Improved Methods and Apparatus for Measuring Electrical Currents.
Year: 1895

page_text: Date of Application, 2nd Jan., 1895
Complete Specification Left, 1st Oct., 1895-Accepted, 7th Dec., 1895
PROVISIONAL SPECIFICATION.
Improved Methods and Apparatus for Measuring Electrical
Currents.
I, OLIVER BLACKBURN SHALLENBERGER, of Rochester, in the County of
Beaver and State of Pennsylvania, United States of America, Electrician, do
hereby declare the nature of this invention to be as follows:-
This invention relates to methods and apparatus for measuring indicating and
registering the energy transmitted by alternating electric currents, particularly
multiphase alternating currents.
It has been demonstrated by experiment that if a closed conducting circuit of
suitable form, mounted so as to be free to rotate, be placed in proper inductive
relation to two alternating magnetic fields of the same periodicity, a torque is
produced which is proportional to the product of three elements; namely, the
strengths of the respective magnetic fields and a function approximating the sine of
the angle representing the difference of phase between them. On this principal are
devised methods of an apparatus for measuring accurately the amount of energy
transmitted by alternating currents.
This invention may be applied in a simple manner by employing a form of
apparatus in which two actuating coils are inductively related to a movable
element, one of these coils being supplied with current proportional to that in the
work circuit, and the other with current proportional to and in quadrature with the
electromotive force impressed upon the work circuit, the current in these coils
producing a resultant shifting field, causing an armature to rotate within it. The
torque thus produced is proportional to the energy transmitted to the work circuit...
A retarding force is applied, such as that produced by the motion of a closed
conductor in a constant magnetic field which is proportional to the velocity of
rotation, so that the total movement during an interval of time is directly
proportional to the time integral of the energy transmitted, and it may be recorded
in any convenient manner.
In the accompanying drawings, illustrating this invention,
Figure 1 is a side elevation of a form of meter which is found to be suitable for
practical use, certain parts being broken away and others shown in section.
Fig. 1 shows a modification.
Fig. 2 is a plan, omitting certain parts.
Figure 24 is a section shewing the relative positions of the armature and coils.
Figures 3. 4. 5. 6 and 7 show diagrammatically various arrangements of the
inducing coils.
Figures 8 and 9 are vertical sections shewing modified forms of the apparatus.
Figure 10 is a diagram showing two phase work circuits and connections between
the same and the meter directly, showing also in dotted lines the connections for
transformers between the main circuits and the meter.
Figure 11 is a diagram of circuits carrying two phase currents with a meter for
each circuit.
Figure 12 is a diagram illustrating a single meter applied to a two phase 4 wire
circuit.
Figure 13 is a diagram shewing a meter applied directly to a two-phase three-wire

page_text: currents.
measuring three-phase
Figures 16 and 17 illustrate modified forms of the movable element of the
meter.
Figure 18 is a side view and Fig. 19 is a section of an inductance coil hereinafter
referred to.
Figure 20 shows a modified form of its core.
Figure 21 is an elevation of a modified construction of meter with diagram of the
circuit connections for a polyphase circuit, Fig. 22 is a plan.
Fig. 23 is a diagram shewing the connections for a three wire two phase
circuit,
Fig. 24 illustrates the connections for a two phase system having branches which
carry different loads, the insstruments indicating the total energy.
Fig. 25 is a diagram shewing the instrument applied to a single phase system.
First may be described the construction and operation of the meter when
employed with, and directly connected in circuits carrying two-phase currents
differing by a quarter period and transmitted over four wires.
A is an inducing coil of comparatively small wire connected in shunt, by means
of wires 5. 6. to the circuit 3. 4. (Figure 10). B and B are inducing coils of
relatively large wire connected in series or in parallel with each other and in series
with the work circuit 1. 2. by means of the loop 7. 8. The circuits 1. 2, and 3. 4,
lead from a two phase generator M to a work circuit containing motors, or other
translating devices.
The various parts of the meter are supported by one or more arms k¹²
extending from the frame K. The coil A is carried by the arm k', and is secured
thereto by means of a suitable clamping device p. The coils B. B' are supported
upon the arm² by means of clamping devices carried by the plate M₁ in any
convenient manner.
The position of the plate M', and therefore of the coils B. B', may be adjusted
by means of the screws r, r', extending through the slot in the arm ², and the
coil A may be adjusted in a similar manner.
Between the coil A and the coils B. B' is mounted a disc D of thin aluminum,
copper or other conducting metal, fixed upon the shaft E which is free to rotate
with a very small amount of friction. It has been found that for this disc D almost
any metal of reasonably high conductivity is suitable but aluminum has the
advantage of lightness so that there is little friction and wear on the bearings. In
order to increase the rigidity of the disc, it is preferred to turn over the edge as
shown at d, by which means the vibration due to the alternating current is
suppressed. The disc may be ribbed or corrugated circumferentially as shown in
Figure 16, or radially as shown in Figure 17, or it may be otherwise stiffened.
The lower bearing L for the shaft E is preferably a cup of agate or other hard
material. Suitable counting or registering mechanism C is geared to the upper
end of the shaft. F and F are permanent magnets between the poles of which
the disc revolves being retarded by the eddy currents induced in it. To save room
laterally F. Fare made of C-shape, having their greatest dimensions perpendicular
to the disc D.
These magnets should be so proportioned in strength to the maximum torque
exerted upon the disc that the resulting speed is slow relatively to that of
synchronism, and also sufficiently slow to avoid appreciable resistance due to
motion through the air.
G is a non-inductive resistance coil connected in series with the shunt coil A,
and provided with a switch arm H for including more or less resistance in the
circuit.
It is important to so arrange the coils A. B. B' that the currents induced in the
disc D by the coil A are within the magnetic field of the coils B and B and
vice versa.
Also the coils B and B should be so connected that the currents
flowing in their adjacent portions are in the same direction so as to have a like

page_text: effect upon the disc. The relative position of the coils may be varied considerably
without seriously affecting the operation of the meter, and one or more of the coils
may be adjustable in position, for the purpose of correcting the constant, the slot
and screw connection shown in Figure 1 being suitable for this purpose. It is not
necessary to employ 3 coils, but the arrangement shown in Figures 1 and 2 is found
convenient and useful. The coils A and B or the coils A and B are alone sufficient,
however, to produce satisfactory results.
Figures 3. 4. 5. 6 and 7 show other arrangements of coils which have proved
satisfactory in practice. In these figures, the coils upon the upper side of the disc
corresponding to coil A of Figures 1 and 2 are shown in full lines and those on the
lower side, corresponding to coils B and B of Figures 1 and 2 in dotted lines.
In
Figure 8 shows a meter of modified construction, in which the rotating member
may, if desired be provided either with a soft iron core or a soft iron rim D' and
which is surrounded by the inducing coils vertically arranged and connected
respectively in shunt and series to the two work circuits as already described.
this meter a separate retarding disc D2 is fixed on the shaft E near its lower end.
The magnets F and F¹ are so arranged that their poles embrace this disc to give
the retarding action.
Figure 9 shows a modification in which the rotating member D³ is of a cylindrical
or cup shape and in which one of the coils; for example, the shunt connected
coil A is placed within the movable element and the other coils B. B₁ are outside
of it. In this form also there is a separate retarding disc D2. In either of the
forms just described the retarding magnets might obviously be applied directly to
the member acted upon by the inducing circuits. One great advantage of the
form of meter shown in Figures 1 and 2 lies in the reduction of the weight of
the moving parts by employing the same conductor for producing the moving and
the retarding forces. This construction also renders the registration independent
of the temperature of the disc, since any change in its resistance. has an equal
effect upon the torque and upon the retarding action. For the same reason the
constant of the meter is practically unaffected by differences in the thickness or
specific resistance of the disc. For the disc D2 may be substituted any closed
conductor of convenient form rotating with the shaft, but it is of advantage in
all cases to construct it of a metal the electrical resistance of which has approxi-
mately the same temperature co-efficient as that of the armature, so that the
retarding effect may be varied by changes of temperature of the surrounding air,
in the same ratio as the variations of torque on the armature from the same
cause.
If the electromotive force impressed upon the shunt circuit of the meter is in
quadrature with the current in the series coils when there is no lag in the work
circuit, then, in order that the shunt current may be also in quadrature, the shunt
connected coil and the resistance coil in series with must contain as little self
induction as possible. The shunt current then will be practically in phase with
its impressed electromotive force. The current for either or both circuits in the
meter may be supplied either directly or by means of transformers of known ratio,
as indicated by dotted lines at T. T¹, in Figure 10 attention being paid to
the proportions so that the phase relations will not be practically disturbed
through the range of working. Such proportioning is well understood and
does not require detailed explanation. If a transformer is used in the series
circuit, causing a lag between the work current and the corresponding magnetic
field in the meter, the shunt current should have a corresponding amount of lag.
Other modifications in the connections and phase relations of the circuits―require
or permit the use of various combinations of resistance, self induction and capacity
in the meter circuits. In all cases the organization must be such as to secure as
nearly as possible a difference of phase of 90 degrees between the magnetic field
produced by the shunt current and the field produced by the work current when
there is no self induction or capacity in the work circuit.
It is well known that the energy transmitted by an alternating current is equal

