Improvements in Methods of and Means for Regulating the Speed of Continuous Current Motors.
Year: 1895

page_text: Date of Application, 11th July, 1895-Accepted, 17th Aug., 1895
COMPLETE SPECIFICATION.
Improvements in Methods of and Means for Regulating the Speed
of Continuous Current Motors.
I, JAMES DEVONSHIRE, Secretary to The British Thomson-Houston, Limited,
of 38, Parliament Street, Westminster, in the County of Middlesex, (a communi-
cation to me from abroad from Merle J. Wightman, of Scranton, County of
Lackawanna, State of Pennsylvania, United States of America, 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 methods of and means for regulating the speed of
continuous current motors, particularly to such motors of the railway type; and
has for its object to provide such a method and means for regulating single motors
of the type described in a manner analogous to that used for regulating two or
more motors, now commonly known in the art as the "series-parallel " system of
control. To effect the purposes of my invention, I embrace also the principle of
changing the magnetic circuit of the motor; that is to say, I permute the number
of poles so that the motor is changed from a two-pole to a four-pole motor and
vice-versa, to obtain variations of speed and torque. The method which I have
devised consists briefly in first operating the motor as a two-pole motor with the
two halves of its armature running in series, and then, by the interposition of
suitable resistance in combination with a shunt around one-half of the motor,
changing this arrangement to one in which the motor operates as a four-pole motor,
with the two halves of its armature in multiple. The particular series of steps
which I have devised will be more fully pointed out hereinafter.
The accompanying drawings show, in Fig. 1, diagrammatic representations of
the motor and controller designed to effect the combinations of my improved method,
while Fig. 2 shows, in diagrams a to h, the particular combinations effected by the
controller and motor.
In Fig. 1, A is the armature of the motor, the two halves of which are treated
herein as separate structures for the purposes of illustration, and are lettered
respectively A1 and A2. B¹ to B are the brushes applied to the commutator ;
B', B being two brushes which are always active, and B2, B4 being those used
as negative brushes when the motor is operated as a four-pole machine. P¹ to P⭑
are the field-magnet poles, two of which are wound poles and two unwound or
consequent poles. The direction of winding upon the poles P³, P is so selected
that when the current passes in series through the two halves of the armature,
both of these poles are magnetized in the same sense, either north or south, as may
be selected. The two upper poles P1, P2 are then of consequent and opposite
polarity to the two lower ones; when the current, however, is reversed in the
pole P³, as presently to be described, this pole becomes of opposite polarity to P*,
and the four poles then alternate in polarity around the armature, converting
the motor into a four-pole motor. At this time the brushes B², B* become
active, having been open-circuited before. A suitable resistance R is provided,
and furnishes further means of regulating the speed and torque, as well as
preventing undue sparking or other trouble incident to the changes of connections.
K is the controller, the cylindrical contacts of which are shown developed in plane.
The controller is provided with contacts C, D, E, F, H, and I, and with certain
cross-connections, and also with fixed contacts or brushes 1 to 7. The dotted lines

