Improvements in Multi-rate Electric Meters.
Year: 1899

page_text: COMPLETE DIEUTTICATION.
Improvements in Multi-rate Electric Meters.
We. THE BRITISH THOMSON-HOUSTON COMPANY, LIMITED, of 83, Cannon Street,
in the City of London, Electrical Engineers, do hereby declare the nature of
this invention (which has been communicated to us from abroad by Elihu
Thomson and Frank 1. Cox, residing, respectively, at Swampscott and Lynn,
both in the County of Essex, State of Massachusetts, United States of America,
Electrical Engineers,) and in what manner the same is to be performed to be
particularly described and ascertained in and by the following statement:―
Our present invention relates to electric meters, and consists of the adaption
of any well known form of meter, the specific construction of which for the
purposes of this invention is immaterial, to a more equitable method of regis-
tration than those with which we are now acquainted.
In the art of electric measurement of energy two systems in addition to the
older one of directly indicating the current flow either in watts or amperes, have
come into use. The old system is to measure the energy in watt-hours or ampere-
hours, as may be desired, and to make to the consumer a charge based entirely
upon the amount consumed. To encourage the use of current at times when the
station is not fully loaded and as nearly as possible equalize the total load, thus
diminishing the cost of energy and increasing the efficiency of the boilers,
engines and generators which, as is well-known, are best adapted to maintain their
full load, (or work at highest efficiency when run near full load), the two other
systems have been devised. One of these methods is to use a two-rate ineter, which.
by various contrivances unnecessary here to detail is adapted to register at one rate
during one part of the day and at a lower or higher rate during a different part
of each twenty-four hours.
Various forms of this device have been claborated, some of which indicate the
two changes on different dials, and some of which merely shift mechanism of
one sort or another so as to effect a direct change in the registration, measuring
all of the energy upon a single set of dials.
Another system which has been developed is the so-called maximum demand'
system of book-keeping, which consists, in its essence, of making a certain
fixed charge proportioned to the maximum energy which may be consumed in a
given branch circuit at any time, and over and above that another charge pro-
portioned to the actual energy consumed.
There are inherent inequitable features in each of these systems. The maxi-
mum demand, for instance, may be established for any month or other period
by factors which do not give a true measure of the probable demand for current
which the station must supply to the branch circuit under consideration. For

page_text: instance, in some forms of such devices an accidental short circuit or a very
unusual supply of current taken for only a brief period might be registered as
a basis for the fixed charge referred to, although such a demand may not occur
again for months or years; and this leads to dissatisfaction on the part of the
customer, and is manifestly unfair. The charge also has no relation to the
station load; and being the same no matter at what time the demand occurs,
has no tendency to encourage consumption at times of small station load.
Similarly, two-rate meters have as heretofore developed have in a measure been
open to some objections; for example, the change of rate is made at a certain
definite time (where it is effected by clock-work attached to each meter), and
this time should vary at different seasons of the year; whereas the mechanism
of a clock is such that the period of high charge is not ordinarily susceptible
of variation. Furthermore, the change in the rate of variation is effected all at
once, so that during the transition from light load at the station to full load,
which is always inore or less gradual, the consumer is paying either at a less
rate or a greater one than is equitable, either to him or to the station.
It is to this class of two-rate meters that our invention is most nearly allied.
It differs, however, from all others with which we are acquainted, in that it takes
into account the error last specified, that is, it effects a registration at a rate
varying from hour to hour with the load upon the station. It consists therefore
not only in the special apparatus illustrated in our drawings, but in the improve-
ment in the art of registering or recording the consumption of electrical energy,
which consists in varying from time to time the rate of registration, and making
this variation such that the rate of registration is dependent upon the load upon
the central station, and preferably in more or less proportion therefo.
.
To effect the purposes of the invention thus indicated, we have devised the
arrangement of apparatus shown and described in this case; but we do not wish to
limit ourselves to any particular type of apparatus, because, so far as we are
aware, we are the first to progressively change the rate of registration in the way
just indicated, and wish to make broad claims to this feature of invention. As
an embodiment of the invention, therefore, the apparatus illustrated in the draw-
ings is to be considered. It consists in general of an ordinary recording watt-
meter; to which is connected a suitable rate-varying means, such as a resistance,
over the contacts of which a switch arm is moved by a cam driven by clock-work
mechanisni, so that at the time when the least load comes upon the station, the
greatest resistance will be in circuit with the meter, and this resistance will be
progressively varied, decreasing as the load comes on and increasing as it falls
off. It is manifest that by varying the shape of the cam which controls the
motion of the resistance switch, this change may be made anything desired. We
havo described it more particularly with reference to an electric lighting station,
but in some other classes of distribution, for instance in an electric railway,
there may be more than one peak to the load; in such cases the cam should be
so shaped that the resistance would be properly varied for each one of the peaks,
and to the degree to which the peak indicated an increase of load. For instance,
in an electric railway, it is common to have large demand for current from seven
to nine o'clock in the morning when people are going to their customary employ-
ments, a similar or smaller peak at the middle of the day, and another and heavier
peak than either of these at the close of the day's business. Of course it is
plain that the proportioning of the cam could be made such as to take these
changes into account. But in a lighting system, where the peak of the load
occurs from five to eight or nine o'clock in the evening, only one change need
be made, if, for example, in a given station the load comes on quite gradually,
so the shape of the cam could be made such as to cut out the resistance quite
gradually, and if the load falls off more rapidly, so the shape of the cam may be
adapted to compensate for this. In other words, our invention will be found of
general applicability to any class of recording electrical measuring instrument

