Improvements in Alternate Current Motors for Single and Polyphase Electric Currents.
Year: 1892

page_text: Date of Application, 17th Dec., 1892
Complete Specification Left, 16th Sept., 1893-Accepted, 21st Oct., 1893
PROVISIONAL SPECIFICATION.
Improvements in Alternate Current Motors for Single and Polyphase
Electric Currents.
1, ENGELBERT ARNOLD, of Weinbergstrasse No. 14 Zurich, Switzerland,
Professor, do hereby declare the nature of this invention to be as follows:
My invention relates to improvements in alternate current motors for single
and polyphase electric currents, which I will describe with reference to the
accompanying diagrammatic drawings.
Fig. 1 shows an iron ring F F on which are wound two opposite wire coils O and O₁
On the
the ends of which are connected to a generator of alternating currents.
central shaft is situated a bobbin K with short circuited windings aud. rotatable
with the shaft: In Fig. 1 this bobbin is indicated by a single closed winding. It
is furthermore assumed that the bobbin K has received such a speed of rotation
that it makes one complete revolution during, the interval of a single period or of
two alternations of current of the currents supplied to the field ring FF, that is to
It is also assumed
say, the bobbin shall have received a synchronous initial speed.
that at the moment in which the field current.J, passes through zero the bobbin is
situated in the position marked A B in Fig. 1.
The electromotive force induced
The bobbin K
in the bobbin K in this case reaches its maximum at that moment.
has a definite self induction. The strength of current. J, of this bobbin will
therefore not coincide with the phase of the induced electromotive force.
I will indicate the angle of the phase displacement by a. The current J, will
only attain its maximum when, the bobbin moving synchronously has passed
through the angle a, Fig. 1, or when it has passed out of the position A B into the
position CD. The current J, has meanwhile attained. the strength J₁ sin a if. J,
denotes the maximum value of the field. current. If H indicates the maximum
H sin a.
intensity of the field produced by J, then the simultaneous field intensity
1
=
The amount D. of the turning moment which is exercised on the bobbin K in the
position CD will be obtained if the strength of field is multiplied by the strength
of the current and by the.extent of the surface which the current flows measured
in the direction of the lines of force which is equal to f sin a if f denotes the
surface of the bobbin K.. Consequently:
DJ,,Hsin a.
A further calculation shows also that. the mean. turning moment for one
revolution becomes positive even when in place of a single bobbin, K several,
for instance m bobbins rotate in the alternating current field and which form an
angle of rm with each other and of. which. either each one is separately short
circuited or several are connected together to form a short circuited winding.
The initial rotation of the armature will be obtained by this turning moment
without requiring the armature to be bound. to accurate synchronism on account of
the interchangeability of the separate bobbins. The indicated arrangement. con-
sequently contains the motor principle of au a = synchronous single phase alternate
current motor.
In order to impart to the armature the necessary speed for starting and to give
it the faculty of starting with considerable torque various means may be adopted.
The starting can be effected by hand or by a motor suitably arranged for this
purpose.
I will describe in the following some electric starting apparatus.
Inzkio. 2 the armature. A is assumed: to be a Gramme ring.
As in a.continuous

page_text: The
current machine the separate bobbins are connected with the segments of a
collector C on which slide two brushes P and P. On starting the motor the
primary current J, is supplied not only to the field, but also to the armature.
alternate current motor now works with correct position of the brushes as a series
motor for continuous current. The maximum current in the armature always
coincides with the maximum field. The motor will consequently start under
favorable conditions and with considerable torque. The resistance R included in
the circuit allows the strength of current and torque to be regulated.
As soon as the armature approaches the synchronous motion, which takes place
in a short time, the collector segments are short circuited with each other. For
this purpose serves an insulated ring S capable of sliding on the shaft and which is
slid by means of a lever against the collector plates. The current now passes
directly from one brush to the other. The sparking on the collector is entirely
obviated and the armature works as a short circuit armature in the manner
indicated, with reference to Fig. 1. By the use of a short circuiting device the
brushes can be entirely removed from the collector after starting the machine. By
means of a centrifugal governor the putting in and out of gear of the short
circuiting ring can be effected automatically.