page_text: represent the different working positions of the controller, corresponding to the
diagrams a to h in Fig. 2.
The paths of the current through the controller and motor as just described, are
as follows Beginning in position a, the current passes from the trolley T to the
contact 1, thence to contact-plate C, thence to the contact 2, through the
resistance R to the lead 8 around the field-magnet pole P4, to the brush B', through
the armature, out at the brush B³, around the field-magnet pole P³, by the lead 10
to the contact 6, to contact-plate I, to contact 7 and out to ground at G. This.
position is illustrated in diagram a of Fig. 2, in which the two halves of the
armature are indicated at A1, A2 respectively, the same notation being used through
the series of diagrams. The only change made in diagrams b and c is that in
diagram ba part of the resistance is cut out, and in diagram c, it is entirely short-
circuited, so that the motor is running as an ordinary bi-polar motor with no
resistance in circuit. This is a running position, it being understood that those
positions marked RP are running positions, and that the others are only to be
used while the motor is changing its speed. In position d, indicated in diagram d,
a shunt is thrown around one-half of the motor, the half-armature A2 and pole. P³
of the field-magnet being shunted. In this position the paths of the current are
as follows: Entering from the trolley, to the contact 1, to contact-plate C, thence
through the resistance to the lead 8, around the pole P₁ to the brush B', out at
brush B or B', to the contact 5, to contact-plate E, by cross-connection to contact-
plate I, to contact 7 and out to ground at G. The current also divides in the
armature, and passes out at the brush B³, around the pole P³, to contact 6, which
still touches the contact-plate I, thence to contact 7 and out at ground. As pointed
out, this forms a shunt around one-half of the motor. In position e, the brush or
contact 6 connected to the pole P³ is open-circuited, the path of the current
remaining otherwise as before, and is as indicated in diagram e. In position f
indicated in diagram f, the two halves of the motor are in multiple with the
resistance in series on both halves. In this case the path of the current is from
the trolley in contact-plate C, thence through the resistance to the lead 8, around
the field-magnet pole P4 to the brush B', thence out at the brush B2 or .B*, to the
brush 5, to contact-plate E, contact-plate I, brush 7 and ground. The current
also. passes from the lead 8 to the brush 4, to contact-plate D, by cross-connection
to contact-plate F, to the brush 6, around the pole P³, to the brush B³,.. and
through. the armature to the brush B or the brush B³, depending upon the
direction of rotation. At this step the direction of the current through the
winding of the pole P³ is opposite to that in which it first passed around that pole ;
the pole is consequently magnetized in the opposite sense, and the motor becomes a
four-pole. machine. The subsequent steps, illustrated in diagrams 9 and h, are
resistance steps merely, until, in position h, the resistance is cut out, and the normal
speed of the motor operating with four poles, is attained.
The contact-plates E, I, and C, of the controller are so shaped that the
resistance is all cut in immediately before the change at the fourth step; while, in
rotating the controller backward, the shape of the plate C is such that the
resistance is cut in in a series of steps, in order to avoid burning the contact
fingers by cutting it in in too great an amount at once.
The method which I have devised, as above pointed out, is one well adapted to
single motor equipments in railway work, or other single motor apparatus, and by
its use a saving of current and power is effected.
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. The method of regulating an electric motor herein set out, which consists in
starting the motor as a two-pole motor, then changing it to a four-pole machine by
shunting a portion of the motor, and then throwing the parts of the armature,
winding into multiple and running the motor as a four-pole motor.

page_text: 2. The method of running an electric motor herein set out, which consists in
starting the motor with the two halves of its armature in series with a resistance
in a two-pole field, then gradually cutting out the resistance, then including the
resistance and shunting one-half the motor, then opening the circuit of the shunted
half and throwing the two halves of the motor in multiple in a four-pole field, and
finally, cutting out the resistance.
3. The method of operating an electric motor herein set out, which consists in
changing the armature connections from series to multiple, then shunting part of
the motor and at the same time changing the magnetic field of the motor from
two-pole to four-pole.
4. The method of operating an electric motor herein set out, which consists in
changing the armature connections from series to multiple, then shunting a part
of the motor and simultaneously or successively commuting the field poles.
5. The method of operating an electric motor herein set out, which consists in
changing the armature connections from series to multiple, then shunting a part of
the motor, simultaneously or successively commuting the field poles, and including
a resistance in the circuit while making changes of connection.
6. The method of operating an electric motor herein set out, which consists in
changing the armature connections from series to multiple and changing the field
from a two-pole to a four-pole by shunting part of the motor, including a resistance
while making the changes of connection, and gradually withdrawing the resistance
until the motor is running without resistance in circuit.
7. The method of operating an electric motor herein set out, which consists in
starting the motor in a two-pole field with its armature winding in series, with a
resistance in circuit, and then cutting out the resistance gradually, then reinserting
the resistance and closing the circuit around one-half of the motor, then opening
the circuit of the shunted half, then throwing the two halves of the motor in
multiple, at the same time converting the motor into a four-pole machine, and then
gradually cutting out the resistance.
8. In combination, an electric motor provided with a plurality of field poles,
switching mechanism adapted to change the connections of the armature, to
commute the field poles, and to shunt a part of the motor while making such
changes.
9. In combination, an electric motor provided with a plurality of field poles,
switching mechanism adapted to change the armature connections from series to
multiple or vice-versa, commuting the field poles of the motor, to shunt a part of
the motor while making the connections, and to include a resistance in the circuit
or cutting it out.
10. In combination, an electric motor provided with four field-magnet poles, a
switching mechanism adapted to change the armature connections from series to
multiple, to shunt part of the motor while effecting such change, to commute the
field-magnet from two-pole to four-pole or vice-versa, and to include a resistance in
the circuit while making such changes and to cut it out gradually when the changes
are completed.