Apparatus for Varying the Speed of Electromotors.
Year: 1896

page_text: Apparatus for Varying the Speed of Electromotors.
I, CHARLES DENTON ABEL, of No. 28 Southampton Buildings, Chancery Lane,
in the County of London, Consulting Engineer, and Chartered Patent Agent,
do hereby declare the nature of this invention (communicated to me from abroad
by Berliner Maschinenbau-Actien Gesellschaft vormals L, Schwartz Kopff of
Berlin, in the German Empire) to be as follows:-
This invention relates to apparatus for varying the speed of electromotors.
The invention consists in certain connections of switchers and resistances, which
make it possible to alter the number of active windings on the armature of the
motor, without throwing it out of connection with the source of electricity by which
it is being driven.
In the accompanying drawings, Figure 1 is a diagram showing the general
arrangement forming the subject of this invention; Figures 2 and 3 are diagrams
of different connections illustrating the working of the arrangement.
In Figure 1, C is the core of the armature of an electromotor, A1 and A2 are
two armature windings, both preferably wound upon one and the same core C.
The ends of both armature windings are carried out to separate commutators C¹
and C. B and B are binding posts supposed to be connected with a source of
electricity, such as for instance, a main carrying the necessary working current
generated in a central station. M is the winding of the electro-magnet repre-
sented in the diagrams to be simply connected as a shunt winding that is placed
between the binding posts B1 and B2, but it should be understood that if in any
special case it should appear desirable to vary the excitation of the electromagnet,
a special rheostat would be inserted in any usual way together with the winding M,
or else the winding M would be divided into a number of sections, which could be
partly thrown out of connection so as to vary the number of the windings.
R is a rheostat, provided in the usual way with a lever i. The diagrams 2 and 3
show the way in which the rheostat R and the motor are connected. All the
letters of reference correspond to the letters of reference in the more detailed
diagram Figure 1, 1, 2, 3, 4 and 5 being resistances inserted between the
contact buttons of the rheostat R.
Arrangements have become known by which the speed of an electromotor can
be varied by employing more than one complete winding on the armature, thus
for instance, the arrangement described in the German patent No. 78789, of my
correspondents, but these arrangements imply that the motor must be thrown out
of connection every time an alteration of its speed is to be effected.
By the present arrangement all possible variations of speed can be effected
while the motor is working. In Figures 2 and 3 a constant pressure is supposed
to be acting between the two conductors B1 and B. In Figure 2 the armature
winding connected to the commutator C¹ is supposed to have twice as many turns
as the winding connected to the commutator C, but it should be understood that

page_text: the ratio between the numbers of turns of the two windings can be given any other
suitable quantity.
In the position shown in the diagram Figure 2, both armatures C and C³
are out of connection. When the motor is to be started, the lever i is moved from
right to left. As soon as it reaches the contact button 2, it will be seen that both
armature-windings are now inserted between the conductors B and B in series,
the resistances we likewise being placed in series between them. Thus the motor
will be started in the usual way by gradually moving the lever i to the left and
thereby throwing out the resistances we'. When the lever has reached the contact
button 4 the whole of the resistance is out of connection and the motor will now
normally run at its lowest speed. To increase the speed the lever i is moved
further to the left. When it reaches the contact button 5, the resistance wis
placed between the two armatures. This part of the operation however is of no
importance when the lever is being moved from right to left. The
importance of the resistance we only comes into play when the speed of the motor
is to be lowered by moving the lever i from left to right. Going on to button 6
it will be seen that now only the armature connected to the commutator C¹
remains in connection, the armature connected to the commutator C3 being
altogether thrown out. As, according to the assumption made above, the armature
connected to the commutator C₁ posseses double the number of windings as com-
pared with the armature connected with the commutator C3, and as the speed of the
imotor will vary inversely as the number of active windings on the armature, the
speed now obtained will be one and a half times greater than the speed originally,
but for the resistance w³ which still remains inserted in series with the armature
connected to the commutator C¹. By continuing the leftward motion of the
lever i, the resistance w³ is gradually thrown out, until the lever i reaches the
contact button 8, when the motor will run normally at the speed 1.5, assuming
the original speed to be 1. As the leftward motion of the lever i continues, the
armature connected with the commutator C¹ is thrown out in its turn, and the
armature connected with the commutator C is inserted instead. Again a resis-
tance, namely, is placed in series with it to avoid the shock resulting from the
alteration of speed, and by continuing the leftward motion of the lever again,
this resistance is gradually thrown out until contact button 11 is reached, when
only the armature winding connected with commutator C remains inserted, and
the motor now runs normally at the speed 3.
In order to decrease the speed, the whole operation is simply reversed by turning
the lever i from left to right. When this is done, however, it will be perceived
that a shock would occur every time an alteration in the number of active windings
inserted takes place, if the resistances w and we were not provided. Even if the
resistances w5 and 3 were proportioned in such a way that the transition from the
employment of a lower number of active windings to a higher did not cause a
jump in the speed of the motor, nevertheless, a shock would take place, because the
potential difference acting on the motor would be suddenly increased, thus suddenly
causing a serious increase of current. This is the reason why the resistances w
and are provided and this is the main feature by means of which this invention
constitutes an improvement over similar arrangements hitherto employed and by
which is obtained the possibility of varying the speed of a motor without throwing
it out of connection.
Figure 3 shows a somewhat simpler arrangement which can be employed when
only one variation of speed is required. In that case both armature windings
connected with the commutators C and C are provided with the same number of
turns, and by the movement of the lever i from right to left, first both armature
windings are connected in series and when the lever progresses from contact
button 6 to contact button 7, the armature-winding connected to commutator C
is thrown out of connection and consequently the speed of the motor varies from
1 to 2, allowing for the variable resistance 1. In fact, the whole arrangement
shown in Figure 3 is substantially identical with the arrangement shown in