This arrangement can also be used for polyphase motors by a corresponding
increase in the number of the brushes. For a three-phase motor the collector
would have three brushes placed at an angle of 120° relatively to each other. The
current which such a motor would require for starting would be considerably decreased
by the use of a collector with short circuiting ring (short-circuit collector).
It is not, of course, necessary that all bobbins of the armature should be
connected with the collector; only part thereof need be used for the starting
arrangement. Fig. 3 shows such an arrangement. The ends of the bobbins oo
are connected with the collector segments. The short circuiting thereof is again
effected after starting the motor by means of the ring S. The ends of the
bobbins p p are on the other hand directly short circuited. The two windings oo
and p p may be arranged one above the other instead of side by side as at Fig. 3.
Generally speaking, it will not be advisable to directly short circuit the bobbins pp
because at the starting of the motor, that is to say when the motor is at rest they
will act as the secondary short circuited windings of a transformer, that is to say
they consume a large amount of energy without doing anything towards starting
the motor. In order to avoid this defect the ends of the bobbins p p are led to a
second short circuiting device situated on the shaft, and they are only short
circuited after the armature has attained a certain speed. Such an armature with
two separate windings of which the one is connected to the collector and the other
to a simple short circuiting apparatus, allows of the following mode of action of the
motor.
The bobbins oo which are connected with the collector have only a few windings, so
that no material sparking takes place on the collector and the collector plates are not
short circuited during the working of the motor so that the field current J, continually
flows through the armature bobbins o o. Two different moments now operate on
the rotation of the motor, namely, firstly a rotation moment resulting from the
bobbins oo, and secondly a rotation moment which corresponds to the short
circuited bobbins p p. The second rotation moment is dependent on a nearly
synchronous motion of the motor and will be equal to zero when the velocity of
the motor decreases too much. The first rotation moment is, on the other hand,
only dependent on the strength of current J. The strength of current, however,
will be the greater, the farther the motor remains behind the synchronous motion.
The first moment therefore has the tendency to maintain the motor in synchronous
motion. Such an alternate current motor with two separate windings on the
armature of which the one consists of short circuited bobbins and the other is
connected in series with the field current will consequently behave in a very
similar manner to a motor with rotary field.
In order not to obtain too high a speed large alternate current motors will always

page_text: be made multipolar. The connection of the bobbins with the collector can in that
case be effected according to a scheme for either parallel connection or series
connection. The series connection has the advantage that there are only two
brushes used; also, in this case it is not necessary to short circuit all the collector
plates. If the number of pole couples = n and the number of the collector
plates = 2, then it will suffice if z+1÷n collector plates are short circuited.
In Fig. 4 is shown a four pole arrangement with series connection of the
armature bars. The armature has at the circumference 26 bars and the
collector has 13 plates. If by means of the ring segment S 7 plates are
short circuited then every 4 bars will form a short circuited winding, for
instance a, 11, 11, 5, 5, b.
For the proper action of an alternate current motor of the described kind, it is
of great importance that the magnetic field produced by the alternating current
shall be as homogeneous as possible and the polar surface as large as possible.
These conditions are best fulfilled if each pole is divided into several separate
poles of the same sign. Fig. 5 shows for instance a two-pole arrangement of the
magnetic field. The north and south poles are each divided into 8 separate poles ;
nn indicate the north and ss the south poles. In this manner if one takes into
consideration the lateral radiation of the lines of force, the whole circumference of
the armature is utilised as polar surface, and the exciting spools distributed over
the entire polar surface produce a field as homogeneous as possible. With small
motors there is not sufficient room for placing the magnet windings on the poles,
but the same end will be attained by the use of a ring provided with projections in
the recesses of which the exciting winding is placed in the manner shown at Fig. 6.
