improvements in Operating Electric Railway Trains or Vehicles.
Year: 1885

page_text: improvements in Operating Electric Railway Trains or Vehicles.
I THOMAS JOHN HANDFORD of 42 Southampton Buildings in the County of
Middlesex Patent Agent do hereby declare the nature of this invention for
"IMPROVEMENTS IN OPERATING ELECTRIC RAILWAY TRAINS OR VEHICLES" a com-
munication to me from abroad by Frank Julian Sprague of New York City in
the County of New York and State of New York, United States of America
Electrical Engineer, to be as follows:-
The object of this invention is to provide an effective method of braking,
slowing-down or reducing the speed of a train or vehicle on an electric railway,
which shall not entail that loss of energy incurred in the methods of braking
which have heretofore been used or proposed both in steam and electric railways.
This method consists in changing the electro dynamic motor which receives
current from the line and propels the train, into a dynamo electric generator
receiving energy from the momentum of the train and giving current to the line,
and under perfect control to vary the braking power.
Therefore, instead, as in the case of a mechanical brake, of using energy to stop
or slow down the train, by this invention, such act of stopping or slowing-down
gives current to the line and relieves the generating stations by furnishing
additional power to the motors of other trains.
In the provisional specifications accompanying my former applications for
Letters patent dated the 29th November 1884 N° 15768 and the 18th March 1885
N° 3524, is set forth a method of varying the mechanical effects in an electro-
dynamic motor, by an inverse. varying of the strength of the field magnets of the
motor. The present method of changing the railway motor into a generator is
based upon the same principle. By a continued increase of field strength the
mechanical effects of the motor are decreased and finally reversed.
When the machine is running as a motor it develops a certain counter electro-
motive force which taken with the initial electro-motive force determines the
effective electro-motive force and hence the armature current. This counter
electro motive force depends upon the strength of field and the velocity of the
armature and is independent of everything else.
•
It is evident therefore that if the strength of the field magnet is increased,
the counter electro motive force is also increased, and if the increase of field is

page_text: continued, the initial and counter electro motive force will become equal and then
the counter electro motive force will predominate. The machine has now become a
generator and gives current to the line and its mechanical effects are inversed, so
that it brakes the train instead of propelling it, and the current generated by it
and the braking power or reversed mechanical effect are now controllable by further
increasing or by re-diminishing the strength of field.
It will be seen that mechanical energy is received by the reversed motor
according to the mass of the train and its velocity. If a train should start on a
down gradient unprovided with a brake the energy of falling would tend to
increase its speed; but when this method of braking is used this mechanical energy
is transformed in the machine into electrical energy delivered to the line and
augmenting that supplied from the generating stations to the other trains which
may be moving upon upgradients or on levels.
When it is desired to slow down a train on a level gradient the field is increased
as before until the counter electro motive force predominates over the initial, and
the energy stored up in the moving train is exerted to run the machine as a braking
dynamo. As the train slows however, the diminution of speed of the armature
will tend to diminish the counter electro motive force and the increase of field
strength must therefore be continued so as to still maintain the counter electro
motive force above the initial and keep the machine running as a generator as long
as practicable, when any other method of braking may be applied.
An instance to show how effectively this invention may be employed may be
given premising that when large masses of iron are used in the field magnets, the
strength of the field can be varied within effective limits four or five hundred
per cent, and also that a well constructed armature can carry, for a short time, fifty,
seventy-five, or perhaps even one hundred per cent more current than it can stand
for any long run.
Assume the arinature of the motor in question to have a resistance of 3 of an
ohm, with its field magnet in shunt relation to its armature (which is always the
preferable manner of connection) and provided with suitable means for varying its
strength.
Assume the initial electro motive force to be 500 volts and 40 horse power to be
required from the motor when running at its maximum. Allowing for losses in
conversion this 40 horse power would be about 32000 watts. The counter electro
motive force would be 480 volts, the effective electro motive force 20 volts and the
current 67 amperes. The electrical efficiency of the armature would be 96 per cent.
Assume the strength of the field to be increased about 4 per cent, the speed
remaining the same, the motor running on a down gradient. The counter electro
motive force will be increased to 500 volts and the motor armature will then be
perfectly passive electrically, neither taking from nor giving to the line.
Let the field strength be increased again 1 per cent and let the increase be
continued in the same ratio. The result is shown in the following table:-

