Year: 1886

page_text: I THOMAS JOHN HANDFORD of 50 Bedford Row in the County of Middlesex
Patent Agent do hereby declare the nature of this invention a communication to
me from abroad by Frank Julian Sprague of New York in the County and State
of New York, United States of America, Electrical Engineer, to be as follows :—
In the use of electro-dynamic motors difficulty has heretofore arisen from the
necessity of shifting the commutator brushes when the armature current is varied
or reversed.
The object of the present invention is mainly to obviate this difficulty, though
the invention relates further to certain means of regulation employed in conjunc-
tion with the main features of the invention.
The invention is especially applicable for use with railway motors, and motors
for working elevators, and other motors in parallel circuit, in the operation of
which it is necessary to vary the speed and to reverse the direction of rotation of
the armature, and sometimes also to change the motor into a generator and to
regulate it while in this condition.
As is well known, the reversal of direction of rotation of the armature of a
motor or generator causes a reversal of the direction of lead of the brushes, and
this lead is proportional to the armature current and is also dependent inversely
on the strength of the free field.
In motors heretofore built for railway work, it has been customary to provide
two sets of commutator brushes, one adapted to be used when the motor runs in
one direction, and the other for the opposite direction of rotation. These are set
for different leads and means are usually provided for changing the lead of each
set. A single set of tangential brushes could not be employed because of the
changes of lead and the sparking and burning which must attend such changes.
Automatically operating devices have been proposed for changing the lead, but
these are complicated contrivances and are therefore not well adapted for railway
purposes where only the simplest apparatus should be employed.
In the provisional specification accompanying my application for a patent dated
the 10th August 1885 No. 9526 is described a mode of winding for a motor by

page_text: which the non-sparking points are maintained constant under varying armature
currents. In this arrangement there is a set of series field coils and a set of shunt
field coils, part of the series coils being wound on two diagonally opposite legs of
the field magnet in a manner to act cumulatively with the main or shunt field
coils and the rest wound on the other two legs in a manner to differentiate the
shunt coils, the differential being stronger than the cumulative series coils. This
method is only for a machine running always in the same direction and at a
determined speed on a constant potential circuit and keeps the non-sparking point
at a fixed position by opposing the distortion caused by the armature current by a
counter distortion set up by the governing or series coil.
While, if the current in the armature and consequently the direction of rotation
is reversed, the distortion and counter distortion are also reversed, yet because of
the uneven magnetizing effect of the two series coils the amount of distortion is
not the same as when running in the normal direction.'
This arrangement also, therefore, cannot be used for the purposes above set forth.
By the present invention, however, a machine is constructed with such a system
of winding that it may run in either direction on a circuit of constant or of
varying potential with a single or double set of tangential or end contact brushes,
with no change of lead and consequently no necessity for changing the position
of the brushes. By it, the operation of the brushes, having been once properly
adjusted, is made independent of the amount of work the machine is doing or the
speed at which it is running or whether it is acting as a motor or as a generator.
It is independent also of the strength of field or armature current and hence of
the speed and power developed. Means are further provided for varying strength
of field and armature current either independently or simultaneously.
In carrying the invention into effect, it is preferred to use a machine having a
field magnet such as is commonly known as the Siemens form, that is, one having
two poles each produced by the combined action of two oppositely placed sets
of coils.
This field magnet is wound with two sets of coils. One a fine coil, in shunt
relation to the armature which is wound to produce the main poles in the part of
the field adjacent to the armature; the other, of very low resistance, is in series
with the armature either inside or outside the terminals of the main field shunt
and is wound equally upon all the cores in such manner as to produce magnetic
poles in a line at right angles to that of the poles produced by the fine coil, and
less powerful ones. On two diagonally opposite legs the coarse coils act cum-
latively with the fine coils, and on the other two they act differentially as set
forth in the said former provisional specification, but differing from the arrange-
ment therein described in that the coils are wound equally on all the legs.
One part of the series coil may be arranged in parallel circuit to the other part.
A reversing switch is preferably placed in the series coil and armature circuit,
and preferably also an adjustable resistance.
In the fine coil shunt circuit an adjustable resistance also may be placed, and
this may also have a reversing switch. A circuit making and breaking switch,
preferably forming part of the reversing switches, may be placed in each circuit.
There is also placed in the coarse coil circuit a switch, whose function is to
reverse either diagonal portion of the coarse coils leaving the rest unchanged,
whereby all the coarse coils may be made cumulative, or all differential, at will.
In the normal arrangements of circuits just described, the two sets of field coils,
fine and coarse, combine to set up a resultant polar line which is distorted or
rotated in the plaue of rotation of the armature or so as to counteract the distor-
tion due to the armature or to the main field coils.
Since any increase in the armature current is just the same in the series field
coils, the tendency to distortion by these two elements will always vary to the
same extent and the resultant position will be always the same no matter what is
the extent of variation of current. If the field magnet strength is varied inde-
'pendently of the armature by changing the resistance in the shunt field circuit, or

