Improvements in Single Phase Alternate Current Motors.
Year: 1895

page_text: Date of Application, 26th Nov., 1895
Complete Specification Left, 11th Aug., 1896-Accepted, 12th Sept.,
1896
[Communicated from abroad by SIEMENS & HALSKE, of Berlin, in the Empire of
Germany, Electrical Engineers.]
Improvements in Single Phase Alternate Current Motors.
We, SIEMENS BROS. & Co. LIMITED, of 12 Queen Anne's Gate, Westminster,
in the County of London, Electrical Engineers, do hereby declare the nature of
this invention to be as follows :-
Single phase current motors with induction armature are, as is well known, best
started by allowing them to commence running as polyphase current motors, the
currents of different phases being obtained by subdivision of the single phase
current.
The means for this purpose are known, and consist in imparting to the two
circuits connected in parallel different self induction or different capacity.
This method is indicated already by Ferraris in his discourse "Rotazioni
electrodinamische &c." of 17 March 1888.
As in asynchronous alternate current motors (even when supplied with a single
current) a rotating field is produced which, at a speed approaching synchronism, is
nearly circular, that is, possesses nearly constant intensity and constant speed of
rotation, the iron parts of such motors must be constructed in the same manner as
those of polyphase current motors.
The two kinds of motors will only differ materially in the mode of winding.
The auxiliary circuit, which is only used for starting the motor and is
disconnected when the motor is normally at work, is so located that, as little as
possible of the winding space required for the main circuit is encroached upon.
At the same time it is of importance that the winding should be as far as ever
possible situated in grooves upon the operative surface. This implies for the inner
part a drum winding and for the outer annular part a winding that shall be
entirely on the inner surface of the cylinder and on the end surfaces, and which
can be designated as a hollow drum winding.
It is advisable for this purpose to arrange the winding as follows.
Assuming the outer annular part to be the receiver of the current and the inner
revolving core to be the part with induced windings, theu as shewn at Fig. 1 of
the accompanying drawing, there are for each pole three grooves on the inner side
of the ring. In these grooves the coils a and b are wound in such manner that the
middle groove of the three remains empty.
The windings a are traversed by a current passing through all of them in one
direction, while in the windings 6 the current flows in the contrary direction.
Consequently when the coils a for example produce a north pole at the inner ring
surface, the coils b will produce a south pole.
The middle lines of the alternate opposite poles will coincide exactly with the
middle of the empty grooves.
In each two of these empty grooves an auxiliary coil c is wound, as at Fig. 2, so
that a coil c is situated exactly in front of two coils a and b, its middle line lying
exactly between the coils a and b.
The coils c are all coupled up in the same sense, so that they all produce
simultaneously either north poles or south poles on the surface. The opposite
poles are then always situated between the coils c.

page_text: The coils a and b are traversed by the main current while grouped in any desired
manner, either parallel or in series; the coils care similarly traversed by the
auxiliary current being also grouped in any desired manner, and they are
disconnected during the normal working.
The action of such an arrangement of the winding is as follows. Assuming the
coils a and b on the one hand and the coils c on the other hand to be traversed by
currents of different phase then, considering first the moment when the currents
ine are just equal to zero then the moment when the currents in a and b are cqual
to zero, it will be found, that at these moments the poles will be shifted relatively
to each other to an extent equal to one and a half times the distance apart of the
grooves and consequently by one quarter of the wave length.
With polyphase currents therefore there will be a progressive shifting of the
poles.
It will be observed that with this arrangement the coils c embrace a greater
section of iron than the coils a and b, and on the other hand that the coils a and b
together occupy double as much winding space as the coils c.
The auxiliary circuit only has half as much winding space as the main circuit,
and occupies that part of the winding space that is but little suited for the
reception of wires for the main circuit. The symmetry required for polyphase
currents is in this case entirely dispensed with and the advantage is thereby
attained that for the main circuit there is available as much winding as possible in
an exceedingly advantageous position.
Each groove might also be divided into several, such as two or three. Fig. 3
shews the division into two grooves.
The characteristic feature always remains that the main winding has a coil for
each pole while the auxiliary winding only has one coil for each pair of poles, if
for instance in Fig. 3 the part of the winding situated in each four grooves be
called a coil.
The induced part of the motor is constructed in the same manner, and it is
provided with the same devices for starting as for a polyphase current. Either an
absolute short circuited winding can be used or the winding can be arranged as a
polyphase current winding and be connected to sliding contact rings, so that on
starting resistances can be introduced, or the arrangement described in the
Specification to Letters Patent No. 21141 of 1894 can be employed.
Dated this 26th day of November 1895.
ABEL & IMRAY,
Agents for the Applicants.
Improvements in Single Phase Alternate Current Motors.
We, SIEMENS BROS. & Co. LIMITED, of 12 Queen Anne's Gate, West-
minster, in the County of London, Electrical Engineers, 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 :-
Single phase current motors with induction armature are, as well known, best
started by allowing them to commence running as polyphase current motors, the
currents of different phases being obtained by subdivision of the single phase
current.
The means for this purpose, are known, and consist in imparting to the two
circuits connected in parallel different self induction or different capacity.
is
This method is indicated already by Ferraris in his discourse Rotazioni electro-
dinamische &c." of 17th March 1888.
As in asynchronous alternate current motors (even when supplied with a single

