Improvements in Electric Railways and Controlling Devices therefor.
Year: 1899

page_text: Date of Application, 30th Oct., 1899-Accepted, 27th Jan., 1900
COMPLETE SPECIFICATION.
Improvements in Electric Railways and Controlling Devices therefor.
We, THE BRITISH THOMSON-HOUSTON COMPANY, LIMITED, of 83, Cannon Street,
in the City of London, Electrical Engineers, do hereby declare the nature of our
said invention (which has been communicated to us from abroad by William B.
Potter, of Schenectady, in the County of Schenectady, 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:-
-
In the normal operations of electrically equipped vehicles, and particularly
in modern high speed train work in which rapid acceleration and frequent stops
are required it has become necessary to employ after each stop enormous starting
currents so as to secure the maximum permissible speed as rapidly as possible
and, thereafter, to drift nearly to the point where the next stop is to be made,
and then to suddenly apply the brakes.
The result of this practice, a practice rendered necessary by commercial
requirements is that each car or train takes at starting from the generating
station an amount of energy more than sufficient to carry it past the next stop.
A large part of such energy is, therefore, necessarily wasted in the brakes, whether
they are of the electrical or mechanical type.
In addition, any car or train which descends an appreciable grade, receives
thereby an inconveniently large amount of energy which must be wastefully.
absorbed by the brake shoes.
In addition to the wastefullness of this practice, it frequently becomes
inconvenient and sometimes impossible, to dissipate this energy with sufficient
rapidity to keep the brake shoe cool enough to run.
It is obvious that these inconveniences would be avoided and great economy
would be secured if the energy absorbed in retarding the car or train could be
returned to the line. Various attempts have been made to accomplish these
result, but they have been uniformly unsuccessful, for the reason that they have
one and all involved the use of shunt wound motors, which are not adapted to
traction work.
This invention aims to return to the distributing system the energy absorbed
as above described. Its main feature consists in connecting motor armatures
in series when it is desired to return energy, so that their electro-motive forces
act to supply current to the line at a voltage in excess of that impressed thereon
by the main generator or generators.
Another feature of this invention consists in converting the ordinary motors,
actually employed for traction work, into separately-excited generators, when it
is desired that they should return energy. Their voltage is thus made independent
of their output.
Our invention also consists in various combinations and combinations to be
hereinafter more particularly described and claimed.
The accompanying drawings show, in Fig. 1, a controlling device in which the
connections for the practice of our invention have been embodied; Fig. 2, shows

page_text: in diagram the first power point of the controller, and Fig. 3 shows the first point
in which our invention will be applied.
The motors are shown as divided into two groups, of two each, these groups
are operated as units in series or in parallel. The controlling device shown is one
in which the step from the series position to parallel is taken by first shunting a
part of the motors.
This type is in general so well known that no extended description of the con-
troller will be found necessary.
In Fig. 1 this controller is shown, developed at K. The contacts are divided
into two general groups. The upper part of the controller contains contacts for
grouping the motors; the lower part is a resistance switch. The contacts on the
right of the upper part of the controller arrange the motors in series When the
fixed brushes 1 to 5 pass the centre of the developed contacts, they make contacts
with the plates on both the right and left side of the controller, and in this
position one pair of the motors is shunted, and when the contacts on the right
have passed so far as to be out of circuit, the motors are in multiple. In the same
figure there is shown a reversing switch RS', RS2, and in addition we have shown
a regulating switch CS, CS2. In the drawing this switch is developed into two
parts but it is to be understood that the parts marked CS2 may be on the same
cylinder as CS', being arranged on the back of the cylinder. Other equivalent
mechanical connections may be made. The first running position of the controller
as shown in Fig. 2 may be traced as follows: it being premised that the ammeter
marked in Fig. 2 AM, and the volt-meter marked V, are not shown in Fig. 1,
their application being too well known to require illustration.
In this position the brushes of the switches K, CS and CS2 stand on the
line 2-2, and the brushes of the reversing switch RS', RS stand on the left hand
line of contacts.
Current enters the switch K from the trolley T at contact 13 passing through
the cross connection to the contact 6, thence it flows through resistance R, to
contact 12. At this point the current divides, a portion passing from the con-
tact 12, to the contact 59 on the switch CS2, thence to contact 58, then back
to contact 18 on RS', thence by cross connection to contact 20, to the armature A¹,
to contact 19, by cross connection to contact 21, to contact 56 on the switch CS2,
thence through contact 57, to the field magnet F1, to the contact 45 and to con-
tact 46. 46 is a point on the equalizer wire 46-E, shown in diagram in Fig. 2.
Returning now to contact 12, on the switch K, it will be seen that a second
path leads to contact 17 on RS, thence by cross connection to contact 15, through
the armature A³, to contact 16, thence by cross connection to contact 14, to
contact 43, on the switch CS', to contact 44, through the field magnet F, to the
equalizer point E¹.
Starting again at equalizer 46-E1, the current divides, a portion flowing
through the contact 5, on the controller K, thence by cross connection to contact 3,
to contact 41 on the switch CS¹, thence to contact 42, to contact 25 on the second
portion RS3 of the reversing switch, by cross connection to contact 23, through the
armature A³, back to the contact 24 on the reversing switch RS2,
by cross connection to the contact 22, to contact 51 on the switch CS2, to contact 52,
thence through the field magnet F³ to contact 54, and to ground at G.
Returning now to the equalizer 46-E1, the second path is as follows:
From E to 5, to 3, to contact 41, thence to contact 40 and to contact 26 on the
reversing switch RS3, thence by cross connection to contact 28, through the
armature A', back to contact 27, by cross connection to contact 29, to contact 48
on the switch CS1, thence to contact 47, through the field magnet F, to contact 53
on the switch CS2, through contact 55 to ground.
It will be seen that the motors are thus connected in the position shown in
Fig. 2. in two multiple groups of two each, the two groups being arranged in
series with the equalizer between.
Further rotation of the controller K acts to cut out, step by step, the resis-