page_text: by a variation of potential on the line, while there is a tendency to change the
armature distortion, there is an equal and opposite tendency to change the distor-
tion due to the series field coils and so this also has no effect. If the direction
of the armature current is changed so also is that of the current in the series field
and so the direction of each distortion is changed but they still oppose each other
and vary equally and oppositely as before, and there is still no change in the non-
sparking points. It is immaterial whether the change in direction of armature
current is due to a change of terminals in changing direction of rotation of the
motor, or is caused in changing the motor into a generator by strengthening the
field till the counter electro-motive force overcomes the initial.
Reversal of direction of rotation of the motor can also be accomplished by
reversing the main field, but in this case also the non-sparking points are still
governed in the same way.
THE J. HANDFORD,
50, Bedford Row, London, W.C.

page_text: I THOMAS JOHN HANDFORD of 50 Bedford Row 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 :-
In the use of electro-dynamic motors difficulty has heretofore arisen from the
necessity of shifting the commutator brushes when the armature current is varied
or reversed.
The object of the present invention is mainly to obviate this difficulty..
The invention is especially applicable for use with railway motors, and motors for
working elevators, and other motors in parallel circuit, in the operation of which
it is necessary to vary the speed and to reverse the direction of rotation of the
armature, and sometimes also to change the motor into a generator and to regulate
it while in this condition.
As is well known, the reversal of direction of rotation of the armature of a motor
or generator causes a reversal of the direction of lead of the brushes and this lead
is proportional to the armature current and is also dependent inversely on the
strength of the free field.
In motors heretofore built for railway work, it has been customary to provide
two sets of commutator brushes, one adapted to be used when the motor runs in
one direction, and the other for the opposite direction of rotation. These are set
for different leads and means are usually provided for changing the lead of each
set.
A single set of tangential brushes could not be employed because of the
changes of lead and the sparking and burning which must attend such changes.
Automatically operating devices have been proposed for changing the lead but
these are complicated contrivances and are therefore not well adapted for railway
purposes where only the simplest apparatus should be employed.
In the specification to Letters Patent granted to me dated the 10th August 1885
No. 9526 is described a mode of winding for a motor by which the non-sparking
points are maintained constant under varying armature currents. In this arrange-
ment there is a set of series field coils and a set of shunt field coils, part of the
series coils being wound on two diagonally opposite legs of the field inagnet in a
manner to act cumulatively with the main or shunt field coils and the rest wound
on the other two legs in a manner to differentiate the shunt coils-the differential
being stronger than the cumulative series coils. This method is only for a machine
running always in the same direction and at a determined speed on a constant
potential circuit and keeps the non-sparking point at a fixed position by opposing
the distortion caused by the armature current by a counter distortion set up by
the governing or series coil.
While, if the current in the armature and consequently the direction of rotation
is reversed, the distortion and counter distortion are also reversed, yet because of
the uneven magnetizing effect of the two series coils the amount of distortion is
not the same as when running in the normal direction.
This arrangement also therefore cannot be used for the purposes above set forth.
By the present invention, however, a machine is constructed with such a system
of winding that it may run in either direction on a circuit of constant or of

