Improvements in Alternating Current Electric Meters.
Year: 1899

page_text: Date of Application, 30th Dec., 1899-Accepted, 20th Oct., 1900
COMPLETE SPECIFICATION.
Improvements in Alternating Current Electric Meters.
We, THE BRITISHI THOMSON-HOUSTON COMPANY, LIMITED, of 83, Cannon Street,
in the City of London, Electrical Engineers, do hereby declare the nature of
our said invention (which has been communicated to us from abroad by Charles
P. Steinmetz, residing at Schenectady, in the County of Schenectady, State of
New York, United States of America, Electrical Engineer), and in what manner
the same is to be performed, to be particularly described and. ascertained in
and by the following statement:—
66
Our invention is particularly applicable to watt meters of the so-called
multiple-rate" type. In alternating-current system's in which power is sup-
plied to inductive translating devices, for example, such as induction motors,
a part of the current is almost invariably wattless, that is, it does not represent
power delivered. Nevertheless, since wattless currents represent power con-
sumed on the lines and in transformers, because of the C2R loss, and since such
currents consume generator capacity, it is fair that a charge should be made,
though perhaps at a smaller rate than the rate charged for actual power delivered,
for this loss in the system, since such a charge would form a check on customers
using motors too large for the work demand upon them, and running therefore
at light loads, with consequent excessive lagging current. Moreover the fact
that some charge is made for wattless current constitutes an inducement for
customers to cut out of circuit entirely, except when in actual use, all inductive
apparatus, such as transformers or motors, which take at no load an excessive
lagging current.
It is the object of our invention to provide a meter recording not only the
power delivered, but also a part at least of the power lost on the line due to
the lagging or wattless currents.
We accomplish this object by producing in some of the actuating coils of a
meter, such as the Thomson recording watt meter, or an induction watt meter,
or whatever type may be preferred, a relative inductive reactive effect, and a
resultant relative shifting of the magneto motive forces which act on the armature
to cause it to actuate the registering or indicating mechanism. In a Thomson
recording watt meter, for instance, by properly adjusting the relative amount
of reactance and non-inductive resistance in the potential circuit of the instru-
ment, the amount of lagging currents recorded can be adjusted as desired, and
consequently a corresponding rate of charge can be established.
The power in an alternating current circuit is equal to volts into amperes
multiplied by the cosine of the phase angle between the volts impressed on the
circuit and the current flowing. The readings in a recording watt meter are
proportional to the current in the potential circuit, that is, the current due to
the difference of potential across the mains, into the main current multiplied
by the cosine of the angle of phase difference between these two currents.
Moreover, if the potential circuit is in phase with the impressed volts, the
reading of the watt meter will be proportional to the power.
We have found that if we insert in the potential circuit of the watt meter

page_text: a suitable inductive reactance, and adjust it so as to cause the magnetism due to
the current in the potential circuit to lag, say a° behind the phase which it would
have were the instrument to register the actual energy consumed, and then
so adjust the watt meter as to read correctly at non-inductive load, by properly
proportioning the windings or adjusting the recording or registering mechanism,
the reading of the instrument will not be volts by amperes by cosine of the
phase angle between the impressed volts and the resultant amperes, but it will
be volts by amperes by cosine of an angle a less than the angle of lag in the
circuit. The cosine of this angle is obviously greater than the cosine of the
phase angle itself.
For example, suppose a = 200 and the lag of the current due to the inductive
load is 200, then the power delivered is volts by amperes by cosine of the angle
of 20°, the cosine of 20° being .94, that is, in this instance, the actual power
delivered is slightly less than the apparent power.
cos 20°
Let us consider what would be the readings of the instrument when a device
having inductance, or an inductive resistance, is included in the potential circuit
of the watt meter. It is evident if the instrument is not readjusted, that it
will register less than the energy consumed in the circuit, since the energy
consumed with a non-inductive load on the circuit is volts by amperes, while
the readings of the instrument would be volts by amperes by .94. Therefore,
the instrument should be readjusted to give at non-inductive load the same
reading, that is, volts by amperes, as if the inductive resistance was omitted
from the potential current circuit. The instrument is therefore made to read
higher than the equation would make it read, in the ratio which unity bears
to the cosine of 20°. Suppose the main line, current lags by 20, then the dif-
ference of phase between the current in the main line and that in the potential
circuit is (-20)°, and the equation would give, for the meter registration, volts
by amperes by cos (° -20°); but as the meter has been readjusted as above
described, it results that its reading would be volts by amperes by
cos (20 - 20°)
With the reactance causing a lag of 20° in the potential circuit, the instrument
being adjusted to read correctly at non-inductive loads, the reading of the instrument
will be at 20° load lag, volts by amperes by
cos (200. 20° Cos (၂ဝ
or 1:06 +,
cos 20°
cos 20°°
so that the instrument will register a small percentage over what it would register
with the inductance eliminated from the potential circuit, and therefore there would
be a small charge for wattless current at a time when the lag caused by load is rela-
tively small.
