Improved Means for Counterbalancing the Frictional Resistance in, Alternating Current Motor-meters.
Year: 1898

page_text: Date of Application, 25th Feb., 1893
Complete Specification Left, 19th Nov., 1898-Accepted, 14th Jan., 1899
Improved Means for Counterbalancing the Frictional Resistance in,
Alternating Current Motor-meters.
We, SIEMENS BROTHERS & Co. LIMITED, of 12, Queen Anne's Gate, West-
minster, S.W., Electrical Engineers, do hereby declare the nature of this invention
(which has been communicated to us from abroad by Siemens & Halske Aktien-
Gesellschaft, Markgrafen Strasse, 94, Berlin, S.W., Germany, Electrical Engineers)
to be as follows:-
In order, with electricity meters that are constructed on the principle of motor
meters, to counterbalance the inaccuracy arising from the friction of the trunnions
of the rotating part and of the counter mechanism, it is advantageous to impart
to the motor of the meter even when no working current is passing through it,
such a turning moment that the resisting turning moment caused by the friction
shall be just counterbalanced so that the motor will begin to move as soon as
there is the slightest increase of the driving turning moment, that is, as soon as a
working current exists.
The present invention relates to an arrangement for providing such a turning
moment with motor-meters for single or polyphase alternating currents operating
with a rotary field. Such a meter is constructed as follows:-Referring to Fig.
of the accompanying drawing A, A, A, A, is a stationary ring built up of insulated
layers of sheet iron having 4 radial inward directed polar extensions B₁ B, B, B.
Within this ring and concentric therewith is a fixed cylinder E E also of insulated
sheet iron.
Between the cylindrically hollowed ends of the polar extensions B, &c., and the
cylinder E is a small space in which is a copper drum F that can revolve on the
axis G.
The polar extensions, B, B₂ have windings of thick wire, through which the work-
ing current passes while the poles B, B, have windings of thin wire, the current
passing through which is shifted 900 relatively to the working current by any
suitable means.
Such a device is shewn for instance in the Specification to Application No. 2559
of 1897, and also in Fig. 4 of the accompanying drawing. By this means a rotary
field is produced in the iron parts which effects the rotation of the drum, the rota-
tion being the faster, the greater is the strength of the working current in the
thick wire windings C, with a constant strength of current in the thin wire wind-
ings D.
The rotation of the drum is transmitted to a counter in any suitable manner.
The object of the present invention is to impart to the drum F a slight turning
moment even when the windings C have no current passing through them and only
the windings D are supplied with current.
It has already been proposed to effect this object by providing the iron body of
the meter, in addition to the two windings through which the working current
and shunt current pass respectively with a third unsymmetrically arranged short

page_text: circuited winding. Such a short circuited winding can be easily so regulated by
the insertion of a suitable resistance that it will produce, in combination with the
shunt winding alone, a weak turning moment which will be just sufficient to
counterbalance with sufficient accuracy the frictional resistance in the bearings of
the motor axis and of the counter.
"
For this purpose it suffices to provide a few turns W of a suitable wire wound
at a point A round the ring A, A, A, A, and short circuited.
The direction of rotation will vary according to the position of this winding
relatively to the winding of the shunt circuit. If, namely, the short circuited
winding be placed at A, instead of at A₁, the direction of rotation of the drum will
be reversed. The explanation of this is as follows:-
If the windings are open at A, then, under the influence of the currents in the
windings D, magnetic circuits I, I, I, I will be produced, in the direction of the
arrows, which will be exactly balanced in the pole pieces B₁ and B. In other
words, the lines of force only pass at the pole pieces B, B₁ out of the outer ring,
through the copper drum into the inner part E, and thence outward again.
If the windings W are closed then currents are induced therein which have a
throttling action upon the circuit I, of the lines of force, while the other circuits
will remain undisturbed.
The magnetic circuit I, will therefore, without having its strength materially
affected, be subject to a slight shifting of phase relatively to the circuit I, as at
Fig. 2.
The two magnetic circuits I, and I, therefore produce in the pole piece B, a
resultant I, that will be shifted in phase nearly 90° relatively to I, and I. There
is consequently produced in addition to the pulsating field a very weak superposed
rotary field that will exercise a slight turning moment on the copper drum F.
If the short circuited winding were provided at A, instead of at A₁, the mag-
netic circuit I, will be slightly shifted in phase as at Fig. 3. In consequence
hereof there would be produced a resultant I which has a phase shift of about 180°
relatively to the resultant in Fig. 2. This will have the effect that the drum will
now tend to revolve in the contrary direction.
This arrangement however causes a serious disadvantage. It follows from the
above considerations that the strong current winding in combination with the
short circuited winding will produce a turning moment in the contrary direction
to that which is produced by the weak current winding and the short circuit wind-
ing; because A, is situated relatively to CC in the same way as A, is situated
relatively to DD. If therefore the additional turning moment which is to com-
pensate for the frictional resistance, is to remain uniform with all strengths, of
the working current, the strength of the working current must not produce any
turning moment with the short circuited winding.
This is accomplished according to the present invention by the arrangement
shewn at Fig. 4. The adjusting resistance P, P₂ by means of which the short
circuited windings W are closed is at the same time included in the circuit of the
working current. The adjusting resistance can then be so chosen that the poten-
tial difference between the terminals P₁ P₂ is equal to the electro motive force
produced in the windings W by the working current, and has almost the opposite
phase thereof.
1 2
It will then be found that the coils CC do not induce any current W when the
coils DD have no current.
As shewn at Fig. 5, the magnets motive force is composed of Hc and H t, of
which He is derived from the current in the coils C C and H t from the currents
in the copper drum.
The resultant magnets-motive force is therefore H, and the magnetism produced
is M. The electro motive force in the short circuited coils is shifted 90° rela-
tively to M, and has therefore the phase E, while the potential difference between
P, and P, must have the phase of the currents in CC, and therefore the phase
of H c. It will be seen that E and H c are directed almost opposite to each other.
1

