Improvements in or connected with Electric Meters.
Year: 1898

page_text: Date of Application, 6th Aug., 1898
Complete Specification Left, 8th May, 1899-Accepted, 6th Aug., 1899
PROVISIONAL SPECIFICATION.
Improvements in or connected with Electric Meters.
We, HENRY REASON, of 112, Glo'ster Road, Brighton, in the County of Sussex,
Electrical Engineer, and THE MUTUAL ELECTRIC TRUST LIMITED, of 111,
Glo'ster Road, Brighton, in the County of Sussex, do hereby declare the nature
of this invention to be as follows:-
This invention relates to electric current meters of the so-called motor type
and by its means several advantages are obtained.
A known method of operating such meters is to employ a shunt winding for
magnetising purposes and a series winding for carrying the current to be mea-
sured; both windings acting on a single core circuit, so to speak, that core
circuit being a magnetic one. Now it has been discovered by one of us, namely
by Henry Reason, that great advantages may be secured by the employment
of what we may term, for the purposes of this specification a compound parallel
core circuit, that is to say a core circuit which in part at least consists of two
parallel re-uniting branches one of the said branches being a magnetic one
and the other a non-magnetic, or partially non-magnetic, one.
In certain cases the non-magnetic branch may be a mere break but not the
break or clearance space which exists between the so-called pole pieces of an
ordinary core circuit, that is to say the space in which the armature or movable
part of the motor lies. The magnetic branch should be of sufficient size to be
saturated by the current in the shunt circuit but not so large that it can be
further saturated by the current of the series winding. By this means the lines
of force produced by the current in the series winding, instead of passing
through the magnetic branch, will be forced through the non-magnetic branch
or air space constituting said branch. By this means we obtain what is prac-
tically a closed magnetic circuit for the purposes of the shunt winding and an
open magnetic circuit for the purposes of the series winding.
A further improvement embodied in our invention consists in so arranging or
adapting the parts that the position of the shunt winding upon the core circuit
can be altered at will for the purpose of altering the initial magnetism which
it is necessary to employ in order to overcome the so-called static friction of
the meter. This may be effected by sliding the shunt winding upon the core
circuit towards or from the clearance space.
Or the same result may be attained by movably attaching a piece of iron or
other magnetic material so that it may offer a magnetic path to the lines of
force which would otherwise traverse the air. By making the position of this
adjustable as for example by an adjusting screw the magnetic resistance may be
varied at will.
It has further been discovered by the said Henry Reason that when the mov-
able part of the motor consists of a disc retarded by vanes or the like in a mer-
cury bath or its equivalent it is very advantageous to construct such disc and
such bath of what at present would be considered abnormally large diameter.

page_text: Thus we contemplate making such a bath with a diameter equal to sixteen or
even twenty times its depth and using a disc of commensurate diameter, say
of four or more inches.
Improvements in or connected with Electric Meters.
We, HENRY REASON, of 112, Glo'ster Road, Brighton, in the County of Sussex,
Electrical Engineer, and THE MUTUAL ELECTRIC TRUST LIMITED, of 111,
Glo'ster Road, Brighton, in, the County of Sussex, do hereby declare the nature
of this invention and in what manner the same is to be performed, to be particu-
larly described and ascertained in and by the following statement: —
Our invention relates to improvements in electric current meters of the so-
called motor type, the said improvements being hereinafter specified in detail
and illustrated by the accompanying drawings, of which,
Figure I is a diagram illustrating a well known form of core circuit.
Figure II is a diagram illustrating what we term a re-uniting branched core
circuit.
Figure III is a diagram illustrating a re-uniting branched core circuit with
the position of the shunt coil movable thereon.
Figure IV is a diagram illustrating the application of a magnetic shunt piece
to a re-uniting branched core circuit.
Figure Villustrates an actual meter constructed in accordance with the
present invention.
In the said figures, similar numerals of reference indicate similar parts.
A known method of operating such meters is to employ a shunt winding for
magnetizing purposes and a series winding for carrying the current to be mea-
sured, both windings acting on a single core circuit so to speak, that core circuit
being a closed (or practically closed) magnetic one, that is to say the core circuit
is a completely magnetic one (that is consisting of magnetic material) except at
the clearance space which exists betwen the so-called pole pieces or in other
words the space in which the armature or movable part of the motor lies.
Such a core circuit is diagrammatically represented in Figure 1, in which 1
represents a core circuit of iron broken at the clearance space 2. 3 is the shunt
widing used for magnetizing purposes and 4 the series winding for carrying the
current to be measured.
Now it has been discovered by one of us, namely by Henry Reason, that great
advantages may be secured by the employment of what we may term for the
purposes of this specification a re-uniting branched core circuit (in our Pro-
visional Specification termed a compound parallel core circuit), that is to say
a core circuit which in part consists of two parallel re-uniting branches, one
of the said branches being of magnetic material and the other of non-magnetic
or partially non-magnetic material.
Such a form of circuit is illustrated diagrammatically in Fig. II, in which 1
is the core circuit of magnetic material as before but it is divided into the two
re-uniting branches 5, 6 which it will be seen branch off say at point 7 and re-
unite say at point 8. Branch 5 consists of magnetic material and branch

