Improvements in Transforming Alternating into Continuous Electric C Currents or vice versa.
Year: 1897

page_text: PROVISIONAL SPECIFICATION.
Improvements in Transforming Alternating into Continuous Electric
C Currents or vice versa.
We, ADOLPH MÜLLER, of 90, Bergstrasse, Hagen, Westphalia, in the German
Empire, Director, and HENRI TUDOR, of Rosport, in the Grand Duchy of Luxem-
bourg, Engineer, do hereby declare the nature of this invention to be as follows:
This invention relates to improvements in transforming alternating and con-
tinuous. electric currents.
-
An alternating current cannot be directly employed for charging electric
accumulators or secondary batteries because, as is well known, its tension or
voltage alternates rapidly from a positive to a negative maximum approximately
according to a sine curve, whilst the opposing electromotive force generated
when charging storage or secondary batteries has a positive tension which depends
solely upon the charging operation and only changes slowly.
It is, however, possible by means of a commutator, operated synchronously
with the alternating current employed, not only to change the direction of the
current at each alternation so as to give rise to a continuous current, but also to
switch the storage battery to be charged in or out of the circuit at the moment
in the phase in which the tension of the alternating current begins to rise above
or fall below that of the battery. It is, therefore possible at this instant, to dis-
connect without disadvantage the source of the alternating current as at this
moment the tension of the primary current is exactly equal to the opposing
electromotive force so that there is no current flowing through the circuit.
There are, however, several practical difficulties which stand in the way of
carrying out this theoretical principle. Fluctuations occur in the tension of the
current phases on account of variations in the speed of the driving motor and
also of variations in load, and it is also impossible always to operate the com-
mutator so that it move's exactly synchronously with the phases of the alternating
current.
Various arrangements have already been designed in which it is rendered
possible always so to adjust the brushes of the commutator that the deviation
from the moment for disconnecting, the battery from the circuit of the same
tension is as small as possible. As, however, the current fluctuations, especially
those which are caused by the alteration in the phase occasioned by the unavoid-
able asynchronism of the commutator take place, very quickly it is not possible
to obtain a sufficiently accurate coincidence between the instant of the equalizing
of the tension and the switching in or out of the circuit so that considerable
sparking takes place at the commutator.
Now this invention has for its object an arrangement whereby an alternating
current can be used for charging accumulators or secondary batteries (for the
purpose of transforming the said alternating current into a continuous current)
without giving rise to the above described disadvantages. This is effected by

page_text: arranging that the charging-current, whilst the direction of its flow is being
charged or diverted by the commutator, is not interrupted and that during the
space of time in which the charging-circuit is disconnected from the battery
to be charged, it is maintained closed by a separate polarization battery.
This polarization battery is composed of elements the number of which corre-
sponds to the tension or electromotive force of the accumulator or secondary
battery, but it has as small a capacity as possible so that an exceptionally small
quantity of electricity suffices for charging it. The tension of the said polarization
battery, therefore, can always immediately suit itself to the changing tension of
the alternating current so that during the time it is connected up in the circuit,
the electromotive force of the alternating current always remains approximately
equal to the opposing electromotive force of the polarization battery.
When changing the connections, the alternating current is first divided, that
is to say, one branch of the current is connected to the polarization battery, and
the connection between the charging-current and the battery is then unbroken.
By this mean's any interruption or break in the flow of the alternating current is
quite avoided so that no appreciable sparking can take place at the commutator.
In a suitable arrangement for transforming alternating and continuous currents
according to my invention two conductors or leads pass from an alternating current
dynamo to a commutator arranged at a suitable distance therefrom and which is
kept synchronously rotating by means of a motor driven by the alternating
-current. The commutator carries a number of contact pieces in connection
alternately with two inner rings so as to form with them two continuous contact
picces separated from one another by a serpentine insulating groove. In the
insulating spaces between every two adjacent contact pieces there are arranged
intermediate .contact pieces which are alternately connected by conductors with
two outer rings. Above the contact pieces and the intermediate contacts I provide
.brushes hereinafter referred to as contact brushes which slide. on the contacts
and are arranged at a distance apart equal to the accumulator divisions and are
slightly thicker than the breadth of the insulating space between the contact
pieces and the intermediate contacts. These brushes are connected with the
alternating current dynamo by the main connections or leads. The current is
taken from the inner rings by brushes hereinafter referred to as ring brushes
and the poles of the accumulator or secondary battery are connected with the ring
- brushes by suitable conductors.
Brushes slide upon the outer rings and conductors pass from the said brushes
to the poles of the polarization battery.
The change in direction of the current is effected in this arrangement as
follows. So long as the contact brushes slide upon the contact pieces the alternat-
ing current flows from the motor through one of the main conductors one of the
said brushes, a contact piece one of the inner rings the brush in contact with
the said ring and thence to the battery to be charged. From the battery
it then flows to the other inner ring through the brush in contact with it and
from the ring it is collected by the second brush and conducted back to the
motor through. the second main conductor or lead so that the battery is charged.
Before the brushes leave the contact pieces they come in contact with the inter-
mediate contacts. In this position, therefore, the current is divided in such a
manner that the current from one brush flows through the intermediate contact,
to the outer ring to which it is connected and is collected from the ring by the
brush provided for the purpose and sent to the polarization battery after passing
through which it flows to the other outer ring, to the intermediate contact con-
nected to the same and so back to the motor.
By this means the polarization battery is instantly brought to the momentary
tension of the alternating current so that when switching off the battery to be
charged from the circuit there exists equality of tension and no current flows
through the circuit. No sparks are, therefore, formed at the brushes when they
leave the contact pieces.

