Improvements in Controllers for Electric Motors.
Year: 1898

page_text: Date of Application, 20th Sept., 1898-Accepted, 19th Nov., 1898
COMPLETE SPECIFICATION.
Improvements in Controllers for Electric Motors.
We, THE BRITISH THOMSON-HOUSTON COMPANY, LIMITED, of 83, Cannon Street,
in the City of London, Electrical Engineers, do hereby declare the nature of this
invention (which has been communicated to us from abroad by Frank E. Case,
residing at Schenectady, County of Schnectady, State of New York, United
States of America, Electrical Engineer), and in what manner the same is to be
performed to be particularly described and ascertained in and by the following
statement:-
The present invention relates to controllers for electric motors, it has for its
object to avoid a difficulty which sometimes arises with controllers controlling a
number of motors usually propelling a car or train, which may be grouped in
different combinations in series or parallel for the purpose of changing the speed
an torque, in well known ways. With all such devices it is important to provide
cut-out switches by which any particular motor may be taken out of circuit in
case of accident. To cut out a particular motor however may under some circum-
stances make it difficult or impracticable to regulate the remaining motors by
the series parallel method. To avoid this difficulty, it has been proposed to
operate the motors in pairs which are treated as units; assuming for instance,
that there are two pairs of motors, the pairs would be coupled in series, so that
the motors would really be in series parallel combination, and latter they would
be connected in parallel; with this arrangement, when one motor was cut out,
the connections were so arranged that a corresponding motor of the other pair
would also be cut out, thus in the case assumed, dividing the propelling power
by two and perhaps overloading the remaining motors. In modern developments
it is desirable to keep all the motors in service as far as possible, so as quickly
accelerate the car or train, particularly in high-speed inter-urban, suburban, or
trunk line services where practically it is necessary to keep in circuit every motor
possible. This, however, with the motors arranged in pairs in the way pointed
out, renders impracticable to regulate them by the series parallel method, as
the groups would be thrown out of balance. The apparatus employed is therefore
so arranged that whenever the cut-out switch of any one motor is thrown to
disconnect it from the line, the connections are so changed that all the remaining
motors will be connected in parallel and will be regulated by resistance control.
In the accompanying drawings is illustrated a controller with its connections,
by which the result indicated may be attained. The controller is adapted for
four motors but it is within the scope of the invention to use more than this
number. They may, as already pointed out, drive the different axles of a truck,
car or train, or they may be connected in any way to a common load, or be
The necessary
simultaneously running in any relation and for any reason.
arrangements to adapt the apparatus to other numbers of motors will be readily
understood.
In the drawings Fig. 1 is a development of a controller, with the motors shown
diagrammatically, and cut out switches for each motor, a reversing switch being

page_text: also provided, as is customary. Fig. 2 shows the groupings motors in the series
position of the controller, Fig. 2 showing the grouping conventially. Fig. 3
shows the arrangement with one motor cut-out, Fig. 3 showing the grouping
arranged in the simplest form.
In Fig. 1 the controller contacts are developed in plane at K, K. It is to be
understood that a cylindrical switch is used, with contacts on opposite sides of
the cylinder, and two rows of brushes numbered respectively from 1 to 8, and
from 9 to 15. The various contacts of the controller are correspondingly num-
bered 1ª, etc. Resistances R¹ to R8 are also indicated, which are connected in
multiple so that, as each resistance is cut in, the current carrying capacity will
be increased, as is customary in controlling devices where motors taking large
currents are employed. Motors A¹, A³ are connected as one pair, A2, A4 as
another; the preferred arrangement being that one motor of each group shall
be on different trucks of the train or car, so that as many trucks as possible
shall be kept available in case of accident, so as to obtain maximum traction.
The motor armatures and fields are represented. at A¹, FI, etc. Cut-out switches COL
to CO are also indicated; these are three-blade switches, the third blade of
which opens or closes a connection D, for a purpose presently pointed out. By
throwing one of the switches, its corresponding motor is cut out at both ends,
so that it may be handled without danger. In the first position of the controller,
one of the resistances R is in circuit, and the motors are coupled in pairs, the
pairs being in series. This is the arrangement shown in Fig. 2 and Fig. 2.
As the controller is rotated additional resistances are included, until when con-
tacts 9, 10 reach the respective contacts 9", 10", a short-circuit is thrown around
the resistances, so that the motors act in series multiple without resistance. When
the contact 8 touches contact 8, it will be found that a shunt is thrown around
the second pair of motors, which are then momentarily disconnected as the con-
tact 7 passes off the contact 7, and finally reconnected in multiple with the first
pair when contact 15 touches contact 15b, this being a well known way of effecting
the change from series to multiple. It will be perceived that the part of the
switch shown on the left makes its contacts immediately after they are made on
the part of the switch shown on the right. For instance, contact 3 first touches
the contact 3"; immediately afterwards contact 11 touches contact 11, then
contacts 4 and 12 and so on; this arrangement separates contacts carrying current,
so that the circuit is not broken at adjacent ones, thus preventing short circuiting,
which some large currents might occasion. The heavy contacts at the top of
the controller are for carrying full current direct from the trolley, and the next
adjacent contacts 10", 2ª, etc., are arranged to break the circuit after it is broken
on the larger contacts, and after resistance greater or less as may be required,
is inserted. In general resistances are used whenever the circuit connections
are to be shifted, or minor speed changes made, as is now well understood in the
art.
The circuit in the first position of the controller, with the cut-out switches in
the position shown, is as follows: starting from the trolley T, representing any
connection with a suitable source of current, contact 2 first touches
contact 2, thus bridging the gay between its two parts; current then flows to
all of the resistances but as contact 3 is the only resistance terminal the circuit
of which is completed, it can pass only through the first section R¹ of resistance.
It passes from there by the cross-connection shown to the blade B¹ of the cut-out
switch CO¹, thence to contact 19 on the reversing switch, to contact 18, to arma-
ture A¹, to contact 17, contact 16, through field F¹, across the blade B³ of the
switch CO¹, to the lead E. From the trolley lead, before it reaches the cut-out
switch CO¹, a tap passes from the point y across the blade B of the cut-out
switch CO³, to contact 20 upon the reversing switch, contact 21, to armature A³,
contact 22, contact 23, through field F3, across the blade B³ of the cut-out
switch C03, to the lead E, thence across the blade B2 of the cut-out switch CO,