page_text: in which the load factor at the station is to be taken into account, and to this
extent we consider the claims which we make generic.
In the drawings, Fig. 1 shows a wattmeter with the invention applied thereto;
Fig. 2 is a chart of the load curve of the station; Fig. 3 shows a recording
ammeter with another form of the invention; Fig. 3 is a diagram like Fig. 2 to
which the form of meter shown in Fig. 3 is adapted; Fig. 4 is a modified arrange-
ment for affecting the registration.
In Fig. 1, A is a wattmeter, with the fields A', A¹ connected in series, and an
armature B connected across the lines of a branch circuit, including the lamps L,
which may represent any load whatever. E is the counter, F the usual resistance
in series with the armature, and D the damping mechanism. All of these parts
are well known.
is a rate varying means consisting of a resistance, in this case shown in
series with the armature. It is cut into and out of circuit progressively by the
movement of the switch arm 12. A spring f¹ holds the arm at the maximum
resistance position during the greater part of the revolution of the cam C.
This cam is driven so as to rotate once in twenty-four hours, by means of gear-
ing C driven from a clock C, and is provided with a projecting portion or toe C
operating a cam roller f, and depressing the rod F connected to the resistance
Of course
a twenty four hour clock may be employed instead of the
twelve-hour clock shown, as illustrated in connection with the modified form of
the invention shown in Fig. 3.
עינה
The operation of the parts shown in Fig. 1 is as follows:-As the clock
rotates, the cam C rotates with it, and when the toe C is in line with the rod F³
all of the resistance F is cut out, the meter recording at its normal rate. This
is about eight or nine o'clock, in the particular combination of apparatus shown,
and coincides with the peak of the load, as shown in Fig. 2. A little later, when
lights are turned out, the switch begins to cut in more of the resistance F until
finally all of it is in circuit, and the meter records at its minimum rate. This
condition is maintained, in the particular case illustrated, until a little after
three p.m., when the resistance again begins to be cut out. The shape of the
cam corresponds in a general way to the shape of the average load shown in
Fig. 3, so that the meter reading instead of being / ECdt or Cdt, be-
comes HCf (L)dt or Cf (1)dt or even / ECLdt or CLdt, where E, C, and t
are electromotive force, current and time, respectively, and L is the station load.
That is to say, our improved meter integrates not the quantities usually measured,
but the same quantities modified by a continuous function of the load on the
station.
In Fig. 3 we show the same invention as applied to a recording ammeter,
measuring the current supplied to the motor M the ammeter having its fields
in series and its armature separately excited from the battery N, or other source
of constant potential. In this case the resistance is included in a shunt
around the meter, and here the cam C works in the reverse way, the larger
part of the cam being concentric, when the least resistance is in the shunt. It is
manifest of course that some resistance must always be in the shunt, when its
circuit is closed in order to permit the meter to operate. When the depres-
sion C coincides in. position with the roller f a greater amount of resistance is
included in the shunt, and a larger proportion of the total current is forced
through the ammeter, which accordingly registers at a greater rate; while when
the depression C reaches the roller, the shunt is open-circuited, and the meter
records at its maximum rate, all of the current passing through it.
Fig. 3 is a chart showing a station record different from that shown in Fig. 2.
It is supposed to represent an electric railway distribution, in which there are
two peaks to the load, one occuring in the morning and the other in the after-
noon. With such a load curve, and with the twenty-four hour clock shown in
Fig. 3, the particular form of cam shown can be employed. We prefer to use