page_text: Whilst the tension of the alternating current varies within a certain limit the
brushes remain in contact with the intermediate contacts so that only the polariza-
tion battery remains connected up in the circuit. The opposing electromotive
force of the said polarization battery follows the variation in the tension of the
alternating current as, both remaining the same, they first drop to zero, then
change in sign and rise to the charging tension of the battery to be charged.
At this instant the brushes even before they leave the intermediate contacts
come into contact with two other contact pieces so that the current, the, direction
of flow which is now reversed, flows in the same direction as before through the
brushes to the polarization battery. The said battery is then (when the brushes
leave the intermediate contacts) switched off and the whole operation is repeated
in the same manner. The alternating current is, therefore, never broken or
interrupted.
The battery to be charged is, therefore, charged by.continuous current impulses
which succeed one another at a high velocity and at short intervals. The dis-
charge of the battery can be effected in the ordinary manner. A continuous
current can, however, be obtained from the poles of the battery through conductors
which form continuations of the conductors connecting the said poles to the inner
rings of the commutator, without cutting off the charging current. The battery
in this case only serves the purpose of compensating for the differences in the
tension of the alternating current and to give to the discharge current.constant
tension, its electromotive force, with the exception of the periodical fluctuations
connected with the above described action, remaining practically unaltered..
The above described arrangement can also be used in the reverse manner, that
is to say, to transform a continuous current into an alternating current.
In this case the continuous current, which is conveyed through the conductors
in connection with the battery is converted by the commutator into current
impulses flowing in opposite directions. The two batteries perform the same
role as above described but the motor must be driven by the continuous current
if the alternating current. motor employed in lieu of the dynamo is to work auto-
matically.
Instead of the commutator described above, any other suitable current.changing
device can be employed, which before interrupting the charging-current switches
a polarization battery into the circuit, for example a suitably arranged switch
would serve the purpose.
The polarization battery can be formed as desired with the necessary number
of elements. For this purpose, steel plates in a potash solution, platinum plates
in sulphuric acid, or plain lead plates in sulphuric acid, etc., can be employed. The
polarization battery can also be replaced by condensers.
In cases where the absolute continuity of the continuous current obtained is
not of so much importance, the storage battery can be dispensed with. In such.a
case an intermittent current can be obtained consisting of impulses which follow
one another at short intervals.
.
Poly-phase or multi-phase currents can also be transformed into continuous
currents in exactly the same manner as that above described, and vice versa
continuous currents can be transformed into poly-phase currents. In this case
the poly-phase current is passed through a suitably constructed commutator and
the different phases are connected to, or disconnected from, the discharging-
circuit at the moment at which the tension of the latter is passed. During the
time in which the break in the circuit remains, the poly-phase current
circuit is connected to a polarization battery exactly in the same manner
as described above for the simple alternating current.

