Improved Methods of and Means for Controlling Electric Motors.
Year: 1896

page_text: [Communicated from abroad by THE WESTINGHOUSE ELECTRIC AND MANUFACTUR-
ING Co., of Pittsburg, in the County of Allegheny and State of Pennsylvania,
United States of America, Manufacturers.]
Improved Methods of and Means for Controlling Electric Motors.
I, REGINALD BELFIELD, of 32, Victoria Street, in the City of Westminster,
Electrician, do hereby declare the nature of this invention to be as follows:-
This invention relates to methods of and means for controlling electric motors
and is especially applicable for use with two electric motors arranged to drive one
vehicle.
The objects of the invention are to provide methods and apparatus whereby
changes in the connections of the motors may be made quickly and effectively
without injury to the contacts by the formation of sparks at the time of changing
the connections. The invention has further objects and advantages which will be
hereinafter set forth.
The improved controllers take the form of a cylinder supported in suitable
bearings in which it can be rotated by means of a handle, various contact bars
being secured to said cylinder adapted to connect with fixed contact pieces to
which the terminals of the motors and resistances are joined. The shape, number,
and general arrangement of the contact bars on the cylinder varies according to
the method of control adopted as will be readily understood. The general method
of control is as follows. In the first working position of the controller the two
motors are in series with all the resistances, as the cylinder is turned to successive
positions the resistances are gradually cut out until the two motors are running
in series without resistance. In the next set of working positions of the cylinder,
the motors are in parallel one or more resistances being in series with each
motor separately or in series with the two motors in parallel, in the
final working position of the cylinder the two
two motors are joined in
parallel without resistance. To ensure the working positions of the cylinder
being readily found by the operator we provide a spring controlled arm
which engages in notches in a disc secured on the shaft of the controller handle
when the cylinder is in a working position but which runs on the smooth periphery
of the disc when the cylinder is in intermediate positions. When the cylinder is
being rotated from the last working position with the motors in series to the first
position with the motors in parallel we arrange that the change of connections shall
not occur suddenly but that in the intermediate positions of the cylinder, the
resistances shall first be gradually reinserted in the motor circuit, then the whole
circuit broken, and lastly the motors connected in parallel each with resistances
in series with it. Or after the reinsertion of the resistances one of the motors is
shunted by a resistance, then cut out of circuit and finally connected in parallel
with the other motor the shunting resistance being shortcircuited.

page_text: In order to avoid injurious sparks occuring at the contacts when the changes
in connection are made we provide that the fixed contacts shall be supported on a
block of magnetic material surrounded by a coil of wire which is always in the
motor circuit, the magnetic field set up at the contact preventing destructive
sparking. A construction of fixed contact which we prefer to use comprises an
arm pivoted in a cradle secured to the magnetic block aforementioned, said arm and
cradle are both of magnetic metal but the contact piece carried by the arm may
be of brass or copper or the like. A spring is provided to press the arm towards
the cylinder. A switch of any suitable construction is provided for reversing the
direction of the current through the field magnets of the motors and so reversing
the direction of rotation of the motors and it is sometimes arranged that said
reversing switch cannot be rotated unless the cylinder of the controller is in such a
position that the motor circuit is broken. It is furthermore preferred to so arrange
that the handle of the reversing switch can only be removed when the said switch
is in a position intermediate between its two working positions, that is to say when
the circuit is broken, by this means when the operator removes the handle of the
reversing switch any tampering with the controller cylinder handle will have no
effect. For a similar purpose the controller cylinder may be arranged so as to be
rotatable when the reversing switch is in one or other of its working positions, and
not when said switch is in any other position.
