A Method of Measuring Electrical Power and Appliances for that purpose.
Year: 1897

page_text: A Method of Measuring Electrical Power and Appliances for that
purpose.
I, MICHAEL BIRT FIELD, of Bruggerstrasse, Baden, Aargau, Switzerland, Electrical
Engineer, do hereby declare the nature of this invention to be as follows:-
My invention relates to means of measuring the electrical power supplied to any
circuit. For this purpose, I make my instruments indicate more or less directly in
the manner hereinafter described the mean value of the product of the current
supplied to the circuit and the difference of potential at its terminals, by making
use of one or other, or a combination of the following algebraic identities. Writing
C for the current at any instant, and V for the said difference of potential at any
uctant we have
and it is obvious that, if we substitute V for C, and C for V in the above, we get two
more similar expressions. (1) The various circuits of the appliances which I employ
are arranged so that some carry currents which are proportional to C, others currents
proportional to V, to the sum of C and V, and to the difference of C and V respec-
tively, and I place in these various branches indicators which indicate the mean
square values of the above mentioned quantities, so that, by the algebraic addition
and substraction of these indications, I obtain a measure of the power VC supplied
to the circuit. The several indicators may be arranged to co-operate with one another
in such a manner that they automatically indicate the sun or difference of the
quantities in the above equations and thus directly shew the mean value of the
product VC.
I interconnect these circuits with resistances, choking coils and transformers,
switches, when necessary, and indicators so as to obtain currents proportional to the
above mentioned quantities of suitable value that the said product VC is more or less
directly indicated without causing the undue waste of power incident to the
methods known as the "3 voltimeter method," "3 ammeter method," and
others.
Figure 1 of the accompanying drawings is a diagram shewing one way of inter-
connecting the circuits. A B D represents a circuit the power supplied to which it
is required to measure. R represents a small non inductive resistance through which
the main current C passes. This resistance, is such that the potential difference at
its terminals when the maximum current is flowing through it, is, compared with the
whole difference of potential of the circuit, very small indeed. Tt represents a
small specially constructed transformer the primary of which T is connected across
the mains AD of the circuit. The secondary winding t consists of only a few turns
giving an electro-motive force comparable with the difference of potential at the ter-

page_text: minals of the resistance R. The middle of the secondary winding is connected to
the outer main D), while the two extremes are both connected to the further terminal
of the resistance R, forming branches ab, cb. If now the resistance of these two
branches be sufficiently great, the difference of the mean square values of the
currents in them will be a measure of the product VC, according to equation (3).
This measurement may be effected by so connecting an indicator together with a
two way switch that in one position of the switch the indicator is in the branch ab,
and in the second position in the branch cb, so that the algebraic difference of these
two indications may represent directly the product of VC. Two separate indicators,
one in each of the branches ab cb, may be employed without a switch and pointers
on these indicators may be so combined that these move over the same scale, and
stops may be arranged to hold them in position while a reading is taken. The
branches ab bc may together form the circuit of a single indicator so that its scale
reading indicates the difference of the mean square values of the currents flowing in
the two parts ab bc of the indicator circuit. The indicator may be constructed
according to any of the well known principles for measuring current strength, prefer-
ably the hot wire system, and the scale may be calibrated to represent such a multiple
of the mean square of the current passing through the indicator as will best facilitate
the determination of the value of the product VC.
In Figure 2 the arrangement of connections is the same as in Figure 1, with the
indicator diagrammatically shewn.
The dotted line abc in Figure 2 represents one or more fine wires which are
equivalent to the branches ab bc in Figure 1. These fine wires elongate or
expand when current is passing through them, and in expanding deflect the index so
that it indicates on the scale a certain multiple of the difference of the mean square
current strengths in the fine wires. By suitably choosing this inultiple the instru-
ment can indicate directly the power supplied in " Watts."
Figure 3 represents another arrangement where the secondary wire of the trans-
foriner is not subdivided, but the resistance R is divided. The indicator is such that
each of the fine wires ab be actuates a separate pointer moving over the same scale.
By means of a stop lever L both pointers can be fixed in position while a reading is
taken, and afterwards released.
Figure 4 again represents an arrangement where a specially constructed resistance
or choking coil C, connected as shewn, is substituted for the transformer Tt. The
indicator in this case has a single pointer actuated by the expansion of a single fine
wire, but is combined with a switch S in such a way that the end 6 of the fine wire
may be connected to either of the terminals a or c. For the determination of the
power, a reading is taken in each of the two switch positions.
Dated this 24th day of June 1897.
ABEL & IMRAY,
Agents for the Applicant.
A Method of Measuring Electrical Power and Appliances for that
purpose.
I, MICHAEL BIRT FIELD, of Bruggerstrasse, Baden, Aargau, Switzerland, Electrical 4
Engineer, 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 :―
My invention relates to means of measuring the electrical power supplied to
שמש

page_text: circuit. For this purpose, I make my instruments indicate more or less directly in
the manner hereinafter described the mean value of the product of the current
supplied to the circuit and the difference of potential at its terminals, by making use
of one or other, or a combination of the following algebraic identities. Writing C
for the current at any instant and V for the said difference of potential at any
instant we have
and it is obvious that, if we substitute V for C, and C for V in the above, we get two
more similar expressions. (1) The various circuits of the appliances which I employ
are arranged so that some carry currents which are proportional to C, others currents
proportional to V, to the sum of C and. V, and to the difference of C and V respectively,
and I place in these various branches indicators which indicate tlie mean square
values of the above mentioned quantities, so that, by the algebraic addition and sub-
traction of these indications, I obtain a measure of the power VC supplied to the
circuit. The several indicators may be arranged to co-operate with one another in
such a manner that they automatically indicate the mean..sum or difference of the
quantities in the above equations and thus directly show the mean value of the
product VC.
I interconnect these circuits with resistances, choking coils and transformers,
switches, when necessary, and indicators so as to obtain currents proportional to the
above mentioned quantities of suitable value that the said product VC is more or less
directly indicated without causing the undue waste of power incident to the methods
known as the "3 voltmeter method," "3 ammeter method" and others.
The measurements may be effected by so connecting an indicator together with,
say a two-way switch that in one position of the switch the indicator is in one of the
branches, and in the second position another so that the algebraic difference of the
two indications may represent directly the product of VC.
Or two separate indicators, one in each of. say, two branches may be employed
without a switch, and pointers in these indicators may be so arranged that they move
over the same scale and stops may be arranged to hold them in position while a read-
ing is taken. Or the two branches may together form the circuit of a single indicator
so that its scale reading indicates the difference of the mean square values of the
currents flowing in the two branches of the indicator circuit. The indicator may be
constructed according to any of the well known principles for measuring current
strength, preferably the hot wire system, and the scale may be calibrated to repre-
sent such a multiple of the mean square of the current passing through the indicator
as will best facilitate the determination of the value of the product VC.
In carrying the method according to this invention into practice I employ as will
be seen from the diagrams of connections referred to hereinafter, circuits carrying
currents not strictly proportional to the sum and difference of the current and
electromotive force in the circuit whose power is to be measured, but proportional to
suitable multiples of these.
In the accompanying drawings
Figures 1 to 13 inclusive are diagrams illustrating alternative methods according.
to this invention of interconnecting the circuits and appliances to obtain the desired.
measurement.
Figures 14 and 15 are front elevation and central vertical section respectively of
one construction of instrument for measuring power being a combination of two
instruments of well-known construction for the measurement of current or electro-
motive force.
Figure 16 shows an alternative method of combining the instruments.
Figure 1 of the accompanying drawings is a diagram showing one way of
interconnecting the circuits. A B D represents a circuit the power supplied to which