page_text: Improvements in Transforming Alternating into Continuous Electric
Currents or vice versa.
We, ADOLPH MÜLLER, of 90, Bergstrasse, Hagen, Westphalia, in the German
Empire, Director, and HENRI TUDOR, of Rosport, in the Grand Duchy of Luxem-
bourg, Engineer, 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 improvements in transforming alternating and con-
tinuous electric currents.
An alternating current cannot be directly employed for charging electric
accumulators or secondary batteries because, as is well known, its tension or
voltage alternates rapidly from a positive to a negative maximum approximately
according to a sine curve, whilst the opposing electromotive force generated
when charging storage or secondary batteries has a positive tension which depends
solely upon the charging operation and only changes slowly.
It is, however, possible by means of a commutator, operated synchronously
with the alternating current employed, not only to change the direction of the
current at each alternation so as to give rise to a continuous current, but also to
switch the storage battery to be charged in or out of the circuit at the moment
in the phase in which the tension of the alternating current begins to rise above
or fall below that of the battery. It is, therefore, possible at this instant, to dis-
connect without disadvantage the source of the alternating current as at this
moment the tension of the primary current is exactly equal to the opposing
electromotive force so that there is no current flowing through the circuit.
There are, however, several. practical difficulties which stand in the way of
carrying out this theoretical principle. Fluctuations occur in the tension of the
current phases on account of variations in the speed of the driving motor and
also of variations in load, and it is also impossible always to operate the com-
mutator so that it moves exactly synchronously with the phases of the alternating
current.
Various arrangements have already been designed in which it is rendered
possible always so to adjust the brushes of the commutator that the deviation
from the moment for disconnecting the battery from the circuit of the same
tension is very small. As, however, the current fluctuations, especially those
which are caused by the alteration in the phase occasioned by the unavoid-
able asynchronism of the commutator, take place very quickly it is not possible
to obtain a sufficiently accurate coincidence between the instant of the equalizing
of the tension and the switching in or out of the circuit so that considerable
sparking takes place at the commutator.
Now this invention has for its object an arrangement whereby an alternating
current can be used for charging accumulators or secondary batteries (for the
purpose of transforming the said alternating current into a continuous current)
without giving rise to the above described disadvantages. This is effected by
arranging that the charging-current, whilst the direction of its flow is being
changed or diverted by the commutator, is not interrupted and that during the
space of time in which the charging-circuit is disconnected from the battery
to be charged, it is maintained closed by a separate polarization battery.
This polarization battery is composed of elements the number of which corre-
sponds to the tension or. electromotive force of the accumulator or secondary
battery, but it has as small a capacity as possible so that an exceptionally small

page_text: quantity of electricity suffices for charging it. The tension of the said polarization
battery, therefore, can always immediately adapt itself to the changing tension of
the alternating current so that during the time it is connected up in the circuit,
the electromotive force of the alternating current always remains approximately
equal to the opposing electromotive force of the polarization battery.
When. changing the connections, the alternating current is first divided, that
is to say, one branch of the current is connected to the polarization battery, and
the connection between the charging-current and the battery is then broken.
By these means any interruption or break in the flow of the alternating current is
avoided so that no appreciable sparking can take place at the commutator.
In the accompanying drawing.
Figure 1 is a diagrammatic view illustrating the invention, the commutator
being shewn developed.
Figures 2 and 3 shew diagrams hereinafter described.
Two conductors or leads a¹, a² pass from an alternating current dynamo A
to a commutator B arranged at a suitable distance therefrom and which is kept
synchronously rotating by means of a motor C driven by the alternating current.
The commutator B carries a number of contact' pieces 61, 62, 63, 64, 65, of which
61, 63, 65 are in connection with a ring d¹ and 63, 64 with a ring d² so as to form
with them two continuous contact pieces separated from one another .by a
serpentine insulating groove. In the insulating spaces between every two
adjacent contact pieces there are arranged intermediate contact pieces 61, 623,
63 645 which are alternately connected by conductors with two outer rings f¹, f.
Above the contact pieces b1, b2 etc. and the intermediate contacts 613, 623 etc. I
provide brushes E1, E2 which slide of the contacts and are arranged at a distance
apart equal to the breadth of the commutator divisions and are slightly thicker
than the breadth of the insulating space between the contact pieces and the inter-
mediate contacts. These brushes are connected with the alternating current
dynamo by the connections a¹, a². The current is collected from the rings d¹, d²
by brushes D1, D2 to which the poles of the accumulator or secondary battery G
are connected by conductors g¹, g³.
Brushes F¹, slide upon the rings f¹, f2 and conductors h³, h² pass from the
said brushes to the poles of the polarization battery H.
The change in direction of the current is effected in this arrangement as
follows. So long as the brush E¹ slides upon the contact piece b¹ and the brush Ea
upon the contact piece 62 the alternating current flows from the dynamo A through
the conductor at the brush E', contact piece b¹ the ring d', the brush D¹ and
thence through the wire g¹ to the battery G to be charged. From the battery
it then flows through the wire g², brush D2 and ring d² from which it is collected
by the brush E2 and conducted back to the motor or dynamo A through the
conductor a² so that the battery G is charged.
This period corresponds to the well known alternating current diagram repre- .
sented in Figure 2 and in which the abscissae indicate time and the ordinates
tension. The distance i, k represents the time occupied whilst the tension varies
according to the curve l, m, n; the electromotive force remains constant during
this period as indicated by the straight line 1, n.
Before the brushes E¹, E leave the contact pieces 61, 62 they come into contact
with the intermediate contacts 61 and 623 as shewn in Figure 1. In this position,
therefore, the current is divided in such a manner the the current from'
the brush E flows through the intermediate contact 612, and the wire f to the
ring fis collected from the said ring by the brush F¹ and flows through the
wire h¹ to the polarization battery H after passing through which it flows througli
the wire 2, brush F2, ring f2 wire f contact 63, brush E. and so back to the
dynamo.
By these means the polarization battery H is instantly brought to the momentary
tension of the alternating current so that when switching off the battery G from
the circuit there exists equality of tension and no- current-flows through the