page_text: In this way the detrimental influence of the working current upon the short
circuited windings can be neutralised.
In order to enable the strength of current in the short circuited windings to
be brought to the desired value, it is convenient to introduce a small adjusting
resistance R into the circuit as shewn at Fig. 4. This adjusting resistance will
also generally consist of a short length of wire.
Both the said adjusting resistances can therefore be combined, and the short
circuited windings W be closed by a suitable resistance P₁ P₂ of which one
part P, P, is at the same time included in the working current circuit, as shewn
in the modified arrangement at Fig. 6.
Dated thio 25th Joy of Fohruary 1808
ABEL & IMRAY,
Agents for the Applicants.
Improved Means for Counterbalancing the Frictional Resistance in
Alternating Current Motor-meters.
We, SIEMENS BROTHERS & Co. LIMITED, of 12, Queen Anne's Gate, West-
minster, S.W., Electrical Engineers, do hereby declare the nature of this invention
(as communicated to us from abroad by Siemens & Halske Aktien-Gesellschaft, of
Markgrafen Strasse, 94, Berlin, S.W. Germany, Electrical Engineers) and in
what manner the same is to be performed to be particularly described and ascer-
tained in and by the following statement:-
In order with electricity meters that are constructed on the principle of motor
meters, to counterbalance the inaccuracy arising from the friction of the trunnions
of the rotating part and of the counter mechanism, it is advantageous to impart
to the motor of the meter even when no working current is passing through it,
such a turning moment that the resisting turning moment caused by the friction
shall be just counterbalanced so that the motor will begin to move as soon as
there is the slightest increase of the driving turning moment, that is, as soon as a
working current exists.
The present invention relates to an arrangement for providing such a turning
moment with motor-meters for single or polyphase alternating currents operating
with a rotary field. Such a meter is constructed as follows:--
Referring to Fig. 1 of the drawings accompanying our Provisional Specification
AAAA is a stationary ring built up of insulated layers of sheet iron having
four radial inward directed polar extensions B, B, B., B. Within this ring and
concentric therewith is a fixed cylinder E E also of insulated sheet iron.
Between the cylindrically hollowed ends of the polar extensions B₁ &c., and the
cylinder E is a small space in which is a copper drum F that can revolve on the
axis G.
The polar extensions, B, B₂ have windings of thick wire, through which the work-
ing current passes while the poles B3 B4 have windings of thin wire, the current
passing through which is shifted 900 relatively to the working current by any
suitable means.
Such a device is shewn for instance in the Specification to Application No. 2559
of 1897, and also in Fig. 4 of the drawings accompanying the Provisional Specifica-
tion. By this means a rotary field is produced in the iron parts which effects the
rotation of the drum, the rotation being the faster, the greater is the strength of
the working current in the thick wire windings C, with a constant strength of
current in the thin wire windings D.