page_text: it is required to measure, R represents a small non-inductive resistance through
which the main current C passes. This resistance is such that the potential
difference at its terminals wheu the maximum current is flowing through it is,
compared with the whole difference of potential of the circuit, very small indeed.
Tt represents a small transformer the primary of which T is connected across the
mains AD of the circuit. The secondary winding t consists of only a few turns
giving an electro-motive force comparable with the difference of potential at the
terminals of the resistance R. The iniddle of the secondary winding is connected to
the outer main D, while the two extremes are both connected to the further
terminal of the resistance R, forming branches ab, cb. If now the resistance
of these two branches be sufficiently great, the difference of the mean square
values of the currents in then will be a measure of the product (4) VC,
according to equation (3).
In Figure 2 the arrangement of connections is the same as in Figure 1 with
the indicator diagrammatically shown. The dotted line abc in Figure 2
represents one or more fine wires which are equivalent to the branches ab bc in
Figure 1. These fine wires elongate or expand when current is passing through
them, and in expanding deflect the index so that it indicates on the scale a
certain multiple of the difference of the mean square current strengths in the
fine wires. By suitably choosing this multiple the instrument can indicate directly
the power supplied in "Watts."
Figure 3 represents another arrangement where the secondary wire t of the
transformer is not subdivided, but the resistance R is divided. The indicator is
such that each of the fine wires ab be actuates a separate pointer moving over
the same scale. By means of a stop lever L both pointers can be fixed in
position while a reading is taken, and afterwards released.
Figure 4 again represents an arrangement where a specially constructed resistance
or choking coil E, connected as shown, is substituted for the transformer Tt. The
indicator in this case has a single pointer actuated by the expansion of a single fine
wire, but it is combined with a switch S in such a way that the end of the fine
wire may be connected to either of the terminals a or c. For the determination of
the power, a reading is taken in each of the two switch positions.
The arrangement of circuits in Figure 5 is such that the secondary winding t of
the transformer may be connected by means of the reversing switch S 8¹ (the two
arms of which are linked together) so that its electromotive force is either assisted
or opposed by that electromotive force which is the difference of potential of the
terminals of the resistance R. A reading having been taken in each position of
the switch the power may be determined from the difference of the indications in
accordance with equation 3.
In Figure 6 a switch S is indicated by which the electroinotive force of one or the
other half of a divided transformer secondary may be put in series with
the electromotive force acting along the resistance R or in other words the
electromotive force which is the potential difference at the terminals of
the resistance R one of the half windings assisting the other opposing the
electromotive force in the resistance. In the arrangement shown in Figure 7 the
switch S may be employed to put the electromotive force acting along first one and
then the other half of the divided resistance R in series with the transformer
winding t, the indicator circuit being represented as before by ab.
Figure 8 is a diagram showing connections for measurement of power in a
three-phase circuit of which A1, A2, A3, are the mains.
In each of the mains A1, A2, is a divided non-inductive resistance as shown at
R¹, and R, whose middle points are connected respectively to one end of the
transformer windings t¹, t, the other ends of these windings being connected
respectively to the points b₁, bª.
The primary T¹ to the secondary t is connected across the mains A¹ and A³ and the
primary T of the secondary t across the mains A² and A³.
There are thus two measuring devices formed of the kind already described;

page_text: the circuits ab¹, c'b¹, a²b², cb, may represent four instruments or preferably the
two circuits of two indicators of the kind shown in Figure 2 or Figure 3.
The total power in the three-phase circuit can be shown to be given by the sum
of the two power readings thus obtained from the two indicators. Or each of the two
indications may be obtained in any of the ways hereinbefore described with reference
to Figures 1 to 7.
The method shown in Figure 8 is applicable to either a three-phase circuit or
a three-wire single phase system or any system of three conductors meeting at a
point, with any currents and electromotive forces acting in them whatever.
In Figures 9 and 10 is shown a method of combining the circuits of the indicators
in one instrument L¹. The two circuits through the instrument connected in
Figure 9 between ab and cb respectively indicate say hot wire apparatus the readings
of each of which may be taken simultaneously or practically so and thus afford an
indication of the true power in watts. A simple change-over switch of any suitable
well-known construction external to or combined with the instrument may be
arranged to change the connections to those shown in Figure 10 in which case the
indicator whose circuit is connected to the transformer indicates volts and the other
amperes, and by dividing the product of amperes and volts into the true power
obtained from the connections in Figure 9 the value of the cosine of the angle of
lag may be obtained, the two readings viz. :-true power and volts and amperes
being obtainable with such rapidity one after the other that the conditions of working
will usually not have changed. Instead of employing instruments whose indications
depend upon current flowing through them as in the arrangements herein before
described, electrostatic instruments, inay for the purposes of the present invention be
substituted in the well known manner.
For example, each of the circuits ab cb shown in Figure 3 and described as fine
wires may be replaced by an electrostatic instrument one of which will register the
square of the vector sum of the voltage of the transformer secondary and that acting
down one half of the resistance R, and the other the square of the vector difference
of these quantities, i.e. of the said transformer voltage and that acting down the
other half resistance.
I prefer however to combine the two instruments in one as indicated diagrammati-
cally in Figure 11, in which figure is also shown one method of connecting the
instrument. The instrument as indicated comprises four "cells" ог
inductors P1, P2, P³ P' and two or more vanes P³ Po which two latter are mounted
on the same axis P7. The turning moment on the axis is the difference of the
turning moments due to the two vanes, and thus automatically effects the
difference.
In the case shown in Figure 11 this is without serious error proportional to 2 Vv
if V be the difference of potential across the mains and. v the fall of potential down
the non-inductive resistance.
Where the voltage of the circuit is small it may be transformed up as shown in
Figure 12 for with the electrostatic system it is preferable to have a large difference
of potential existent between vanes and inductors.
Where a transformer Tt is available or preferred the instrument may be connected
as in Figure 12 and a scheme of connections for a three-phase or three-wire system
is shown in Figure 13.
The instrument illustrated in Figures 14 and 15 is one construction of appliance
according to this invention for the purpose of carrying out the method of measurement
according to this invention.
Upon a base plate I aud inner plate I¹ are supported the parts H and J which
represent two measuring devices of any well-known construction, preferably not
electro-magnetic, provided with pointers H¹, J' respectively, working over a cominon
scale I provided if necessary with two sets of graduations.
The pointer H¹ is bent over at the top as at He to bring its extremity over the
graduations.
To the plate I are attached two pins by which two paper strips K are rotatably

