Improvements in and Connected with Dynamo Electric Machines and Electric Motors for Direct Currents.
Year: 1888

page_text: Date of Application, 1st Oct., 1888
Complete Specification Left, 1st July, 1889-Accepted. 1st Oct.. 1889
PROVISIONAL SPECIFICATION.
Improvements in and Connected with Dynamo Electric Machines and
Electric Motors for Direct Currents.
1, JAMES SWINBURNE of Shona, Chelmsford, Essex, Electrical Engineer do hereby
declare the nature of this invention to be as follows:-
-
My invention relates to improvements in dynamo electric machinery & motors for
direct currents. To make a low tension dynamo whose electromotive force can be
varied as desired, I arrange one pair of brushes to collect the exciting current, the
field magnets being wound in shunt; & another pair to collect the main current.
The main electromotive force is then varied by shifting the main brushes.
Owing to the low electromotive force of the machine there is little sparking, &, in a
small machine especially, the main electromotive force can be varied through wide
ranges without the field being lost. Machines arranged thus are especially suitable
for electro deposition, & for use as exciters.
Low tension, or large current machines are apt to give trouble through the
armature conductors heating when passing into or out of a field. I have already
patented a method of obviating this difficulty in direct current dynamos. To prevent or
lessen the heating according to the present invention, I make the conductors of several
strands or wires, but these are not twisted, but are laid side by side on the outside of
the armature.
Each external conductor is not laid in a plane passing through the axis of the
armature, but is laid so as to form part of a screw of very long pitch, so that one end
of it comes under the polepicce before the other.
The same or a similar result may be obtained, by making the pole pieces so that
one part is in advance of the other. The sets of wires are then laid parallel to the
axis of the armature.
There is some difficulty in making motors for series work so that the torque can
be regulated as desired. To obviate this, I wind a series motor so as to give the
maximum torque desired with the brushes in the normal position. To reduce the
torque the brushes are shifted backwards & the field is weakened by the same move-
ment. The amount of weakening of the field at any position of the brushes is so
arranged that there is no sparking, the gist of the invention being so arranging the
brushes & excitation that there is no sparking. The field is weakened by cutting coils
out, or by shunting it.
Dated this Thirtieth day of Sentember 1888.
JAS. SWINBURNE.
COMPLETE SPECIFICATION.
Improvements in and Connected with Dynamo Electric Machines and
Electric Motors for Direct Currents.
I, JAMES SWINBURNE of 49 Queen's Road, Wimbledon, Surrey, electrical engineer
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:
My invention relates to improvements in dynamo electric machines and motors for
direct currents.
For exciting alternating current machines, and for electrode position of metals it is
desirable to be able to regulate the electromotive force of a dynamo without incurring
the waste of power consequent on the use of resistances.
I make a low tension machine whose electromotive force can be varied us desired,

page_text: with two pair of brushes. One pair collects the current for exciting the field magnets,
and the other pair collects the main current. The main electromotive force is then
varied by shifting the main brushes. Owing to the low electromotive force of the
machine there is little sparking, and, in a small machine especially, the main electro-
motive force can be varied through wide ranges without the field being lost. The
main brushes may have the well known device of inserted resistances to lessen the
sparking. The field should be wound so as to be very stable; or the main brushes
should be shifted back to reduce the electromotive force of the dynamo, otherwise it
may tend to lose its field.
Low tension or large curront machines, whether for electro deposition or for other
purposes often give trouble through the armature conductors heating when passing
into or out of a field. I have already patented a method of obviating this difficulty.
According to the present invention I make the conductors of several strands or
wires, but these are not twisted, but are laid side by side on the outside of the arma-
ture. The conductors are laid so that each is not in a plane with the axis, but forms
part of a screw of long pitch, so that one end comes under the pole corner before the
other. A similar result can be obtained by shaping the pole pieces so that one part is
in advance of the other. The sets of wires are then laid parallel to the axis of the
armature.
There is difficulty in making motors for series work so that the torque can be regu-
lated as desired. To obviate this, I wind a series motor so as to give the maximum
torque desired with the brushes in the normal position To reduce the torque the
brushes are shifted backwards and the field is weakened by the same movement. The
amount of weakening of the field at any position of the brushes is so arranged that
there is no sparking; and the gist of this part of my invention is so arranging the
brushes and excitation that there is no sparking. The field is weakened by cutting
out coils, or by shunting it through resistances. The brushes may be moved by any
suitable mechanical attachment to the rocker or brush holder. The same mechanism
moves a contact over a series of studs. If the field is weakened by resistances in
shunt, the proper' resistance to be included between each pair of studs is found by
trial. If coils are cut in and out the coils are connected to the studs & the position of
each stud is found by trial so that there is no sparking. For tramway work, or for
electric locomotives the brushes & contact gear are connected to a handwheel
resembling the ordinary brake-wheel. In cases where an abnormal torque is required
for starting, the fields may be altered as to coupling, say from all. parallel to. two
parallel two series, or all series. Where constant speed is needed, as in the case of
arc circuit motors, the brush & contact gear is controlled by the governor:.
A corresponding arrangement is suitable for regulating are dynamos within wide
limits.
DESCRIPTION OF THE DRAWINGS.
Fig. 1. is a diagrammatic representation of a dynamo whose field magnets a are
excited by a current collected by special brushes d d, while the current for the external
work m is collected by the separately movable brushes / 1.
Fig. 2. shows an armature n with one turn of split conductor o wound so as not to
be parallel to the axis of the armature.
Fig. 3 shows one field magnet of a single magnet machine with pole pieces shaped
so as to avoid foucault currents in a split conductor. 97 are points' so that a con-
ductor coming under the influence of a pole comes under one point first; thus entering
the field gradually.
Fig. 4 is a diagram of the connections for a series motor. is the commutator. The
hrushes are electrically an

page_text: If the torque is to be lessened, the brushes & rubbers are shifted against the
direction of the arrow, & this cuts out the field coils in the right proportion to prevent
sparking.
Thus, when the rubber is on 8 there is only one portion of the field coils in circuit.
A farther movement brings the rubbers on h h and g at the same time, & short
circuits the motor. A still farther movement reverses the motor, & then gradually
increases the torque. is a stop to prevent too great a movement.
In the position
shewn the motor moves as shewn by the arrow.
In Fig. 5 a is the field magnet, & c is a resistance in shunt to it. In the position
shown there is no torque. At right angles to it there is no path through the shunt
resistance, so the field is fully excited. The reversal &c. is the same as before.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is.
1.) In a direct current dynamo, separate main and excitation brushes capable of
independent movement, substantially as described.
2.) In a direct current dynamo or motor, divided armature conductors arranged so
as to pass into or out of the field gradually, substantially as described.
3.) In combination with a series motor or dynamo, mechanism to shift the brushes
and weaken the field simultaneously for the purpose explained.
Dated this 30th day of June 1889.
JAS. SWINBURNE.