Improvements in and relating to Electricity Meters.
Year: 1893

page_text: Date of Application, 19th July, 1893
Complete Specification Left, 19th Apr., 1894-Accepted, 30th June, 1894
PROVISIONAL SPECIFICATION.
Improvements in and relating to Electricity Meters.
I, SEBASTIAN ZIANI DE FERRANTI, of Charterhouse Square London E.C.
Electrician, do hereby declare the nature of this invention to be as follows:-
This invention has for its object improved means of manufacturing and testing
electricity meters and other similar instruments, and also rectifying electric.currents
applicable to such testing and other purposes.
In a Patent No. 5926, 1883 granted to me for electricity meters in which the
rotation of mercury is recorded by a train of wheels for the purpose of measuring
the current passed through the meter, the mercury was surrounded by a metal
ring which acted as contact to carry the current. This ring in some cases I
now prefer to make of insulating material, such for example as ebonite or vulcanised
fibre or the like.
In order to conduct the current to or from the bath of mercury 1 pierce this
ring with a number of holes, and in these boles insert metallic contact pieces,
which are by preference made of steel or iron, in order to effectually save the
contact pieces from being attacked by mercury. The magnetic lines diverted
from the useful field by these pieces of metal are not sufficiently serious to affect
the working of the meter. Thus a meter with a mercury bath constructed in this
way is specially applicable to meters working with alternating currents as the
metallic mass in which currents may be induced is less but it may be also useful
for meters working with continuous currents.
In the same form of meter I now prefer to make the upper magnetic pole of
an independent piece of magnetic metal and force it down into a good junction
with the mercury ring by means of the pressure obtained from an independent
screw washer screwed into the outer magnetic shell of the meter. This enables
the train which I fix upon the magnetic pole, to be kept square with the meter
as the above mentioned ring is screwed down.
I bore out the upper magnetic pole for the spindle to come through from the
fan in the mercury bath, and support the end of the fan spindle in a jewel
carried in this hole in order to ensure the upper jewel being perfectly central
with the lower one which is carried in the ordinary way in the lower pole piece.
This upper pole is cut away on two sides to receive the train and gear wheels
which gear into a worm cut in the centre spindle.
In order to transmit the motion of the spindle to the train of wheels fitted
with recording dials employ a subsidiary train which may be of the same size
for all sized meters, notwithstanding the voltage at which the meters may be
required to read Board of Trade units or the speed at which the meter rotates.
This small train is formed to swing upon an adjustable centre, which is the same
as the centre of the first wheel gearing into the worm. This adjustable centre is
movable but can be fixed by means of a screw when once the gearing of the first
wheel has been determined.
The last wheel of this adjustable train of wheels gears into a wheel on the
registering train of variable size and number of teeth according to the ratio that.
it is desired to give to the revolutions of the meter and the record on the dials.
The adjustable train is then further locked by screws which move in suitable
slots.
In alternating current meters especially such as is described in my Patent 701,
1887. in which a shunt coil is used to compensate the magnetic field of the meter

page_text: so as to give a true reading from a small load to a large one, it has hitherto been
found necessary to put a large amount of non-inductive resistance in series with
this coil in order that the registration may be made at all satisfactory. This is due
to the high self induction of the shunt coil so that the current in it is out of phase
with the current in the main coil which takes the current to be registered by the
meter. The amount of current taken by the shunt coil is therefore very great in
comparison to the amount of useful work done by it. I get over this difficulty,
and I may also regulate the amount of current taken by the shunt, by means of a
condenser of suitable capacity placed in series with the shunt coil. The effect of
this condenser is to nullify or compensate the self-induction of the shunt coil and
thus put the current in the shunt as nearly as possible in phase with the current in
the main coil. In some cases I may also use an ordinary resistance in series with
the condenser and the shunt where such is found desirable, for the purposes of
compensation or adjustment.
Ordinarily I prefer to adjust the correct constant of the meter by varying the
amount of the capacity in series with the shunt coil after the best number of turns
for the shunt coil have once been fixed upon.
This arrangement and use of a condenser is applicable to all forms of alternating
electricity meters using shunt and series circuits whether they are to give a
permanent record or simply an indication.