A magnetic field constructed according to Figs. 5 and 6 enables a starting device
to be employed which is useful under certain circumstances. It is shown
diagrammatically at Fig. 7. A indicates the armature with a number of short
circuited bobbins. The field winding F F forms a single helical coil closed in
itself which is connected at two points with the alternate current generator.
It is now possible to produce a rotary field for starting the motor. For this
purpose the field winding is divided into several sections as with a continuous
current motor and from two points which for a two pole arrangement are
diametrically opposite, wires lead to the opposite brushes of a rotating current
reverser.
In Fig. 7 the corresponding points are indicated by 11, 221, 33¹ and the
corresponding brushes by a a, b b₁ce. Two diametrically opposite plates q' and q³
are connected with the sliding rings S1 S2 to which the current is supplied by the
brushes P¹ P. If the current reverser be turned in the direction of the arrow, the
magnetic field produced in the motor will move in the direction 1 2 3, and the motor
will start in the same way as a polyphase motor. The current reverser can be
driven by any suitable motor; a synchronous motion is not necessary.
When the motor has attained a certain speed, it will develop a powerful torque
and the current reverser can now be held stationary in any position.
The apparatus will be somewhat simpler if the contact brushes a be a₁ b₁ c₁ are
connected rigidly with the segments and the brushes P₁ P, are connected rigidly
with the sliding rings, while two brushes, of which the one connects the ring S₁
with
and the other connects the ring S, with ga, are made to rotate.
It will be evident that the winding with short circuit collector for a ring
armature can also be used with drum and disc armatures. Also, the arrangement
above described can be reversed, the armature being stationary while the magnetic
field rotates. Instead of connecting the armature winding in series with the field
current for starting the motor, it may also be connected in shunt therewith.
Fig. 8 shows a diagram with the armature connected in a shunt circuit.
Pr indicates the primary and S' S² the secondary windings of a transformer.
The field winding Flies in the one part S¹ and the armature winding in the other
part S of the secondary winding. The short circuiting arrangement of the

page_text: collector is such that on putting the same in gear the brushes are automatically
raised from the collector.
When the armature has two windings, of which the one is short circuited while
the other is connected to the plates of the collector, the secondary windings S, can
be gradually cut out of the armature circuit, while at the same time the number of
windings in the field circuit are increased. Fig. 9 shows this arrangement. The
field winding is situated between the contacts K and e. The contact Kis movable
so that the proportion between the windings S, and S, is thereby rendered variable.
If K is moved to e, the brushes P, P, are short circuited. If, however, it be
desired to raise the brushes off the plates, the short circuiting ring S must be pushed
in, otherwise this second winding of the armature will be inoperative.
An armature with collector and short circuiting device can also be applied as
follows in polyphase motors. Only the field is supplied with current.
On starting the motor the
other, or only a few plates are
connected in series in groups.
collector brushes are connected directly with each
short circnited, so that the wires of the armature are
Only after the motor has attained a certain speed,
are all the plates short circuited. The strength of current necessary for starting
will be diminished by this arrangement.
Dated this 16th day of December 1892.
ABEL & IMRAY,
Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in Alternate Current Motors for Single and Polyphase
Electric Currents.
I, ENGELBERT ARNOLD, of Weinbergstrasse No. 14ª Zurich, Switzerland,
Professor, 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 alternate current motors for single and
polyphase electric currents, which I will describe with reference to the drawings
accompanying my Provisional Specification.
1
Fig. 1 shows an iron ring F F on which are wound two opposite wire coils O
and O, the ends of which are connected to a generator of alternating currents.
On the central shaft is situated a bobbin K with short circuited windings and
rotatable with the shaft. In Fig. 1 this bobbin is indicated by a single closed
winding. It is furthermore assumed that the bobbin K has received such a speed
of rotation that it makes one complete revolution during the interval of a single
period or of two alternations of current of the currents supplied to the field
ring F F, that is to say, the bobbin shall have received a synchronous initial speed.
It is also assumed that at the moment in which the field current J₁ passes through
zero the bobbin is situated in the position marked A. B. in Fig. 1. The electro-
motive force induced in the bobbin K in this case reaches its maximum at that
.moment. The bobbin K has a definite self induction. The strength of current J,
of this bobbin will therefore not coincide with the phase of the induced
electromotive force.
1
I will indicate the angle of the phase displacement by a. The current J, will
only attain its maximum when the bobbin moving synchronously has passed through
the angle a, Fig. 1, or when it has passed out of the position A B into the
position CD. The current J, has meanwhile attained the strength J, sin a if J₁
denotes the maximum value of the field current. If H indicates the maximum
intensity of the field produced by J, then the simultaneous field intensity H sin
The amount D of the turning moment which is exercised on the bobbin K in the
position (CD will be obtained if the strength.of field is multiplied by the strength
=

page_text: of the current and by the extent of the surface round which the current flows
measured in the direction of the lines of force which is equal to f sin a if ƒ denotes
the surface of the bobbin K. Consequently:
DJ, Hf sin a.
A further calculation shows also that the mean turning moment for one revolution
becomes positive even when in place of a single bobbin K several, for instance
m bobbins rotate in the alternating current field and which form an angle of m
with each other and of which either each one is separately short circuited or
several are connected together to form a short circuited winding. The initial
rotation of the armature will be obtained by this turning moment without requiring
the armature to be bound to accurate synchronism on account of the inter-
changeability of the separate bobbins. The indicated arrangement consequently
contains the motor principle of an a = synchronous single phase alternate current
motor.
In order to impart to the armature the necessary speed for starting and to give
it the faculty of starting with considerable torque various means may be adopted.
The starting can be effected by hand or by a motor suitably arranged for this
purpose.
I will describe in the following some electric starting apparatus.
In Fig. 2 the armature A is assumed to be a Gramme ring. As in a continuous
current machine the separate bobbins are connected with the segments of a
collector C on which slide two brushes P and P2. On starting the motor the
primary current J, is supplied not only to the field but also to the armature. The
alternate current motor now works with correct position of the brushes as a series
motor for continuous current. The maximum current in the armature always
coincides with the maximum field. The motor will consequently start under
favorable conditions and with considerable torque. The resistance R included in
the circuit allows the strength of current and torque to be regulated.
For
As soon as the armature approaches the synchronous motion, which takes place
in a short time, the collector segments are short circuited with each other.
this purpose serves an insulated ring S capable of sliding on the shaft and which
is slid by means of a lever against the collector plates. The current now passes
directly from one brush to the other. The sparking on the collector is entirely
obviated and the armature works as a short circuit armature in the manner
indicated with reference to Fig. 1. By the use of a short circuiting device the
brushes can be entirely removed from the collector after starting the machine.
means of a centrifugal governor the putting in and out of gear of the short
circuiting ring can be effected automatically.
By
This arrangement can also be used for polyphase motors by a corresponding
increase in the number of the brushes. For a three phase motor the collector
would have three brushes placed at an angle of 120° relatively to each other.
The current which such a motor would require for starting would be considerably
decreased by the use of a collector with short circuiting ring (short circuit
collector).
It is not of course necessary that all bobbins of the armature should be connected
with the collector; only part thereof need be used for the starting arrangement.
Fig. 3 shows such an arrangement. The ends of the bobbins o are connected
with the collector segments. The short circuiting thereof is again effected after
starting the motor by means of the ring S. The ends of the bobbins p p are on
the other hand directly short circuited. The two windings oo and p p may be
arranged one above the other instead of side by side as at Fig. 3. Generally
speaking, it will not be advisable to directly short circuit the bobbins p p because
at the starting of the motor, that is to say when the motor is at rest they will act
as the secondary short circuited windings of a transformer, that is to say they
consume a large amount of energy without doing anything towards starting the
motor. In order to avoid this defect the ends of the bobbins p p are led to a second

page_text: short circniting device situated on the shaft and they are only short circuited after
the armature has attained a certain speed. Such an armature with two separate
windings of which the one is connected to the collector and the other to a simple
short circuiting apparatus, allows of the following mode of action of the motor.
