Improvements in Controlling Electric Motors and Apparatus for that purpose.
Year: 1899

page_text: Date of Application, 4th May, 1899
Complete Specification Left, 3rd Feb., 1900-Accepted, 10th Mar.,
1900
PROVISIONAL SPECIFICATION.
Improvements in Controlling Electric Motors and Apparatus for that
purpose.
I, HENRY LEITNER, of No. 207, Piccadilly, in the County of London, Electrical
Engineer, do hereby declare the nature of this invention to be as follows:
My invention relates to means of controlling electric motors particularly such
as are employed for propelling vehicles.
For this purpose I employ a main battery and also a small battery which
excites the field magnets of the motor. The cells of the small battery have the
same capacity as those of the large battery, but there are only a few of them,
for example four.
The large battery is preferably divided into two parts which may be connected
in parallel or in series so as to alter the EMF of the current supplied to the
motor.
Two motors may also be employed or a motor with two independent armature
windings, which may also be connected in series or in parallel for different speeds.
The small battery or exciter is so connected in series with the main battery
as to be in opposition to the EMF of the latter, or for certain speeds it is dis-
connected from the main battery so that the field magnet is separately excited and
independent of the main battery.
When the two batteries are connected the EMF of the current supplied to
the armature is that of the main battery less that of the exciter.
On disconnecting the exciter the full EMF of the main battery is utilised.
When the exciter is in the main circuit the armature current passes through it
as its resistance is much less than that of the field magnet coils and the main
current not only charges the exciter but keeps its voltage at a high point so that
the field magnet is highly excited and great torque is produced in the motor.
The exciter may also be divided into parts, placed in series or in parallel to
alter the strength of the field and the speed of the motor.
To stop the motor the field alone is excited and the armature short circuited.
The speeds are controlled by altering the grouping of the main battery and arma-
ture windings and by placing the exciter into the main circuit (in opposition to
the main battery) or into an independent field circuit. Thus a large number of
driving speeds can be obtained.
In the case of cars driven from a central station the central generator takes
the place of the main battery.
The controlling apparatus, which may serve for various arrangements of motor
and generators, comprises two cylinders carrying bridging contacts which have no
cross connections in the cylinders..
One of the cylinders serves for the armature connections and the other for the
field connections.
The cylinders are turned simultaneously by a pinion between them operated by
a handle and gearing with toothed wheels on the cylinders,

page_text: Between the cylinders are mounted two sets of brushes one set for each cylinder,
connected to the motor and the batteries. Each brush is divided longitudinally
into two or more parts, so as to have several points of contact with the bridging
contacts on the cylinders.
Between the two sets of brushes is placed a pneumatic tube which bears
against both sets of brushes and acts as a spring pressing Them equally on the
contacts.
The cylinders are held in any position to which they are turned by a spring
pawl engaging in the hollow of a star wheel.
To prevent accidental reversal a spring bolt is provided to hold the handle at
the stopping position and this bolt has to be purposely withdrawn, by pressing a
button or otherwise, before the handle can, be moyed farther. An indicator may
be provided to shew at a glance the position to which the controller is set.
Dated this 4th day of May 1899.
ABEL & IMRAY,
Agents for the Applicant.
CUMILELE SEULE ALION.
Improvements in Controlling Electric Motors and Apparatus for that
purpose.
I, HENRY LEITNER, of No. 207, Piccadilly, in the County of London, Electrical
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:-
My invention relates to means of controlling electric motors, particularly such
as are employed for propelling vehicles. It comprises an arrangement of motors
and generators and apparatus for varying the connections between the motors and
the generators, as I shall describe by way of example, referring to the accom-
panying drawings.
Fig. 1 is a diagram of the motors and generators. Fig. 2 shews the surfaces of
the two commutator cylinders developed with their conducting segments. Fig. 3
is a side view partly sectional; Fig. 4 is an end view and Fig. 5 is a plan of the
controlling commutator.
Referring to Fig. 1, a, are the armatures of two motors, b, indicate their
commutators and c, e the coils of their field magnets.
These two motors may be variously connected to a pair of batteries or gener-
ators dd and a pair of exciting generators or batteries.ce. Instead of two separate
motors, a single motor may be employed having two independent windings and
commutators on, a single shaft which can be grouped in series or in parallel
as can the two separate motors.
The main battery or generator is in two parts dd which can be placed in series
or parallel, and a second and smaller battery, which may consist of four cells, is
also divided into two parts e, e. This small battery or exciter is for the field
magnets and is sufficiently strong to keep them powerfully excited independently
of the main circuit.
The exciter ee is placed in the main circuit in opposition to the main genera-
tor d, d or it might be in an independent field circuit. Besides the various vol-
tages and speeds obtained by different groupings of the armatures and main
battery, certain intermediate speeds are obtained by transferring the exciter to