In alternating current meters using a shunt coil I make a condenser or external
resistance for the shunt in a box carrying the return lead terminal from which one
pole of the condenser or resistance receives its current, attached to the box. This
box with its terminal is placed in the bottom of the meter and is held in position
by the meter being fixed down upon it. In pressing the meter down on to the box
containing the condenser or resistance a piece of metal projecting from the under
side of the meter makes connection through a spring contact to the other pole of
the condenser or resistance in the box. It is thus possible to quickly and easily
change the condenser or resistance for the purpose of adjusting the constant of the
meter without having any connections to make, these being made automatically by
placing the box within the meter case.
I
In testing alternating current electricity meters and similar instruments,
especially those using a shunt coil, it is impossible to get a correct test of a number
of such instruments in series, and yet it is very necessary to test a number of
meters in series for practical reasons. I therefore put a number of these meters
in series on a circuit and also a variable condenser in series with the meters.
then vary the capacity of the condenser in order to bring the current into phase
with the E.M.F. which is the condition of a current and E.M.F. when the meter
is recording the current passing to non-inductive work such as lamps.
Where a
constant E.M.F. is used for this testing and the number of meters may be variable
and the loads they are tested on is variable I may use non-inductive resistances in
series with the above named meters and variable condenser.
The resistance in series with the meters may be of the liquid form made up of a
number of cells for example, containing lead plates in water, then a certain capacity
will be obtained from this resistance which will form a portion or the whole of the
condenser compensation necessary. Or in some cases I use a liquid resistance
only, of a sufficient number of cells to give the necessary capacity for
compensation.
This portion of my invention by which the current and E.M.F. are brought into
phase with each other is also applicable to a commutator for commutating
alternating into direct currents. It is found that with this apparatus the self-
induction and the work fed by it causes the current to be out of phase with
the E.M.F. and it is therefore not possible to commutate an alternating current by
it without a certain amount of sparking on reversing the contacts. I therefore use
a similar arrangement to that above described for rectifying the current for testing
instruments, and place a certain amount of capacity in series with the circuit and
the current to be commutated in order that the current may be brought into phase

page_text: with the E.M.F. and the current broken and reversed at the same time as
the E.M.F.
In order to ascertain when the current is in phase with the E.M.F. I use an
indicator which is similar to a Watt meter, and consists of a series and shunt coil.
The shunt coil being preferably arranged with as little self-induction as possible.
This instrument is placed upon the circuit and is calibrated upon non-inductive
work, and the deflection noted for various currents in the main coil and E. M.F. in
the shunt coil at the different periodicities at which it is desired to work. The
greatest deflected is obtained when the current and E.M.F. are in phase.
There are other means of calibrating and using the instrument in which separate
ampère meters and volt meters are required in connection with it, but I prefer the
method of calibration on actual work.
COMPLETE SPECIFICATION.
Improvements in and relating to Electricity Meters.
I, SEBASTIAN ZIANI DE FERRANTI, of Charterhouse Square, London, E.C.,
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 has for its object improved means of manufacturing and testing
electricity meters and other similar instruments, and also rectifying electric
currents applicable to such testing and other purposes.
In a Patent No. 5926, 1883 granted to me for electricity meters in which the
rotation of mercury is recorded by a train of wheels for the purpose of measuring
the current passed through the meter, the mercury was surrounded by a metal ring
which acted as contact to carry the current.
This ring in some cases I now
prefer to make of insulating material, such for example as ebonite or vulcanised
fibre or the like.
In order to conduct the current to or from the bath of mercury I pierce this
ring with a number of holes, and in these holes insert metallic contact pieces,
which are by preference tipped with steel or iron, in order to effectually save
the contact pieces from being attacked by mercury. The magnetic lines diverted
from the useful field by these pieces of metal are not sufficiently serious to
affect the working of the meter. Thus a meter with a mercury bath constructed
in this way is specially applicable to meters working with alternating currents
as the metallic mass in which currents may be induced is less but it may be
also useful for meters working with continuous currents.
In the same form of meter I now prefer to make the upper magnetic pole of an
independent piece of magnetic metal and force it down into a good junction with
the mercury ring by means of the pressure obtained from an independent screw
washer screwed into the outer magnetic shell of the meter. This enables the
train which I fix upon the magnetic pole, to be kept square with the meter as the
above mentioned ring is screwed down.
I bore out the upper magnetic pole for the spindle to come through from the fan
in the mercury bath, and support the end of the fan spindle in a jewel carried in
this hole in order to ensure the upper jewel being perfectly central with the lower
one which is carried in the ordinary way in the lower pole piece.
This upper pole is cut away on two sides to receive the train and gear wheels
which gear into a worm cut in the centre spindle.