page_text: to the product of the current, the impressed electromotive force and a factor
depending upon the difference of phase between them. This factor is commonly
called the power factor and when the waves are sinusoidal it is equal to the cosine
of the angle measuring the difference of phase. For simplicity of explanation the
action of the apparatus is described in the ordinary terms employed in connection
with sinusoidal waves but the invention is not limited to the measurement of currents
of any particular wave form.
In Watt meters of the ordinary construction it is customary to connect one set
of coils in series with the work circuit, and an armature carrying another set of
coils in shunt to the same circuit through a suitable resistance, the deflection or
speed being then proportional to the power transmitted and a maximum when the
shunt and series currents are in the same phase. Here are reversed the usual
conditions as to the phase relation between the currents in the shunt and series coils,
and in the meter herein described the torque is zero when the two currents are
a quarter period apart. This being the case the shunt coil is connected in a circuit
so organized that the current in it differs in phase a quarter period from the
impressed electromotive force in the series circuit, and is proportional in amount to
that electromotive force under which conditions a maximum indication is given
when there is no lag in the work circuit the shunt and series currents being then
a quarter period apart. If now the work current is caused to lag from this normal
relation, by the presence of an inductive load, the shunt and series currents
approach each other in phase, giving a diminishing indication in the meter, and if
the lag amounts to a quarter wave length, so that no work is being done in the
circuit, the series current is in phase with the shunt current and no rotation is
produced. The torque for any given current and electromotive force is, in fact,
proportional to the sign of the angle representing the displacement of phase
between the currents in the shunt and series coils, which under the conditions here
stated is equal to the cosine of the lag angle in the work circuit. Since the torque
is also directly proportional to the product of the currents in the shunt and
series coils, .t is directly proportional to the power transmitted, and the retarding
force being proportional to the speed, the registration is also directly proportional
to the power transmitted.
If the same meter is intended to be used for measuring currents of different
periodicities, the resistance of the shunt circuit may be varied by the adjustable
rheostat G, the sections of which are marked to correspond with the periodicities
required. In this way a meter may be made suitable for the whole range of
periodicities in ordinary use, say from 25 to 133 periods per second, by introducing
the proper resistance into the shunt circuit. Other means may be employed for
the proper adjustment of the constant of the meter, such for instance, as changing the
position of the coils with reference to the disc, or varying their effect by introducing
iron cores, as indicated, for instance, in Figure 1 at a by dotted lines, or by varying
the retarding force by changing the position of the magnets or varying their air
gap, or the meter may be adjusted for a fixed periodicity and a suitable coefficient
applied to the readings dependent upon the conditions when used. The last named
method is, however, somewhat inconvenient in practice. The indications of the
dial may be directly in kilowatt-hours, or horse power hours, or in other convenient
units. If the power transmitted by each of two currents in quadrature is the
same or proportional, a single meter connected as shown in Figure 10 may be used
with sufficiently accurate results for all ordinary purposes. If, however, there is
for any reason an inequality, a meter may be placed in a similar manner
on each circuit, as shown in Figure 11, the series coil of the meter Y, and the
shunt coil of the other meter Z being connected to the first circuit 1. 2. the second
circuit 3. 4 being similarly related to the remaining coils.
A single meter may also be used by combining in it the effects of the currents
in the two circuits, as will be readily understood by reference to Fig. 12. In this
arrangement there are two distinct sets of coils A, B, and A' B', which may be
arranged as shewn in plan in Figure 4. The coil B is connected in series in the

page_text: circuit 1. 2. and the coil A in shunt to the circuit 3. 4 upon which the impressed
electromotive force is in quadrature to that upon 1. 2. in the organization shown.
These electromotive forces are practically equal under usual conditions. The
coils A and B produce a torque therefore proportional to the energy transmitted
over the circuit 1. 2. independently of the coils A¹ B¹. In like manner the
coils A B produce a torque proportional to the energy transmitted over the
circuit 3. 4. The combined effect upon the armature is therefore equal to the sum
of two separate actions, producing a torque, and consequently a registration or
indication proportional to the whole energy transmitted. It is important that the
coils A and A' be so situated that no torque is produced by currents of different
phase in them alone, and also that the coils B and B be so situated that they
alone produce no torque, since such action would vary as the produce of the currents
in the coils A. A', and not in proportion to the energy transmitted, which is equal
to the sum of that transmitted over the respective circuits.
The arrangement shewn in Figure 12 is diagranımatic and intended merely to
illustrate this organization of the meter. The form and arrangement of the parts
may be varied in many ways, and the same arrangement of the meter may be used
to measure the energy transmitted over any two circuits, separate or connected and
of any phase relation, by suitable attention to the methods of connection shown on
the various drawings.
In Figure 13 is shown a convenient and practicable method of connecting the
meter with a three wire distribution circuit carrying two-phase currents. In this
figure the source of the two-phase current is illustrated at I, which may be any
suitable device such as one or more transformers or the armature of a generator.
The currents supplied to a motor or other device suitable for two phase currents
at M may be assumed as practically equal, and the impressed electromotive forces
of the two branches is also nearly equal or proportional in practice.
The ordinary variations from exact equality, due to slight differences in the
windings of the devices in the work circuit, affect the accuracy of the meter in a
very small degree, so that the energy supplied to any device not radially defective
is correctly measured. The conductor 9 is the conductor which is common to both
circuits 9. 10 and 9. 11 and carries a resultant current differing in phase 45 degrees
from the component currents in the circuits 9. 10. and 9. 11. The resultant
impressed electromotive force upon the conductor 9, through the combined
circuits 10. 11, also differs 45 degrees in phase from the electromotive forces
impressed upon the circuits 9. 10. and 9. 11. The coils B. B¹ are connected in
series with the conductor 9, directly as shown, or inductively if desired.
In order to impress upon the circuit 5, including the shunt coil, an electromotive
force in quadrature with the resultant electromotive force impressed upon the
conductor 9 the circuit 5 is connected across tho conductors 10. 11, either directly
or inductively. The maximum electromotive force upon the conductor 9 occurs
when the electromotive forces of the circuits 9. 10 and 9. 11 are equal, at which
time they are opposite with respect to the circuit 5 across the conductors 10. 11 so
that the resultant electromotive force in circuit 5 is zero at this instant; that is to
say, the electromotive forces impressed upon the two circuits containing the coils A
and the coils B. B', respectively, are in quadrature. Under these conditions, the
meter will measure the true energy delivered, if the constant is properly adjusted
to the conditions under which it is used.
In Figure 14 a meter is shown as applied to a three-phase circuit. In this
figure the coil A is connected in shunt between the conductors 10 and 11, and the
coils B. B', are connected in series with the conductor 9. The same relations of
electromotive forces exist so far as the meter is concerned in this organization as
described with reference to Figure 13, so that although the difference of phase
between the impressed electromotive forces upon the three branches is 120 degrees,
that between the circuits including the respective coils A and B B4 is 90 degrees.
In a three-phase distribution, or in any symmetrical multiphase system of con-
catenated circuits, the current flowing over any given conductor may be considered

page_text: as the resultant of two currents differing in phase and as having a phase relation
intermediate to the phases of the component currents. It may also be said that an
electromotive force is impressed upon each conductor, the circuit being completed
through other conductors symmetrically related to it, and the phase of this electro-
motive force is intermediate to and differs by an equal angle from the separate
electromotive forces across the adjacent circuits. This electromotive force differs
in phase from the current flowing in the conductor upon which it is impressed, by
the lag angle of the work current. It is difficult to express the phase relations in
tri-phase and certain other multiphase circuits in the ordinary terms applicable to
simple circuits; and here are adopted certain forms of expression for the sake of
simplicity and clearness, and such expressions are defined and explained to avoid
ambiguity.
Several forms of winding have been adopted for the armatures of multiphase
generators, variously known as "star windings," "delta windings" etc., but in any
concatenated system of distribution the currents flowing in the individual wires
may be regarded as the resultant of two currents differing in phase, flowing in
adjacent conductors of an equivalent system of double the number of wires, each
winding of the generator having a complete independent circuit. The phenomena
of currents in concatenated circuits may often be expressed in terms of such
component currents with greater clearness than by treating the resultant currents
alone, and the same may be said of electromotive forces.
In applying the meter herein described to multiphase circuits, the connections
necessary to obtain the required relation of quadrature between its shunt and series
circuits may be readily determined by a consideration of the phase relations in the
manner indicated. Having connected the coils B. B or their equivalents in scries
with none of the conductors, the shunt circuit 5 must be connected across a pair of
conductors symmetrically related on either side of the said series conductor, so that
the electromotive forces of the separate or component circuits are impressed in
series upon the circuit 5. Figure 14 shows this method of connection as applied to
a 3 phase circuit. When as in a two-phase system of distribution, a difference of
phase of 90 degrees is readily obtained more directly, this method of connection is
unnecessary in many cases, but the variety of useful or possible combinations is so
great that it is not attempted herein to more than indicate clearly the general
methods to be adopted.
In Figure 15 an arrangement is shown in which a transformer T is used to
obtain the required phase relation of the electromotive force impressed upon the
shunt circuit of the meter. As here shown, a rotating field is produced in the
transformer by connections 12. 13 and 14, to the multiphase circuit 9. 10. 11, and
currents having the required phase relation are derived through the conductors 15. 16.
which are connected to the shunt coil A of the meter. The transformer may be
of any suitable form and may contain a single coil, or a separate primary and
secondary, and should be connected to the transmission circuit in a manner suitable
to the phase relations so as to obtain a rotating field. Two transformers may be
used to produce a resultant electromotive force of the proper phase relation if
desired.
It will be understood that the constant of the meter must be adjusted to suit the
requirements of any particular method of connection in the circuits. While the
indications of any given meter if connected in various ways, would be proportional
to the energy transmitted it might require the application of a co-efficient,
depending for its value upon the known conditions. It is usually more convenient
in practice to design the meter with reference to its proposed use so that it will
directly indicate the energy transmitted.
In order that the actual energy transmitted may be thus accurately measured
it is of course necessary that the registration should be directly proportional to the
electromotive force. Any ordinary construction of the shunt circuit as for instance
one including an inductance coil having a closed magnetic circuit would not secure
this result because the current through it would not vary in direct proportion with