If the lag of the current is comparatively great, for example, say 60°,
the power of the circuit is one-half the volts by amperes, since the cosine of 60° is
one-half. The reading of the instrument would be, in this case, volts by amperes by
cos 60° 20)
or volts by amperes by
cos 40°
or volts by amperes ·83.
In this case,
cos 20°
it will be apparant that the instrument registers about 1.66 times the actual power
delivered. In this case the charge for wattless currents is evidently almost two thirds
of the charge for energy current. If the lag of the circuit is 80°, then the instru-
ment will indicate volts by amperes by
which is volts by amperes by
that is, the instrument instead of charging 17 + times the volt amperes, charges
94;
54 times the volt amperes. In this case the charge is for the actual power, and for
something over one-third of the wattless currents.
cos 20°
cos 600
cos 20°
-
or
+50
By adjusting the relative amount of inductance in the potential current coils
of the watt meter, we can vary the readings of the instrument so as to charge
at different rates of increase according to different adjustments made. By
cutting out entirely the inductive resistance or reactance, we can change the
instrument back into a watt meter of the ordinary type, which registers simply
the actual power supplied, in which case the reading of the recording watt

page_text: meter becomes again potential current by main current by cosine of the angle
between the two. By properly adjusting the non-inductive and inductive
resistance of the potential circuit of the watt meter in different proportions,
we get different readings, so that the instrument when combined with a regulable
inductive and a regulable non-inductive resistance in its potential current
circuit, becomes a multiple rate meter, that is, a meter capable of giving
different reading in accordance with the relative amount or reactance in its
potential current circuit.
The same principle can be applied to any recording watt meter based on the
mutual action of potential current coils and the main current coils. For instance,
in, the induction watt meter where the currents in the two coils are approxi-
mately 90 degrees separated from each other, and act on an armature wound
with closed coils or on simply a disc of conducting material in which eddy
currents are generated, the same effect may be secured by making the potential
current lag more than 90 degrees behind the impressed electro-motive force
as by producing an inductive reactive effect in certain of the coils of the instru-
ment; and by adjusting this inductive effect various readings may be obtained.
It results from a motor constructed as described, that a customer may be
given a certain discount for taking leading currents, but this is not objectionable,
since such currents tend to raise the power factor of the system.
Referring to the drawings, Fig. 1 illustrates our invention in connection with
a Thomson recording watt meter, in which A, B, represent constant potential
mains supplied with energy direct or through intermediation of transforming
apparatus and Fig. 2 represents diagrammatically the application of our inven-
tion to an induction watt meter.
In Fig. 1, A¹ indicates the armature coils of the watt meter. and K, K' indicate
the field magnet coils of the watt meter, here shown as of a usual and well
known construction. X is the shaft which carries the armature coils, supported
in the usual manner in adjustable jewel bearings; M is the damning disc acted
upon by the permanent magnets M. M. L. L are incandescent lamps, or other
similar devices, arranged in multiple on the constant potential circuit A. B:
C is the commutator of the armature, upon which rests brushes C¹, by which
commutator and brushes, a current in multiple with the mains A. B, and corre-
sponding in magnitude and phase to the electro-motive force impressed on the
translating devices, may be supplied to the coils A¹; D represents any of the
well known form's of registering mechanism, such as a train of gearing with
indicating dials: R is an adjustable non-inductive resistance of any well known
Hype; and R is an inductive resistance or reacting device, such as is involved
in our invention. It will be noticed that this reactance device is adjustable.
The points of contact of the coils over which the switche's pass are connected at
such points of the winding of the inductive resistance, with relation to the
non-inductive resistance, the instrument and the circuit in which it is connected,
as to permit the adjustment which renders our apparatus a meter of the multiple
rate type.