page_text: The rotation of the drum is transmitted to a counter in any suitable manner.
The object of the present invention is to impart to the drum F a slight turning
moment even when the windings C have no current passing through them and only
the windings 1) are supplied with current.
It has already been proposed to effect this object by providing the iron body of
the meter, in addition to the two windings through which the working current
and shunt current pass respectively with a third unsymmetrically arranged short
circuited winding. Such a short circuited winding can be easily so regulated by
the insertion of a suitable resistance that it will produce, in combination with the
shunt winding alone, a weak turning moment which will be just sufficient to
counterbalance with sufficient accuracy the frictional resistance in the bearings of
the motor axis and of the counter.
For this purpose it suffices to provide a few turns W of a suitable wire wound
at a point A round the ring A, A, A, A, and short circuited.
The direction of rotation will vary according to the position of this winding
relatively to the winding of the shunt circuit. If, namely, the short circuited
winding be placed at A, instead of at A, the direction of rotation of the drum will
be reversed.
The explanation of this is as follows:-
If the windings are open at A, then, under the influence of the currents in the
windings D, magnetic circuits I, I, I, I will be produced, in the direction of the
arrows, which will be exactly balanced in the pole pieces B, and B
In other words the lines of force only pass at the pole pieces B, B. out of the
outer ring, through the copper drum- into the inner part E, and thence outward
again.
If the windings W are closed then currents are induced therein which have a
throttling action upon the circuit I, of the lines of force, while the other circuits
will remain undisturbed.
The magnetic circuit I will therefore, without having its strength materially
affected, be subject to a slight shifting of phase relatively to the circuit I, as at
Fig. 2.
The two magnetic circuits I, and I therefore produce in the pole piece B, a
resultant I, that will be shifted in phase nearly 90° relatively to I, and I. There
is consequently produced in addition to the pulsating field a very weak superposed
rotary field that will exercise a slight turning moment on the copper drum F.
If the short circuited winding were provided at A₂ instead of at A, the mag-
netic circuit I will be slightly shifted in phase as at Fig. 3. In consequence
hereof there would be produced a resultant I which has a phase shift of about 180°
relatively to the resultant in Fig. 2. This will have the effect that the drum will
now tend to revolve in the contrary direction.
This arrangement however causes a serious disadvantage. It follows from the
above considerations that the strong current winding in combination with the
short circuited winding will produce a turning moment in the contrary direction
to that which is produced by the weak current winding and the short circuit wind-
ing; because A, is situated relatively to CC in the same way as A, is situated
relatively to DD. If therefore the additional turning monrent which is to com-
pensate for the frictional resistance, is to remain uniform with all strengths, of
the working current, the strength of the working current must not produce any
turning moment with the short circuited winding.
This is accomplished according to the present invention by the arrangement
shewn at Fig. 4.
The adjusting resistance P₁P2 by means of which the short circuited wind-
ings Ware closed is at the same time included in the circuit of the working
current.
The adjusting resistance can then be so chosen that the potential difference
between the terminals P₁ P, is equal to the electro motive force produced in the
windings W by the working current, and has almost the opposite phase thereof.
2

page_text: coils DD have no current.
As shewn at Fig. 5, the magneto motive force is composed of He and Ht, of
which He is derived from the current in the coils CC and Ht from the currents
in the copper drum.
The resultant magneto motive force is therefore H and the magnetism produced
is M.
The electro motive force in the short circuited coils is shifted 90° relatively
to M, and has therefore the phase E, while the potential difference between P₁
and P₂ must have the phase of the currents in CC, and therefore the phase
of Hc. It will be seen that E and Hc are directed almost opposite to each other.
In this way the detrimental influence of the working current upon the short
circuited windings can be neutralised.
In order to enable the strength of current in the short circuited windings to
be brought to the desired value, it is convenient to introduce a small adjusting
resistance R into the circuit as shewn at Fig. 4. This adjusting resistance will
also generally consist of a short length of wire.
Both the said adjusting resistances can therefore be combined, and the short
circuited windings W be closed by a suitable resistance P₁ P₂ of which one
part P, P, is at the same time included in the working current circuit, as shewn
in the modified arrangement at Fig. 6.
Having now particularly described and ascertained the nature of this invention
and in what manner the same is to be performed, we declare that what we claim
is:-
Counterbalancing the frictional resistance in alternating current induction
motor-meters of the kind herein referred to, by providing on the annular iron
body of the motor one or more windings branched from a suitable part of the
working circuit and arranged and operating, substantially as herein described for
rendering the counterbalancing action independent of the working current.
Dated this 19th day of November 1898.
ABEL & IMRAY,
Agents for the Applicants.