page_text: varying potential with a single or double set of tangential or end contact brushes,
with no change of lead and consequently no necessity for changing the position
of the brushes. By it the operation of the brushes, having been once properly
adjusted, is made independent of the amount of work the machine is doing or the
speed at which it is running or whether it is acting as a motor or as a generator.
It is independent, also, of the strength of field or armature current, and hence of
the speed and power developed. Means are further provided for varying strength
of field and armature current either independently or simultaneously.
In carrying the invention into effect, it preferred to use a machine having a
field magnet such as is commonly known as the Siemens form, that is, one having
two poles each produced by the combined action of two oppositely placed sets
of coils.
This field magnet is wound with two sets of coils. One, a fine coil, in shunt
relation to the armature which is wound to produce the main poles in the part of
the field adjacent to the armature; the other, of very low resistance, is in series with
the armature either inside or outside the terminals of the main field shunt and is
wound equally upon all the cores in such manner as to produce magnetic poles
in a line at right angles to that of the poles produced by the fine coil, and less
powerful ones. On two diagonally opposite legs the coarse coils act cumulatively
with the fine coils and on the other two they act differentially as set forth in the
specification to the said former patent but differing from the arrangement therein
described in that the coils are wound equally on all the legs.
One part of the series coil may be arranged in parallel circuit to the other part.
A reversing switch is preferably placed in the series coil and armature circuit,
and preferably also an adjustable resistance.
In the fine coil shunt circuit an adjustable resistance also may be placed and
this may also have a reversing switch. A circuit making and breaking switch,
preferably forming part of the reversing switches, may be placed in each circuit.
There is also placed in the coarse coil circuit a switch whose function is to
reverse either diagonal portion of the coarse coils leaving the rest unchanged
whereby all the coarse coils may be made cumulative or all differential, at will,
In the normal arrangements of circuits just described, the two sets of field coils,
fine and coarse, combine to set up a resultant polar line which is distorted or
rotated in the plane of rotation of the armature or so as to counteract the distortion
due to the armature or to the main field coils.
Since any increase in the armature current is just the same in the series field
coils, the tendency to distortion by these two elements will always vary to the
same extent and the resultant position will be always the same no matter what is
the extent of variation of current. If the field magnet strength is varied indepen-
dently of the armature by changing the resistance in the shunt field circuit or
by a variation of potential on the line, while there is a tendency to change
the armature distortion, there is an equal and opposite tendency to change the
distortion due to the series field coils and so this also has no effect. If the direction
of the armature current is changed so also is that of the current in the series field
and so the direction of each distortion is changed but they still oppose each other
and vary equally and oppositely as before and there is still no change in the non-
sparking points. It is immaterial whether the change in direction of armature
current is due to a change of terminals in changing direction of rotation of the
motor, or is caused in changing the motor into a generator by strengthening the
field till the counter electro-motive force overcomes the initial.
Reversal of direction of rotation of the motor can also be accomplished by
reversing the main field, but in this case also the non-sparking points are still
governed in the same way.
The invention is illustrated in the accompanying drawings the figures of which
are diagrams of motors embodying the features of the invention, each of which will
be described in detail.

page_text: In these figures, 1, 2 is the line, T is the armature, and B is the field magnet of
a motor. C, C are fine or shunt field coils and D, D¹---- D', are coarse or
Beries field coils.
In figure 1, only the series coils D are shown. These are wound in the manner
shown, equally on all the legs of the magnets, so as to produce poles at N¹, S¹, at
opposite ends of the magnet.
Figure 2 shows the same motor with the poles due to the series coil reversed by
reversing the armature current that is, by throwing switch E to the left.
Figure 3 shows the fine main or shunt coils alone. These also are wound
equally on all the magnet legs but so as to produce poles in the usual manner
at N S.
Figure 4 shows the motor complete with both shunt and series coils. The
resultant polar line produced by the combined action of the shunt and series coils
is at N, Su, while the line of distortion due to the armature and main field is
at A, R.
The consequent polar line then is at N, S, and it is evident from what has
already been explained that it will always remain so. For, if the armature current
is increased so that A, R, tends to turn against the direction of rotation, then the
magnetizing effect of D, D, is also increased and N¹¹, Su, equally tends to turn in
the opposite direction; and if the magnetizing effect of C C is increased, then,
while A, R, tends to move towards N, S, so also does Nu S, and vice versa.
And if the armature rotation is reversed A, R, assumes the position N¹¹, Su, but
then the poles N¹, S¹, are reversed also and N", S" assumes the position A, R 80
that N, S remains the same. The fine and coarse coils can be wound side by side
instead of superposed.
Figures 6 and 7 show the same motor provided with the various regulating
devices which have been already briefly referred to.
F is the resistance apparatus for armature and main field circuits.
Resistance coils a a are in the shunt field circuit and are connected to contact
blocks bb. Coils c c are in the armature circuit and are connected to blocks d d.
Long block e is for the field circuit and long block f for the armature circuit.
Moving arms ġ, g' travel on the blocks and are both connected with the line and
preferably move together. When arm g moves on blocks b b and varies field
resistance, arm gl is on block f and armature resistance is not affected. On the
other hand, when arm g is on blocks d, to vary armature resistance, g' is one and
field resistance is not affected.
From the terminal of coils c armature circuit wire 3 extends to block h of
switch E. From block h¹ wire 4 extends, which is finally connected through
switch G with commutator brush k. From h' wire 5 goes to brush k¹. From h³
a wire extends to main conductor 2. Bridging plates i ¹are carried by pivoted
switch arm l. When the switch arm is down, as in figure 6, the current is in one
direction in the armature and series field, and when in the horizontal position of
figure 7, the armature and series field current is reversed. The arrow beads in all
cases show direction of current.
It
G is the switch or commutator for reversing portions of the series field coils.
consists of eight plates m, m³, m³.
m arranged in a circle, and four moving
bridging plates n, n¹, n³ and n³ carried by pivoted arm o.
As has been stated, a portion of the series coils D¹, D³, is wound to act cumula-
tively with the shunt coils C and a portion D³, D, is wound to differentiate them.
The function of switch G is to make all the series coils cumulative so as to make a
very strong field as in starting the machine, or to make them all differential if
desired so as to weaken the field.
In figure 6 all the coils are normal. Here the armature and series coils circuit
is by wire 5 to brush k¹, brush k, wire 6 to m', plate n¹ to m³, wire 7 to coils D*,
8 to D³, 9 to plates m³, n, m³, n³, m³, wire 10 to D¹, 11 to D³, 12 to m³, n³ to m,
and wire 4 back to switch E and to the line. Now if handle o of switch G is
thrown to its right hand position, shown by dotted line, the circuit is-5, k¹, k, 6,

