An Improved Method of and Means for Facilitating the Starting of Single or Polyphase Alternating Current Motors and like Apparatus.
Year: 1898

page_text: Date of Application, 29th Jan., 1898-Accepted, 7th May, 1898
COMPLETE SPECIFICATION.
An Improved Method of and Means for Facilitating the Starting
of Single or Polyphase Alternating Current Motors and like
Apparatus.
I, MAX DERI, of Wipplingerstrasse 30 Vienna, in the Empire of Austria,
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:—
In electric motors for single or polyphase alternating currents and in alternating
current apparatus generally, where short circuited induction coils are used, it is
necessary under certain circumstances, especially upon starting motors, to inter-
pose resistance in the circuit of these induction coils in order to modify the phase
angle for the purpose of increasing the circumferential power.
For this purpose there are usually arranged upon the armature, in both single
and polyphase induction motors, contact rings which by means of brushes are
inserted in the circuit of the armature winding resistance, which latter are again
either cut out or short circuited as soon as the armature has attained a suitable
speed of rotation.
This method, however, entails various disadvantages and complications in 'the
construction of the armature. Thus, for example, the formation of the armature
winding is more difficult and its induction less effective; contact rings, brushes,
connections and so forth are also necessary.
In other cases,
in the case of single phase alternating current motors for instance,
a collector is interposed in the short circuit winding of the armature, in order to
produce by means of this collector, through oblique placing and short circuiting
of brushes, a considerable circumferential power for starting the motor. The
conduction of the induced currents through the collector and brushes is, however,
only necessary during the starting of the motor and is interrupted when the arma-
ture has attained a certain speed; from this time the armature is kept rotating
by means of the induction of the short circuited armature windings and the cur-
rents in the collector and in the brushes are then not only superfluous but even
disadvantageous.
The object of this invention is to obviate the defects named in the construction
and use of alternating current motors and apparatus, and consists essentially in
connecting the groups of coils or bobbins upon the armature with resistance or
with collectors and brushes and in varving the members of poles in such a manner
that the resistance or collectors and brushes may be put into or out of action
according to requirements, that is to say, they may either conduct current or not.
In the accompanying diagrammatic drawing;
Figure 1 represents a constructional form of connection of a series of windings
with resistance wires.

page_text: :
Figure 2 shows a constructional form of the connection of a series of bobbins
with resistance wires.
Figure 3 shows a constructional form of the connection of armature windings
with a collector, and
Figure 4 shows a constructional form of the arrangement of the field magnet
winding for the variation of the number of poles.
As shown in Figures 1 and 2, the windings or coils upon the armature are
arranged and connected in such a manner that they (being exposed to a four pole
alternating field, for example as represented in Figures 1" and 2") conduct the
induced currents in series and form a short circuited circuit, whilst in a two pole
alternating 'field (Figures 1 and 2) the sum of the electro motive forces induced
in the collective windings or coils of the group is nil in every position alike.
In the four pole system, of induction represented the path of the current will be
as diagrammatically shown in Figures 1 and 2, 1-1-2-2-3-3¹, -41-4–1
and, as will be apparent, no difference of potential exists between the points of
connection a and a or a and a¹; with two pole induction, on the contrary,
differences of potential exist between a and a, and also between a¹ and a¹ If
therefore the points a and a or a¹ and a¹ are connected by conductors, currents
will flow in these latter with two pole induction and the windings or coils also
will in this case be conductors. The connecting conductors will however become
dead as soon as the induction is produced by a four-pole field.
If then, upon the armature such four pole, short circuited windings or coils
are arranged and the connection points a, a... connected by means of suitably
. dimensioned resistances 1.
which thus form invariable component parts
of the armature winding, the result is obtained that with two pole induction the
resistances are in action, whilst, if after the attainment of the desired speed the
induction is made four polar, the resistances are put out of action. The armature
windings are of course employed to better effect with four-pole induction, if resis-
tances are interposed both between the points a, a. and between the points a¹. . .
whereby a kind of linking of the induced coils is effected.
The manner in which, in accordance with this invention the connection of the
armature windings with a collector is effected in single phase induction motors
for the purpose of the production of the starting rotating moment, is shown dia-
grammatically in Figure 3.
In this case the points of connection of the windings, are not, as above, connected
to single closed circuits, but the points a³ b b c¹
n2 al are connected in
pairs with the commutator strips in a manner similar to that of the drum winding
of an ordinary dynamo armature. The separate four-wire windings are treated
as simple diametral windings and combined in the known manner so as to form
a continuous armature winding.
In this case also it is preferable to form the connecting wires between the
points a, b, c. . . and the commutator strips of wire of sufficiently great resis-
tance to obtain the necessary closing resistance for giving the desired starting
moment and also to prevent sparking at the brushes. The brushes B, B which
as is well known, are arranged obliquely to the field, are then short circuited one
with the other.
:
If an armature constructed in this manner is submitted to the influence of a
two-pole alternating field difference of potential will exist between the points a¹ a²
61 62 ...; induced currents will therefore flow through the brushes and produce
a rotating moment which will start the armature. When the required speed is
attained the field is converted into a four-pole field as above described, the induced
currents then flow through the short circuited windings without resistance and
produce the circumferential force which maintains the armature in rotation.
Between the points a¹ a²-6¹ b² no difference of potential now exists, and conse-
quently no: current exists in the commutator strips and brushes. In order to
fully utilise the induction of the armature winding, with a two pole field, a com-
mutator may also be arranged upon each side of the armature, and each commu-