In order to transmit the motion of the spindle to the train of wheels fitted with

page_text: recording dials I employ a subsidiary train which may be of the same size for all
sized meters, notwithstanding the voltage at which the meters may be required to
read Board of Trade units or the speed at which the meter rotates. This small
train is formed to swing upon an adjustable centre, which is the same as the centre
of the first wheel gearing into the worm. This adjustable centre is movable but
can be fixed by means of a screw when once the gearing of the first wheel has been
determined.
The last wheel of this adjustable train of wheels gears into a wheel on the
registering train of variable size and number of teeth according to the ratio that it
is desired to give to the revolutions of the meter and the record on the dials.
The adjustable train is then further locked by screws which move in suitable
slots.
In alternating current meters especially such as is described in my Patent 701,
1887 in which a shunt coil is used to compensate the magnetic field of the meter so
as to give a true reading from a small load to a large one, it has hitherto been
found necessary to put a large amount of non-inductive resistance in series with
this coil in order that the registration may be made at all satisfactory. This is
due to the high self-induction of the shunt coil so that the current in it is out of
phase with the current in the main coil which takes the current to be registered by
the meter. The amount of current taken by the shunt coil is therefore very great
in comparison to the amount of useful work done by it. I get over this difficulty
and I may also regulate the amount of current taken by the shunt, by means of a
condenser of suitable capacity placed in series with the shunt coil. The effect of
this condenser is to nullify or compensate the self-induction of the shunt coil and
thus put the current in the shunt as nearly as possible in phase with the current in
the main coil. In some cases I may also use an ordinary resistance in series with
the condenser and the shunt where such is found desirable, for the purposes of
compensation or adjustment.
Ordinarily I prefer to adjust the correct constant of the meter by varying the
amount of the capacity in series with the shunt coil after the best number of turns
for the shunt coil have once been fixed upon.
This arraugement and use of a condenser is applicable to all forms of alternating
electricity meters using shunt and series circuits whether they are to give a
permanent record or simply an indication.
In alternating current meters using a shunt coil I make a condenser or external
resistance for the shunt in a box carrying the return lead terminal from which one
pole of the condenser or resistance receives its current, attached to the box. This
box with its terminal is placed in the bottom of the meter and is held in position by
the meter being fixed down upon it. In pressing the meter down on to the box
containing the condenser or resistance a piece of metal projecting from the under
side of the meter makes connection through a spring contact to the other pole of
the condenser or resistance in the box. It is thus possible to quickly and easily
change the condenser or resistance for the purpose of adjusting the constant of the
meter without having any connections to make, these being made automatically by
placing the box within the meter case.
On Sheets 1 and 2 I have shewn two examples of meters having the above
improvements applied to them.
The meter shewn on Sheet 1 is an alternating current meter and that on Sheet 2
a continuous current meter.
Figures 1 and are vertical sections of the alternating current meter. Figures 3,
4 and 5 are horizontal sections of the same.
Figure 6 is a vertical section of the continuous current meter. Figure 7 is a side
elevation of the upper pole piece and gearing and recording train carried by it.
Figure 8 is a plan of the same and Figure 9 a vertical section on a larger scale.
In Figures 1 to 5 A is a ring of insulating material surrounding the mercury
bath.
A' are radial conducting pieces tipped with iron embedded in the ring-the

page_text: outer extremities of all these conducting pieces are in electrical connection with
one end of the main coil L of the meter-the other end is connected to the
terminal Y.
In order to bring the train of wheels square with the internal parts of the meter
when the same are screwed together and to ensure the spindle being perfectly
upright I form the meter in the following manner.
I take the outer magnetic shell D which is bored out to receive the laminated pole
pieces. In this I place a number of thin discs E of sheet iron which are split and
made to form a cone as shewn. These are held in position by means of a contact
piece H which stands up centrally from the bottom of the shell-this contact piece
also holds in position the lower pole piece I made of laminated iron which is wound
of strip iron coned at the lower edge and split. When this has been rivetted in
position I put in the outer laminated magnetic shell J which is also made of sheet
iron split, as shewn at K Figure 3. I then put in position the main or series
coil L and connect the same to the conducting pieces A¹ which pass through the
ring A as above described.
After the shunt coil L' has been placed in position I put in the upper magnetic
pole piece. This consists of a central contact piece H₁ bored through the centre
and screwed at its upper end. Round it is placed a laminated pole piece I' of
similar construction to I and above I' a laminated pole piece E' similar in
construction to E.