page_text: power of effective work to a perfectly passive machine allowing the train to run
absolutely free. Then by increasing the field 10 part the motor at once exerts a
positive braking force and on an increase of about 8 per cent above its original
strength, it will give back to the line current equal to that which was originally
taken from it sufficient evidently to run some other motor of the system which may
at that time require that amount of current; and by increasing the original field
10 per cent the machine acts as a dynamo requiring more than 50 per cent more
energy than is demanded to run it as a motor developing 40 horse power.
This method of braking it will be seen is under perfect control, and it is the
most economical system possible for an electric railway, since whenever a train
descends a gradient and whenever a train stops the energy stored up in the moving
train is delivered in the form of electrical energy upon the line.
This advantage is most readily appreciable by comparing the action of this
invention with that which occurs on a steam railway train. Suppose it to be
ascending a gradient, then the engine exerts more than its average amount of
power. When it reaches the top and enters upon a down gradient steam is shut off,
and when the train begins to run faster than is desired steam is admitted to the
vacuum brake ejector, pressure is applied to the trucks, and the energy of the train
is then converted into heat on the rims of the wheels and on the brake shoes.
In other words all the energy in excess of that necessary to run the train on a
level which has been required to climb the gra lient is now thrown away in going
down the gradient instead of being utilized as in the improved system, and
furthermore additional steam is actually required to check the tendency to
augmented speed.
Then, when the train approaches a stopping place or wherever it is necessary to
slow the train down quickly steam has to be employed to actuate the brakes and
all this additional power is simply thrown away. By the method of working
herein set forth the greater part of this loss is entirely obviated.
It is true that not all of the energy will be converted into electricity but a
large proportion of it will be. On a double track road with both tracks supplied
from the same main circuit the energy given to one track is also communicated to
the other. The up gradients on one track being always balanced by the down
gradients on the other track it is evident that the total up gradients of the whole
system is equal to the total down gradients thereof. Therefore energy being
expended on the up gradients and given out to nearly the same extent on the down
gradients the energy required in the system is that sufficient to move a train upon
a level with a slight per centage added. But on a steam railway the energy
required is not only that sufficient to run a train on a level but in addition that
necessary to raise it from the lower to the higher gradients on both tracks no
matter how many of such gradients there may be.
Any effective method may be employed for varying the strength of the field.
An adjustable resistance may be used or sections of the field coils may be cut in
and out or the current in a greater or less number of said coils may be reversed.
My foreign correspondent prefers however to employ such methods as have been
set forth in the said former provisional specifications relating to the regulation of
electro dynamic motors.