page_text: circuit. No sparks are, therefore, formed at the brushes E1, E2 when they leave
the contact pieces b1, b2.
Whilst the tension of the alternating current varies according to the curve n,
o, p the brushes E, Eremain in contact with the intermediate contacts 612, 623
so that only the polarization battery remains connected up in the circuit. The
opposing electromotive force of the said polarization battery follows the variation
in the tension of the alternating current as, both remaining practically the same,
they first drop to zero, then change in sign and rise to the charging tension of
the battery G.
At this instant the brushes E¹, E2 even before they leave the intermediate
contacts 612, 623 come into contact with two other contact pieces 62, 63 so that the
current, the direction of flow which is now reversed (from a² to d¹) flows in the
same direction as before through the brushes E, E to the polarization battery H.
The said battery H is then (when the brushes E1, E2 leave the intermediate
contacts 12, 623) switched off and the whole operation is repeated in the same
manner. The alternating current is, therefore, never broken or interrupted.
The battery G is therefore, charged by continuous current impulses which
'succeed one another at a high velocity and at short intervals and the tension of
which is expressed by the curve i, 1 m, n, k. The discharge of the battery can be
: effected in the ordinary manner. A continuous current can, however, be obtained
from the poles of the battery through the conductors 93, 94 which form continua-
tions of the conductors g¹, g2 without cutting off the charging current. The
battery G, which is connected up between the conductors g¹, g, and g², g4 in
this case only serves the purpose of compensating for the differences in the tension
of the alternating current and to give to the discharge current constant tension,
its electromotive force, with the exception of the periodical fluctuations connected
with the above described action, remaining practically unaltered.
The above described arrangement can also be used in the reverse manner, that
is to say, to transform a continuous current into an alternating current.
In this case the continuous current, which is conveyed through the con-
ductors g³, g and g, g² in connection with the battery, is converted by the com-
inutator into current impulses flowing in opposite directions and the tension of
which is indicated by the curve shewn in Figure 3. The two batteries G and H
perform the same rôle as above described but the motor C must be driven by
the continuous current if the alternating current motor A employed in lieu of
the dynamo is to work automatically.
Instead of the commutator described above, any other suitable current changing
device can be employed, which before interrupting the charging-current switches
a polarization battery into the circuit or for example a suitably arranged switch
would serve the purpose.
The polarization battery can be formed as desired with the necessary number
of elements. For this purpose, steel plates in a potash solution, platinum plates
in sulphuric acid, or plain lead plates in sulphuric acid, etc., can be employed. The
polarization battery can also be replaced by condensers.
In cases where the. absolute continuity of the continuous current obtained
is not of much importance, the storage battery G can be dispensed with. In
such a case an intermittent current can be obtained from the wires g', gið
and g², g¹ consisting of impulses which follow one another at short intervals and
the tension of which varies according to the curve i, l, m, n, k Figure 2.
Poly-phase or multi-phase currents can also be transformed into continuous
- currents in exactly the same manner as that above described, and, vice versa
continuous currents can be transformed into poly-phase currents. In this case
the poly-phase current is passed through a suitably constructed commutator and
the different phases are connected to, or disconnected from, the discharging-
circuit at the moment at which the tension of the latter is passed. During the
time in which the break in the circuit remains, the poly-phase current

page_text: circuit is connected to a polarization battery exactly in the same
as described above for the simple alternating current.
manner
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:-
In transforming alternating currents into continuous currents and vice vercâ
by the employment of a commutator device arranged to operate synchronously
with the alternating current, the arrangement whereby a polarization battery
is introduced into the alternating current circuit before disconnecting the
alternating and continuous current circuits, the said battery being of very small
capacity and remaining in the alternating current circuit during the period of
disconnection for the purpose of preventing the flow of circuit in the alternating
current circuit by opposing to the electromotive force of the said current an
electromotive force of equal value, substantially as hereinbefore described.
The 21st dow of Webruary 1898
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicants.