Improvements in Electric Meters.
Year: 1891

page_text: ate of Application, 1st Sept., 1891-Accepted, 24th Dec., 1891
COMPLETE SPECIFICATION.
[Communicated from abroad by LA COMPAGNIE ANONYME CONTINENTALE
POUR LA FABRICATION DES COMPTEURS À GAZ ET AUTRES APPAREILS, an
Incorporated Company, of No. 9, Rue Petrelle, Paris, France.]
Improvements in Electric Meters.
I, CHARLES DENTON ABEL, of No. 28 Southampton Buildings, Chancery Lane
in the County of London, Consulting Engineer and Patent Agent, 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 relates to that class of electric meters termed motor meters,
which include a motor mechanism moving at a speed proportional to the electro
motive force to be measured.
The meters of known construction working according to this system are generally
composed of an electro motor the inducing and induced parts of which are arranged
on the circuit to be measured; the motor is connected to a magnetic or other
brake so that the speed is made proportionate to the electro motive force of the
current.
With such a meter, the motor measuring apparatus has to overcome passive
resistances, such as the friction of bearings, of the commutator brushes, the
counter, air resistance &c., which give rise to error that may be considerable for
low speeds.
In the meter of this kind which forms the subject of the present invention, the
current to be measured passes through an electro dynamometer, and the motor is
actuated by a current from any source, such for example as a shunt current from
the main current. The speed of the motor is regulated by a current regulator
controlled by the electro dynamometer.
By this arrangement all causes of error such as above indicated can be obviated,
as will be shewn later on
I will proceed to describe the improved meter with reference to the accompanying
drawings in which
Figure 1 shews a side view and Figure 2 a front view of the same.
It consists in principle of a vertical axis A mounted to move freely, and suspended
from a torsion thread. This axis carries firstly, one of the bobbins constituting
an electro dynamometer Wattmetre, such as the bobbin B with fine wire for
example, I being the bobbins traversed by the main current; and secondly it
carries a circular metal disc D by preference of copper, attached to the piece G
fixed on A. by means of rods F.
Secondly, the instrument consists of an axis C forming an extension of A and
carrying two or more magnets E E, so arranged as to form magnetic fields passing
through the disc D.
Thirdly, of an electro motor M of any suitable form which puts the axis C
in motion by means of toothed gear or otherwise; or it might be mounted directly
on the axis C.
The parts being thus arranged, if the axis C be turned there will be produced
in the disc D local induced currents which will tend to make it revolve at a speed
strictly proportional to the speed of the axis C. The same effect may be produced
by fixing D on C and E on A.
When the current passes through the electro dynamometer, it causes the axis A
to turn in the direction of the arrow, which direction is opposed to the rotation
of the magnets, with a force proportional to the strength of the current. If

page_text: therefore the speed of C be regulated by any suitable means, so that at each
moment the axis A remains in equilibrio under the action of these two opposed
forces, namely the couple exerted by the electro dynamometer and the couple
produced by the induced currents in D, the speed of C will at every moment be
proportional to the strength of current passing through the electro dynamometer.
It will consequently be sufficient to register the number of revolutions made
by C for measuring the energy expended in the circuit on which the meter is
mounted.
This regulation is effected by a contact t¹ which is made and broken by the
oscillations of B and which controls the passage of the current in the motor M.
The construction of the various above described parts are as follows.
The magnetic fields for acting on the disc D are by preference composed of two
series of small V shaped magnets E as shewn in detail at Figure 3; these series
of magnets, of which 4 are shewn, are placed respectively above and below the disc.
The poles of opposite sign being arranged opposite each other, so as to form twice
four magnetic fields passing through D. Each series is mounted upon a piece
which can be shifted on the axis C, and the regulation can be effected by moving
the two sets of magnets to or from each other.
means of
The advantage of this arrangement is that a very powerful effect is produced by
magnets of comparatively small mass, and if any one of these should vary
in power, this variation amounts only to of 4 in the regulation.
The motor M Figures 1 and 2 consists of two fixed bobbins N forming induction
coils and of three fixed bobbins N¹ on an iron plate n mounted on the axis, forming
the armature.
These bobbins are connected to a collector with three contacts, on which slide
the brushes. A fly wheel V is mounted on the axis m for rendering the motion
uniform.
The axis A, on the mobility of which the susceptibility of the apparatus depends,
is suspended on a torsion thread, which must be made of such fineness that the
torsion couple which it exerts can be neglected. For preventing the breaking of
such a thread in consequence of snocks, and compensating for its extension, the
arrangement shewn at Figure 4 may be used. The fine thread a by preference of
silver wire, is fixed at a to the lower part of the hollow axis A and at a² to a
nipper A which can slide with slight friction in its support and carries a cross
piece A, shewn in plan at Figure 5. The axis A has at its lower part a reduced
end guided and centered in an adjustable bush a³ Figure 1. The nipper A' is
supported by a spring A2 forming a lever under the piece A', and which is regulated
by means of the screw A³.
The spring A2 is raised until the piece A* approaches close to the head of the
rod a'. This rod is fixed to the milled button a. By this means in the case of a
shock, the spring A2 is deflected and the thread a can only be subjected to a tension
equal to that of A².
The button and the rod a' which is engaged in a slot of A* as shewn at
Figure 5, serves to impart more or less twist to the thread, in case of want of
proper equilibrium, so that the effort exerted by the thread will not influence the
bobbin B when no current is passing, that is to say, when the meter does not
register.
The current regulator of the motor must regulate the speed of the latter in such
manner as to constantly maintain the axis A in equilibrio, that is to say, it must
produce an increase of current when the action of the electro dynamometer
preponderates, and a reduction in the contrary case. These variations should be
produced at the slightest movements of the axis A in order to prevent exaggerated
oscillations.
For obtaining perfect regularity a fly wheel of sufficient mass is placed on the
axis of the motor and the arrangement of regulator shewn in plan at Figure 6 is
adopted, which avoids sparking on breaking contact in an almost perfect manner.
A contact t mounted upon A carries with it in the motion of A an insulating