page_text: or from the main circuit. When e e is in the main circuit it is in opposition to
the EMF of the main battery reducing its effective voltage, but when ee is not
in the main circuit the full voltage of the main battery d is utilised.
When the exciter ee is in circuit with the main battery dd the armature
current is supplied almost entirely through it, the resistance of the field being
much greater than that of the exciter and the main current acts so as to charge
the exciter to its fullest extent keeping its voltage up to the extreme limit and
thus highly exciting the field:
The exciter also serves to choke off any sudden rush of current to the armature
on starting of increasing the voltage.
The exciter prevents any danger of reversal of the field, owing to the motor
acting as a generator as may occur in the case of the motors of a vehicle when
the vehicle descends a gradient.
Any current so generated serves to charge the main battery.
The controlling commutator comprises two cylinders f, g each having bridging
contacts which are arranged so as to have no cross connections. The two cylin
ders are turned simultaneously by a handle and gearing i so as to bring narrow
sets of bridges (one set for each grouping of motors and generators) against
brushes connected to the terminals of the motors and generators.
As shewn at Fig. 2 there are nine sets of bridge contacts numbered from I to
IX in each group the similarly numbered sets in each group being used together.
The vertical dotted lines indicate the positions of the brushes and. the connections
are indicated by numerals corresponding to those marked on Fig. 1 for the
various terminals, 1, 2, 3, 4 are the armature brushes, 5 and 6 the field magnet
terminals, 7, 8, 9, 10 are the poles of the main battery and 11, 12, 13 and 14
are the poles of the exciter.
The positions I and II are for backward driving with the polarity of the field
reversed. III is the stopping position with electric brake. IV to IX are the
positions for forward driving with progressively increased speed. In position I,
the connections are such that the armatures a are in series, the divisions of both
batteries & and e in series, the field is connected to exciter e and one pole of
exciter e is connected to the like pole of the main battery d, the other pole of
the exciter e being connected to one of the armature brushes. The main current
thus passes to the armature through exciter e in opposition to its EMF.
In position II, the only change is that the two parts of the main battery d, d
are in parallel the voltage and consequently the speed being thus reduced.
In position III, the armatures b, b are short circuited and the field c is excited,
but in the direction for forward driving.
In this case any motion of the motor would set up a current in the armature
which would resist further motion and so act as a brake tending to stop the motor.
In position IV the direction of driving is forward but otherwise similar to II
and position V is similar to I. These give the two slowest forward driving speeds.
In position VI, both the armatures b. and the parts of the main battery
are in series, but the exciter c, e is cut out of the main circuit and forms an
independent circuit with the field. In position VII the armatures bb are in
parallel while d remain in series and the exciter ee is again introduced. In
position VIII the connections are as in VII but with the exciter ee in an indepen-
dent circuit.
In position IX, the two parts of the exciter ee are in parallel and the field is
therefore weakened, as the voltage of the exciter is not sufficient to excite the
field fully except when all its cells are in series. This position gives the highest
attainable speed, as the full voltage of the main generator is utilized the arma-
tures are in parallel and the field is reduced in strength.
In order that the cylinders ƒ and g when they are turned by the handle h may
always take such a position that the brushes & are on the contact pieces one of the
cylinders has on its axis a star wheel the teeth of which are engaged by a spring

page_text: pawl having a roller which springing in between two of the teeth of j brings
the cylinders to rest in the proper position.
Between the two cylinders are the brushes which are hinged at their lower
ends and are pressed against the two cylinders fg by the pneumatic cylinder m
which is inflated through a valve . Thus the brushes are pressed quite evenly
on the cylinders and separate springs are not required. In order to retain the
controlling commutator in the position for stopping and to prevent accidental
reversal the handle h has a spring rod o with a projection p at its lower end which
engages in a notch inside a saddle piece q which is concentric with the operating
spindle. To move the handle from this position the button at the top of the
rod o has to be pressed down.
An indicating plate is provided having on it the numbers I to IX so that the
operator can see at a glance the position of the controlling commutator.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what
I claim is: -
1. An arrangement for controlling electric motors comprising a main battery
or generator preferably in two parts, a smaller battery also preferably in two parts
for exciting the motor field, this battery when connected to the main having its
poles in opposition thereto a pair of motors or a duplex motor and a controlling
commutator for effecting various connections of the electric parts.
2. A controlling commutator comprising two cylinders geared together so
as to be simultaneously revolved, these cylinders being provided with bridging
contacts having pairs of brushes which are mounted between the cylinders pressed
against them by an inflated pneumatic tube, substantially as described.
Dated this 3rd day of February 1900.
ABEL & IMKAY,
Agents for the Applicant.