The bobbins oo which are connected with the collector have only a few windings,
so that no material sparking takes place on the collector and the collector plates
are not short circuited during the working of the motor so that the field current J₁
continually flows through the armature hobbins o o. Two different moments now
operate on the rotation of the motor, namely, firstly a rotation moment resulting
from the bobbins o o, and secondly a rotation moment which corresponds to the
short circuited bobbins PP.
The second rotation moment is dependent on a nearly
synchronous motion of the motor and will be equal to zero when the velocity of
the motor decreases too much. The first rotation moment is, on the other hand,
only dependent on the strength of current J. The strength of current, however,
will be the greater, the farther the motor remains behind the synchronous motion.
The first moment therefore has the tendency to maintain the motor in synchronous
motion. Such an alternate current motor with two separate windings on the
armature of which the one consists of short circuited bobbins and the other is
connected in series with the field current will consequently behave in a very similar
manner to a motor with rotary field.
In order not to obtain too high a speed large alternate current motors will always
be made multipolar. The connection of the bobbin with the collector can in that
case be effected according to a scheme for either parallel connection or series
connection. The series connection has the advantage that there are only two
brushes used; also, in this case it is not necessary to short circuit all the collector
plates. If the number of pole couples n and the number of the collector plates
then it will suffice if + 1 collector plates are short circuited.
In Fig. 4 is shown a four pole arrangement with series connection of the armature
bars. The armature has at the circumference 26 bars and the collector has
13 plates. If by means of the ring segment S 7 plates are short circuited then
every 4 bars will form a short circuited winding, for instance a, 11, 11, 5, 5, b.
For the proper action of an alternate current motor of the described kind, it is
of great importance that the magnetic field produced by the alternating current
shall be as homogeneous as possible and the polar surface as large as possible.
These conditions are. best fulfilled if each pole is divided into several separate poles
of the same sign. Fig. 5 shows for instance a two pole arrangement of the magnetic
field. The north and south poles are each divided into 8 separate poles ;
nn indicate the north and ss the south poles. In this manner if one takes into
consideration the lateral radiation of the lines of force, the whole circumference of
the armature is utilised as polar surface, and the exciting spools distributed over
the entire polar surface produce a field as homogeneous as possible. With small
motors there is not sufficient room for placing the magnet windings on the poles,
but the same end will be attained by the use of a ring provided with projections in
the recesses of which the exciting winding is placed in the manner shown at
Figure 6.
A magnetic field constructed according to Figs. 5 and 6 enables a starting device
to be employed which is useful under certain circumstances. It is shown
diagrammatically at Fig. 7. A indicates the armature with a number of short
circuited bobbins. The field winding F F forms a single helical coil closed in
itself which is connected at two points with the alternate current generator.
It is now possible to produce a rotary field for starting the motor. For this
purpose the field winding is divided into several sections as with a continuous
current motor and from two points which for a two pole arrangement are
diametrically opposite, wires lead to the opposite brushes of a rotating current
reverser.
In Fig. 7 the corresponding points are indicated by 1 11, 2 2¹, 3 3¹ and the
corresponding brushes be a abbcc Two diametrically onnosite plates o' and o'

page_text: are connected with the sliding rings S₁ S to which the current is supplied by the
brushes P P². If the current reverser be turned in the direction of the arrow,
the magnetic field produced in the motor will move in the direction 1, 2, 3, and the
motor will start in the same way as a polyphase motor. The current reverser can
be driven by any suitable motor; a synchronous motion is not necessary.
When the motor has attained a certain speed, it will develop a powerful torque
and the current reverser can now be held stationary in any position.