page_text: and by the lead D back to the controller, to contact 7; and from this contact
the connection passes to blades B₁ on the respective cut-out switches CO2 and CO+;
from the switch CO2 the circuit leads to contact 27 on the reversing switch,
contact 26, through armature A2, contact 25, contact 24, through field F³, to
the lead H.
From the switch CO the circuit is to contact 28 on the reversing switch,
contact 29, through armature A, contact 30, contact 31, through field F and
thus to the lead H at the point x. The lead H is grounded at G, being the
ordinary ground wire of the controller. This is the combination shown in Figs. 2
and 2, except of course the resistance is included and cut-in or out by the
revolution of the controller in the usual way. It is unnecessary to trace the other
circuits.
:
Let us
now assume that cut-out switch CO) is thrown to the dotted line
position this will open the circuit of the lead 1) and will take the blades B¹, B³
of the switch from the contacts a, b and place them in the contacts d, c.
will be the combination shown in Fig. 3, and still more simply in Fig. 3.
This
Starting as before at the trolley, and passing to contact 3, through the resis-
tance R', current then passes down to the point y as before, across blade B¹ of
the switch CO3, through contacts 20 and 21 an the reversing switch to the
armature A3, contacts 22 and 23, through the field F3, across blade B33 of the
cut-out switch CO³, thence to the left, to contact c on the cut-out switch CO¹
(the blade 133 of that switch being now in its dotted line position), and thence
to the conductor H and to ground. Returning to the point y, current passes
to the left and so by the blade B on the switch CO to contact ; thence to
the point z, passing across the blade B¹ of the cut-out switch CO2, contacts 27
and 26, through armature A2, contacts 25 and 24, through the field F2, across
blade B3 of the cut-out switch CO2, to conductor H, and to ground.
From z current passes to the left, to the point w, thence through the switch CO
at the blade B¹, contacts 28 and 29, armature A+, contacts 30 and 31, field F,
across the blade B3 of switch CO+, conductor H and to ground.
The office of the middle blade in each of the cut-out switches is to open the
conductor D; it will be found by inspection that if any one of these switches
be thrown to the dotted line position, like the switch CO¹, the others of course
remaining closed, a similar set of connections to that just described will be made,
so that any one of the motors will, by its corresponding cut-out switch, be open-
circuited at both ends, and the other three motors shown be connected in parallel;
similarly, if any two of the motors be cut-out, the remaining two will be con-
nected in parallel; while if three should be cut-out, the controller would operate
as a resistance controller to regulate the remaining motor. It is unnecessary
to trace the circuits for the several combinations, as they will be readily apparent.
Any arrangement of cut-out switches which will act to so change the connec-
tions of a number of motors that those not cut-out will be coupled only in parallel
by throwing the cut-outs, whereas before they could be run both in series and
parallel, will be considered within the scope of the present invention. The
swiches may embrace in a single piece of apparatus the necessary contacts, fixed
and movable, as in Fig. 1 or two or more switches may be used, as in Figs. 2
and 3; changes in design or arrangement would not effect the essence of the
invention.
Having now particularly described and ascertained the nature of our said
invention (as communicated to us from abroad) and in what manner the same
is to be performed, we declare that what we claim is:--
1-The combination of four or more electric motors, a switch for operating
the motors in series or parallel as may be desired, and cut-out switches, one
for each motor, the combination of contacts and connections being such that when
the cut-out switch for any motor is operated, the remaining motors will be
operated only in parallel.

page_text: 2 The combination of a number of motors, a switch for operating the motors
in pairs in series or in parallel and for cutting in and out resistances in any
desired manner in affecting the changes in speed or connection, and a cut-out
switch for each motor; the contacts and connection being so arranged that when
any of the cut-out switches is operated, the remaining motors will be connected
only in parallel and be regulated by the resistance steps of the controller.
3-The combination of a number of motors driving a common load, a switch for
operating the motors in series or in parallel as desired, cut-out switches for each
motor, and contacts and connections arranged to be so changed by throwing any
cut-out switch that the motors not cut out are operated only in parallel.
4 The combination of a number of motors operatively connected to the axles
of a truck, car or train, a controlling device operating the motors in pairs in
series or in parallel, and cutting in or out suitable resistance in affecting changes
of speed, with cut-out switches, one for each motor, the contacts and connections
of which are arranged to throw the remaining motors in parallel with each other
and in series with the resistance upon the operation of any of the cut out switches.
5 In a controller for electric motors operated in pairs in series and parallel,
three-blade cutout switches for each motor, two of the blades of which shift
the motor connections, and the third blade of which opens a connection common
to all the switches as described.
6 In a controller for electric motors operating them in pairs in series or in
parallel, three-blade cut-out switches for each motor, the outer blades of which
shift the motor connections so that the motor corresponding to any switch operated
is cut out at both ends, and the remaining motors are connected in parallel,
and the middle blade of which opens a connection common to all the switches.
Dated this 20th day of September 1898.
THE BRITISH THOMSON-HOUSTON CO., LTD).
A. R. MONKS,
Director.
ALFRED CLEMENTS,
Assistant Secretary.