A plug switch is inserted in the circuit of each motor by means of which the
motor can be cut out when desired, and interlocking mechanism is preferably
arranged so that when either of the motors is cut out the handle of the controller
can only be turned to its "half speed" position, that is, to that position in which
ordinarily the two motors are joined in series without resistance. The plugs for
these switches are conveniently constructed from a cylindrical piece of metal having
a rounded end. This piece is split from the base or part nearest the handle so as
to form three separated longitudinal strips connected at their outer ends, the two
outside strips being free at their inner ends. The cylinder is now split longi-
tudinally from the outer rounded end as far as the handle, the slits being
perpendicular to those above described. The plug will now consist of nine strips
alternately united at the inner and outer ends, a form which is very compressible,
the resiliency of the metal ensuring a good electrical connection when the plug is
inserted in its socket.
Dated this fun day or September, 1896.
I, REGINALD BELFIELD, of 32, Victoria Street, in the City of Westminster,
England, Electrician, 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:-
The invention relates to methods of and means for controlling electric motors
and is especially applicable for use with two electric motors arranged to drive
one vehicle.
The objects of the invention are to provide methods and apparatus whereby
changes in the connections of the motors may be made quickly and effectively

page_text: without injury to the contacts by the formation of sparks at the time of changing
the connections. The invention has further objects and advantages which will
be hereinafter set forth.
In order that the invention may be clearly understood I will now proceed to
describe the same with reference to the accompanying drawings in which
Figure 1 is a front elevation of a controller constructed according to this
invention.
Figure 2 is a transverse section on the line - Figure 1 drawn to an enlarged
scale.
Figures 3 to 5 are views of details, and
Figures 6 to 10 are diagrams hereinafter explained.
Referring now to Figures I and 2 the controller is provided with a drum 4 of
insulating material supported in suitable bearings in which it can be rotated by
means of a handle in the usual manner. Various contact bars 110 to 119 are
secured to said cylinder adapted to connect with fixed contact pieces 143 to 153
to which the terminals of the motors and resistances are joined. In order to
minimise the spark at the contacts when the connections are altered by rotating
the drum, plates or pieces of iron 31 are interposed between the various contact
pieces 110 to 119 and the insulation of the druni 4 and the stationary contacts 143
to 153 are mounted upon an oblong iron boss 37 formed upon the base 1 of the
controller, said hoss constituting the pole or core of a magnetized coil 38. The
stationary contacts each comprise an iron base 39 and an iron extension or finger 40
pivoted thereto and extending upward along the side of the drum 4. Said finger
is provided with a copper contact shoe 41 and is pressed toward the drum by a
spring 42 the pressure of which is regulated and the position of the finger deter-
mined by a screw and nut 54. These arrangements are clearly shown in Figure 3
which is a perspective view of one of the contacts.
It will be readily understood from the foregoing description and the accom-
panying illustration that any injurious arcs which may form or tend to form
between the movable and stationary contacts upon the separation of the same will
be interrupted by the magnetic lines of force produced by the coil 18 and flowing
through the pole 37, the stationary contact lases and fingers the drum and the
base 1. By extending the magnet alongside the controller drum and utilizing
the stationary contacts as pole pieces therefor the least number of parts are
employed consistent with successful operation and at the same time a compact
arrangement of the same is secured. Furthermore by this arrangement the
magnetic lines of force are localized where they will be most effective, and an equal
magnetisation of all the contact fingers ensured. The reversing switch in this
controller is located below the drum 4 and comprises a cylinder 55 provided with
contact strips 56 to 63 co-operating with fixed contacts 70 to 77. The drum 55
is rotated when necessary through the medium of segment gears 64 and 65 the
latter of which is carried on a shaft 66 operated by a handle on its squared upper
end. The shaft 66 also carries a notched segment 68 with which a spring pawl 69
engages for the purpose of retaining the druin 55 in one of its operating positions.
