Improvements in Apparatus connected with the Charge and Discharge of Storage Cells in Systems of Electrical Distribution.
Year: 1898

page_text: Date of Application, 15th Nov., 1898
Complete Specification Left, 15th Aug., 1899-Accepted, 11th Nov., 1899
Improvements in Apparatus connected with the Charge and Discharge
of Storage Cells in Systems of Electrical Distribution.
We, ERNEST WILSON, of 64, St. John's Park, Blackheath, in the County of
Kent, M.I.E.E., and JOHN MCILVAINE CATER, of "Southdown," The Downs,
Wimbledon, in the County of Surrey, Engineer, do hereby declare the nature of
this invention to be as follows:-
One object of this invention is to kept the potential difference between two
points in a discharge circuit constant, or nearly constant, during charge and
discharge of storage cells, forming part of the circuit without subdivision of the
battery as is generally the case. For this purpose we provide a dynamo wound
with two magnetising coils, on the same magnetic circuit or provided with two
magnetic circuits if desirable one for each coil such dynamo being driven by a
The armature of
shunt or compound wound motor or by other suitable means.
this dynamo is placed in series with one of the magnetising coils and next to the
battery in the discharge circuit. It rotates in such direction and, when the
battery is being discharged, is magnetised by the discharge current in suchwise
that its potential difference aids that of the battery. The extent to which the
potential difference of the battery has to be increased in this way in order to
maintain the potential difference between the two points in the discharge circuit
constant or nearly so, depends upon the ohmic resistance of the circuit, the current
in the circuit, and armature reaction. When, however, the battery is being
charged the other circuit on the dynamo is made use of; it may be made to carry
the whole of the charging current, or any fraction thereof; i.e. it may be
placed in the charge circuit or may form a shunt thereto; or it may be placed
across the battery or a portion thereof or between any two points in the discharge
circuit if desirable as a shunt circuit. When this magnetising coil forms a
shunt circuit, it may be automatically made or broken by the aid of the charge
current and an electro magnetic switch which may be adjusted in suchwise that
this shunt circuit is only made or broken when the charge current has a pre-
determined value below which the switch will not make the circuit. If desired
this operation may of course be performed by hand. The magnetising force
due to the second magnetising coil is opposed to the magnetising force due to the
discharge current in the first coil. The relative strengths of these magnetising
coils are such that during the charging of the battery the dynamo machine has
its polarity reversed, i.e., it subtracts from the potential difference of the battery
but the effect of the discharge current in the first coil is still felt. It reduces
the potential difference of the dynamo in approximate proportion to the increase
of the discharge current instead of increasing it as is the case when the charge
current is zero, or small as determined by the electro-magnetic switch previously
alluded to, if the second circuit be a shunt. We may provide an adjustable
resistance in the shunt circuit of this dynamo for the purpose of adjustment and
work it automatically or by hand so that when the potential difference of the

page_text: battery is small the resistance in circuit is great. When the motor employed to
drive the dynamo is shunt wound we may place it across the battery or a portion
thereof, or across the conductors leading from the dynamo and battery to the
discharge circuit in which case the current due to such motor passing through
the dynamo must be allowed for. The motor may be provided with two circuits
and be compounded to run at constant speed or over or under compounded to
run quicker or slower on load. If the motor be shunt wound and placed across
the battery it will run at greater speed if its field is not increased in the same
proportion as the potential difference of the battery when charging commences.
This may be allowed for in the dynamo if necessary but it can be arranged with
a weaker field if desirable so as to run at more constant speed. We may insert
an adjustable resistance in the shunt circuit of the motor for adjustment of speed
We may also insert a switch in the charge circuit which can be employed to
directly connect the feeder used for charging purposes to the discharge circuit,
thereby severing connection with the battery. Obviously the coils on the dynamo
need not oppose one another if the direction of rotation be reversed, or the dia-
charge current reversed in its maguetising coil. The dynamo and motor may be
bi- or multipolar and of ordinary construction. We may if we wish allow the
current in the motor to pass through the magnetising coil on the dynamo which
is used for the discharge current, or we may combine these two methods of
regulation. We may so arrange that the potential difference between the points
in the discharge circuit is increased or decreased instead of being kept constant
by suitably arranging the speed or magnetising forces or both simultaneously.
When the battery is placed at a distance from the power source the control of
the apparatus herein described may be effected electrically by any of the well
known methods. We may employ another dynamo preferalily shunt wound, for
the purpose of increasing the potential difference of the battery for charging
purposes, such dynamo being driven by the motor herein described or by other
suitable means and located either in the power station or near the battery.
Dated this Fifteenth day of November 1898.
Improvements in Apparatus connected with the Charge and Discharge
of Storage Cells in Systems of Electrical Distribution.
We, ERNEST WILSON, of 64, St. John's Park, Blackheath, in the County of
Kent, Professor of Electrical Engineering, and JOHN MCLLVAINE CATER, of "South-
down," The Downs, Wimbledon, in the County of Surrey, Engineer, do hereby
declare the nature of this invention and in what manner the same is to be per-
formed to be particularly described and ascertained in and by the following
statement:-
Our invention relates to systems of electrical distribution, and in particular to
those systems wherein storage cells are used in conjunction with a main generator
to supply current to a work circuit containing translating devices.
The object of our invention is to provide for maintaining the potential differ-
ence between the two points in a discharge circuit constant, or nearly constant,
during charge or discharge of the storage cells.
The accompanying drawings are diagrams illustrating systems of electrical
distribution in accordance with our invention:-A and B are conductors connected
to the main generator E and to the storage battery K; B and C are the line con-