page_text: supported. These strips serve to check the vibrations of the pointers when a reading
is being taken. For this purpose they are operated from a knob K³ by means of
a lever K¹ and link K2, in such a manner that the rotation of the knob K³ causes the
strips to press upon the pointers.
If desired the non-inductive resistance employed in my method may be
arranged within the cavity I2 at the back of the instrument.
A glass
whole enclosed in a suitable
front 13 is provided as usual, and the
casing.
In the alternative construction shown in Figure 16 a motion of rotation is
imparted by any two known measuring devices to the drums N1 N2 respectively, in
the directions of the arrows n¹ n² respectively. A flexible tie N is stretched between
two springs No whose joint effect is to move the tie No as a whole downwards the
lower being slightly stronger than the upper. This tie passes round the axle, or
a pulley O on the same, of a pointer O and any vertical movement of the tie is trans-
formed into a rotational movement of the pointer O.
The tie N³ is connected by other flexible ties N° N to drums N1, N2 respectively
and when the drums rotate the tie No receives from the springs No vertical motion
which depends on the difference of the motions of the two drums, and this difference
is therefore indicated by the pointer O.
Departure may obviously be made from the schemes of connections and from the
arrangements of apparatus herein before described and illustrated without departing
from the spirit of this invention, the fundamental basis of which is set forth in the
equations herein before given and numbered (1) (2) and (3) and the two similar
expressions referred to as obtainable by substituting V for C and C for V, and 1 do
not confine myself to the precise connections or arrangements described or illustrated
which are merely by way of example and in explanation of some of the ways in which
I may carry out this invention. For example it is often convenient to connect the
transformer T on the other side of the resistance R to that on which it is shown
connected in the diagrams. Further whereas reference has herein before been
principally made to the arrangement and interconnection of apparatus for carrying
out the principle expressed in equation (3), the principles expressed in the equa-
tions 1 & 2 may be readily effected by measuring the quality proportional to
(C+V) or to (C-V) in any of the ways described and by measuring the quan-
tities C and V2 in any well known
Also whereas I use the word
"connection" in the Claims 8, 9 10 and 11 following, I wish thereby the "connect-
ing up electrically" to be understood.
manner.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed I declare that what
I claim is
1. The method of measuring power in an electric circuit by which quantities
proportional to the mean square values of current and electro-motive force and
to the sum or difference thereof or of known multiples thereof in the circuit
or difference of such
are measured the power being determined from the sum
quantities.
2. The method of measuring power in an electric circuit by which quantities
proportional to the mean square values of the sum and of the difference of current
and electro-motive force or of known multiples thereof in the circuit are measured,
the power being determined by the difference of such quantities.
3. The combination of a current measuring appliance and a potential measuring
appliance, or of two potential measuring appliances to form apparatus for the
measurement of power in an electric circuit in such a manner that both operate
in conjunction with a common scale substantially as described, from which scale
by the difference of the two indications thereon the power in the circuit may be
determined.
4. The combination substantially as described of a current measuring appliance
and a potential measuring appliance, or of two potential measuring appliances

page_text: a common scale and a switch or switches whereby the angle of phase lag may be
determined.
5. The combination of a current measuring appliance and a potential measuring
appliance or of two potential measuring appliances to form one apparatus for the
purpose described in such a manner that the deflections of the two instruments
are transmitted to a common index so that it indicates the difference of the
deflections.
6. The combination, in one instrument for the purpose described of two
measuring instruments having their moving parts mounted on a common axis in
such a manner that the resulting deflection indicates the difference of the two
deflecting forces.
7. A three-phase watt-meter, substantially as described.
8. The combination and connection of apparatus for the measurement of power in
a three-phase or a three-wire circuit substantially as described and illustrated in
Figure 8 or in Figure 13 of the accompanying drawings..
9. The arrangement and connection of parts to form an electrostatic watt-meter
substantially as described and illustrated in Figure 11 of the accompanying
drawings.
10. The arrangement and connection of apparatus for the measurement of electric
power substantially as described and illustrated in Figures 1 to 13 inclusive of the
accompanying drawings.
11. The arrangement and connection of apparatus for the measurement of phase
lag substantially as described and illustrated in Figures 9 and 10 of the accompany-
ing drawings.
12. The combination of two instruments in one substantially for the purpose
described and illustrated in Figures 14 and 15 or in Figure 16 of the accompanying
drawings.