78 and 79 are terminals through which connection is made hetween the reversing
switch and the stationary contacts 147 and 151 of the controller and 80 and 81
are cut out plugs either or both of which may he readily moved from their sockets
in the terminals 78 and 79, when desired in order to cut either or both of the motors
out of circuit. A suitable construction of plug for the purpose is shewn in
Figures 4 and 5 which are plan and elevation of a plug. 82 is the portion of the
plug which fits in the terminal sockets and is preferably in the form of a cylinder
having a rounded end. This cylinder is split from the base nearly to the rounded
end so as to form three separated longitudinal strips connected at their outer ends,
the outside strips being free at their inner ends, as shewn in Figure 4.1 The
middle strip is firmly seated in a suitable base or handle 83 formed of insulating
material. The metal portion 82 of the plug is also split longitudinally from the
outer or rounded end nearly to the hase or inner end into three separated strips;

page_text: the slits being at right angles to those above described. It will thus be seen that
by reason of the structure described the part 82 may be compressed sufficiently
to permit of its ready insertion into the terminal sockets, and that, when inserted,
the resiliency of the metal will serve to effect a close fit between the said parts,
thus inserting a good electrical connection.
Figure 6 shews one method of joining up the various terminals of the controller
drum to the motors and resistances, Figure 7 exhibits the various circuits which
may be formed by manipulating the controller, and Figure 8 is a diagram shew-
ing the wiring of a car having two motors with a controller at each end of the car.
The contact strips on the controller drum are denoted by the numerals 110 to 130
and the stationary contacts co-operating therewith are denoted by the numerals 143
to 153. 85 represents the conductor through which the current is led into the
apparatus. 86 is a safety fuse block, 87 a lightning arrester, 88 the ground
connection 91 and 92 rheostats each divided into two separate sections so that the
whole or a part only of the resistance may be included in the circuit as desired.
Assuming now that the right hand controller of Figure 8 is being operated the
connections and changes will be as follows, the various positions of the controller
drum being denoted by reference to Figure 6.
Assuming that the stationary contacts 70, 71, 72, and 73 of the reversing switch
are resting upon the contacts 56, 57, 58 and 59, and that the contacts 74, 75, 76,
and 77 are resting upon the contacts 60, 61, 62, and 63, in the first position of
the controller drum designated as a, the circuit will be through contacts 143, 110,
111, 144, 148, 115, 112 and 145 to the rheostat 91, through both resistances to
contact 147, through terminals 78 and plug 80 and contacts 74, 60, 62, and 76
of the reversing switch to motor 89, through the motor field magnets to contact 75,
through contacts 61, 63, and 77 of the reversing switch, through the armature of
the motor 89 to contact 152, through contacts 119, 116, and 149 to rheostat 92,
through both resistances to contact 151, through the terminals 79 and plug 81
and contacts 70, 56, 57, and 71 of the reversing switch, through the field magnets
of motor 90 to and through contacts 72, 58, 59 and 73 of the reversing switch, to
and through the armature of motor 90 to the ground.
In the position of the controller drum designated by bit will be readily seen
that the circuits are the same as those in the position a except that a portion of
the resistance in each of the rheostats 91 and 92 is cut out, leaving the remaining
resistances and the two motors in series.
In position e both rheostats are entirely cut out, thus leaving the two motors in
series without resistance.
In position d the circuits are the same as in position b, and in position e
are the same as in position a.
they
In the next two positions of the controller drum, not designated by letters of
reference, the entire circuit is broken, both motors and rheostat being cut-out.
In position f the two motors are placed in parallel, the resistance of rheostat 91
being in series with motor 89 and those of rheostat 92 in series with motor 90.
In position g, the motors are also in parallel, a part of the resistance of each rheostat
being cut out, and in position h the motors are placed in parallel with all of the
resistance cut out.
The circuits, when motor 90 is cut out from the removal of plug 80 from
terminals 79 are as follows:--Starting when the stationary contacts are in
position f on the controller drum, the circuit is so completed through contacts 143,
120, 122, and 145, rheostat 91, contacts 147, terminals 78 and plug 80, reversing
switch contacts 74, 60, 62, and 76, the motor field magnet, reversing switch
contacts 75, 61, 63, and 77, the motor armature, and contacts 152, 129, 130 and 153
to the ground. In position g a portion of the resistance of rheostat 91 is cut out
and in position h the motor is in circuit without resistance.