By placing the switch arm S2 on the second contact, as shown, enough of
the coils of the inductive resistance will be in circuit with the armature A¹
and potential circuit P. to cause a lag of the current in the armature. of, say,
20 degrees, when placed on the next contact to the right, a lag of 30 degrees
would he produced in the armature circuit and so on.
Turning to Fig. 2. which illustrates, as we have stated, our invention in con-
nection with an induction watt meter in outline, T represents a transformer
through which energy is supplied at constant potential and lowered pressure to
the circuit A2, B2, in which are arranged incandescent lamps or other trans-
lating device 7, 1. Of course the energy may be supplied to the lamps directly
without the use of a transformer. C2. C3 represent the main current coils of
the watt meter. and S1, S2 represent the potential coils of the watt meter, con-
nected across the mains A2, B2. These coils conjointly act upon an armature A³,

page_text: here shown as a cylinder of conducting metal. R2 is an inductive resistance or
phase-retarding device connected, as usual, in the circuit with the potential
coils to produce a lag of current in the potential coils as near 90° as possible.
But the current in the potential coils, with the arrangement thus far described,
can never lag quite enough behind the impressed electro-motive force to cause
the meter reading at all. loads to be EC cos a, when E is the electro-motive
force, C the current, and the angle of lag. Our invention requires, however,
that the reading should correspond to EC cos (e + a), or, say, EC cos (+ 20°).
It therefore becomes necessary to artificially retard the phase of the current
flowing in the coils S1, S2. We prefer to produce this result by shunting them
with a phase-advancing device, preferably a non-inductive resistance, as shown
at R3. This device will divide the current in the branch circuit, already lagging
by, say, 85°, into a leading component and a lagging component. The lagging
component, which will obviously be behind the current in the coil R2, will pass
through the coils S1, S2. Then by properly adjusting the effect of this device,
(which is here shown as an adjustable resistance) the lag of the current in the
potential coils may be made, for example, 110°.
In addition to the resistance R³, we may wind a coil or set of coils $³, St, on
the magnetic circuit of the coils S1, S2. These coils, closed on themselves with
or without an adjustable resistance R4, will tend to beat back the flux due to
the coils S1, S2, and to retard it in phase, as is well understood in the art, and
produce an additional lag in the magnetism, due to the potential coils.
Though we have shown two separate coils acting to retard this flux, working
conjointly, it is obvious that either one alone may be used.
By varying the amount of resistance of these respective sets of coils, we can
vary their relative magnetizing effect, and thus in turn effect the displacement
in phase of their resultant. magnetic flux.
We do not limit ourselves to any particular form of alternating current
electrical measuring instrument, since we consider that we are the inventors of
the broad method and apparatus for so shifting the relationship of the actuating
magneto-motive forces which set in motion the armature of an alternating
current indicating or registering instrument, such as a meter or galvanometer,
.as to establish such lag either in current or magneto-motive forces, as will,
when the registering mechanism is properly adjusted, record a predetermined
amount of wattless current in an alternating current circuit.
Having now particularly described and ascertained the nature of our said
invention (which has been communicated to us from abroad) and in what manner
the same is to be performed, we declare that what we claim is:-
1 The method of registering a predetermined proportional amount of watt-
less current in an alternating current circuit, which consists in producing in
one or more of the coils of an electric registering or indicating instrument, an
inductive reactive effect and a resultant relative shifting of the actuating
magneto-motive forces, corresponding to the proportionate amount of wattless
current to be measured, and actuating properly adjusted registering or indicating
mechanism, by the said magneto-motive forces due to the currents in the coils of
the instrument.
2-The method of registering a predetermined proportional amount of watt-
les's current in an alternating circuit, which consists in producing in one of
the coils of an electric registering or indicating instrument, a predetermined
lag of current corresponding to the proportionate amount of wattless current
to be measured and actuating properly adjusted registering or indicating
mechanism by the currents in the coils of the instrument.
3 The method of registering a predetermined proportionate amount of watt-
les's current in an alternating current circuit, which consists in producing in
one of the coils of an electric registering or indicating instrument a predeter-
mined lag of current, and thus causing a different degree of phase difference

page_text: between the currents in the respective coils of the instrument than normally
would exist, and actuating properly adjusted registering or indicating mechanismi
by the currents of adjusted phase flowing in the coils of the instrument.