page_text: tator connected in the manner described with the points of the armature windings
turned towards it, or a commutator may be joined to the reciprocal connection
points of the armature windings.
It is advantageous in practice to employ the smaller number of poles for the
arrangement for starting motors and other apparatus, and the larger number of
poles for their normal working, but it is of course apparent that the same result
may be obtained if the employment of the larger number and the smaller number
of poles is transposed.
In order that the field winding may be so reversed in all the above cases that
the number of poles for starting is either a multiple or an aliquot part of that for
normal working, the field winding is connected with a reversing device of any
suitable kind; one form of such device is represented diagrammatically in Figure 4,
in which the arrows indicate the direction of the magnetic flux. By suitable
switching either a is connected with d and b with c, which corresponds to a
two pole field, or a is connected with c and b with d, whereby a four pole field
is obtained.
This form relates to the mono phase winding of the motor field; the arrangement
can however be employed with a corresponding multiple reversing device for poly-
phase fields or for linked field windings.
The reversing device may be actuated either by hand or automatically.
In the constructional forms represented by way of example the number of poles
has been taken as two and four respectively for the sake of greater clearness, and
a corresponding number of windings and bobbins selected. It will, however, of
course be understood that any number of poles or a multiple of the same may be
employed and the field and armature winding and also the reversing device corre-
spondingly arranged without thereby in any way departing from the spirit of
the invention.
Having now particularly described and ascertained the nature of my said in-
vention and in what manner the same is to be performed, I declare that what I
claim is
_
1. A method of increasing the starting rotating moment in monophase or multi-
phase alternating current motors and apparatus generally, characterised by the
fact that groups of windings or coils upon the armature are connected with resis-
tance or with commutators and brushes in such a manner, and the number of poles
so varied in any suitable manner for starting the machine, that the resistance or
collectors and brushes are conductors of current upon the starting of the motor
or other apparatus, and non-conductors of current upon the attainment of the
normal speed of rotation.
2. A form of carrying out the method described in Claim 1, characterised by
the fact that resistance r,.rl are interposed between the connection points a, a,
a¹, a¹... of correspondingly grouped windings or coils of the armature in such
a manner that they are conductors of current with the X-pole alternating field
formed for starting the apparatus and effect the desired phase displacement,
whilst on the contrary they become non-conductors of current with the number
of poles alternated to a multiple or to an aliquot part of X upon the attainment
of the normal speed of rotation. (Figures. 1 and 2).
3. A form of carrying out the method described in Claim 1, characterised by
the fact that the strips of a commutator are connected with the connection points
of the correspondingly grouped windings or coils of the armature in such a manner
that with the X-pole alternating field formed for starting the apparatus the com-
mutator and the brushes B, displaced with respect to the motor field in the known
manner are conductors of current, whilst on the contrary the commutator, brushes
and likewise all the connecting wires thereto appertaining become non-conductors
of current with the number of poles altered to a multiple or to an aliquot part
of X upon the attainment of the normal speed of rotation (Figure 3).
4. For carrying out the method described in Claim 1, a reversing or switching

page_text: device for actuation either by hand or automatically, by means of which the field
winding may be reversed in such a manner that the number of poles of the
field may be thereby varied according to requirements. (Figure 4).
Dated this 29th day of January 1898.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.