Improvements in Electric Meters.
Year: 1888

page_text: Date of Application, 20th Sept., 1888
Complete Specification Left, 19th June, 1889-Accepted, 20th July, 1889
PROVISIONAL
SPECIFICATION.
Improvements in Electric Meters.
I, SEBASTIAN ZIANI DE FERRANTI, of 120 Fellows Road, Hampstead, in the
County of Middlesex, Electrician, do hereby declare the nature of this invention to be
as follows:-
This invention relates more especially to the class of alternate current meters in
which an unwound magnetic armature is employed, and is magnetised by coils so
as to produce diametrically opposite poles and in which the armature so magnetised
is contained in a magnetic field induced by other coils; from which arrangements
movement results.
Now in such meters it has been usual for the armature to be a light disc of iron in
one piece but so constructed the meters do not perform well. I obtain much
better results by using a heavier armature built up in layers or of laminae insulated
the one from the other. In order to lessen the friction on the pivot which other-
wise would result from the increase of mass I partially float the armature in a liquid.
Or I fix a float up the lower part of the armature spindle beneath the armature.
The float in these meters may replace the fan and serve to produce the necessary
retardation.. Also I magnetise this armature by means of a coil of comparatively
few turns; these precautions 1 take in order that the magnetisation of the armature
may not approach saturation. Sometimes I make the armature with laminae of
steel in lieu of iron.
The method described of partially floating the armature is applicable also to meters
of other constructions.
The float may be entirely immersed to avoid the effect of surface tension. The
armature when itself immersed may be hollow to increase its floatation. Or if a
heavy liquid like mercury be employed a weight in air may be applied to overcome
the floatation of the armature.
Dated this 20th day of September 1888.
CARPMAEL & Co.,
Agents.
COMPLETE SPECIFICATION.
Improvements in Electric Meters.
I, SEBASTIAN ZIANI DE FERRANTI, of 120 Fellows Road, Hampstead, in the
County of Middlesex, Electrician, do hereby declare the nature of this inven-
tion 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 more especially to the class of alternate current meters in
which an unwound magnetic armature is employed, and is magnetised by coils so as
to produce diametrically opposite poles and in which the armature so magnetised is
contained in a magnetic field induced by other coils; from which arrangements
movement results.
Now in such meters it has been usual for the armature to be a light disc of iron in
one piece but so constructed the meters do not perform well. I obtain much better
results by using a heavier armature built up in layers or of lamine insulated the one
from the other. In order to lessen the friction on the pivot which otherwise would
result from the increase of mass I partially float the armature in a liquid. Or [fix
a float up the lower part of the armature spindle beneath the armature. The float in
these meters may replace the fan and serve to produce the necessary retardation.
Also 1 magnetise this armature by means of a coil of comparatively few turns
'

page_text: these precautions I take in order that the magnetisation of the armature may not
approach saturation. Sometimes I make the armature with laminae of steel in lieu
of iron.
The method described of partially floating the armature is applicable also to meters
of other constructions.
The float may be entirely immersed to avoid the effect of surface tension. The
armature when itself immersed may be hollow to increase its floatation. Or if a
heavy liquid like mercury be employed a weight in air may be applied to overcome
the floatation of the armature.
In order that my said invention may be fully understood and readily carried into
effect I will proceed to describe the drawings hereunto annexed.
In order that my said invention may be fully understood and readily carried into
effect I will proceed to describe the drawings hereunto annexed.
DESCRIPTION OF THE DRAWINGS.
Figure 1 is a vertical section of a meter constructed in accordance with my
invention.
Figure 2 is a plan of the same.
Figure 3 is a vertical section and shows a modification.
Figure 4 is a vertical section and shows another modification.
In Figures 1 and 2 a is a spindle it has a pivot a¹ at its lower end and a bearing a²
at the top. Upon this spindle is a float b which may or may not be hollow. The
float, is contained in a vessel c containing liquid. Mercury may be employed in which
case it is essential that the float should be completely immersed; with other liquids
this is less important. d is the armature also mounted on the spindle a. e is a
pinion on the spindle a giving motion to the train of counting wheels f, this is an
ordinary meter train. 9 is a coil in which the current to be measured flows; it is an
alternating current derived usually from a dynamo. h is another coil in which also
an alternating current is passed; this second current is usually derived from a shunt
across the leads and so the second current remains approximately uniform whatever
may be the fluctuation of the main current passing in the coil g. This arrangement
of the coils forms however no part of my invention.. The armature d is built up of
dises of iron or steel; these discs should not exceed one hundredth of an inch in
thickness and they should be insulated the one from the other with thin paper. The
weight of the discs in this armature should not be less than ounce per convolution
of the coil g for a maximum current of 100 ampères passing by the said coil through
the meter, and so in proportion for a larger or smaller current. The object in
adopting these dimensions is to ensure that the magnetisation of the iron in the
armature shall in no case approach saturation. In some cases I make the armature
of laminae of steel in place of iron: this is expedient when the alternations of the
current are less rapid than is usual.
In Figure 3 the armature d is shown immersed in mercury contained in a vessel c
within the coils and a weight i compensates the excessive floatation of the armature.
In Figure 4 an armature consisting of a hollow shell of thin iron is represented;
it is made in two parts insulated from each other at d. This armature is immersed
in a light liquid such as paraffin oil.
In cach case the floatation is so adjusted as to leave but little pressure on the pivot
at a¹.
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 an electric meter in which a rotating armature is used supporting the rotating
armature by a float to lessen the weight upon its pivot without the armature being
immersed in liquid.
2. In an electric meter in which an unwound rotating armature magnetised by a
stationary coil building up the said armature of laminae of iron or magnetic metal
insulated the one from the other and so proportioning the mass of metal in the

page_text: armature to the number of convolutions of the coil that the current in the coil
cannot magnetically saturate the armature.
3. In an electric meter in which an unwound rotating armature is magnetised
by a stationary coil making the said armature of insulated luminae of steel.
4. In an electric meter in which an unwound rotating disc armature is mag-
netised by a stationary coil in a plane at right angles to the plane of the disc
partially floating the said armature so as to lessen the weight upon the pivot.
5. In an electric meter an armature on a spindle which at its lower part beneath
the armature carries a float immersed in liquid and which serves to lessen the weight
upon the pivot.
6. In an electric meter a hollow armature immersed in liquid which serves to
lessen the weight upon the pivot.
7. Electric meters arranged substantially as herein before described and illustrated
in the drawings annexed.
Dated this 10th day of June 1880
CARPMAEL & Co.,
Agents.