4-The method of registering a predetermined proportional amount of watt-
less current flowing in an alternating current circuit, in addition to registering
the actual power delivered, which consists in producing, in one of the coils of
an electric registering instrument, a predetermined lag of current, and thus
causing a different degree of phase difference between the currents in the respec-
tive coils of the instrument than normally would exist, actuating the recording
mechanism of the instrument by the currents of adjusted phase in the coils
thereof, and causing the registering mechanism to register at such a rate as at
non-inductive load to indicate the power delivered.
5-The method of registering a predetermined proportional amount of watt-
less current flowing in an alternating current circuit, in addition to registering
the actual power delivered, which consists in producing, in one of the coils of
an electric registering instrument, a predetermined lag of current by inductive
reactive action, and thus causing a different degree of phase difference between
the currents in the respective coils of the instrument than normally would
exist, actuating the recording mechanism of the instrument by the currents of
adjusted phases in the coils thereof, and causing the registering mechanism to
register at such a rate as at non-inductive load to indicate the power delivered.
6 The method of registering a predetermined proportional amount of watt-
less current flowing in an alternating current circuit in addition to registering
the actual power delivered which consists in producing in one of the coil's of
an electric registering instrument, a predetermined lag of current by inductive
reactive action and thus causing a different degree of phase difference between
the currents in the respective coils of the instrument than normally would
exist, actuating the registering mechanism of the instrument by the currents
of adjusted phase in the coils thereof, causing the registering mechanism to
register at such a rate as at non inductive load to indicate the power delivered,
and varying this current lag to register at different proportions of the wattless
energy.
7 The method of registering a predetermined proportional amount of watt-
less current flowing in an alternating current circuit, in addition to registering
the actual power delivered, which consists in producing in one of the coils of
an electric registering instrument a predetermined lag of current by inductive
action, and thus causing a different degree of phase difference between the
currents in the respective coils of the instrument than normally would exist,
actuating the registering mechanism of the instrument by the currents of adjusted
phase in the coils thereof, causing the registering mechanism to register at
such a rate as at non-inductive load to indicate the power delivered, and varying
this current lag to register different proportions of the wattless energy by
varying the amount of relative inductive effect in the potential current circuit
of the watt meter.
8-In an alternating current watt meter, or indicator, the combination of the
actuating coils, a reactance device included in one of said coils and properly-
adjusted registering or indicating mechanism actuated by the currents in said
coils to register or indicate a proportionate amount of wattless current.
9--In an alternating current measuring instrument, the combination of the
actuating coils and adjustable reactance device included in the circuit of one
of said coils, and properly adjusted registering or indicating mechanism actuated
by the currents in the said coils, to register or indicate a predetermined propor-
tionate amount of wattless current.
10-In an alternating current watt meter, the combination of the actuating
coils, a reactance device included in one of the said coils, and registering mechanism
adjusted so as to record the power delivered, and in addition thereto to record
a portion of the wattless current.

page_text: 11 In an alternating current watt meter, the combination of the main
current coils, the potential current coils, the armature actuated by the current
flowing in these respective coils, a reactance device included in the potential
current circuit, and registering mechanism adjusted to record accurately at
non-inductive load the power delivered, whereby a proportionate amount of
wattles's current is registered in addition to the power delivered.
12 In an alternating current system of electrical distribution the combination
of the actuating coils of a registering watt meter, an adjustable reactance
device included, and registering mechanism adjusted relatively to the reactance
to record accurately at non-inductive load the power delivered.
13 In an alternating current watt meter, the combination of the potential
current coils, the main current coils, the armature whose windings are included
in the circuit of the potential current coils, suitable retarding apparatus acting
on said armature, an adjustable non-inductive resistance, an adjustable induc-
tance device, or inductive resistance, in the potential current circuit, and
registering mechanism actuated by said armature so adjusted as to record at
non-inductive load the power delivered."
14 The method of increasing the lag of current in the potential coil of a
watt meter, which consists in shunting a non-inductive resistance around the
said coil.
15 The combination in a watt meter, of a current coil, a potential coil, and
a phase retarding device in series with the potential coil, and a phase advancing
device in shunt to the potential coil.
1000