page_text: the electromotive force owing to variations in the co-efficient of self-induction,
but in some other proportion dependent upon the quality of the iron cores
employed and the degree of magnetic saturation. As a result the variations in
the registration of the meter would be quite different from the variations of
electromotive force. To obviate this difficulty a shunt circuit is so organised that
the magnetic field acting upon the armature is directly proportional to the
electromotive force of the circuit.
Meters heretofore devised have been sensitive to changes in the rate of
alternations of the current to such a degree as to render them unfitted for use
upon circuits employing a rate of alternation other than that for which they were
specially designed or upon circuits having wide fluctuations in periodicity. In the
meter devised the torque for given currents in the coils and for a given difference
of phase is directly proportional to the periodicity. This is because the inductive
effects produced in the movable element of the meter a proportional to the field
strength and the number of reversals per second and consequently the torque.
which depends upon these inductive effects is also proportional to the number of
reversals for a given strength of the inducing field. For a given periodicity the
torque is also proportional to the strength of the field in the shunt circuit other
conditions remaining constant. It follows from these two considerations that in
order to obtain a registration of the energy independent of the periodicity the
strength of the magnetic field dependent upon the shunt circuit must vary inversely
as the periodicity. That is to say any tendency to increase the torque for instance
by increased periodicity must be exactly counteracted by a proportional diminution
of the field produced by the shunt circuit. The shunt circuit of the meter herein.
described is so organised as to effect this compensation through a wide range.
It is also important that the form of the current wave in the shunt circuit
shall follow as nearly as possible the form of the wave of electromotive force so-
that the indication or registration shall be accurate independently of the exact
wave form of the generator. If an inductance coil of ordinary construction that is
with a closed magnetic circuit were placed in the shunt circuit of the meter the
current would be much distorted as to its wave form by reason of the well known
magnetic peculiarities of iron such as varying permeability and hysteresis. This
difficulty also is overcome by the use of the form of inductance coil herein
described.
In an inductance coil having a closed iron core the mass of iron necessary to
secure at low magnetization a sufficient shunt current say one-tenth of an ampere-
at ordinary potentials, is inconveniently large in practice and moreover the lag is
insufficient owing to the small ratio between the apparent energy of the magnetizing
current and the actual energy expended in hysteresis losses. At high magnetization
the lag may be somewhat greater although it cannot be made sufficient for the
purpose except by working the iron entirely beyond practical limits. In any case
whether the magnetization be high or low the permeability of the iron and
consequently the coefficient of self induction of the coil varies not only under
moderate variations of the mean impressed electromotive force but during variations
of a single alternation, so that from this cause and the effects of hysteresis both.
the current and the form of its waves are greatly modified. On the other hand it.
is well known that an air core inductance coil may possess an approximately
straight line law of magnetization but difficulties are encountered in obtaining a
sufficiently great lag angle. The degree of lag of an alternating current is directly
dependent upon the ratio of the true energy of the current to the so called apparent
energy, hence it is necessary to avoid as far as possible all actual consumption of
energy in any circuit in which a large lag angle is desired.
In an air core inductance coil the number of turns required is necessarily large in
order to secure a high coefficient of self induction. This causes a high resistance
and corresponding expenditure of energy proportional to the square of the current
and consequently such coils do not produce a very large lag under practical.

page_text: conditions. The same may be said or a coll with a straight core as oramariy
constructed.
In order to overcome these difficulties an inductance coil is employed with an
interrupted magnetic circuit consisting of a laminated or otherwise divided core
enclosing the winding and having an air gap of definite length. The exact
proportions in a given coil must be found by calculation and are determined with
reference to the requirements and precautions hereinbefore indicated and the
instructions which follow.
The length of the air gap should be sufficient to render the total reluctance or
resistance of the magnetic circuit greatly in excess of the reluctance of the iron
portion alone and its exact length is determined also with reference to the current
permitted in the shunt circuit of the meter and of the winding of the inductance
coil. The winding must be adapted to the working range of the meter and must
have a sufficient number of turns to maintain a high coefficient of self induction
without requiring either a high magnetization or an inconveniently great cross
section in the magnetic circuit. On the other hand it must be of low resistance,
relatively to the self induction which makes it necessary to give the air gap
only a moderate length so that the reluctance is not too great to be suited to such
a winding.
The winding and the cross-section of the iron must also be so proportioned to
each other as to make the sum of the losses in the iron and those due to resistance
as nearly a minimum as possible over the working range so as to increase the lag
angle to the greatest degree possible. These proportions are all modified by the
permissible dimensions of the coil and the quality of the iron used, but having
assumed these, the proportions are susceptible to exact calculation.
In the meter shewn in Fig. 14 which is substantially the same as that shewn in
Fig. 1 for carrying the various parts of the meter. The shunt coil A being
designed to carry a small current is wound therefore with a considerable number of
turns of small wire. Its resistance should be as low as is consistent with these
requirements. This coil may be connected in shunt with the work circuit or
receive an impressed electromotive force proportional to that of the work circuit,
as for instance through a transformer or its equivalent. B. and B₁ represent as
before the series coils connected with the translating devices or receiving a current
proportional to that delivered to the translating devices, as for instance, through a
transformer. These coils B, B₁ may be connected either in parallel or in series
with each other and should be wound with wire cf sufficient size to carry the
maximum current without undue heating.
The coil A is connected across the conductors 1. 2. leading to the work circuit W
as indicated by means of conductors 3 & 4. In this shunt circuit there is interposed
the inductance coil T. which is shewn in detail in Figs. 18 & 19. It consists of a
coil of insulated wire applied to a laminated solt iron core t² having one or more
interruptions in its circuit which are shewn at t³. These interruptions or air gaps
may be placed at any convenient point in the magnetic circuit provided they
intersect all the lines of force through the iron. Instead of the two air gaps t3
single air gap as shewn in dotted lines at t may be used; or a single magnetic
circuit with a single air gap to may be used as shewn in Fig. 20. The exact
proportions of the parts of the inductance coil can be readily determined in
accordance with the considerations herein set forth as applied to a meter designed
for any given range of working.
a
It is sometimes of advantage to provide oue or more of the coils as for instance
the shunt coil A with a core a which may be adjustable in position as indicated in
Fig. 2. The form of core shown consists of a central portion a which may be
adjustable in the coil and two side portions a', extending across the top and down the
sides of the coil towards the disc D. This core serves to direct the lines of force
through the disc and at the same time affords a convenient means of adjusting the
constant of the meter. It is however not necessary to employ a core in the coil A.