page_text: current) a rotating field is produced, which, at a speed approaching synchronism, 15
nearly circular, that is, possesses nearly constant intensity and constant speed of
rotation, the iron parts of such motors must be constructed in the same manner as
those of polyphase current motors.
The two kinds of motors will only differ materially in the mode of winding.
The auxiliary circuit, which is only used for starting the motor and is disconnected
when the motor is normally at work, is so located that, as little as possible of the
winding space required for the main circuit is encroached upon. At the same time
it is of importance that the winding should be as far as ever possible situated in
grooves upon the operative surface. This implies for the inner part a drum
winding and for the outer annular part a winding that shall be entirely on the
inner surface of the cylinder and on the end surfaces, and which can be designated
as a hollow drum winding.
It is advisable for this purpose to arrange the winding as follows.
Assuming the outer annular part to be the receiver of the current and the
inner revolving core to be the part with induced windings, then as shown at
Fig. 1 of the drawing accompanying our Provisional Specification, there are for
each pole three grooves on the inner side of the ring. In these grooves the
coils a and b are wound in such manner that the middle groove of the three remains
empty.
The windings a are traversed by a current passing through all of them in one
direction, while in the windings 6 the current flows in the contrary direction.
Consequently when the coils a for example produce a north pole at the inner ring
surface, the coils b will produce a south pole.
The middle lines of the alternate opposite poles will coincide exactly with the
middle of the empty grooves.
In each two of these empty grooves an auxiliary coil c is wound, as at Fig. 2 so
that a coil c is situated exactly in front of two coils a and b, its middle line lying
exactly between the coils a and b.
The coils c are all coupled up in the same sense, so that they all produce simul-
taneously either north poles or south poles on the surface.
The opposite poles are then always situated between the coils c.
The coils a and b are traversed by the main current while grouped in any desired
manner, either parallel or in series; the coils c are similarly traversed by the
auxiliary current being also grouped in any desired manner, and they are disconnected
during the normal working.
The action of such an arrangement of the winding is as follows: Assuming the
coils a and b on the one hand and the coils c on the other hand to be traversed
by currents of different phase, then, considering first the moment when the currents
in c are just equal to zero then the moment when the currents in a and b are equal
to zero, it will be found, that at these moments the poles will be shifted relatively
to each other to an extent equal to one and a half times the distance apart of the
grooves and consequently by one quarter of the wave length.
With polyphase currents therefore there will be a progressive shifting of the
poles.
It will be observed that with this arrangement the coils c embrace a greater
section of iron than the coils a and b, and on the other hand that the coils a and b
together occupy double as much winding space as the coils c. The auxiliary circuit
only has half as much winding space as the main circuit, and occupies that part of
the winding space that is but little suited for the reception of wires for the main
circuit.
The symmetry required for polyphase currents is in this case entirely dispensed
with and the advantage is thereby attained that for the main circuit there is
available as much winding as possible in an exceedingly advantageous position.
Each groove might also be divided into several, such as two or three. Fig. 3
shews the division into two grooves.
The characteristic feature always remains that the main winding has a coil for

page_text: each pole while the auxiliary winding only has one coil for each pair of poles, if for
instance in Fig. 3 the part of the winding situated in each four grooves be called a
coil.
The induced part of the motor is constructed in the same manner, and it is
provided with the same devices for starting as for a polyphase current. Either an
absolute short circuited winding can be used or the winding can be arranged as a
polyphase current winding and be connected to sliding contact rings, so that on
starting resistances can be introduced, or the arrangement described in the Specifi-
cation to Letters Patent No. 21141 of 1894 can be employed.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, we declare that what we
claim is :-
-
In single phase alternate current induction motors, a method of winding for the
current receiving part consisting in providing for the main winding a coil for each
pole, while for the auxiliary winding there is only one coil for each pair of poles
which coil embraces a greater section of iron than the others and the middle of
which is shifted relatively to the middle of the first named coils a distance equal to
half the distance apart of the poles, substantially as and for the purposes
described.
Dated this 11th day of August 1896
ABEL & IMRAY,
Agents for the Applicants.