page_text: ductors supplying current to translating devices and between which it is desired
to maintain the potential difference constant: M is a motor which drives an
auxiliary generator D, the field magnet of said generator being provided with
two coils one of which, S, is in series with the armature and with the work
circuit, being connected between the conductors A and C: T is a switch by
means of which the main generator E can be connected to the conductor A as
shewn in Figure 1, or to the conductor C as shewn in Figure 2, or to both of
said conductors as shewn in Figure 3. The generator D is provided with a
second magnetizing coil which is so arranged as to magnetize the field magnet
in the opposite direction to that in which the coil S magnetizes said field magnet,
so that the electromotive force supplied by said generator depends on the
difference between the magnetism due to the coil S and that due to the second
coil. In Figures 1 and 2 the second coil is marked S', and is joined as a shunt
to the generator D being provided with the usual adjustable resistance R, but
in Figure 3 the second coil marked S is joined in series between the main
generator E and the generator D.
The operation of the system is as follows:-The generator I rotates in such
a direction and, when the battery K is supplying current to the work circuit,
is magnetized by the discharge current passing through the coil S in such a
direction that its electromotive force aids that of the battery, that is to say,
the potential difference between B and C is greater than that between B and A.
The extent to which the potential difference of the battery K has to be increased
in this way in order to maintain the potential difference betwen B and C con-
stant, or nearly so, depends upon the ohmic resistances of the battery, the
generator D, the coil S, and the necessary connecting leads, and upon the dis-
charge current and armature reaction in said generator. When, however, the
battery K is being charged by a current conveyed to it from the main generator E
through the conductors A and B the second magnetizing coil on the field magnet
of the generator 1) is energized, and the electromotive force supplied by the
generator D is reduced according to the strength of the charging current supplied
by the main generator E. By this means the potential difference between the
conductors B and C is maintained approximately constant, whereas, if the
generator D be omitted the potential difference supplied to the work circuit will
be greater when the battery K is being charged than when it is being dis-
charged.
In Figures 1 and 2, the second magnetizing coil S₁ of the generator D is
arranged as a shunt, being provided with a switch G, by means of which its
circuit is opened and closed. Said switch may be operated by hand, but in some
cases it is desirable to arrange that it shall be automatically operated to close
the circuit as soon as a charging current is supplied to the battery K. For this
purpose an electromagnetic device may be provided, as illustrated diagrammati-
cally in these figures, by a solenoid G' arranged with a co-operating magnet
core G³, which, when the coil is energized, is attracted and completes the con-
nection between the shunt circuit S¹ and the conductor A. This switch may be
arranged in any well-known manner so that it does not make the circuit until
the current rises to a predetermined value. If desirable said switch may be
operated at a distance by the aid of separate conductors, instead of by the charging
current in the conductor A.
It is clear from what has already been stated that if the current through the
coil S¹, Figures 1 and 2, or through the coil S3, Figure 3, is so large as to reverse
the polarity of the generator D the electromotive force of said generator will
oppose that of the battery K, that is to say, the potential difference between
the conductors A and B is greater than that between B and C. The effect of
the discharge current in the coil S is, however, still felt as it reduces the electro-
motive force of the generator D in approximate proportion to the increase of
the discharge current instead of increasing it, as is the case when the charging
current is zero or small.

page_text: The motor M may be of any suitable type. In Figure 1, a compound wound
motor, and in Figures 2 and 3 a shunt motor is illustrated. In the diagram
Figure 2 the current for operating the motor passes through the generator D
and must be allowed for in adjusting the magnetizing coils of said generator.
It is obvious that in lieu of maintaining the potential between the conductors B
and C constant we may arrange that the same shall be increased or decreased
by suitably arranging the speed or magnetising forces or both of the generator D.
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 a system of electrical distribution, the combination of a main generator,
a storage battery, in parallel therewith, a work circuit operated by current from
the generator and the battery aforesaid, and an additional generator provided with
differentially magnetising coils, the armature of one of said coils being in series
with the work circuit and another of said coils being including in a circuit
shunting the main generator, and a switch in the main generator circuit by
means of which the said generator may be connected to the battery or the line,
or to both as desired.
2. In a system of electrical distribution, as set forth in Claim 1, an automatically
operated switch on the circuit shunting the main generator which will make the
circuit when the current supplied to the battery from the main generator rises
to a given amount substantially as described.
3. The improved system of electrical distribution arranged and operating sub-
stantially as described and illustrated diagrammatically in the accompanying
drawing.
Dated the 15th day of August 1899.
W. P. THOMPSON & Co.,
322, High Holborn, London, W.C., Patent Agents for the Applicant.