The apparatus will be somewhat simpler if the contact brushes abc a₁ b₁₁ are
connected rigidly with the segments and the brushes P, P2 are connected rigidly
with the sliding rings, while two brushes of which the one connects the ring S₁
with and the other connects the ring S, with g, are made to rotate.
It will be evident that the winding with short circuit collector for a ring armature
can also be used with drum and disc armatures. Also, the arrangement above
described can be reversed, the armature being stationary while the magnetic field
rotates. Instead of connecting the armature winding in series with the field
current for starting the motor, it may also be connected in shunt therewith.
Fig. 8 shows a diagram with the armature connected in a shunt circuit.
Pindicates the primary and S' S² the secondary windings of a transformer. The
field winding F lies in the one part S' and the armature winding in the other part S²
of the secondary winding. The short circuiting arrangement of the collector is
such that on putting the same in gear the brushes are automatically raised from
the collector.
The
When the armature has two windings, of which the one is short circuited while
the other is connected to the plates of the collector, the secondary windings S, can
be gradually cut out of the armature circuit, while at the same time the number of
windings in the field circuit are increased. Fig. 9 shows this arrangement.
field winding is situated between the contacts K and e. The contact K is movable
so that the proportion between the windings S, and S, is thereby rendered variable.
If K is moved to e,, the brushes P, P, are short circuited. If, however, it be
desired to raise the brushes off the plates, the short circuiting ring S must be
pushed in, otherwise this second winding of the armature will be inoperative.
An armature with collector and short circuiting device can also be applied as
follows in single and polyphase motors. Only the field is supplied with current.
On starting the motor the collector brushes are connected directly with each
other, or only a few plates are short circuited, so that the wires of the armature
are connected in series in groups. Only after the motor has attained a certain
speed are all the plates short circuited. The strength of current necessary for
starting will be diminished by this arrangement.
If the motor can be constructed so that only a small amount of sparking can
take place at the collector, the short circuiting arrangement can be entirely
dispensed with.
The above described alternate current motor can be applied with peculiar
advantage when great starting power is required; it can therefore be usefully
combined with the known constructions of synchronous motors, for effecting the
starting of these.
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. An alternate current motor consisting mainly of a magnetic field excited by
alternating currents, and an armature the windings of which are so arranged that
the whole or part thereof are arranged and connected with the plates of a collector
in the same way as the armature windings of a bi or poly polar continuous current
motor, and which can be short circuited in themselves by means of a suitable short
circuiting device substantially as described.
2. An alternate current motor having an armature arranged and operating as set

page_text: forth in the first claim, the windings of which are connected with the alternate
current generator when the motor is first started, substantially as described.
3. An alternate current motor having an armature arranged and operating as
set forth in the first claim, the windings of which are short circuited through
resistance on first starting, by means of brushes sliding on a collector, substantially
as described.
4. An alternate current motor consisting mainly of a magnetic field excited by
alternating currents, and an armature arranged and operating as set forth in the
first claim, in combination- with a transformer so arranged that the field magnet
winding is included in the one part, and the armature winding in the other part of
the secondary coil of the transformer the proportion of the parts into which the
secondary coil is divided being adjustable by means of a sliding contact,
substantially as described.
5. An alternate current motor consisting mainly in the reverse of the arrangement
set forth in the first claim, that is to say consisting of an armature with short
circuited windings and a magnetic field the exciting windings of which are arranged
and connected to the plates of a collector in the same manner as the armature
windings of a continuous current motor, substantially as described.
6. In alternate current motors such as are referred to in the preceding claims,
the use of a magnetic field in which each pole consists of several separate poles of
the same sign, cach one being provided with a separate winding, substantially as
described.
7. The use of alternate current motors such as are referred to in the preceding
claims in combination with a synchronous single or polyphase alternate current
motor, for the purpose of starting the same with synchronous motion.
Dated this 16th day of September 1893.
ABEL & IMRAY,
Agents for Applicant.