These are fixed in position relatively to one another by screwing H₁ into the
upper pole piece N which is carefully turned at the edge so that the magnetic
pole which carries the train of gear wheels may stand perfectly upright as regards
the working parts.
The upper magnetic pole which consists of H' and I' E' and N is forced into
position by means of the screw washer C₁ which is screwed into the top of the
outer shell so that a mercury tight joint is effected on the ring A.
The magnetic pole N has a vertical hole bored centrally through it to receive a
jewel P. The jewel is fixed in a small tubular plug which fits into the upper part
of the vertical hole formed through the pole piece. This ensures the upper pole
being perfectly central with the lower one which is carried in the ordinary way at
the point P in the lower pole piece. The tubular plug can be raised or lowered
and when adjusted in position can be held by a horizontal set screw.
The upper pole piece N is cut away on two sides to receive the recording train (
and gear wheels that gear into a worm cut on the central spindle.
The arrangement of the recording train and gear wheels is best seen in
Figures 6 to 9 which shew the improvements applied to a continuouз current
meter.
S is the subsidiary train of gear wheels. The first wheel of this train is a worm
wheel which is made to gear with a worm on the vertical spindle Q. The frame
which carries the train of wheels S is capable of being turned around a pivot T which
is concentric with the spindle of the worm wheel. "S' S² are binding screws by
which the frame can be locked in any desired position to the frame which carries
the recording train O. The pivot T is movable so that the gearing together of
the worm and worm wheel may be adjusted. In the drawings it is shewn to be
carried by the lower end of a small lever which turns on a centre at T' and which
can be locked in the required position by a binding screw T2 when the gearing of
the worm wheel with the worm has been adjusted.
On the spindle R³ of the last wheel of the adjustable train of wheels S is a
pinion which can gear into a wheel R² of variable size according to the ratio that
it is desired to give of revolutions of the spindle Q to the record on the dials of
the train O.
When it is desired to change or put on a ratio wheel R² the screws S¹ S² are
slackened the subsidiary train S is turned aside around the pivot T-a wheel R² of
the required size is put on to the spindle of the first wheel of the train of wheels O
the train S is then turned back again until the pinion on the spindle R³ is brought

page_text: into gear with the wheel R2 and the binding screws S₁ S' are tightened up again
to lock the train in this position.
In Figures 2 and 3 Sheet 1 U is the condenser euclosed in a spun metal casing U'.
Contact is made between each set of plates and the screw pins U2 and U³
respectively. U2 is connected with the spun casing U' and with the terminal V.
Figure 4. U³ is connected through a spring with one end of the shunt coil L'
the other end of the shunt coil being connected to terminal X. The terminals V
and X are connected to the source of power and the terminals V and Y to the
point at which the supply is required. One end of the main or series coil L is
-connected to the terminal X the other to the terminal Y.
In testing alternating current electricity meters and similar instruments, especially
those using a shunt coil, it is impossible to get a correct test of a number of such
instruments in series, and yet it is very necessary to test a number of meters in series
for practical reasons. I therefore put a number of these meters in series on a
-circuit and also a variable condenser in series with the meters. I then vary the
capacity of the condenser in order to bring the current into phase with the E.M.F.
which is the condition of a current and E.M.F. when the meter is recording the
current passing to non-inductive work such as lamps. Where a constant E.M.F.
is used for this testing and the number of meters may be variable and the loads
they are tested on are variable I may use non-inductive resistances in series with
the above named meters and variable condenser.
The resistance in series with the meters may be of the liquid form made up of a
number of cells for example, containing lead plates in water, then a certain capacity
will be obtained from this resistance which will form a portion or the whole of the
condenser compensation necessary. Or in some cases I use a liquid resistance
only, of a sufficient number of cells to give the necessary capacity for compensation.
This portion of my invention by which the current and E.M.F. are brought
into phase with each other is also applicable to a commutator for commutating
alternating into direct currents. It is found that with this apparatus the self
induction and the work fed by it causes the current to be out of phase with the
E.M.F. and it is therefore not possible to commutate an alternating current by it
without a certain amount of sparking on reversing the contacts. I therefore use a
similar arrangement to that above described (for rectifying the current for testing
instruments) and place a certain amount of capacity in series with the circuit and
the current to be oommutated in order that the current may be brought into phase
with the E.M.F. and the current broken and reversed at the same time as
the E.M.F.
In order to ascertain when the current is in phase with the E. M.F. I use an
indicator which is similar to a Watt meter and consists of a series and shunt coil.