page_text: Improvements in Operating Electric Railway Trains or Vehicles.
I THOMAS JOHN HANDFORD of 42 Southampton Buildings in the County of
Middlesex, Patent Agent 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 object of this Invention is to provide an effective method of braking, slowing
down or reducing the speed of a train or vehicle on an electric railway, which shall
not entail that loss of energy incurred in the methods of braking which have
heretofore been used or proposed both in steam and electric railways.
This method consists in changing the electro-dynamic motor which receives
current from the line and propels the train, into a dynamo-electric generator
receiving energy from the momentum of the train and giving current to the line,
and under perfect control to vary the braking power.
Therefore, instead, as in the case of a mechanical brake, of using energy to stop
or slow down or reduce the speed of the train, by this invention such act of
stopping or slowing down or reducing speed gives current to the line and relieves
the generating stations by furnishing additional power to the motors of other
trains.
In the specification to a former patent granted to me dated the 29th November
1884 N° 15,768 and in the specification to my application for a Patent dated the
18th March 1885 N° 3524 are set forth methods of varying the mechanical effects
in an electro-dynamic motor, by an inverse varying of the strength of the field
magnets of the motor. The present method of changing the railway motor into
a generator is based upon the same principle. By a continued increase of field
strength the mechanical effects of the motor are decreased and finally reversed.
When the machine is running as a motor it developes a certain counter electro-
motive force which taken with the initial electro-motive force determines the
effective electro-motive force and hence the armature current. This counter electro-
motive force depends upon the strength of the field and the velocity of the
armature and is independent of everything else.
It is evident, therefore, that if the strength of the field magnet is increased the
counter electro-motive force is also increased, and if the increase of field is con-
tinued, the initial and counter electro-motive force will become equal and then the
counter electro-motive force will predominate. The machine has now become
a generator and gives current to the line and its mechanical effects are inversed,
so that it brakes the train instead of propelling it, and the current generated by it
and the braking power or reversed mechanical effect are now controllable by
further increasing or by re-diminishing the strength of field.
It will be a-en that mechanical energy is received by the reversed motor according
to the mass of the train and its velocity. If a train should start on a down
gradient unprovided with a brake the energy of falling would tend to increase its
speed; but when this method of braking is used, this mechanical energy is trans-
formed in the machine into electrical energy delivered to the line and augmenting
that supplied from the generating stations to the other trains which may be moving
upon up-gradients or on levels.

page_text: When it is desired to slow down or reduce the speed of a train on a level gradient
the field is increased as before until the counter electro-motive force predominates
over the initial, and the energy stored up in the moving train is exerted to run
the machine as a braking dynamo. As the train slows, however, the diminution of
speed of the armature will tend to diminish the counter electro-motive force and
the increase of field strength must therefore be continued so as to still maintain
the counter electro-motive force above the initial and keep the machine running as
a generator as long as practicable, when any other method of braking may be
applied.
An instance to show how effectively this invention may be employed may be
given, premising that when large masses of iron are used in the field magnets, the
strength of the field can be varied within effective limits four or five hundred per
cent, and also that a well constructed armature can carry, for a short time, fifty,
seventy-five, or perhaps even one hundred per cent more current than it can stand
for any long run.
Assume the armature of the motor in question to have a resistance of 3 of an
ohm, with its field magnet in shunt relation to its armature (which is always the
preferable manner of connection) and provided with suitable means for varying
its strength.
Assume the initial electro-motive force to be 500 volts, and 40 horse power to
be required from the motor when running at its maximum. Allowing for losses
in conversion, this 40 horse power would be about 32,000 watts. The counter
electro motive force would be 480 volts, the effective electro motive force 20 volts,
and the current 67 ampères. The electrical effeciency of the armature would be
96 per cent.
.
'
Assume the strength of the field to be increased about 4 per cent, the speed
remaining the same, the motor running on a down gradient. The counter electro-
motive force will be increased to 500 volts and the motor armature will then be
perfectly passive electrically, neither taking from nor giving to the line. Let the
field strength be increased again I per cent and let the increase be continued in
the same ratio. The result is shown in the following table.
From the above it will be seen that by simply increasing the field strength
th part the machine is converted from a motor driving a train with forty horse
power of effective work to a perfectly passive machine allowing the train to run
absolutely free. Then by increasing the field 10th part, the motor at once exerts
a positive braking force, and on an increase of about 8 per cent above its original
strength, it will give back to the line current equal to that which was originally
taken from it, sufficient evidently to run some other motor of the system which
may at that time require that amount of current; and by increasing the original
field 10 per cent the machine acts as a dynamo requiring more than 50 per cent
more energy than is demanded to run it as a motor developing 40 horse power.
This method of braking, it will be seen, is under perfect control, and it is the
most economical system possible for an electric railway, since whenever a train