page_text: Figure 2 with the exception that the resistances w and w³ with their contact
buttons are left out.
Dated this 10th dor of Ontaiha1000
ABEL & IMRAY,
Agents for the Applicant.
Apparatus for Varying the Speed of Electromotors.
I, CHARLES DENTON ABEL, of No. 28 Southampton Buildings, Chancery Lane,
in the County of London, Consulting Engineer, and Chartered Patent Agent,
do hereby declare the nature of this invention (which has been communicated to
me from abroad by Berliner Maschinenbau-Actien Gesellschaft vormals] L.
Schwartzkopff, of Berlin, in the German Empire) 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 apparatus for varying the speed of electromotors.
The invention consists in certain connections of switchers and resistances, which
make it possible to alter the number of active windings on the armature of the
motor, without throwing it out of connection with the source of electricity by which
it is being driven.
In the drawings accompanying my provisional specification, Figure 1 is a
diagram showing the general arrangement forming the subject of this invention;
Figures 2 and 3 are diagrams of different connections illustrating the working
of the arrangement.
In Figure 1, C is the core of the armature of an electromotor, A¹ and A2 are two
armature windings, both preferably wound upon one and the same core C. The
ends of both armature windings are carried out to separate commutators C and C³.
B1 and B2 are binding posts supposed to be connected with a source of electricity,
such as for instance, a main carrying the necessary working current generated in
a central station. M is the winding of the electro-magnet represented in the
diagrams to be simply connected as a shunt winding that is placed between the
binding posts B1 and B2, but it should be understood that if in any special case
it should appear desirable to vary the excitation of the electromagnet, a special
rheostat would be inserted in any usual way together with the winding M, or
else the winding M would be divided into a number of sections, which would be
partly thrown out of connection so as to vary the number of the windings.
All
R is a rheostat, provided in the usual way with a lever i. The diagrams 2
and 3 show the way in which the rheostat R and the motor are connected.
the letters of reference correspond to the letters of reference in the more detailed
diagram Figure 1, 201, 202, 203, and w being resistances inserted between the
contact buttons of the rheostat R.
Arrangements have become known by which the speed of an electromotor can
be varied by employing more than one complete winding of the armature described
in the German Patent No. 78789, of my correspondents, but these arrangements
imply that the motor must be thrown out of connection every time that an altera-
tion of its speed is to be effected.
By the present arrangement all possible variations of speed can be effected
while the motor is working. In Figures 2 and 3 a constant pressure is supposed
to be acting between the two conductors B' and B. In Figure 2 the armature
winding connected to the commutator C is supposed to have twice as many turns
as the winding connected to the commutator C, but it should be understood that

