Improvements in or relating to Dynamo Electric Machinery.
Year: 1897

page_text: PROVISIONAL SPECIFICATION.
Improvements in or relating to Dynamo Electric Machinery.
I, CONRAD LUDVIG ROSENQVIST, of 28, Bedford Place, in the County of London,
Engineer, do hereby declare the nature of this invention to be as follows:-
My invention relates to dynamo electric machinery and in particular to machines
which are adapted to be operated either as single phase alternating current motors
or as direct current motors. Some of my improvements are furthermore applicable to
motors and generators of the ordinary type.
The chief object of my invention is to provide a single phase alternating current
motor which shall he capable of operating efficiently on circuits of any desired
periodicity, which shall be effective in starting, and in which the current consumption
will be regulated in proportion to the work done without causing any fluctuation
in the lights operated from the same circuit.
The chief features of my invention consist in an improved construction of dynamo
machine armature, also in a new method of winding the field magnets of those
alternating current motors in which two sets of windings are provided on the field
magnet, whereby when a current is flowing in one set of windings the secondary
currents developed in the other set of windings are neutralised, also in an improved
construction of field magnets for dynamo machines, whereby the central portion of
the pole piece is more strongly magnetised than the side portions thereof. My
invention further comprises an improved indicator which can be adjusted so that a
lamp shall be lighted or an alarm given when the machine spindle attains a pre-
determined speed of rotation, and a method and means for varying the excitation of
the field magnet of a generator or motor in accordance with the torque.
My improved armatures are constructed with two or more separate cores placed side
by side upon the same spindle. Each core is wound with coils, and said coils are
connected in succession to a single commutator. The several cores are staggered,
that is to say, are secured to the shaft so that the coils on said cores are displaced
relatively with regard to each other. The coils are connected in any suitable manner,
but preferably in series and in succession so that any one coil has one of its ends
joined to coils which are not upon the same core as itself. By this means I increase
the distance between the coils on each core and thereby the effective polar surface of
the core without diminishing the total number of coils or commutator bars for the
entire armature. In the case of a single phase alternating current motor such an
armature as above described will be provided with two collecting rings in addition to
the commutator, said rings being connected to suitable points of the armature
winding or to suitable commutator bars according to the number of field magnet
poles with which the machine is provided. The method of operating is somewhat as
follows:-
The source of alternating current is first connected with the cominutator brushes,
and the armature thereby caused to rotate, its speed increasing until synchronism is
attained when the mains are connected to the collecting ring-brushes so that the
armature will be supplied with an alternating current and the field magnet coils are

page_text: connected to the commutator brushes so that a rectified pulsating current is supplied
thereto.
My improved method of preventing currents from being developed in one winding
of a field magnet when an alternating current is passed through the other winding
consists in displacing the coils of the one winding relatively to the other so that the
secondary currents induced in the coils of one winding by the flow of alternating
currents in the other winding neutralise or approximately neutralise each other.
When I desire to arrange that one portion of a pole shall be more strongly
magnetised than another I slot the pole piece in a suitable manner so that an extra
coil may be wound on the portion required to be strongly magnetized. Said extra
coil may be in series or not with the remainder of the field coils.
In order that a warning may be given when a synchronous motor has attained its
correct speed I use a simple form of indicator in which a flexible spring is adjustably
mounted on the armature shaft; said spring carries at its end a contact which is
moved radially outwards by centrifugal force when the shaft rotates, and is so adjusted
that at a predetermined speed of rotation the contact touches one of the collecting
rings or a concentric ring connected with the circuit and causes a lamp to be lighted
or an alarm to sound. Such a device can be used to indicate when any rotating
shaft has attained a predetermined speed.
My arrangements for causing the excitation of the field magnet of a machine to
vary with the torque are as follows:-The armature pulley of the machine is not
fixed to the shaft and is prevented from moving longitudinally by a collar at
one end which is fixed to the shaft, and at the other end by a sleeve which can move
axially along but not rotate on the shaft. Said sleeve is maintained in contact with
the pulley by means of a spiral spring and the contiguous faces of the pulley and
sleeve are shaped to the form of an interlocking spiral. The sleeve is connected with
a suitable resistance in circuit with the field magnet coil so that its movement along
the shaft varies the resistance in circuit and the excitation of the field magnet.
The operation of the device is as follows:-
Assuming that the load on the pulley is increased the pulley will be retarded and
thereby move the sleeve moved along the shaft compressing the spring and cutting
out resistance from the field magnet circuit. An increased torque is thereby
developed by the motor capable of coping with the increased load on the pulley.
This device can be applied to generators as well as to motors, as will be readily
understood.
Improvements in or relating to Dynamo Electric Machinery.
I, CONRAD LUDVIG ROSENQVIST, of 345, Albert Road, Aston, Birmingham, in the
County of Warwick, late of 28, Bedford Place, in the County of London, Engineer,
do hereby declare the nature of this invention and in what manner the same is to
be perforined to be particularly described and ascertained in and by the following
statement:-
My invention relates to dynamo electric machinery and in particular to
machines which are adapted to be operated either as single phase alternating
current motors or as direct current motors. Some of my improvements are
furthermore applicable to motors and generators of the ordinary type.

page_text: The chief object of my invention is to provide a single phase alternating
current motor which shall be capable of operating efficiently on circuits of any
desired periodicity, which shall be effective in starting, and in which the current
consumption will be regulated in proportion to the work done without causing any
fluctuation in the lights operated from the same circuit.
The chief features of my invention consist in an improved construction of dynamo
machine armature, also in a new method of winding the field magnets of those
alternating current motors in which two sets of windings are provided on the field
magnet, whereby when a current is flowing in one set of windings the secondary
currents developed in the other set of windings are neutralised. My invention also
comprises an improved indicator which can be adjusted so that a lamp shall be
lighted or an alarm given when the machine spindle attains a pre-determined speed
of rotation. A further object of my invention is to provide a method and means
for varying the excitation of the field magnet of a generator or motor in accordance
with the torque.
My invention is illustrated in the accompanying drawings in which
Figure 1 is an elevation somewhat diagrammatical of a four-pole machine having
an armature constructed and wound according to my invention.
Figure 2 is a side elevation of the same illustrating also my improved means for
varying the excitation of the field magnet in accordance with the load on the shaft
of the armature.
Figure 3 is a diagram illustrating another method of connecting the armature
coils.
Figure 4 is a diagram shewing the development of a drum armature constructed
in accordance with my invention.
Figure 5 is a horizontal section of a field magnet wound in an improved manner
hereinafter explained.
Figure 6 is an elevation illustrating my improved device for lighting a lamp when
a desired speed of rotation of a shaft has been obtained, and will be hereinafter fully
explained.
Referring now more particularly to Figures 1 and 2, my improved armatures are
constructed with two or more separate cores, three being shewn in the drawing
marked A, B, C, secured side by side on the same spindle 1. In Figure 1 the cores
are shewn one outside the other in order that the position of the arinature coils may
be somewhat more clearly indicated. Each core is wound with coils 2, and said coils
are connected in succession to a single commutator 3. The cores A, B, C are
staggered, that is to say, are secured to the shaft 1 in such a manner that the coils 2
thereon are displaced relatively with regard to each other as clearly shewn in Figure 1.
In Figures 1 and 2 the coils are connected in series and in succession so that any
one of the coils has its ends joined to coils which are not upon the same core as itself,
for example, the ends of a coil on a core A are joined to coils on cores B and C, one
on each side. The commutator bars in a multipolar machine are cross connected in
the usual manner as shewn in Figure 1, so that the two halves of the armature will
be joined in parallel. The coils may, however, if desired be so wound as to obviate
the necessity for cross connecting the commutator bars as shewn for example in
Figure 3 in which a four-pole machine with a twelve part commutator is shewn.
The holes through which the coils are wound are shewn as being of different sizes
to indicate on which core of the arinature the coil is situated, the large slots marked 4
being in the core A for example, the next size marked 5 being in the core B, and the
smallest 6 in the core C. Starting from the commutator bar 7, the winding passes
through a slot 4 on the core A then to another commutator bar 8, then through a
slot 6 on the core C, and back to a cominutator bar 9 next in front of the bar 7, from
thence it passes to another slot 6 on the core C opposite the first slot 6 to a
commutator bar 10 and through a slot 5 on the armature core B. Without tracing
the winding throughout, it will be sufficient to say that after passing through two
diametrically opposite slots in one core, the winding passes through two similar

page_text: slots on the next core, and then on the next core; the coils being thereby
connected in series.
In applying my improved method of construction to a drum armature I arrange
that each armature slot shall be capable of accommodating three wires as shewn in
Figure 4.
In order, however, to equalize and distribute the windings I prefer that
the wire shall not pass through the same three slots in succession, for example,
starting from the commutator, bars 40 the conductor passes through slot 41 in the
armature core A thence through slot 42 in core B and slot 43 in core C, the wire is
then carried so as to embrace three teeth of the core C and down through the slot 44
of said core, slot 45 of core B and slot 46 of core C and then to the next commutator
bar 47; the shape of the next coil is not the same as the previous one, after passing
through the slots 41 and 42 the wire is taken through the slot 48 of core C and then
through slot 49 embracing three teeth of the core passing again through slots 45
and 46 to commutator bar 50. The third coil passes through slot 41 of core A,
slot 51 of core B and slot 48 of core C, and back through slot 49 of core C, slot 52
of core B and slot 46 of core A to the next commutator bar 53. Without tracing the
winding throughout in detail it will be readily seen that successive turns of the coil
pass through different slots in one only of the cores and the scheme of winding will
be readily understood from the figure, a few of the coils only being drawn to avoid
confusion. By passing three conductors through each slot I reduce the amount
of insulation that is required, because the difference of potential between the wires
in one slot is small and the ordinary insulation between them is sufficient, they will
require to be, however, heavily insulated from the iron core of the armature. If,
however, each conductor were placed in a slot by itself the insulation between it and
the iron core would be the same while there were three times as many slots as before;
consequently the area of the iron core would be reduced.
It will be observed that by this construction of armature, I increase the distance
between the coils of each core, and thereby the effective polar surface of the core
without diminishing the total number of coils or commutator bars for the entire
armature, furthermore, the number of slots in one of the cores will be only one half
or one-third or less part of the whole number of slots or armature coils.
The machine illustrated in Figures 1 and 2 is intended for use as an alternating
current synchronous motor, and is provided with a pair of collecting rings 11, 12, one
of said rings is joined to one commutator segment, and the other of said rings is
joined to a commutator segment which is 90 degrees from the first segment, the
difference of potential between said segments being a maximum with a four-pole
machine. The points with which the collecting rings are connected to the armature
will of course vary with the number of field magnet poles with which the machine
is provided. The method of operating is as follows:-
A source of alternating current is first connected in the commutator brushes 13, 14
and the armature thereby caused to rotate its speed increasing until synchronism
with the generator is obtained. The mains are now connected to the brushes 15, 16
bearing on the collecting rings 11, 12 and at the same time the field magnet coils are
connected to the commutator brushes so that a rectified pulsating current is supplied
to them.
In operating machines in this manner the field magnet coil through which an
alternating current passes before synchronism is obtained must necessarily be com-
posed of a few turns only, while that through which the rectified current from the
commutator brushes passes when the motor is running in synchronism with the
generator, should be composed of a large number of turns. Difficulty is experienced
when running the motor up to synchronism from the fact that the alternating current in
the field magnet coils induces in the coaxial coils secondary currents of very high
electro-motive force, which may break down the insulation. To obviate this, I dis-
place one set of coils with regard to the other as indicated in Figure 1, where the
alternating current coils are shewn at 17 being wound in slots 18 in the pole pieces,
while the direct current coils 19 are wound on the pole pieces in the ordinary way.
On consideration it will be found that the alternating current flowing in one coil 17

page_text: induces a current in the over-lapping coil 19, the said coil 19 has also a current
induced in it from the coil 17 next adjacent to the first mentioned, and this
second induced current being opposite in direction to the first, the total effect of
the two currents will be nil.
This method of winding the field magnets has the disadvantage that the com-
mutator brushes require to be in a different position when starting to that which
they have when the motor is running in synchronism, because the position of the
poles of the field magnet is altered, for example, in a four pole machine such as
illustrated in Figure 1 the poles are shifted through one-eight of the circumference
and therefore the brushes will require to be shifted the same amount. This altera-
tion of the brush position gives rise to some complications and in order to obviate
this and at the same time reduce the electro-motive force of the secondary currents
induced in the shunt coils I arrange that the series coils shall each cover a portion
only of the polar surface so that more series coils will be required to produce the
same amount of magnetism. The shunt coils, however, are wound so as to embrace
the entire polar surface, consequently the ratio of the number of turns in the series
coils to that in the shunt coils will be diminished and the electro-motive force induced
in the shunt coils correspondingly reduced.
In Figure 5 one method of arranging the field magnet winding in accordance with
the above principles is indicated, the polar surface is divided by slots into three parts
corresponding with the three sections of the armature core, each portion of the polar
surface is wound with the series coils, the shunt coils therefore surround the whole
polar surface as clearly shewn in the Figure. Under these circumstances, since each
series coil magnetises one-third of the pole three times the number of coils would
be required as would be necessary if the coils embrace the entire polar surface. The
shunt coils are unaltered and therefore the electro-motive force induced therein
depends upon the ratio of the number of turns in the shunt coil to a number of turns
in the series coil, the electro-motive force will only be one-third of what it is with
an ordinary arrangement.
My improved method of arranging the field magnet winding is not confined to
four-pole machines such as illustrated and furthermore the series coils may, if
desired, be divided into more than three sets. Preferably, however, the number of
sets of series coils should correspond with the number of cores in the armature.