If the motor 89 be cut out by removing the plug 80 from terminals 78, and the
controller he moved through the positions above described, the circuit will be
first through the entire resistance of rheostat 92 and motor 90, second through a

page_text: 5
ortion of the resistance and the motor, and third, through the motor without
sistance, as will be readily seen without tracing the circuits in detail.
It is to be observed that in each position of the controller cylinder except of
ourse when the circuit is entirely broken, the current passes through the magnet
It will be readily understood without"
oil 38 before entering the controller.
racing the circuits and connections in detail that if the drum of the reversing
witch be rotated so that the contacts 74 to 7 rest upon the contacts 56 to 59,
nd the contacts 70 to 73 rest upon contacts 60 to 63, the direction of rotation of
he motor armature will be in the opposite direction from that herein before
escribed.
Figure 9 is a diagram shewing a different arrangement of contact strips on the
ontroller drum 4 said strips being designated by the numbers 178 to 195, and
Figure 10 is a diagram shewing the various circuits formed when the controller
Irum is rotated. The rheostat 92 is formed of one section only instead of two
as in the armature first described. The various positions of the controller drum
with reference to the stationary contacts 167 to 177 being as before represented
by letters a, b, c, d, e, f, and g it will be seena that in the position of the con-
roller, the circuit will be through contacts 167, 178, 179, and 168, resistance 91,
contacts 170 and 171, motor 89, resistance 92, contacts 176, 195, 193, 174, 172, 191,
192, and 173 and motor 90 to the ground. Without tracing the currents in detail for
the remaining positions of the contacts, it will be readily seen that the following
combinations will occur. In position &, resistance 92 is cut-out, leaving the other
two resistances and the motors in series. In the position call the resistances are
cut out, leaving the two motors in series. In the position designated by d the
following changes occur: first, the motors end part of resistance 91 are in series:
second, the motors and whole of resistances 91 are in series; third, resistance 91
and motor 89 are in series and motor 90 is shunted through resistance 92; and
fourth, all the resistance and motor 89 are in series, motor 90 being cut-out; these
changes are made very rapidly. In position e resistance 91 is in circuit, resist-
ance 92 is cut out, and the motors are in parallel.. In position f the motors are in
parallel and a portion of resistance 91 in circuit. In position g, the motors are in
parallel without resistance.
I am aware that various methods of controlling two motors in a somewhat similar
manner to those above described have been suggested and it will be understood
that the present invention is limited to the method above described although the
specific details of construction may be varied.
By the methods of control set forth above the desired change from series to
parallel connection is made quickly without causing a sudden and violent change
in the speed of the car which is liable to occur if the connections are not properly
arranged.
The methods also obviate to a considerable degree the formation of arcs at the
contacts when they are separated.
Having now particularly described and ascertained the nature of the said
invention, and in what manner the same is to be performed as communicated to
me by my foreign correspondents I declare that what I claim is:-
1. For electric motors, a controller having the fixed contacts mounted upon the
core of an electro-magnet which is always in circuit when the motors are running
the supports for the said fixed contacts being magnetic and forming the pole
pieces of the electro-magnet, as described with reference to Figures 1 and 2 of
the accompanying drawings.
2. For controllers, fixed contacts constructed substantially as described with
reference to Figure 3 of the accompanying drawings for the purpose specified.
3. For electric plug switches, a plug constructed substantially as described with
reference to Figures 4 and 5 of the accompanying drawings.
4. The method of controlling electric motors which consist in making the

page_text: changes in the circuit as described with reference to Figure 6 to 8 or to Figures 9
and 10 of the accompanying drawings.
5. For electric motors, controllers having movable contact strips and fixed
contacts arranged to co-operate as shewn and described with reference to either
Figures 6 to 8 or to Figures 9 and 10 of the accompanying drawings.
Dated the 8 day of June.
2.
W. P. THOMPSON & Co.,
Of London, Liverpool, Manchester and Birmingham,
Patent Agents for the Applicant.