page_text: tance R, to shunt one motor, and finally, to connect the two multiple groups of
motors in parallel, as already mentioned above.
These changes form no part of our present invention and need not be more fully
considered herein, since the invention may be applied to any preferred type of
controller.
Suppose now, that the controllers are in the position above described, and that
it is desired that the car shall begin to return energy. The controller K is thrown
to the off position, thus breaking all the circuits, the regulating switches CS¹, CS
are thrown to the line 3-3, and the switch K is again closed.
The connections are then as shown in Fig. 3.
With this arrangement it will be seen, that the armatures A³, A³, and A' are
connected in series across the line and that the armatures acts solely to furnish
current to the field magnets of all four motors, the magnitude of this and, there-
fore, the excitation of the motors, being controlled by the resistance R¹ connected
to the upper portion of the switch CS. It thus appears that the three motors A³,
A3, A4, will act as separately-excited generators to return energy to the line.
The voltage at which the current is returned to the line may be controlled by
manipulation of the switch CS, while the amount of current returned may also
be regulated by the resistance R of the controller K.
It will be noted that the armature A¹ has been reversed. This is done as in
any case in which it is desired that a series motor shall be turned into a series
generator, and shall continue to have current flow through its armature in the
same direction as before.
It will be noted that upon closing the switch CS', for the generating position,
the switch K has first been opened. The result is that the field magnet F¹ has
been deprived of current and must build itself up by its residual megnetism, as
in the case of any series wound machine. The switch K should not again be closed
to return energy to the line, until the voltage of the three armatures A2, A3, A4,
connected in series, as indicated by the volt meter V, is greater than the line
voltage.
In the first braking point the circuit may be traced as follows, remembering
that the controller K stands on the line 2-2, and that the reversing switch RSI,
RS bears on the left hand contacts and that the switches CS¹, CS2 are thrown to
the line 3-3.
Starting from the left hand brush of the armature, the current passes to
contact 20 on the reversing switch RS, to contact 18, to contact 58 on the
switch CS, to contact 37, then through the field F¹ to contact 45, to contact 44,
through the field F3, contact 46, contact 47, through field F* contact 53, contact 52,
through the field F³, contact 39, through the field regulating resistance R¹, con-
tact 30. contact 21, contact 19, and back to the other side of the armature A¹.
This is the circuit of the four field magnets and the armature A¹. It will be
apparent that the further motion of the switch CS will gradually cut out the
resistance R¹.
The circuits of the three generating armatures may be traced as follows: start-
ing from the left hand brush A', current passes to contact 28, to contact 26, to
contact 50, to contact 51, contact 22. contact 24, through the armature A³, to
contact 23, contact 25, contact 42, contact 43, contact 14, contact 16 through
the armature A. contact 15, contact 17, through the. resistance R, to contact 6
upon the controller K, to contact 13, to the trolley, returning from ground at
contact 49, then to contact 48, contact 29, contact 27, and so to the other side
of the armature A*.
Any further rotation of either the switch K or the switch CS¹, will now effect
the amount of energy returned to the line, as above explained.
The control of out-put is thus rendered perfect, inasmuch as the strength of the
fields and the resistance of the line circuit may be independently regulated.
By this means the best results from our invention may be obtained, it being
for its purposes desirable to keep the voltage at just such a point as will return
the maximum currents to the line without undue retardation of the train.

