Improvements in Electric Meters.
Year: 1896

page_text: Date of Application, 31st Mar., 1896-Accepted, 6th June, 1896
COMPLETE SPECIFICATION.
Improvements in Electric Meters.
1, JAMES DEVONSHIRE, Secretary of The British Thomson Houston, Limited,
of 38 Parliament Street, Westminster, London, (a communication from abroad by
Charles P. Steinmetz, Electrical Engineer, of Schenectady, in the State of
New York, United States of America), 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:-
The present invention relates to certain means for metering or measuring the
energy consumed in an electric distribution system, in which the energy is supplied
by what are now known as monocyclic generators, and the electro-motive forces
thus generated are transformed by a suitable arrangement of converters, or any
other desired way, such as a three-phase or quarter-phase relation of electro-motive
forces.
In monccyclic systems as now used, the energy consumed may be measured by a
watt-meter, one element of which is energized by the current flowing in the system,
and the other element by an electro-motive force proportional to the energy voltage
existing between the two outside mains of the system. When, however, such a
system is converted into a system of different phase relation, for example, one in
which the electro-motive forces have the three-phase relation, it is no longer
possible to energize one element of the meter by a single coil connected directly
through transformers across any one pair of mains, for this would no longer
represent the energy voltage in the new system, as neither of the electro-motive
forces between the different pairs of mains in the transformed system represents
the energy voltage of the system. It is, therefore necessary, first, to provide means
for measuring the energy voltage. This 1 accomplish by deriving from the electro-
motive forces on the transformer system a new electro-motive force which will
represent the energy voltage, and this electro-motive force is supplied to one
element of the meter, the second element being supplied with the main current
flowing in the system. In this way it becomes possible to measure the energy in
such a system with any ordinary meter without multiplying the meters in the
different branches of the system.
In one modification of the invention where the monocyclic system is transformed
into a system having three-phase electro-motive forces, the three-phase mains are
so connected that one of them serves as a common return, and therefore carries all
of the current The energizing coils of one element of the meter, for example,
the field coils, will then therefore be included in series with the main forming the
common return. By an arrangement of transformers properly connected to the
three-phase mains, an electro-motive force is derived therefrom which represents
the energy voltage, and the circuit in which this electro-motive force is inaintained
is connected with the second element of the meter, for example, the armature.
In another modification of the invention, one element of the meter, as before,
may be supplied with the current flowing in the metered system in the same manner
as before, but the energy voltage is secured by a compensator connected across the
secondary mains corresponding to the primary mains carrying the main energy
voltage. The second element of the meter may then be connected between the
common return and the center of the compensator.
In still another modification the energy voltage may be derived in either of the
ways already described, but the current is secured by field coils in the circuit of
each of the outgoing mains instead of in the common return.

page_text: In the accompanying drawings, attached to and made a part of this Specification
Fig. 1 is a diagrammatic view of a distribution system with a meter connected
in circuit;
Fig. 2 is a modification, and Fig. 3 is a still further modification.
In Fig. 1, A represents a monocyclic generator, with the main coil B connected
by means of rings and brushes to the mains a and b, and the teaser coil C connected
to the main c. A separate exciter D is provided with a suitable controlling
rheostat d, and is used for exciting the field of the main machine. M is the load
for the secondary system, which in this case represents a three-phase induction
motor.
Current is supplied to the motor M by means of transformers E, E' the primaries
of which are connected between the main a and b with a connection taken from the
teaser main c to a point midway between the two. The secondaries of these
transformers are arranged to form a three-phase system by having one secondary
connected in the reverse direction to the other. Extending from these secondaries
are leads e, f and g.
The field F of the meter consists of a number of turns of wire, and is connected
in circuit with one of the mains, for example, e, which being the common return
for the other two mains, carries the total current flowing in the system. The
armature H, which may be of the well-known type used in the Thomson recording
watt meter, is connected to the secondaries of the transformers G, G', which are
connected together in series. The primaries of these transformers are connected
between the mains fand g, with a connection taken from a point between the two
to the common return e. The transformers thus connected will supply to the
armature H an electro-motive force the phase relation of which will correspond to
that of the main line.
A suitable recording mechanism J is connected to the armature H so that the
revolution of the same may be recorded; this may, through a suitable train of
gears, be made to indicate in what is known as "watt hours."
In Fig. 2. a modification of the invention is shown, in which the field coil of the
motor is supplied with current from the common return as before, and the energy
volts of the system are obtained by connecting a compensator coil between the
mains g and f, and between the center of the coil and the common return e the
armature H is connected.
In Fig. 3 a second modification of my invention is shown, in which the armature H
is supplied with an electro-motive force as in Fig. 1, but the two field magnet
coils are connected in circuit with the out-going mains f and g.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed as communicated to me from
abroad I declare that what I claim is:
1. The combination of a system of mains in which poly-phase electro-motive
forces are maintained from a single phase main source of energy, with means for
deriving from the poly-phase mains the single phase energy voltage of the system,
and a meter having one element supplied with the energy voltage and the other
element with the current flowing in the system.
2. A meter for measuring the consumption of energy in a system of the
character described, consisting of a field magnet coil connected in a series circuit
relation with the load, means for establishing a phase relation of the electro-motive
forces corresponding to that of the supply mains, and an armature supplied by the
said means.
3. A meter for a system of the character described consisting of a field magnet
supplied by a resultant source of energy, transformers for establishing phase
relations corresponding to those of the main line, and an armature supplied by the
transformer.
4. A meter for a system of the character described, consisting of a field-magnet
supplied by two of the mains, two transformers connected between the "mains, une

page_text: of which is reversed, supplying the armature, and a recording mechanism operated
by the armature.
5. In a monocyclic system, the combination of transformers establishing a poly-
phase relation of the electro-motive forces on the secondary system, a meter for
recording the energy consumed, consisting of a resultant field-magnet, transformers
for establishing new phase relation of the currents, an armature revolving in the
field supplied by current from the transformers and a recording device operated by
the armature.