page_text: The arrangement and operation of the coils A. B. B' and magnets F. F' are
substantially the same as already described with reference to Fig. 1.
Some of the advantages due to the peculiar character of the inductance coil
herein described may be utilised in connection with armatures of various construc-
tions, thus the armature may contain more or less iron for the purpose of increasing
the torque and may have a closed winding of any suitable form. Certain special
advantages, particularly in connection with this inductance coil are secured by con-
structing the armature without iron and of large superficial area as in the disc form
herein shewn because in this form there is a considerable area over which the
induced currents may flow in proportion to the total cross-section, thereby securing
a non-inductive form that is to say a form having a small coefficient of self
induction. This results in an induction of currents in the disc proportional to the
periodicity and having a small lag. For this reason among others, an armature of
this form is well adapted to be used in connection with the inductance coil described
which varies the shunt current in an inverse ratio to the periodicity, and consequently
causes the meter to compensate for changes of periodicity.
The shunt coil A in Fig. 9 may be connected in series with the inductance coil T.
The special form of inductance coil above described is applicable to other form;
of measuring indicating and controlling devices and to other apparatus as may b
readily understood.
In what precedes there are described forms of meters according to this invention
in which the number of revolutions of a suitably retarded armature or its equivalent
serve as an indication of the energy of the currents which actuate the armature.
There will now be described a form of meter in which the partial rotation of the
armature in opposition to a spring provides the desired indication.
Referring to Figures 21, and 22 the circuits 1. 2 and 3. 4 lead from a two phase
generator I to a work circuit containing motors or other translating devices. An
inducing coil A is connected in shunt by means of wires 5. 6. to the circuit 1. 2.
A second inducing coil or pair of coils B B is connected in series of the work
circuit 3. 4. by means of the loop 7.8. The coils A. B B' disc D and shaft E and
retarding magnets F F¹ are substantially as already described with reference to
Fig. 1 and 2.
The rotation of the shaft E is opposed by a spiral spring N one end of which is
attached to the shaft and the other end to an adjustable support n. The
magnets F F have no effect on the indication of the instrument except that of
damping the oscillation and bringing the moving parts promptly to rest.
A scale Q is attached to the edge of the disc D and moves therewith. This
scale is properly graduated and by its movement past an index P, the amount of
deflection of the disc may be observed.
If the same meter is intended to be used for measuring currents of different
periodicities, the resistance of the shunt circuit may be varied by the adjustable
Theostat G the sections of which are marked to correspond with the periodicities
required.
In this way, a direct reading meter may be made suitable for the whole range of
periodicities in ordinary use say from 25 to 135 periods per second by introducing
the proper resistance into the shunt circuit. Other means may be employed for the
proper adjustment of the constant of the meter, such, for instance as changing the
position of the coils with reference to the disc, or varying their effect by introducing
iron cores as indicated, for instance, in Figure 21 at a by dotted lines, or by
varying the opposing force; or the meter may be adjusted for a fixed periodicity
and a suitable coefficient applied to the readings dependent upon the conditions
when used. The last named method is however, somewhat inconvenient in practice.
The indications of the scale may be directly in kilowatts or horse power or in other
convenient units. If the power transmitted by each of two currents in quadrature
is the same or proportional, a single meter connected as shown in Figure 1 may be
used with sufficiently accurate results for all ordinary purposes. If however, there
B

page_text: 18 for any reason an inequality, a meter may be placed in a similar manner on each
circuit.
Since the torque is proportional to the power transmitted it is necessary to
oppose the motion of the movable element by a force proportional to the angle of
deflection in order to obtain a deflection directly proportional to the energy trans-
mitted I have found that by the use of a spiral spring N, such as is used in the
movement of marine clocks, as the opposing force, the deflection is very nearly
proportional to the energy over a wide range. Any other suitable form of spring
may be used instead of the flat spiral spring shown, and if it is not important that
the deflection be exactly proportional to the energy, the force of gravity may be
substituted or used in connection with springs. The scale in this case should be
graduated to correspond with the deflections by trial.
This instrument has the advantage of being capable of a very large angular
motion without disturbing the proportionality of its deflections and may easily be
arranged to turn through 360 degrees, or more if desired. It is thus possible to
use a very long scale so that the indication may be read with great accuracy.
Certain advantages are secured by mounting the instrument as shown in
Figure 21 with the shaft vertical but it may be mounted horizontally, and upon
kuife edges if desired in a manner well understood.
In order to utilize to the fullest extent the large angular deflection of which the
meter is capable, I have found it of advantage to employ the arrangement of
scale shown in Figure 21 so that the indications may be easily read from a given
point of view. This scale may be of paper or other suitable material such as
aluminium, celluloid or any material sufficiently rigid in proportion to its weight.
In some cases it is desirable to place the scale divisions directly upon the disc, as
indicated at Qiu Fig. 22 or the scale and disc may be formed of a single piece
of metal.
Slight variations due to changes of temperature are apt to
indications of the instrument. These variations may be compensated for by means
occur in the
of the adjustable resistance G¹ Figure 21 connected in series with the shunt
coil A, and in most cases also in series with the adjustable resistance G and may
be graduated to correspond with certain definite changes of temperature.
In Figure 23 is shown a convenient method of connecting the meter with a
three-wire distribution circuit carrying two phase currents. In this figure, the
source of the two phase currents is illustrated at I, which may be any suitable
device such as one or more transformers or the armature of a generator.
The currents supplied to a motor or other device suitable for two phase currents
at M may be assumed as practically equal and the impressed electromotive forces
of the two branches are also nearly equal, or proportional, in practice. The
ordinary variations from exact equality, due to slight differences in the windings
of the devices in the work circuit, affect the accuracy of the meter to a very small
degree, so that the energy supplied to any device, not radically defective, is
correctly measured.
The conductor 9 is the conductor which is common to both circuits 9. 10 and
9. 11 and carries a resultant current differing in phase 45 degrees from the
component currents in the circuits 9. 10 & 9. 11. The resultant impressed electro-
motive force upon the conductor 9 through the combined circuits 10, 11 also
differs 45 degrees in phase from the electromotive forces impressed upon the
circuits 9. 10 and 9. 11. The coils B, B' are connected in series with the
conductor 9. directly as shown or inductively if desired.
In order to impress upon the circuit 5 including the shunt coil, an electromotive
force in quadrature with the resultant electromotive force impressed upon the
conductor 9 the circuit 5 is connected across the conductors 10. 11 either directly
or inductively. The maximum electromotive force upon the conductor 9 occurs when
the electromotive forces of the circuits 9. 10 and 9. 11 are equal at which time
they are opposite with respect to the circuit 5 across the conductors 10. 11 so that

page_text: the resultant electromotive force in circuit 5 is zero at this instant that is to say,
the electromotive forces impressed upon the two circuits containing the coils A
and the coils B. B' respectively are in quadrature. Under these conditions, the
meter will register the true energy delivered, if the constant is properly adjusted
to the conditions under which it is used. A similar method of connection may be
adopted for three phase, and other multiphase circuits.
A single meter may also be used by combining in it the effects of the currents
in the two circuits as will be readily understood by reference to Figure 4. In this
arrangement there are two distinct sets of coils A. B and A'B'. The coil B is
connected in series in the circuit 1. 2 and the coil A in shunt to the circuit 3. 4 upon
which the impressed electromotive force is in quadrature to that upon 1. 2 in the
organization shown. These electromotive forces are practically equal under
usual conditions. The coils A and B produce a torque therefore proportional to
the energy transmitted over the circuit 1. 2 independently of the coils A'B'. In
a like
manner the coils A'B' produce a torque proportional to the energy
transmitted over the circuit 3. 4. The combined effect upon the armature is
therefore equal to the sum of two separate actions producing a torque, and
consequently an indication proportional to the whole energy transmitted. It is
important that the coils A and A¹ be so located that no torque is produced by
currents of different phase in them alone, and also that the coils B and B' be so
located that they alone produce no torque, since such action would vary as the
product of the currents in the coils A. A¹ and not in proportion to the energy
transmitted, which is equal to the sum of that transmitted over the respective
circuits.
The arrangement shown in Figure 24 is diagrammatic and indented merely to
illustrate this organization of the meter.
The form and arrangement of the parts may be varied in many ways and the
same arrangement of the meter may be used to measure the energy transmitted
over any two circuits sep rate or concatenated and of any phase relation by
suitable attention to the methods of connection shown in the various drawings.
In Figure 25 is illustrated a method of applying the invention to a single phase
system of distribution. The series coils B, B' are connected in the circuit 1. 2.
The shunt coil A is connected by the conductors 5. 6 across the circuit 1. 2.
For the purpose of obtaining the required phase relation, there is inserted in
the conductor 5 an inductance coil T adapted to cause the current in the
circuit 5.6 to lag approximately 90 degrees behind the impressed electromotive
force. This coil comprises a winding t¹ and a laminated core 2 having one or
more suitably proportioned air gaps t.
In Figure 25 is shown a form of indicating device different from that shown in
Figures 1 and 2 although it will be understood that either may be employed. In
this instance the scale Q2 is fixed and the index P¹ is fastened to the shaft and
moves over the scale in the usual way.
Thus are illustrated several forms of meters according to this invention and
several arrangements of circuits in connection with them shewing how they may
be applied for measuring the energy of alternating currents whether of one phase
or of several phases.
It is to be understood however that the circuits may be varied in many other
ways, and that the connections to the instrument may be varied to suit these
circuit arrangements subject to the conditions herein before set forth.
Dated this 2nd day of January 1895.
ABEL & IMRAY,
Agents for the Applicant.

page_text: Improved Methods and Apparatus for Measuring Electrical
Currents.
I, OLIVER BLACKBURN SHALLENBERGER, of Rochester, in the County of
Beaver and State of Pennsylvania, United States of America, Electrician, 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 methods and apparatus for measuring indicating and
registering the energy transmitted by alternating electric currents, particularly
multiphase alternating currents.
It has been demonstrated by experiment that if a closed conducting circuit of
suitable form, mounted so as to be free to rotate, be placed in proper inductive
relation to two alternating magnetic fields of the same periodicity, a torque is
produced which is proportional to the product of three elements; namely, the
strengths of the respective magnetic fields and a function approximating the sine of
the angle representing the difference of phase between them. On this principal
are devised methods of an apparatus for measuring accurately the amount of energy
transmitted by alternating currents.
This invention may be applied in a simple manner by employing a form of
apparatus in which two actuating coils are inductively related to a movable element,
one of these coils being supplied with current proportional to that in the work
circuit, and the other with current proportional to and in quadrature with the
electromotive force impressed upon the work circuit, the current in these coils
producing a resultant shifting field, causing an armature to rotate within it. The
torque thus produced is proportional to the energy transmitted to the work circuit-
a retarding force is applied, such as that produced by the motion of a closed
conductor in a constant magnetic field which is proportional to the velocity of
rotation, so that the total movement during an interval of time is directly
proportional to the time integral of the energy transmitted, and it may be recorded
in any convenient manner.
In the drawings accompanying my Provisional Specification illustrating this
invention,
Figure 1 is a side elevation of a form of meter which is found to be suitable for
practical use, certain parts being broken away and others shown in section.
Fig. 1 shows a modification.
Fig. 2 is a plan, omitting certain parts.
Figure 2 is a section shewing the relative positions of the armature and coils.
Figures 3. 4. 5. 6 and 7 show diagrammatically various arrangements of the
inducing coils.
Figures 8 and 9 are vertical sections shewing modified forms of the apparatus.
Figure 10 is a diagram showing two phase work circuits and connections between
the same and the meter directly, showing also in dotted lines the connections for
transformers between the main circuits and the meter.
Figure 11 is a diagram of circuits carrying two phase currents with a meter for
each circuit.
Figure 12 is a diagram illustrating a single meter applied to a two phase 4 wire
circuit.
Figure 13 is a diagram shewing a meter applied directly to a two-phase three-
wire circuit.
Figures 14 and 15 illustrate the use of the meter for measuring three-phase
currents.

page_text: Figures 16 and 17 illustrate modined forms or
meter.
Lit
CICITICUO
Figure 18 is a side view and Fig. 19 is a section of an inductance coil hereinafter
referred to.
Figure 20 shows a modified form of its core.
Figure 21 is an elevation of a modified construction of meter with diagram of the
circuit connections for a polyphase circuit,
Fig. 22 is a plan.
Fig. 23 is a diagram shewing the connections for a three wire two phase circuit,
Fig. 24 illustrates the connections for a two phase system having branches
which carry different loads, the instruments indicating the total energy.
Fig. 25 is a diagram shewing the instrument applied to a single phase system.
First may be described the construction and operation of the meter when employed
with, and directly connected in circuits carrying two-phase currents differing by a
quarter period and transmitted over four wires.
A is an inducing coil of comparatively small wire connected in shunt, by means
of wires 5. 6. to the circuit 3. 4. (Figure 10)-B and B are inducing coils of
relatively large wire connected in series or in parallel with each other and in series
with the work circuit 1. 2. by means of the loop 7. 8. The circuits 1. 2, and 3. 4,
lead from a two phase generator M to a work circuit containing motors, or other
translating devices.
The various parts of the meter are supported by one or more arms k¹ k² extending
from the frame K. The coil A is carried by the arm k³, and is secured thereto by
meaus of a suitable clamping device p. The coils B. B₁ are supported upon the
arm by means of clamping devices carried by the plate M' in any convenient
manner.
The position of the plate M¹, and therefore of the coils B. B¹, may be adjusted
by means of the screws r, r², extending through the slot in the arm k², and the coil A
may be adjusted in a similar manner.
Between the coil A and the coils B. B'is mounted a disc D of thin aluminium, copper
or other conducting metal, fixed upon the shaft E which is free to rotate with a
very small amount of friction. It has been found that for this disc D almost any
metal of reasonably high conductivity is suitable but aluminium has the advantage
of lightness so that there is little friction and wear on the bearings. In order to
increase the rigidity of the disc, it is preferred to turn over the edge as shown at d,
by which means the vibration due to the alternating current is suppressed. The
disc may be ribbed or corrugated circumferentially as shown in Figure 16, or
radially as shown in Figure 17, or it may be otherwise stiffened.
The lower bearing L for the shaft E is preferably a cup of agate or other hard
material. Suitable counting or registering mechanism C is geared to the upper
end of the shaft. F and F are permanent magnets between the poles of which the
disc revolves being retarded by the eddy currents induced in it. To save room
laterally F. F are made of C-shape, having their greatest dimensions perpendicular
to the disc D.
These magnets should be so proportioned in strength to the maximum torque
exerted upon the disc that the resulting speed is slow relatively to that of
synchronism, and also sufficiently slow to avoid appreciable resistance due to motion
through the air.
G is a noninductive resistance coil connected in series with the shunt coil A,
and provided with a switch arm H for including more or less resistance in the
circuit.
vice versa.
It is important to so arrange the coils A. B. B' that the currents induced in the
disc D by the coil A are within the magnetic field of the coils B and B¹ and
Also the coils B and B should be so connected that the currents
flowing in their adjacent portions are in the same direction so as to have a like
effect upon the disc. The relative position of the coils may be varied considerably
without seriously affecting the operation of the meter, and one or more of the coils

page_text: may be adjustable in position, for the purpose of correcting the constant, the slot
and screw connection shown in Figure 1 being suitable for this purpose. It is not
necessary to employ 3 coils, but the arrangement shown in Figures 1 and 2 is found
convenient and useful. The coils A and B or the coils A and B¹ are alone sufficient,
however, to produce satisfactory results.
Figures 3. 4. 5. 6 and 7 show other arrangements of coils which have proved
satisfactory in practice. In these figures, the coils upon the upper side of the disc
corresponding to coil A of Figures 1 and 2 are shown in full lines and those on the
lower side, corresponding to coils B and B' of Figures 1 and 2 in dotted lines.
Figure 8 shows a meter of modified construction, in which the rotating member
may, if desired be provided either with a soft iron core or a soft iron rim D¹ and
which is surrounded by the inducing coils vertically arranged and connected
respectively in shunt and series to the two work circuits as already described. In
this meter a separate retarding disc D2 is fixed on the shaft E near its lower end.
The magnets F and F' are so arranged that their poles embrace this disc to give
the retarding action.
Figure 9 shows a modification in which the rotating member D³ is of a cylindrical
or cup shape and in which one of the coils; for example, the shunt connected
coil A is placed within the movable element and the other coils B. B¹ are outside
of it. In this form also there is a separate retarding disc D². In either of the
forms just described the retarding magnets might obviously be applied directly to
the member acted upon by the inducing circuits. One great advantage of the
form of meter shown in Figures 1 and 2 lies in the reduction of the weight of the
moving parts by employing the same conductor for producing the moving and
the retarding forces. This construction also renders the registration independent
of the temperature of the disc, since any change in its resistance has an equal effect
upon the torque and upon the retarding action. For the same reason the constant
of the meter is practically unaffected by differences in the thickness or specific
resistance of the disc. For the disc D2 may be substituted any closed conductor of
convenient form rotating with the shaft, but it is of advantage in all cases to
construct it of a metal the electrical resistance of which has approximately the
s.me temperature co-efficient as that of the armature, so that the retarding effect
may be varied by changes of temperature of the surrounding air, in the same
ratio as the variations of torque on the armature from the same cause.
If the electromotive force impressed upon the shunt circuit of the meter is in
quadrature with the current in the series coils when there is no lag in the work
circuit, then, in order that the shunt current may be also in quadrature, the shunt
connected coil and the resistance coil in series with must contain as little self
induction as possible. The shunt current then will be practically in phase with
its impressed electromotive force. The current for either or both circuits in the
meter may be supplied either directly or by means of transformers of known ratio,
as indicated by dotted lines at T. T', in Figure 10 attention being paid to the
proportions so that the phase relations will not be practically disturbed through
the range of working. Such proportioning is well understood and does not require
detailed explanation. If a transformer is used in the series circuit, causing a lag
between the work current and the corresponding magnetic field in the meter, the
shunt current should have a corresponding amount of lag. Other modifications in
the connections and phase relations of the circuits-require or permit the use of
various combinations of resistance, self induction and capacity in the meter circuits.
In all cases the organization must be such as to secure as nearly as possible a
difference of phase of 90 degrees between the magnetic field produced by the shunt
current and the field produced by the work current when there is no self induction
or capacity in the work circuit.
It is well known that the energy transmitted by an alternating current is equal
to the product of the current, the impressed electromotive force and a factor
depending upon the difference of phase between them. This factor is commonly
called the power factor and when the waves are sinusoidal it is equal to the cosine

page_text: of the angle measuring the difference of phase. For simplicity of explanation
the action of the apparatus is described in the ordinary terms employed in con-
nection with sinusoidal waves but the invention is not limited to the measurement
of currents of any particular wave form.
given when
In Watt meters of the ordinary construction it is customary to connect one set
of coils in series with the work circuit, and an armature carrying another set of
coils in shunt to the same circuit through a suitable resistance, the deflection or
speed being then proportional to the power transmitted and a maximum when the
shunt and series currents are in the same phase. Here are reversed the usual
conditions as to the phase relation between the currents in the shunt and series
coils, and in the meter berein described the torque is zero when the two currents
are in the same phase and is a maximum when the two currents are a quarter
period apart. This being the case the shunt coil is connected in a circuit so
organized that the current in it differs in phase a quarter period from the impressed
electromotive force in the series circuit, and is proportional in amount to that
electromotive force under which conditions a maximum indication
there is no lag in the work circuit the shunt and series currents being then a
quarter period apart. If now the work current is caused to lag from this normal
relation, by the presence of an inductive load, the shunt and series currents
approach each other in phase, giving a diminishing indication in the meter, and if
the lag amounts to a quarter wave length, so that no work is being done in the
circuit, the series current is in phase with the shunt current and no rotation is
produced. The torque for any given current and electromotive force is in fact,
proportional to the sine of the angle representing the displacement of phase
between the currents in the shunt and series coils, which under the conditions here
stated is equal to the cosine of the lag angle in the work circuit. Since the torque
is also directly proportional to the product of the currents in the shunt and series
coils, it is directly proportional to the power transmitted, and the retarding force
being proportional to the speed, the registration is also directly proportional to the
power transmitted.
If the same meter is intended to be used for measuring currents of different
periodicities, the resistance of the shunt circuit may be varied by the adjustable
rheostat G, the sections of which are marked to correspond with the periodicities
required. In this way a meter may be made suitable for the whole range di
periodicities in ordinary use, say from 25 to 133 periods per second, by introducing
the proper resistance into the shunt circuit. Other means may be employed for
the proper adjustment of the constant of the meter, such for instance, as
changing the position of the coils with reference to the disc, or varying their
effect by introducing iron cores, as indicated, for instance, in Figure 1 at a by
dotted lines, or by varying the retarding force by changing the position of the
magnets or varying their air gap, or the meter may be adjusted for a fixel
periodicity and a suitable coefficient applied to the readings dependent upon the
conditions when used. The last named method is, however, somewhat inconvenient
in practice. The indications of the dial may be directly in kilowatt-hours, or
horse power hours, or in other convenient units. If the power transmitted by
each of two currents in quadrature is the same or proportional, a single meter
connected as shown in Figure 10 may be used with sufficiently accurate results
for all ordinary purposes. If, however, there is for any reason an inequality, a
meter may be placed in a similar manner on each circuit, as shown in Figure 11,
the series coil of the meter Y, and the shunt coil of the other meter Z being
connected to the first circuit 1. 2. the second circuit 3. 4 being similarly related to
the remaining coils.
A single meter may also be used by combining in it the effects, of the currents
in the two circuits, as will be readily understood by reference to Fig. 12. In this
arrangement there are two distinct sets of coils A, B, and A' B¹, which may be
arranged as shewn in plan in Figure 4. The coil B is connected in series in the
circuit 1. 2. and the coil A in shunt to the circuit 3. 4 upon which the impressed

page_text: electromotive force is in quadrature to that upon 1. 2. in the organization shown.
These electromotive forces are practically equal under usual conditions. The
coils A and B produce a torque therefore proportional to the energy transmitted
over the circuit 1. 2. independently of the coils A' B'. In like manner the
coils A B¹ produce a torque proportional to the energy transmitted over the
circuit 3. 4. The combined effect upon the armature is therefore equal to the sum
of two separate actions, producing a torque, and consequently a registration or
indication proportional to the whole energy transmitted. It is important that the
coils A and A be so situated that no torque is produced by currents of different
phase in them aloue, and also that the coils B and B be so situated that they alone
produce no torque, since such action would vary as the produce of the currents in
the coils A. A¹, and not in proportion to the energy transmitted, which is equal to
the sum of that transmitted over the respective circuits.
The arrangement shewn in Figure 12 is diagrammatic and intended merely to
illustrate this organization of the meter. The form and arrangement of the parts
may be varied in many ways, and the same arrangement of the meter may be used
to measure the energy transmitted over any two circuits, separate or concatenated
and of any phase relation, by suitable attention to the methods of connection
shown on the various drawings.
In Figure 13 is shown a convenient and practicable method of connecting the
In this
meter with a three wire distribution circuit carrying two-phase currents.
figure the source of the two phase current is illustrated at I, which may be any
suitable device such as one or more transformers or the arinature of a generator.
The currents supplied to a motor or other device suitable for two phase currents
at M may be assumed as practically equal, and the impressed electromotive forces of
the two branches is also nearly equal or proportional in practice. The ordinary
variations from exact equality, due to slight differences in the windings of the
devices in the work circuit, affect the accuracy of the meter in a very small
degree, so that the energy supplied to any device not radially defective is
correctly measured. The conductor 9 is the conductor which is common to both
circuits 9. 10 and 9. 11 and carries a resultant current differing in phase 45 degrees
from the component currents in the circuits 9. 10. and 9. 11. The resultant
impressed electromotive force upon the conductor 9, through the combined
circuits 10. 11, also differs 45 degrees in phase from the electromotive forces
impressed upon the circuits 9. 10. and 9. 11. The coils B. B₁ are connected in
series with the conductor 9, directly as shown, or inductively if desired.
In order to impress upon the circuit 5, including the shunt coil, an electromotive
force in quadrature with the resultant electromotive force impressed upon the
conductor 9 the circuit 5 is connected across the conductors 10. 11, either directly
or inductively. The maximum electromotive force upon the conductor 9 occurs
when the electromotive forces of the circuits 9. 10 and 9. 11 are equal, at which
time they are opposite with respect to the circuit 5 across the conductors 10. 11 80
that the resultant electromotive force in circuit 5 is zero at this instant; that is to
say, the electromotive forces impressed upon the two circuits containing the
coils A and the coils B. B¹, respectively, are in quadrature. Under these
conditions, the meter will measure the true energy delivered, if the constant is
properly adjusted to the conditions under which it is used.
In this
In Figure 14 a meter is shown as applied to a three-phase circuit.
figure the coil A. is connected in shunt between the conductors 10 and 11, and the
coils B. B', are connected in series with the conductor 9. The same relations of
electromotive forces exist so far as the meter is concerned in this organization as
described with reference to Figure 13, so that although the difference of
phase between the impressed electromotive forces upon the three branches is
120 degrees, that between the circuits including the respective coils A and B B' is
90 degrees.
In a three-phase distribution, or in any symmetrical multiphase system of
concatenated circuits, the current flowing over any given conductor may be

page_text: considered as the resultant of two currents differing in phase and as having a
phase relation intermediate to the phases of the component currents.
It may als
be said that an electromotive force is impressed upon each conductor, the circuit
being completed through other conductors symmetrically related to it, and the
phase of this electromotive force is intermediate to and differs by an equal angle
from the separate electromotive forces across the adjacent circuits. This electro-
motive force differs in phase from the current flowing in the conductor upon which
it is impressed, by the lag angle of the work current. It is difficult to express the
phase relations in tri-phase and certain other multiphase circuits in the ordinary
terms applicable to simple circuits; and here are adopted certain forms of
expression for the sake of simplicity and clearness, and such expressions are defined
and explained to avoid ambiguity.
66
Several forms of winding have been adopted for the armatures of multiphase
generators, variously known as star windings,"
," "delta windings" etc., but in any
concatenated system of distribution the currents flowing in the individual wires
may be regarded as the resultant of two currents differing in phase, flowing in
adjacent conductors of an equivalent system of double the number of wires, each
winding of the generator having a complete independent circuit. The phenomena
of currents in concatenated circuits may often be expressed in terms of such
component currents with greater clearness than by treating the resultaut currents
alone, and the same may be said of electromotive forces.
In applying the meter herein described to multiphase circuits, the connections
necessary to obtain the required relation of quadrature between its shunt and
series circuits may be readily determined by a consideration of the phase relations
in the manner indicated. Having connected the coils B. B' or their equivalents in
series with none of the conductors, the shunt circuit 5 must be connected across a pair
of conductors symmetrically related on either side of the said series conductor, so that
the electromotive forces of the separate or component circuits are impressed in
series upon the circuit 5. Figure 14 shows this method of connection as applied to
a 3 phase circuit. When as in a two-phase system. of distribution, a difference of
phase of 90 degrees is readily obtained more directly, this method of connection is
unnecessary in many cases, but the variety of useful or possible combinations is so
great that it is not attempted herein to more than indicate clearly the general
methods to be adopted.
In Figure 15 an arrangement is shown in which a transformer T is used to
obtain the required phase relation of the electromotive force impressed upon the
shunt circuit of the meter. As here shown, a rotating field is produced in the
transformer by connections 12, 13 and 14, to the multiphase circuit 9, 10, 11,
and currents having the required phase relation are derived through the
conductors 15, 16, which are connected to the shunt coil A of the meter. The
transformer may be of any suitable form and may contain a single coil, or a
separate primary and secondary, and should be connected to the transmission
circuit in a manner suitable to the phase relations so as to obtain a rotating field.
Two transformers may be used to produce a resultant electromotive force of the
proper phase relation if desired.
It will be understood that the constant of the meter must be adjusted to suit the
requirements of any particular method of connection in the circuits. While the
indications of any given meter if connected in various ways, would be proportional
to the energy transmitted it might require the application of a co-efficient,
depending for its value upon the known conditions. It is usually more convenient
in practice to design the meter with reference to its proposed use so that it will
directly indicate the energy transmitted.
In order that the actual energy transmitted may be thus accurately measured it
is of course necessary that the registration should be directly proportional to the
electromotive force. Any ordinary construction of the shunt circuit as for instance
one including an inductance coil having a closed magnetic circuit would not secure
C

page_text: this result because the current through it would not vary in direct proportion with
the electromotive force owing to variations in the co-efficient of self-induction,
but in some other proportion dependent upon the quality of the iron cores employed
and the degree of magnetic saturation. As a result the variations in the
registration of the meter would be quite different from the variations of electro-
motive force. To obviate this difficulty a shunt circuit is so organised that the
magnetic field acting upon the armature is directly proportional to the electromotive
force of the circuit.
Meters heretofore devised have been sensitive to changes in the rate of
alternations of the current to such a degree as to render them unfitted for use upon
circuits employing a rate of alternation other than that for which they were
specially designed or upon circuits having wide fluctuations in periodicity. In the
meter devised the torque for given currents in the coils and for a given difference
of phase is directly proportional to the periodicity. This is because the inductive
effects produced in the movable element of the meter are proportional to the field
strength and the number of reversals per second and consequently the torque which
depends upon these inductive effects is also proportional to the number of reversals
for a given strength of the inducing field. For a given periodicity the torque is
also proportional to the strength of the field in the shunt circuit other conditions
remaining constant. It follows from these two considerations that in order to
obtain a registration of the energy independent of the periodicity the strength of
the magnetic field dependent upon the shunt circuit must vary inversely as the
periodicity. That is to say any tendency to increase the torque for instance by
increased periodicity must be exactly counteracted by a proportional diminution of
the field produced by the shunt circuit. The shunt circuit of the meter herein
described is so organised as to effect this compensation through a wide range.
It is also important that the form of the current wave in the shunt circuit shall
follow as nearly as possible the form of the wave of electromotive force so that the
indication or registration shall be accurate independently of the exact wave form
of the generator. If an inductance coil of ordinary construction that is with a
closed magnetic circuit were placed in the shunt circuit of the meter the current
would be much distorted as to its wave form by reason of the well known
magnetic peculiarities of iron such as varying permeability and hysteresis. This
difficulty also is overcome by the use of the form of inductance coil herein
described.
In an inductance coil having a closed iron core the mass of iron necessary to
secure at low magnetization a sufficient shunt current say one-tenth of an ampere
at ordinary potentials, is inconveniently large in practice and moreover the lag is
insufficient owing to the small ratio between the apparent energy of the magnetizing
current and the actual energy expended in hysteresis losses. At high magnetization
the lag may be somewhat greater although it cannot be made sufficient for the
purpose except by working the iron entirely beyond practical limits. In any case
whether the magnetization be high or low the permeability of the iron and
consequently the coefficient of self induction of the coil varies not only under
moderate variations of the mean impressed electromotive force but during variations
of a single alternation, so that from this cause and the effects of hysteresis both the
current and the form of its waves are greatly modified. On the other hand it is
well known that an air core inductance coil may possess an approximately straight
line law of magnetization but difficulties are encountered in obtaining a sufficiently
great lag angle. The degree of lag of an alternating current is directly dependent
upon the ratio of the true energy of the current to the so called apparent energy,
hence it is necessary to avoid as far as possible all actual consumption of energy in
any circuit in which a large lag angle is desired.
In an air core inductance coil the number of turns required is necessarily large
in order to secure a high coefficient of self induction. This causes a high resistance
and corresponding expenditure of energy proportional to the square of the current

page_text: and consequently such coils do not produce a very large lag under practical
conditions. The same may be said of a coil with a straight core as ordinarily
constructed.
In order to overcome these difficulties an inductance coil is employed with an
interrupted magnetic circuit consisting of a laminated or otherwise divided core
enclosing the winding and having an air gap of definite length. The exact
proportions in a given coil must be found by calculation and are determined with
reference to the requirements and precautions herein before indicated and the
instructions which follow.
The length of the air gap should be sufficient to render the total reluctance or
resistance of the magnetic circuit greatly in excess of the reluctance of the iron
portion alone and its exact length is determined also with reference to the current
permitted in the shunt circuit of the meter and of the winding of the inductance
coil. The winding must be adapted to the working range of the meter and must
have a sufficient number of turns to maintain a high coefficient of self induction
without requiring either a bigh magnetization or an inconveniently great cross
section in the magnetic circuit. On the other hand it must be of low resistance
relatively to the self induction which makes it necessary to give the air gap only a
moderate length so that the reluctance is not too great to be suited to such a
winding.
The winding and the cross-section of the iron must also be so proportioned to
each other as to make the sum of the losses in the iron and those due to resistance
as nearly a minimum as possible over the working range so as to increase the lag
angle to the greatest degree possible. These proportions are all modified by the
permissible dimensions of the coil and the quality of the iron used, but having
assumed these, the proportions are susceptible to exact calculation.
In the meter shewn in Fig. 14 which is substantially the same as that shewn in
Fig. 1 for carrying the various parts of the meter. The shunt coil A being
designed to carry a small current is wound therefore with a considerable number of
turns of small wire. Its resistance should be as low as is consistent with these
requirements. This coil may be connected in shunt with the work circuit or
receive an impressed electromotive force proportional to that of the work circuit,
as for instance through a transformer or its equivalent. B. and B' represent as
before the series coils connected with the translating devices or receiving a current
proportional to that delivered to the translating devices as for instance, through a
transformer. These coils B, B¹ may be connected either in parallel or in series
with each other and should be wound with wire of sufficient size to carry the
maximum current without undue heating.
The coil A is connected across the conductors 1. 2. leading to the work circuit W
as indicated by means of conductors 3 & 4. In this shunt circuit there is interposed
the inductance coil T. which is shewn in detail in Figs. 18 & 19. It consists of a
coil of insulated wire applied to a laminated soft iron core 2 having one or more
interruptions in its circuit which are shewn at t³. These interruptions or air gaps
may be placed at any convenient point in the magnetic circuit provided they
intersect all the liues of force through the iron. Instead of the two air gaps t
a single air gap as shewn in dotted lines at t may be used; or a single magnetic
circuit with a single air gap to may be used as shewn in Fig. 20. The exact
proportions of the parts of the inductance coil can be readily determined in
accordance with the considerations herein set forth as applied to a meter designed
for any given range of working.
It is sometimes of advantage to provide one or more of the coils as for instance
the shunt coil A with a core a which may be adjustable in position as indicated
in Fig. 24. The form of core shown consists of a central portion a which may be
adjustable in the coil and two side portions a¹, extending across the top and down
the sides of the coil towards the disc D. This core serves to direct the lines of
force through the 'dise and at the same time affords a convenient means of
adjusting the constant of the meter. It is however not necessary to employ a core

page_text: in the coil A. The arrangement and operation of the coils A. B. B¹ and
magnets F. Flare substantially the same as already described with reference to
Fig. 1.
Some of the advantages due to the peculiar character of the inductance coil
herein described may be utilised in connection with armatures of various con-
structions, thus the armature may contain more or less iron for the purpose of
increasing the torque and may have a closed winding of any suitable form. Certain
special advantages, particularly in connection with this inductance coil are secured
by constructing the armature without iron and of large superficial area as in the
disc form herein shewn because in this form there is a considerable area over which
the induced currents may flow in proportion to the total cross-section, thereby
securing a non-inductive form that is to say a form having a small coefficient of
self induction. This results in an induction of currents in the disc proportional to
the periodicity and having a small lag. For this reason among others, an
armature of this form is well adapted to be used in connection with the inductance
coil described which varies the shunt current in an inverse ratio to the periodicity,
and consequently causes the meter to compensate for changes of periodicity.
The shunt coil A may be connected in series with the inductance coil T.
The special form of inductance coil above described is applicable to other forms
of measuring indicating and controlling devices and to other apparatus as may be
readily understood.
In what precedes there are described forms of meters according to this invention
in which the number of revolutions of a suitably retarded armature or its equivalent
serve as an indication of the energy of the currents which actuate the armature.
There will now be described a form of meter in which the partial rotation of the
armature in opposition to a spring provides the desired indication.
Referring to Figures 21. and 22 the circuits 1. 2 and 3. 4 lead from a two phase
generator I to a work circuit containing motors or other translating devices. An
inducing coil A is connected in shunt by means of wires 5. 6. to the circuit 1. 2.
A second inducing coil or pair of coils B B is connected in series of the work
circuit 3. 4. by means of the loop 7. 8. The coils A. B B' disc D and shaft E and
retarding magnets F F¹ are substantially as already described with reference to
Fig. 1 and 2.
The rotation of the shaft E is opposed by a spiral spring N one end of which is
attached to the shaft and the other end to an adjustable support n. The magnets F FI
have no effect on the indication of the instrument except that of damping the
oscillation and bringing the moving parts promptly to rest.
A scale Q is attached to the edge of the disc D and moves therewith. This
scale is properly graduated and by its movement past an index P, the amount of
deflection of the disc may be observed.
If the same meter is intended to be used for measuring currents of different
periodicities, the resistance of the shunt circuit may be varied by the adjustable
rheostat G the sections of which are marked to correspond with the periodicities
required.
In this way, a direct reading meter may be made suitable for the whole range
of periodicities in ordinary use say from 25 to 135 periods per second by introducing
the proper resistance into the shunt circuit. Other means may be employed for
the proper adjustment of the constant of the meter, such, for instance as
changing the position of the coils with reference to the disc, or varying their
effect by introducing iron cores as indicated, for instance, in Figure 21 at a by
dotted lines, or by varying the opposing force; or the meter may be adjusted for a
fixed periodicity and a suitable coefficient applied to the readings dependent upon
the conditions when used. The last named method is however, somewhat incon-
venient in practice. The indications of the scale may be directly in kilowatts or
horse power or in other convenient units. If the power transmitted by each of
two currents in quadrature is the same or proportional, a single meter connected
as shown in Figure 1. may be used with sufficiently accurate results for all ordinary

page_text: purposes. If however, there is for any reason an inequality, a. meter may be
placed in a similar manner on each circuit..
Since the torque is proportional to the power transmitted it is necessary to
oppose the motion of the movable element by a force proportional to the angle
of deflection in order to obtain a deflection directly proportional to the energy
transmitted I have found that by the use of a spiral spring N, such as is used in
the movement of marine clocks, as the opposing force, the deflection is very
nearly proportional to the energy over a wide range. Any other suitable form
of spring may be used instead of the flat spiral spring shown, and if it is not
important that the deflection be exactly proportional to the energy, the force of
gravity may be substituted or used in connection with springs. The scale in this
case should be graduated to correspond with the deflections by trial.
This instrument has the advantage of being capable of a very large angular motion
without disturbing the proportionality of its deflections and may easily be arranged
to turn through 360 degrees, or more if desired. It is thus possible to use a very
long scale so that the indication may be read with great accuracy.
Certain advantages are secured by mounting the instrument as shown in Figure 21
with the shaft vertical but it may be mounted horizontally, and upon knife edges
if desired in a manner well understood.
In order to utilize to the fullest extent the large angular deflection of which
the meter is capable, I have found it of advantage to employ the arrangement of
scale shown in Figure 21 so that the indications may be easily read from a given
point of view. This scale may be of paper or other suitable material such as
aluminum, celluloid or any material sufficiently rigid in proportion to its weight.
In some cases it is desirable to place the scale divisions directly upon the disc,
as indicated at Q' in Fig. 22 or the scale and disc may be formed of a single piece
of metal.
Slight variations due to changes of temperature are apt to occur in the indications
of the instrument. These variations may be compensated for by means of the
adjustable resistance G¹ Figure 21 connected in series with the shunt coil A, and
in most cases also in series with the adjustable resistance G and may be graduated.
to correspond with certain definite changes of temperature.
In Figure 23 is shown a convenient method of connecting the meter with a
three-wire distribution circuit carrying two phase currents. In this figure, the
source of the two phase currents is illustrated at I, which may be any suitable
device such as one or more transformers or the armature of a generator.
The currents supplied to a motor or other device suitable for two phase currents
at M may be assumed as practically equal and the impressed electromotive forces
of the two branches are also nearly equal, or proportional, in practice. The
ordinary variations from exact equality, due to slight differences in the windings
of the devices in the work circuit, affect the accuracy of the meter to a very small
degree, so that the energy supplied to auy device, not radically defective, is
correctly measured.
The conductor 9 is the conductor which is common to both circuits 9. 10 and
9. 11 and carries a resultant current differing in phase 45 degrees from the
component currents in the circuits 9. 10 & 9. 11. The resultant impressed..
electromotive force upon the conductor 9 through the combined circuits 10, 11 also
differs 45 degrees in phase from the electromotive forces impressed upon the
circuits 9. 10 and 9. 11. The coils B, B' are connected in series with the
conductor 9. directly as shown or inductively if desired.
In order to impress upon the circuit 5 including the shunt coil, an electromotive
force in quadrature with the resultant electromotive force impressed upon the
conductor 9 the circuit 5 is connected across the conductors 10. 11 either directly
or inductively. The maximum electromotive force upon the conductor 9 occurs
when the electromotive forces of the circuits 9. 10 and 9. 11 are equal at which
time they are opposite. with respect. to the circuit 5 across the conductors 10. 11.so
that, the resultaat electromotive force in circuit 5 is zero at this instant that is to..
37.1.

page_text: say, the electromotive forces impressed upon the two circuits containing the coils A
and the coils B. B' respectively are in quadrature under these conditions, the
meter will register the true energy delivered, if the constant is properly adjusted
to the conditions under which it is used. A similar method of connection may be
adopted for three phase, and other multiphase circuits.
A single meter may also be used by combining in it the effects of the currents
in the two circuits as will be readily understood by reference to Figure 4. In
this arrangement there are two distinct sets of coils A. B and A¹ B¹. The coil B
is connected in series in the circuit 1. 2 and the coil A in shunt to the circuit 3. 4
upon which the impressed electromotive force is in quadrature to that upon 1. 2 in
the organization shown. These electromotive forces are practically equal under
usual conditions. The coils A and B produce a torque therefore proportional to
the energy transmitted over the circuit 1. 2 independently of the coils A¹ B'.
In a like manner the coils A' B₁ produce a torque proportional to the energy
transmitted over the circuit, 3. 4. The combined effect upon the armature is
therefore equal to the sum of two separate actions producing a torque, and
consequently an indication proportional to the whole energy transmitted.
important that the coils A and A¹ be so located that no torque is produced by
currents of different phase in them alone, and also that the coils Band 13' be so
located that they alone produce no torque, since such action would vary as the
product of the currents in the coils A. A¹ and not in proportion to the energy
transmitted, which is equal to the sum of that transmitted over the respective
circuits.
It is
The arrangement shown in Figure 24 is diagrammatic and indended merely to
illustrate this organization of the meter.
The form and arrangement of the parts may be varied in many ways and the
same arrangement of the meter may be used to measure the energy transmitted
over any two circuits separate or concatenated and of any phase relation by suitable
attention to the methods of connection shown in the various drawings.
In Figure 2 is illustrated a method of applying the invention to a single
phase system of distribution. The series coils B, B' are connected in the
circuit 1. 2. The shunt coil A is connected by the conductors 5.6 across the
circuit 1. 2.
For the purpose of obtaining the required phase relation, there is inserted in the
conductor 5 an inductance coil T adapted to cause the current in the circuit 5. 6 to
lag approximately 90 degrees behind the impressed electromotive force. This coil
comprises a winding and a laminated core 2 having one or more suitably
proportioned air gaps t³.
In Figure 25 is shown a form of indicating device different from that shown
in Figures 21 and 22 although it will be understood that either may be employed.
In this instance the scale Q2 is fixed and the index P¹ is fastened to the shaft and
moves over the scale in the usual way.
Thus are illustrated several forms of meters according to this invention and
several arrangements of circuits in connection with them shewing how they may
be applied for measuring the energy of alternating currents whether of one phase
or of several phases. It is to be understood however that the circuits may be
varied in many other ways, and that the connections to the instrument may be
varied to suit these circuit arrangements subject to the conditions hereinbefore
set forth.
Having now particularly described and ascertained the nature of this
invention and in what manner the same is to be performed, I declare that I make
no general claim to means of measuring electrical energy by the rotation of torque
of a disc acted on by currents of different phase, but what I claim is :-
1. The herein described method of measuring electrical energy by recording the
namber of revolutious in a given time of a conducting disc or its equivalent caused
to revolve by the action upon it of two sets of inductor coils the one set situated

page_text: on the one side of the disc and traversed by the alternating currents to be
measured or a fraction thereof, the other set situated on the other side of the disc
but not directly opposite to the former set and traversed by currents which differ
in phase from those in the former set, the rotating disc being retarded by its.
passage through a magnetic field or several such fields.
2. The above described method of measuring electrical energy applied to a disc
or its equivalent acted upon by two sets of inductor coils traversed by currents of
different phase, each coil crossing over and under so as to surround the disc and
the convolutions of the one coil being transverse to those of the other.
3. The modified method of indicating electrical energy by the partial rotation
indicated on a scale of a disc such as is referred to in the preceding claims in
opposition to a spring.
4. An instrument for measuring electrical energy wherein a disc or its equivalent
is caused to revolve by the action of two sets of coils traversed by currents differing
in phase and situated in different angular positions on opposite sides or surrounding
the disc, a magnetic field being arranged to retard the revolution of the disc and a
counter being geared to its spindle, substantially as herein described.
5. The modified instrument for indicating electrical energy wherein the spindle
of the disc, instead of being geared to a counter, is resisted by a spring, an index
and scale being arranged to shew the deflection of the disc, substantially as
described.
6. The modified arrangement of instrument wherein the retardation of the disc
is effected by the passage of a disc separate from but on the same spindle with it,.
through a magnetic field, substantially as described.
7. An inductance coil constructed and operating substantially as described with
reference to Figs. 18, 19 and 20.
8. In combination with one or other of the instruments for measuring electrical
energy referred to in Claims 4, 5 and 6, conducting circuits arranged as
described with reference to Figs. 10 to 15 inclusive.
9. In an instrument for measuring electrical energy of the kind referred to in
Claims 4, 5 and 6, so arranging the coils and their connections that if there were
no self induction or capacity in the circuit the energy of which is measured, the
two sets of currents which actuate the meter, would differ in phase by 90°, as and
for the purpose set forth.
Dated this 1st day of October 1895.