page_text: It is of course to be understood that when the speed of the car has been
so reduced that the electro-motive force of the armatures A³, A³, and A', with the
highest possible field excitation, is too low to permit the further return of
energy; the switch K will be opened.
While of, course the line conductor or trolley system is the one to which the
invention is commonly applied, a storage battery could be used, as indicated
in dotted lines at SB in Fig. 1, without departing from this invention.
When the car is to run backward, the reversing switch RS, RS2, is thrown to
the right hand row of contacts. In this position, manipulation of the controller K
will control the speed of the car, while the proper manipulation of the regulating
switches CS and CS2 will cause the motors to return energy, as above described.
In the use of our invention, the voltmeter V, and the double scale ammeter AM,
shown in the diagram in Figs. 2 and 3, should be carefully watched by the
operator. It is obvious that the main circuits should be kept open when the
switches CSI, CS2 are in the generating position, before the motor A¹ has built
up its own field and the fields F, F, F sufficiently to cause the electromotive
force generated by the three armatures in series to be sufficient to return energy,
or after the speed of the motors has decreased to such an extent as to render the
returning of the energy impossible. While this may be accomplished by intel-
ligent use of the switch K, we prefer to provide in series with the line, switch
contacts S¹, S¹ and a switch blade S. This switch should be so arranged that it is
automatically maintained closed when the voltage of the braking generators is in
excess of the line voltage, and maintained opened when the reverse is the case.
This result. may be secured in many ways, as for example by arranging the
switch-blade on a shaft controlled by the two solenoids S2, S3 like a polorized
relay and actuating it by the differential magnet M. The winding of S2 is shunted
from the trolley direct to the ground at G2, and the winding of S3 is shunted
from the right-hand end of the armature A² to ground at the same point. These
coils are so wound as to attract and close the switch S, S¹, when the line voltage
is in excess of the generator voltage, and to open it when the reverse is the case.
So far as we are aware, we are the first in the electric railway art to combine
motors acting as generators so that their electro-motive forces act summatively to
return current to the line at a voltage equal to or in excess of that supplied by the
power generators. We are also the first to combine motors as momentum-driven,
separately excited generators, or as generators having independent field and arma-
ture control, so that both voltage and output may be regulated.
In the use of our invention it will be found that the current requirements of a
long line operating where grades or stops are frequent will be materially reduced,
as the trains or cars which are coming to a station or running down grade, will
supply a considerable percentage of the power needed in operating other trains
which are still running at speed or are just starting.
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 a number of electric motors, a load for said motors
and means for connecting them to the supply circuit so that their electromotive
forces may act summatively to supply current thereto.
2. 1ue combination of a number of electric motors and a controlling device
having contacts for connecting some of the motors in series in the supply circuit,
and for regulating the voltage of the current supplied by their armatures.
3. The combination of a number of electric motors acting as momentum driven
generators, with means for supplying all the fields from one of the armatures and
means for connecting the other armatures in series to the supply circuit.
4. The combination with the armature and field magnet of a dynamo electric
machine, of means for connecting the field and armature to line, and for con-
necting the armature to line and the field to a separate source of current, at will.

page_text: 5. In an electric railway, the combination of a number of electric motors acting
as momentum driven separately excited generators, with means for regulating the
field and armature currents.
6. In an electric supply system, the combination of a number of electric motors
acting as momentum driven separately excited generators, having some of their
armatures connected in series in the supply circuit, with means for simultaneously
regulating the fields of the motors.
7. In combination a number of motors acting as momentum driven generators
having some of their armatures connected in series in the supply. circuit, a
source of current energizing all the motor fields, a regulating resistance in the
field circuit, and a regulating resistance in the line circuit; whereby the voltage
and output may be independently controlled.
8. In combination, in an electric supply system, a number of motors acting as
momentum driven generators, a switch for connecting all of the fields to one of
the armatures and for connecting the remaining armatures in the supply circuit,
a regulating resistance for regulating the fields controlled by the switch, and
means for regulating the resistance of the armature circuit.
9. The art of operating an electric supply system, for motors, which consists in
connecting motor armatures in series to the line circuit so that their electro-
motive forces act summatively to supply current to the line at a voltage in excess
of the line potential.
10. The art of operating an electric supply system including motors and a
line circuit, which consists in energizing the fields of the motors from a source of
supply and connecting the armatures of some of the motors in series to the line
circuit, thereby supplying to the circuit current at a voltage in excess of the line
potential.