page_text: piece S Figure 6 pivotted at s, and in making contact either with t¹ or with t¹,
thereby establishes the contact t, t¹.
This piece S carries two flexible blades s and s¹ which by the displacements of S
are respectively in contact, the first with the studs 1 or 2, the second with the
studs 3 or 4, these four studs are fixed and electrically connected with the motor M,
as shewn at Fig. 6. The stud 1 is insulated; the studs 2 and 3 communicate
with M through the resistances R and R' which are assumed to be equal, and the
stud 4 communicates directly with M.
S being situated to the left hand and moving to the right, the contacts of s and s
with their studs will be made in the following order:
position of A.
When no current passes through the electrodynamometer, S is in the position No. 1,
5 and as t t is broken, the circuit of the motor is interrupted.
If A moves to the right the contact t t' is made, the circuit of the motor being
then:
Lastly, when comes into position the resistance
and the circuit becomes :
+ Att s4 M - value 3 Fig. 7.
When A moves to the left, the contact t¹ is broken, and the circuit becomes
s-1 s-2 R M.
The current consequently drops suddenly to the value 1 until S passes from the
position 2 to the position 1 where it becomes zero.
It will be seen that by this arrangement, the current is always greater during
the oscillation to the right than during the corresponding oscillation to the left,
and that the breaking of the circuit only occurs when one of the resistances R or R¹
is interposed in the circuit of the motor.
In the normal working of the apparatus the axis A assumes automatically a slight
oscillating movement in a position such that the mean intensity of the current in
the motor is that which imparts to it the required speed for maintaining the axis A
in equilibrio; for diminishing the sparking still further, a considerable resistance
without self induction may be placed on a shunt circuit of the motor circuit.
The registering mechanism consists of a counter of suitable construction actuated
by C or M.
Resistances might also be introduced in the shunt circuit of the electrodynamo-
meter, or the proportional speed between M and the counter may be varied for
adjusting the instrument.
Fig. 8 is a sectional plan shewing the arrangement of the meter on a circuit and
the direction of the shunt currents passing to the electrodynamometer, to the
regulator of current, and to the motor.
The advantages of the above described construction of apparatus and the possible
modifications thereof are as follows
1. All the passive resistances, such as mentioned above are in this case overcome
by the motor and do not produce errors.

page_text: 2. Whatever be the effort exerted by the electrodynamometer, the motor is set
in motion as soon as the contact t t is made, and with a power which may be
as great as desired.
3. When in consequence of the slight variations in the speed of C, the bobbin
assumes an oscillating motion, the friction to be overcome by the axis A will not
cause any sensible error, as they cause sometimes an acceleration and at other times
a diminution in the speed of the motor. These oscillations are however only to the
extent of a few degrees and do not alter appreciably the proportions of the efforts
of the electrodynamometer.
Having now particularly described and ascertained 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. An electric meter for continuous or alternating currents composed of an
electrodynamometer, the effort of which is held in equilibrio by the couple resulting
from local currents produced in a conducting-body of disc, cylinder, wire coil or other
similar form, fixed to the electrodynamometer, by means of the rotation of magnetic
fields passing through the same, these magnetic fields being put in motion by a
motor the speed of which is regulated by a current regulator controlled by the
electrodynamometer, substantially as herein described, and the number of revolutions
of which indicates, according to circumstances, cither electrical energy or the
quantity of electricity expended in the circuit of the electrodynamometer, as herein
described with reference to Figs. 1 and 2 of the drawings.
Dated this 1st day of September 1891.
ABEL & IMRAY,
Agents for the Applicant.