nearly constant amount in excess
of the current going through the armature to supply lamps and other contrivances, so
as to procure such a nearly constant excess turning moment as will nearly overcome
the resistance due to solid friction.
4. The use in motor supply meters of an armature which is a conductor shaped like
a disc or cone or some other figure bounded by coaxial surfaces of revolution
(including an armature shaped like a hollow cylinder only in case one or both of its
dipping lips are smaller than the cylinder itself) receiving and giving out electric
current from and to circular ring mercury troughs, combined with field magnets
either detached or one tubular magnet, the magnetic polar surfaces being arranged in
coaxial surfaces of revolution; the pole pieces being close to the two sides of the
armature.
5. The use in motor supply meters, of an armature which is shaped like a disc, cone
cylinder or some other figure bounded by coaxial surfaces of revolution receiving and
giving out electric current from & to circular ring mercury troughs, combined with
field magnets either detached or one tubular magnet the magnetic polar surfaces being
arranged in coaxial surfaces of revolution, discontinuities existing in these two polar
surfaces, either by there being a number of detached poles or by having gaps cut in
the otherwise continuous surfaces of revolution so that a Foucault current resistance to
motion is produced in the armature.
6. The use in supply meters of which the motor has an armature which is shaped
like a disc, cylinder, cone or some other figure bounded by coaxial surfaces of
revolution, receiving and giving out electric current from and to circular ring
mercury troughs, of field magnets with polar surfaces arranged in coaxial surfaces of
revolution; but with discontinuities or gaps in the magnetic polar surfaces so that a
Foucault current resistance to motion is produced in the armature the magnets being
either of steel or electromagnets excited by nearly constant currents.
7. The use in supply meters of which the motor has an armature which is shaped
1.ke a disc cylinder cone or some other figure bounded by coaxial surfaces of
revolution, receiving and giving out electric current from and to circular ring
mercury troughs, of field magnets with polar surfaces arranged in coaxial surfaces of
revolution; but with discontinuities in the magnetic polar surfaces so that a Foucault
current resistance to notion is produced in the armature, the magnets being electro-
magnets wound with wire connected as a shunt to the supply leads.
8. The use in motor supply meters of a tubular field magnet the polar surfaces of
which lie in coaxial surtaces of revolution, there being however discontinuity in one
or both of these surfaces by gaps in the surfaces or by iron projections from the
surfaces so as to produce a very non uniform field.
9. The supply meter described and shewn in Figures 1 and 2.