Improvements in Recording Watt Meters.
Year: 1895

page_text: Date of Application, 13th Mar., 1895-Accepted, 15th June, 1895
COMPLETE SPECIFICATION.
Improvements in Recording Watt Meters.
1, JAMES DEVONSHIRE, Secretary of The British Thomson-Houston, Limited,
of 38 Parliament Street, in the County of Middlesex, (a communication to me
from abroad by Walter C. Fish, of Lynn, County of Essex, State of Massachusetts,
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 recording Watt meters. The object of the present
invention is to provide an improved meter, by means of which very large currents
may be measured; such, for instance, as represent the entire output of a dynamo
at the central station, while securing at the same time accuracy in registration,
economy of construction, and an apparatus which can be easily installed.
Referring to the accompanying drawing,
Figure 1 is a perspective face view of a meter constructed in accordance with
this invention;
Figure 2 is a diagram illustrating a way of connecting up the circuits of the
meter.
A indicates the insulating base of the meter, and B B two very heavy binding
posts which lead backward through the insulating base A and connect respectively
with the ends of one of the main conductors or omnibus bars, which is divided at
this point for this purpose. To the front end of the binding posts, B, B; and
firmly, mechanically and thoroughly electrically secured thereto, as by a double
joint, as shown, is placed a 'shaped conductor D having a conductivity sufficient
to convey the maximum current which will at any time flow through the main 'in
which it is connected. Upon these binding posts B, B, is carried the entire
mechanism of the meter, as follows: secured to the upper part of the binding
posts B, B, and bridging the same is an arch E, which serves as a support for the
registering mechanism F, as is clearly shown, and which also carries the upper'
bearing for the armature shaft, hereinafter to be referred to. This arch E is
insulated from the binding posts B, B, by means of the 'insulation E' of hard rubber
or its equivalent. From the lower part of the binding posts B, B, there' extend
downwardly two posts G, G, united at their lower ends by a base plate H, arranged
to hold in proper position the permanent magnets I, I, I, which act upon the
damping copper disc K serving as a retarder. In this plate H is also located' a
lower jewelled bearing for the armature shaft L. Upon the armature shaft U is
mounted the armature M, constructed in any way which as may be suitable, which
armature revolves in the field produced by the U-shaped conductor D. The
movements of the armature are registered or counted by the registering
mechanism F geared to the armature shaft L. The posts G, G, are insulated from
the binding posts B, B, by means of the insulation' G¹ of hard rubber or its
equivalent. The same set of bolts may be used to hold both the upper and
lower structures in position. The damping copper disc or retarder K; carried by
the armature shaft L revolves past the poles of the permanent magnets I mounted'
on the base A of the machine. The brushes N which convey current to and
from the armature M, are made of considerable length and wound as a spring
adjacent to their support, preferably, so as to bear upon the commutator with a
moderate and uniform spring pressure.

page_text: It will be seen that with this construction the main field consists of simply
three-quarters of a turn of the main conductor, and this is found in practice to be
amply sufficient to furnish all the field required.
The instrument thus constructed may be mounted inside of a round or other
shaped casing O, provided with a glass front, and placed in a suitable position
upon a switchboard or other support at the station, the binding posts B, B
providing all the support necessary. As shown in the diagram, Figure 2, the
armature of the meter is included in a shunt circuit across the bus bars or circuit
mains P, P, the circuit being passed through the armature by a commutator and
brushes N of ordinary construction. A resistance R will ordinarily be included
in this circuit, and also a field coil e surrounding the armature and furnishing an
initial field or a field which gives torque to overcome the friction co-efficient of
the instrument at the lightest load. The starting coil, however, is not an essential
feature of this instrument.
In cases where very heavy currents are to be measured it is not always necessary
to insulate the arch E and posts G G from the binding posts B B, as the diversion
of current through these alternative paths is so slight as not to prevent the proper
registry at the meter, and in such case the binding posts, arch and posts G G
may be made in one case, if desired, or the arch and posts G G may be
secured to the binding posts without being insulated therefrom. However,
when permanent magnets are employed, as shown, it is usually best to insulate the
posts G G to prevent the current passing through them from influencing the
magnets or the disc D; or, instead to make the posts of relatively high resistance
material.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. In a motor meter, as herein set forth, the combination with an armature of a
U-shaped conductor forming the field winding, said armature being located within
the bend of the U-shaped magnet, and connected in shunt across the circuit
mains.
2. In an electric meter, as herein described, the combination with an armature
connected to a registering mechanism, of a U-shaped conductor having a con-
ductivity sufficient to convey the maximum current which will at any time flow
through the main in which it is connected, the armature being located within the
bend of the U-shaped conductor.
3. In an electric meter, as herein described, the combination with an armature
and a heavy U-shaped conductor, as herein described, of heavy binding posts to
which the conductor is connected, an arch mounted on the binding posts and
insulated therefrom, and carrying the registering mechanism and a retarding
device.
4. In an electric meter, as herein set forth, an armature and registering
mechanism, and retarder connected with the ends of the armature shaft, in com-
bination with a U-shaped conductor, as herein described, having binding posts by
which the U-shaped conductor is supported, and a metallic arch carrying the
registering mechanism and mounted on the binding posts and insulated therefrom.
5. The combination with the recording mechanism of an electric meter, of an
armature connected in shunt across the circuit mains, and a conductor comprising
less than a complete turn in series with one of the circuit mains and in inductive
relation to said armature.
6. The combination in an electric meter, of a set of binding posts adapted to be
connected to the terminals of one of the omnibus bars from a current generating
source, a main field conductor connected between and supported by said binding
posts, supports also carried by said binding posts and serving to sustain the
regulating and registering mechanisms, respectively, and an armature carried upon
a shaft having bearings in said supports.

page_text: 7. The combination in an electric meter of a set of binding posts adapted to be
connected to one of the omnibus bars from a current generating source, a main
field conductor connected between and supported by said binding posts, and
supports for the moveable element of the meter also carried by said binding
posts.
Dated this 12th day of March 1895.