page_text: the ratio between the numbers of turns of the two windings can be given any other
suitable quantity.
In the position shown in the diagram Figure 2, both armatures C¹ and Care
out of connection. When the motor is to be started, the lever i is moved from
right to left. As soon as it reaches the contact button 2, it will be seen that both
armature-windings are now inserted between the conductors B and B in series,
the resistances we likewise being placed in series between them. Thus the motor
will be started in the usual way by gradually moving the lever i to the left and
thereby throwing out the resistances 10. When the lever has reached the contact
button 4 the whole of the resistance is out of connection and the motor will now
normally run at its lowest speed. To increase the speed the lever i is moved
further to the left. When it reaches the contact button 5, the resistance w³ is
placed between the two armatures. This part of the operation however is of no
importance when the lever i is being moved from right to left. The importance
of the resistance to only comes into play when the speed of the motor is to be
lowered by moving the lever i from left to right. Going on to button 6 it will be
seen that now only the armature connected to the commutator C¹ remains in
connection with the armature connected to the commutator C being altogether
thrown out. As, according to the assumption made above, the armature connected
to the commutator C possesses double the number of windings as compared with
the armature connected with the commutator C3, and as the speed of the motor
will vary inversely as the number of active windings on the armature, the speed
now obtained will be one and a half times greater than the speed originally, but
for the resistance w3 which still remains inserted in series with the armature
connected with the commutator C. By continuing the leftward motion of the
lever, the resistance 1 is gradually thrown out, until the lever i reaches the
contact button 8, when the motor will run normally at the speed 1.5, assuming
the original speed to be 1. As the leftward motion of the lever i continues, the
armature connected with the commutator C2 is inserted instead. Again a resis
armature connected with the commutator C is thrown out, in its turn, and the
tance, namely, wo is placed in series with it to avoid the shock resulting from the
alteration of speed, and by continuing the leftward motion of the lever again,
this resistance is gradually thrown out until contact button 11 is reached, when
only the armature windings connected with the commutator C³ remains inserted,
ar the motor now runs normally at the speed 3.
In order to decrease the speed, the whole operation is simply reversed by turn-
ing the lever i from left to right. When this is done, however, it will be perceived
that a shock would occur every time an alteration in the number of active windings
inserted takes place, if the resistances and 10 were not provided. Even if the
resistances to and w³ were proportioned in such a way that the transition from the
employment of a lower number of active windings to a higher did not cause a
jump in the speed of the motor, nevertheless, a shock would take place, because the
tential difference acting on the motor would be suddenly increased, thus suddenly
causing a serious increase of current. This is the reason why the resistances 203
and ware provided and this is the main feature by means of which this invention
constitutes an improvement over similar arrangements hitherto employed and
by which is obtained the possibility of varying the speed of a motor without throw
ing it out of connection."
Figure 3-shows a somewhat simpler arrangement which can be employed when
only one variation of speed is required. In that case both armature windings
connected with the commutators C and C are provided with the same number
of turns, and by the movement of the lever i from right to left, first both armature
windings are connected in series and when the lever progresses from contact
button 6 to contact button 7, the armature winding connected to commutator C
is thrown out of connection and consequently the speed of the motor varies from 1
to 2, allowing for the variable resistance . In fact, the whole arrangement
shown in Figure 3 is substantially identical with the arrangement shown in

page_text: Figure 2 with the exception that the resistances w and w5 with their contact
buttons are left out.
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. In apparatus for varying the speed of electromotors, the combination of
several separate armature windings preferably wound on one core, with separate
commutators connected to the respective armature windings, a switch for placing
one or more of the armature windings in circuit with the source of electricity
and resistances so arranged as to be inserted in series with the motor at every
transition from an armature winding containing a lower number of turns to an
armature winding containing a higher number of turns, substantially as and
for the purpose set forth.
2. In apparatus for varying the speed of electromotors, the combination of
several separate armature windings preferably wound on one core, with separate
commutators connected to the respective armature windings, and a controllable
rheostat provided with the usual switching arrangements for placing one or more
of the said armature windings in circuit with the source of electricity, and also
having resistances so arranged as to be inserted in series with the motor at every
transition from an armature winding containing a lower number of turns to an
armature winding containing a higher number of turns, substantially as and for
the purpose set forth.
D1 1 0 1 1 of T..l.. 1907
ABEL & IMRAY,
Agents for the Applicant.