page_text: consists between the parts 9 and 10 of an air space or of insulating material,
the latter being illustrated by the lines of dots.
The magnetic branch should be of sufficient size to be saturated by the current
in the shunt circuit but not so large that it can be further saturated by the
current of the series winding. By this means the lines of force produced by the
current in the series winding, instead of passing through the magnetic branch,
will be forced through the non-magnetic branch or air space constituting said
branch. By this means we obtain what is practically a closed magnetic circuit
for the purposes of the shunt winding and an open magnetic circuit for the
purposes of the series winding.
This improvements presents the following advantages. The magnetic field
due to the shunt winding may be maintained constant, the magnetic field due
to the series winding can be made proportional to the current passing in the said
winding, and the current required to overcome the initial friction of the meter
may be made very small. Further we obtain all the advantages of using iron
in motor meters without introducing the errors due to residual magnetism.
Another improvement embodied in the present invention consists in so arrang-
ing or adapting the parts that the position of the shunt winding upon the core
circuit may be altered at will for the purpose of altering the intial magnetism
which it is necessary to employ in order to overcome the so-called static friction
of the meter.
One way of effecting this is by sliding the shunt winding upon the core circuit
towards or from the clearance space as is illustrated in Figure III where it
will be seen that the shunt winding 3 may be moved from the position shown in
full lines towards or from the position shown in dotted lines 31.
Or, the same result may be attained by movably attaching a piece of iron or
other magnetic material so that it may offer a magnetic path to the lines of force
which would otherwise traverse the air. This is diagrammatically represented
in Figure IV where the piece of iron or other magnetic material referred to
(and which is hereinafter termed the magnetic shunt piece) is shown at 12 and
which may be moved towards or from the break or space 11 and retained in any
desired position by means of a set screw or the like. The magnetic resistance
of the core circuit may thus be varied at will to suit change of voltage or of
friction.
It has further been discovered by the said Henry Reason that when the mov-
able part of the meter consists of a disc retarded for example by vanes or by
skin friction or the like in a mercury bath or its equivalent, a great advantage
is obtained by constructing the said disc and the said bath of what at present
would be considered abnormally large diameter. Thus we find it advantageous
to make such a bath of a diameter equal to sixteen or even twenty times its
depth and to use therewith a disc of commensurate diameter, say of four, or more
inches. Easy starting with a very small current is thus secured.
Such bath and disc are shown in Figure V which represents an actual meter
as it may be constructed under the present invention. In the said figure, 1 is
the iron core circuit, consisting of two circular iron cylinders 15, 16, between
which is the clearance space 2. The cylinders 15, 16 are kept apart by two
hard rubber rings 17, 18, fitting closely to the edges of the cylinders and be-
tween the said rings is a metallic tee shaped ring 14, the purpose of which will
be hereinafter described. 5, 5 is the branch of magnetic material, consisting
of two iron plates 19, 20, into which is fitted an iron bolt or cylinder 21. The
plates 19, 20 (square as seen in plan) are in close contact with the cylinders 15,
16. 6, 6 is the non-magnetic branch, consisting between the points 9, 10 of
air, and forming with the part 1, and the branch 5, 5, a re-uniting branched
core circuit.
3 is the shunt winding, consisting of a high resistance coil surrounding the
cylinder 21. 4 is the series winding, being a coil of comparatively few turns
of thick wire wound on a bobbin encircling the part 1, 1 of the core circuit.

page_text: Within the clearance space 2 is placed the armature disc 22 carried by a
spindle 23 which rests on a pivot 24, and which is provided with a worm 25
that drives the counting mechanism.
The clearance space 2 has an abnormally large diameter equal, say, to sixteen
times its depth, and is filled with mercury in which the armature disc is
immersed. The current to be measured passes from the ring 14 into the mer-
cury, and makes the armature disc rotate in the well known manner.
12 is the magnetic shunt piece, consisting of an iron bar of a size just suffi-
cient for the shunt current, pivotted at 26. 27 is an adjusting screw bearing
against a lug 28 by which the shunt piece 12 may be moved towards or from
the break space 11. 29 is a spring which forces the adjusting screw 27 towards
the lug 28. 30 is an insulating piece to keep the magnetic shunt piece from the
core circuit. 31 is a cap which can be closed down on the opening 32 to secure
the mercury during transit.
We desire it to be understood that we do not limit ourselves to the position
upon the core circuit which the coils may occupy.
We also desire it to be understood that we may employ our magnetic shunt
piece in connection with other forms of core circuit.
Similarly we do not limit ourselves to the use of such a bath and disc in con-
nection with a re-uniting branched core circuit. Such disc and bath may be
employed with other forms of core circuit.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed, we declare that what
we claim is:-
1. In an electric meter of the so-called motor type, a re-uniting branched
core circuit substantially as set forth.
2. In an electric meter of the so-called motor type, adjusting or altering the
position of the shunt winding substantially as and for the purpose set forth.
3. In an electric meter of the so-called motor type, the employment of a mag-
netic shunt piece substantially as and for the purpose set forth.
4. In an electric meter of the so-called motor type, and in which the movable
part of the meter consists of a disc retarded by vanes or skin friction or the like
in a mercury bath or its equivalent, constructing the said disc and the said bath
of abnormally large diameter substantially as and for the purpose set forth.
Dated this 8th day of May 1899.
J. G. LORRAIN, M.I.E.E., M.I.Mech. E.,
Norfolk House, Norfolk Street, London, W.C., Chartered Patent Agent.