page_text: m², n¹, m³, 7, D4, 8, D³, 9, m³, n, m², wire 13, m³, n³, m², 12, D', 11, D¹, 10, m¹, n³,
m and 4. Coils D¹ and D are thus reversed and made differential instead of
cumulative. Throwing handle o to its left hand position likewise reverses D³ and D'
and makes all the coils cumulative.
This last is what is done in starting the motor when switch E is down, as in
figure 6. Its effect is shown in figure 9. That is, it makes the polar line N¹ S¹
disappear from the normal position and brings it to N, S, and so makes a very
strong field so that the motor starts slowly with a strong torque or rotary effort.
Figure 8 shows the polar condition when the coils are all differential, S¹ being then
brought to N and N¹ to S. This is a condition which will rarely occur in practice.
It will be noticed that in starting the motor in this way no provision is made
for the maintenance of the non-sparking points. My foreign correspondent has
found that this is unnecessary for there is at this time so low a potential
between the commutator blocks that there is practically no sparking and con-
sequently it makes less difference where the commutator brushes are. When the
motor has come up to speed, however, the switch G is maintained at its middle
position and the regulation of the non-sparking points goes on in the manner
explained.
In starting the motor, further, the resistance coils c are placed in circuit and
coils a all out of circuit, coils c are then gradually cut out and such of coils a as
described are placed in circuit. The regulation while running is performed by
varying the shunt field strength by coils a.
Figure 7 shows the armature and series coils circuit reversed at switch E,
Figure 11 shews its effect. This figure illustrates the fact that when this reversal
has taken place, the operation of switch G must be reversed also, the effect thereof
being shewn in Figure 10. That is, when the motor is to run in the direction of
figure 6, switch o is thrown to the left in starting, and when as in figure 7, it is
thrown to the right. In practice, the proper positions for the switches may be
indicated upon them so that an inexperienced engineer can readily handle the
motor if necessary.
Figure 5 shows an arrangement in which,one part of the series coils is in parallel
circuit to the other part. Such arrangement may be used if desired.
It is to be understood that the series coils can be either inside or outside, or part
inside and part outside the fine shunt coil terminal.
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:-
1st. An electro-dynamic motor having shunt field coils and series field coils
arranged to form polar lines at right angles to each other, and the said series coils
being part differential and part cumulative with relation to the shunt coils, in
combination with means for reversing the magnetizing effect either of the said
cumulative or the said differential coils or of both the said sets of coils, substan-
tially as hereinbefore described.
2nd. An electro-dynamic motor having series and shunt field coils wound so
that the series coils distort the poles set up by the shunt coils, in combination
with means for reversing the direction of distortion, substantially as hereinbefore
described.
THB J. HANDFORD,
50, Bedford Row, London, W.C.