page_text: descends a gradient, and whenever a train stops, the energy stored up in the moving
train is delivered in the form of electrical energy upon the line.
This advantage is most readily appreciable by comparing the action of this
invention with that which occurs on a steam railway train. Suppose it to be
ascending a gradient then the engine exerts more than its average amount of
power.
When it reaches the top and enters upon a down gradient, steam is shut off, and
when the train begins to run faster than is desired, steam is admitted to the
vacuum brake ejector, pressure is applied to the trucks, and the energy of the
train is then converted into heat on the rims of the wheels and on the brake shoes.
In other words, all the energy in excess of that necessary to run the train on
a level, which has been required to climb the gradient, is now thrown away in
going down the gradient, instead of being utilised as in the improved system,
and, furtherinore, additional steam is actually required to check the tendency to
augmented speed.
Then, when the train approaches a stopping place, or whereever it is necessary to
slow down or reduce the speed of the train quickly, steam has to be employed
to actuate the brakes, and all this additional power is simply thrown away. By
the method of working herein set forth, the greater part of this loss is entirely
obviated.
It is true that not all of the energy will be converted into electricity, but a large
proportion of it will be. On a double track road with both tracks supplied from
the same main circuit, the energy given to one track is also communicated to the
other. The up gradients on one track being always balanced by the down gradients
on the other track, it is evident that the total up-gradient of the whole system is
equal to the total down-gradient thereof. Therefore, energy being expended on
the up-gradients and given out to nearly the same extent on the down-gradients,
the energy required in the system is that sufficient to move a train upon a level
with a slight per-centage added. But, on a steain railway the energy required is
not only that sufficient to run a train on a level, but in addition that necessary to
raise it from the lower to the higher gradients on both tracks, no matter how many,
of such gradients there may be.
Any effective method may be employed for varying the strength of the field.
An adjustable resistance may be used, or sections of the field coils may be cut in
and out, or the current in a greater or less number of the said coils may be
reversed. My foreign correspondent prefers, however, to employ such methods
as have been set forth in the said former specifications relating to the regulation of
electro-dynamic motors.
The accompanying drawing represents an electric railway system in which the
invention is employed.
A, A, and B, B are respectively the two tracks of an electric railway; there are
two sets of working conductors a, a, and b, b, preferably divided into sections,
from which the motors C and C¹ derive current; and such working conductors are
connected by branch conductors c, c, with the continuous main conductors, P, N,
which extend the whole length of the line and receive current from the generating
stations at D, D by supply conductors pn. The working conductors, instead of
being intermediate rails of the track, may be wires placed overhead or by the side
of the track or in any position where the motor can receive current from them, or
the main rails of the track may form one or both sides of the working circuit.
The main conductors may be placed overhead or under-ground or in any convenient
position.
In the form shown, the motors have contact wheels e, e, on one side and ff, on
the other, which travel on and take current from the working conductors.
E is the armature, F, F the field magnet, and G the commutator of each motor.
Each motor which travels upon the line, is provided with suitable means for
regulating its field-magnet strength.

page_text: As shown, connections g, g, from different points of the main field coils, extend to
contact blocks of a circular commutator h; from one limb of the magnet they
extend to one side of the commutator, and from the other limb to the other
side.
An independent field coil k, k, has its terminals connected to the arms l, l,
which are insulated from each other and are pivotted at m. Portions of these
arins are shown broken away in the drawing. It will be seen, that the independent
coil is thus in a shunt between the two sets of main coils, and by moving the
arms,, the said independent coil is shunted around a greater or less number of
the sections of main field coils, and thereby the magnetizing effect of the said
independent coil and the strength of the field is varied; or by a continued move-
ment of the arms, the current of the independent coil is reversed, so that it
opposes the main field coils with a strength variable at will.
The terminals of the armature are preferably connected to arms o, o, on commu-
tator h, whereby the armature current may be varied or reversed in the same
manner as the independent field coils when so desired.
It is evident, that the use of this invention is not confined to a double track
road, or to a road in which main conductors are used to supply working conductors,
for this method of braking is applicable to any electric railway system which has
been used or proposed.
Having now particularly described and ascertained the nature of my said
Invention, and in what manner the same is to be performed, I declare that what
I claim is :-
.
The method of braking an electric railway train or vehicle which consists in
increasing the counter electro-motive force of the propelling motor until it exceeds
the initial electro-motive force on the line as hereinbefore described.
Dated this 91st day of January 1886