At the bottom of Figure 1, I have shewn a switch by means of which the alterations
in the connections may be readily effected, but as such switch forms no part of my
invention, I do not describe it here.
Referring now to Figure 6, 20 is the shaft of a synchronous motor, 11 and 12
being the collecting rings, and 21 is a flexible spring adjustably mounted in a slot 22
in the shaft 20 and secured therein by a set screw 23. One of the collecting rings 11 is
uninsulated on a portion of its interior surface and when the shaft has attained a
certain speed, the centrifugal force acting on the flexible arm 21 will cause the same
to make contact through the contact point 24 with said ring. To the brush 16
which bears on the other collecting ring 12, one terminal of a signal lamp 25 is
connected, the other terminal of said lamp being connected to the dynamo frame and
through the bearings with the shaft 20 as indicated diagrammatically by the line 26.
The action of this device is as follows:-
When the speed of the shaft 20 reaches a certain amount, which can be regulated
by adjusting the spring 21 in the slot 22, the contact stud at the end of said spring
makes connection with the ring 11, thereby closing a circuit between the two
collecting rings and the lamp 25, and lighting said lamp. In place of the lamp any
suitable signal or alarm may be given, obviously the use of a device similar to that
described is not confined to the shafts of alternating current motors, but may be
used to indicate when any rotating shaft has attained a pre-determined speed.
My arrangements for causing the excitation of the field magnet of a machine to
vary with the torque are shewn in Figure 2. The armature pulley 27 of the machine
is not secured to its shaft 1, and is prevented from moving longitudinally thereon by
a collar 28 secured to said shaft. At the other end of the pulley, I provide a sleeve 29

page_text: which can move axially along, but not rotate on the shaft, and which is maintained
in contact with the pulley 27 by means of a spiral spring 30. The end face 31 of
the pulley and that 32 of the sleeve 29 are shaped in the form of an inter-locking
spiral. The energy is therefore, transmitted froin the pulley to the shaft or vice
versa, by means of the inter-locking faces of the pulley and sleeve, the spring 30
being compressed according to the amount of power transmitted.
resistance in circuit with the field magnet coil which is varied in accordance
with the movement of an arm 34 connected with the sleeve 29.
The operation of the device is as follows:-
33 is a
Assuming that the machine is an electric motor, and that the load on the pulley
is increased, said pulley will be retarded relatively to the shaft and owing to the
inclination of its face 31, will cause the sleeve to move along the shaft compressing
the spring. The movement of said sleeve through the arm reduces the resistance
in the field magnet circuit and increases the excitation of the motor. An increased
torque is thereby developed by the motor shaft capable of coping with the increased
load on the pulley. Other means may be used for causing the resistance in the
field magnet circuit in accordance with the movement of the sleeve on the motor
shaft as will be readily understood. Furthermore, the device is applicable to
generators as well as motors.
Machines constructed in accordance with my invention may be employed for
various purposes, for example, by connecting the shunt field magnet winding to
the commutator brushes the machine will work as an alternate current generator,
or it may be used as a direct current generator or motor. Furthermore, when
supplied with alternating currents it will transform the same into direct currents
without being driven mechanically, and it may also be used for transforming direct
currents into alternating currents; in the latter case the frequency of the alternating
currents may be varied by varying the excitation of the field magnet and thereby
the speed of rotation of the armature.
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. A synchronous alternating current electric motor, whose main field magnet poles
are slotted or perforated near the inner edge, and are supplied with two sets of windings,
one winding surrounding the whole of each main polar projection, and the other
winding surrounding one half or a part of each of two adjacent main polar projections,
for the purpose specified.
2. A synchronous alternating current electric motor having a field magnet the core
of which is composed of two or more magnetically separated sections and provided
with two sets of windings one winding being distributed around the different sections
of the poles and the other winding embracing all said sections, substantially as
described for the purpose specified.
3. For dynamo electric machines, armatures having two or more independent
magnetic cores and constructed substantially as described.
4. A dynamo electric generator or motor supplied with a variable resistance in the
field magnet circuit, and suitable connections between the resistance and the pulley,
so as to cause an automatic variation in the field magnetisation as the strain or torque
on the pulley varies.
5. A dynamo electric machine provided with an adjustable automatic circuit closing
device operated by the centrifugal force, for the purpose of utilising the electric
current to light a lamp, or to cause an alarm to be given when the shaft has attained a
pre-determined speed of rotation, substantially as described.
Dated this and dan of I1900
W. P. THOMPSON & Co.,
322, High Holborn, London, W.C., Patent Agents for the Applicant.