The shunt coil being preferably arranged with as little self induction as possible.
This instrument is placed upon the circuit and is calibrated upon non inductive
work and the deflection noted for various currents in the main coil and E.M.F.
in the shunt coil at the different periodicities at which it is desired to work.
The greatest deflection is obtained when the current and E.M.F. are in phase.
There are other means of calibrating and using the instrument in which separate
Ampère meters and volt meters are required in connection with it, but I prefer the
method of calibration on actual work.
The above described method of testing a number of meters in series is illustrated
in the diagram Figure 10 Sheet 3. In this diagram A is a source of power, B is a
Watt meter and C and D are Ampère and volt meters respectively.
M' M² M³ are the main or series coils of three meters connected in series on
one circuit from the source of power. S¹ SS are the shunt coils of these meters
connected together with their condensers C¹ C C³, in parallel on a branch circuit.
R is a resistance and C' a variable condenser in series with the main coils of the
meters. As the number of meters in circuit is varied the capacity of condenser C4
has to be varied until the reading of the instrument B agrees with the readings
of C and D-the records kept by the several meters can then be noted.

page_text: In Figure 11 I have shewn a diagram of a meter having a shunt coil with
condenser in series with it to bring the phase of current in it to agree with the
phase of current in the main coil. In the diagram L' L L³ are lamps and A the
source of power-the shunt circuit S with condenser Ċ forms a branch circuit
the current through which is not recorded by the meter.
In the diagram view Figure 12 I have shewn a condenser similarly used with a
commutator for commutating alternating into direct currents.
P are the bars of a commutator coupled alternately to two rings P¹ on the axis P*
of a synchronous motor driven by the current from the source of power A. T is a
transformer by which any convenient pressure can be obtained from A. T¹ is the
secondary coil of this transformer, C a variable condenser. Tare brushes bearing
one on one ring P¹ the other on the other. Care brushes on a circuit C¹ in which
work is done. When one brush Cx bears on a commutator bar in connection with
one ring P¹ the other brush bears on a bar in connection with the other ring.
By adjusting the condenser C the phase of current in the circuit C₁ can be
brought to accord with that of the electromotive force and consequently the current
can be broken and reversed at the same time as the E.M.F.
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 electric meters in which a bath of mercury is set into rotation by the
passing current, forming the exterior ring which surrounds the mercury bath of
ebonite or vulcanized fibre or like insulating material with radial metallic
conducting pins passing through it substantially as described.
2. Holding the upper magnet pole down on to the ring which surrounds the
mercury bath by a ring screwing into the upper part of the outer magnetic case-
so that the recording dials carried by the upper pole piece may readily be set
parallel with the meter face substantially as described.
3. The construction of the meter substantially as hereinbefore described to
ensure one spindle being at right angles to the bath substantially as described.
4. The recording train carried by the upper pole piece which is cut away to
receive it substantially as described.
5. The arrangement of a worm in the meter spindle gearing with a worm wheel
forming the first of a subsidiary train of wheels-the frame carrying this train of
wheels being made so that it can be turned around a centre concentric with the
spindle of the worm wheel so that a pinion at the other end of the subsidiary train
of wheels may be made to gear with any sized wheel placed onto the first spindle
of the train of recording wheels substantially as described.
6. In electricity meters using shunt and main or series circuits the insertion of a
condenser into the shunt circuit to compensate for the self induction of the
shunt coil and bring the current in the shunt in phase with the current in the
main coil.
7. The arrangement substantially as described of a condenser or external
resistance for the shunt contained in a box placed at the bottom of the meter
casing and spring contact mechanism whereby when the meter is put into the casing
and pressed down onto the box contacts are made whereby the condenser or
resistance is put into the shunt circuit.
8. The construction of electricity meters substantially as hereinbefore described
and illustrated in the drawings annexed.
9. The herein before described method for enabling a number of alternating
current electricity meters or like instruments to be tested when coupled in series
consisting in placing a variable condenser or liquid resistance in the series circuit
to bring the current in this circuit into phase with the E.M.F.
10. The employment in a similar manner and for the same purpose of a condenser
in series with a coil or coils in other electrical instruments in place of using a non
inductive resistance.

page_text: 11. The employment of a condenser or liquid resistance in the circuit to be
commutated by a synchronous motor commutator for commutating alternating
into direct currents so as to bring the current in the commutated circuit into phase
with the E.M.F. and cause the current to be broken and reversed at the same time
as the E.M.F.
S. Z. DE FERRANTI.