Improvements in Alternating Current Motors.
Year: 1899

page_text: Date of Application, 22nd Apr., 1899-Accepted, 29th July, 1899
COMPLETE SPECIFICATION.
Improvements in Alternating Current Motors.
I, MAX DÉRI, of 1, Reichraths Strasse No. 3, Vienna, Austria, Electrician,
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 arrangements of alternating current motors described in the Specification
to my Patent No. 2426 of 1898, which have for their object to produce a consider-
able starting moment in polyphase and single phase alternating current motors, it
was assumed that the magnetic field is arranged for a definite number of poles
during the starting period, and for a different number of poles, which number is
a multiple or aliquot part of n during the working period.
=N
According to my present invention it is however possible to choose the two
different numbers of poles with a different proportion to that above described,
such as 4: 6; 6: 8; or 8: 12 &c.
In fact every desired proportion between the two numbers may be taken, and
the practical carrying out of the arrangement is only subject to the condition
that the greatest common divisor of the two numbers shall give in the one
case an even quotient and in the other case an uneven quotient. These quotients
are in the above given examples respectively 2 and 3; 3 and 4; 2 and 3.
On the accompanying drawings Figs. 1ª and 1ª shew diagrammatically the
arrangement and connections of the windings on the armature, by way of
example, for a single phase motor. The two sets of polar numbers are here
assumed to be respectively 4 and 6.
The greatest common divisor of these numbers being 2, (corresponding to a
semicircle) the diametrically opposite windings are connected together.
In the six-polar field, of each two corresponding windings S1 and S'; S2
and S&c., the one winding will be opposite the north pole while at the same
time the other will be opposite the south pole, as shewn. On the other hand
in the four-polar field both windings of each pair will be opposite two poles
of the same sign.
If therefore the windings S₁ S¹, S² S², &c., be connected in pairs in such
Bequence that in the field of dissimilar poles their electromotive forces, connected
in series, are short circuited, then in the field of similar poles the windings
will be connected in parallel with respect to their electromotive forces.
Such winding portions of the armature formed by pairs of coils are grouped
in continuous series in connection with the collector, in a similar manner to
that usual with continuous current armatures, as described in the said Specifica-
tion No. 2426 of 1898, so that in the example given on the accompanying
drawing, the armature thus prepared represents in the 4 polar field suitable for
starting an ordinary collector armature while on the other hand in the 6 polar
field it represents a short circuited armature.
Fig. 1 shews the connections, and arrangements of the armature winding
which are suitable for the case where resistance wires are arranged between
the brushes; Fig. 1' on the other hand shews the connections and arrangements

page_text: for the case where the resistance wires r are to form the connections of the pairs
of coils with the collector sections, the short circuit connection being formed
of good conducting wires c.
The application of this method for the winding and connection of the armature
for polyphase motors can be readily determined from the above description. Thus
for example if the armature Fig. 1" belonged to a polyphase motor, the collector
would be dispensed with, and the resistance wires r would be put in conducting
connection with each other at those points where, as shewn in Fig. 1, they
are connected to the collector sections. In this case the corresponding parts of
a pair of coils would be connected together by the resistance wires in the
4-polar field, and would be short circuited without these resistance wires in the
6-polar field.
As regards the connections of the magnet windings alternately for the one and
for the other polar number that is, in the above examples, for the 4-polar and
the 6-polar field, Figs. 3 and 3" shew a method whereby the change of the
connections can be effected in a very simple manner. Fig. 2 shews the scheme of
the arrangement and Figs. 34 and 3* diagrams of the winding circuits in connec-
tion with the contact switch. Fig. 3 shewing the arrangement for a ring
winding, and Fig. 3 for a drum winding.
The magnet winding is divided into such a number of coils which is a common
multiple of the two polar numbers; for example into 12 coils as 12 is divisible
by 4 and 6.
Assuming with reference to Fig. 2 that the consecutively numbered 12 coils
be first arranged for 4 poles (every 3 coils with alternately reversed connection)
and then for six poles (every 2 coils also with alternately reversed connections)
then it will be seen that certain of the coils (namely 1, 2, 3, 4, 6, 11) will have
connections of the same direction for both cases while the other coils (namely 5, 7,
8, 9, 10, 12) will require to have connections of different direction for each
case. The coils are combined in any desired manner in two groups corresponding
to the said two categories, having due regard to the direction of the connections,
so that two groups are formed, having altogether 4 ends (a¹ a², el e²), not including
the two supply terminals 21 2².
In order now to produce at one time 4 poles and at another time 6 poles it
is sufficient to connect in series or in parallel the ends a¹ a² and e¹ by means
of the switch U, either in the one direction or the other. In Figs. 34 and 3"
for example all connections, both those of the separate coils of the two groups,
as also the two groups with each other, are shown connected in series.
According to the position of the switch U, the series is at one time z¹ e¹ e² a² a¹ z²
and at another time z¹ e¹ a² e a¹ z2 whereby the field winding will in one case
be four polar and in the other case six polar.
The above described example only serves to clearly explain the method; it
will be evident that various other combinations for the grouping and connections
can be arranged.
Having now particularly described and ascertained the nature of this
invention and in what manner the same is to be performed, I declare that what
1 claim is:
1. In the arrangements of alternating current motors described in the Specifica-
tion to Patent No. 2426 of 1898, the disposition of magnetic fields excited by
means of alternating currents, now with an optional number of poles and now
with an also optional number of poles but different from the first, in combination
with resistance introduced into the armature winding in such a manner, that they
convey currents on starting the motor in the magnetic field with poles, while
they carry no current when the motor runs in the magnetic field having a number
of poles differing from n substantially as described.
2. In the arrangements of single phase alternating current motors described in
the Specification to Patent No. 2426 of 1898, the disposition of magnetic fields
-

page_text: excited by means of alternating currents, now with an optional number of poles
and now with an also optional number of poles but different from the first, in
combination with a collector on the armature so arranged that on starting the
motor in the magnetic field with n poles the collector conveys currents by means
of brushes and connection wires, while when the motor runs in the magnetic
field having a number of poles different from n, the collector carries no current,
substantially as described."