page_text: a twenty-four hour clock, as the cam can be mounted directly upon the hour
shaft.
In both forms of the invention just described, resistances have been used as the
rate-varying means, and in practice this will be found to be preferable. Other
arrangements might, however, be used, and in Fig. 4 we have indicated such a 5
device. In this figure we have indicated that one of the magnets of the damp-
ing mechanism may be mounted upon a pivot, and when the meter rate is to
be increased, be swung by the action of the cam communicated through any
convenient intermediate mechanism, such as the cam roller shown, towards the
shaft of the notor, thus diminishing its pull upon the damping disc D.
We do not regard this as so good a form of the invention, because it intro-
duces the probability of error in the calibration of the meter, but it might be
usefully employed. All of the forms of the invention which we have shown
are to be regarded as examples, and many others might be conveniently described
which we do not undertake to show; but any apparatus which embodies the ideas 1
of progressively changing the rate of registration of a recording electric meter
of any type so as to increase this rate at the time of large load and diminish it
when the load falls off, we regard as within our invention. In alternating
current systems, for example, we might use impedances, or changes of inductive
relation in coils, as the rate-varying means, but these arrangements are apparent 2
to engineers.
Having now particularly described and ascertained the nature of our said
invention (as communicated to us from abroad) and in what manner the same is
to be performed, we declare that what we claim is;-
-
1. The improvement in the art of recording electric energy,
which consists in
regulating the rate of registration to accord with the station loud.
2. The improvement in the art of recording electric energy, which consists in
progressively varying the rate of registration to accord with the station load.
3. That improvement in the art of recording the electric energy delivered to
a circuit, which consists in progressively increasing the rate of registration as
the load comes ou at the station and decreasing the rate as the load falls.
4. The combination, with a recording electric meter, of means for progressively
varying the rate of registration to accord with the station load.
i
2
3
6. The combination, with a recording electric meter, of means for progressively
increasing the rate of registration as the station load rises, and decreasing the 3
rate as the load falls.
6. The combination, with a recording electric meter, of a rate-varying means,
a clock, and mechanism connecting the clock with the rate-varying means, such
that the rate becomes a continuous function of average station load.
7. The combination with an electric recording meter, of a clock, a cam driven by 4
the clock, and a rate-varying device in the circuit of the meter operated by the cam,
the outline of the cam being such that the rate of the meter is progressively
changed to conform to the station load.
8. The combination of a recording electric meter, a clock, a resistance in the
circuit of the meter, a switch for including different amounts of resistance in
circuit as may be desired, and a cam driven by the clock and operating the switch
to progressively cut out resistance as the load on the station increases, and include
it again in circuit as the load diminishes.
9. The combination of a recording watt meter with a variable resistance in its
armature circuit, and means for varying the resistance so as to change the rate of 5
the meter in accordance with the station load:
10. The combination of a recording wattmeter, a variable resistance in the
armature circuit of the wattmeter, a clock, a cam driven by the clock, and a
resistance changing switch operated by the cam, the contour of the cam being
arranged to cut in resistance as the load diminishes and to cut it out as the load 5
increases.

page_text: 11. The method of registering ourrent or energy in a lamp circuit which con-
sists in integrating the same as modified by a continuous function of station load.
Dated this 20th day of June 1899.
THE BRITISH THOMSON-HOUSTON Co., LTD.,
W. MARTINDALE,
A. R. MONKS,
Directors:
ALFRED CLEMENTS,
Assistant Secretary.