Improvements in the Armatures of Induction-motors.
Year: 1897

page_text: Date of Application, 24th Dec., 1897
Complete Specification Left, 20th Sept., 1898-Accepted, 17th Dec., 1898
Improvements in the Armatures of Induction-motors.
A communication from abroad from the MASCHINENFABRIK OERLIKON, of Oerlikon,
Switzerland
I, WILLIAM LLOYD WISE, of No. 46, Lincoln's Inn Fields, in the County of
London, Consulting Engineer and Chartered Patent Agent, do hereby declare the
nature of this invention to be as follows:-
The winding-arrangements heretofore employed in the inducing system (short
circuited on itself) of induction motors for polyphase and monophase currents are:
(1) The so-called short-circuited armature of Dolivo-Dobrowolsky consisting of
two copper rings or copper discs at the ends of the armature cylinder and a
number of copper bars imbedded in the iron body in an insulated or uninsulated
manner, and arranged parallel to the axis, all the ends of the said copper bars
being directly electrically connected together by means of the copper rings or
plates; and
(2) A so-called phase-armature, with coils of copper wire or copper bars insulated
from the iron body and progressing according to the manner of the drum winding
or gramme winding of continuous-current armatures, the arrangement being such
that a definite number of compartments or phases of these coils are short-circuited
on themselves.
It is essential to the first arrangement that there be a good conductive con-
nexion of the ends of all the bars together at the ends, of the armature, so that
each end of each rod is connected electrically in a direct, and therefore as a rule
mechanical, manner with the adjacent end and with each following one. The
connexion is direct because the current can pass from each end to each other end
without having to pass through a bar or conductor. In the best-known form of
construction, this connexion is effected at each side or end by means of a copper
ring into which all the ends of the bars are soldered, screwed, or riveted. This
arrangement of the conductors has the well-known disadvantages that the cur-
rents induced in the bars accumulate in the connecting pieces between the bars,
and that in consequence of the resistance of these connexions between two
adjacent bars, a uniform distribution of the current-potentials in the bars pro-
portional to the induced electromotive forces, is prevented, and thus the regularity
of the secondary rotary field is disturbed. This construction is also attended, when
carried into practice, by the great difficulty that a good conducting connexion
with a ring must be made for each conductor at two places.. The resistance to
the passage of the current between the bars and the connecting rings may easily
constitute a considerable fraction of the total resistance of the effective current-
circuit.
These disadvantages are obviated by the arrangement of the phase-armature,

page_text: in which the insulated conductors form coils which are connected after
the
of the drum winding or
manner
the ring-winding of continuous
current armatures. In the drum-winding only those axially arranged conductors
are connected directly with one another that are situated almost at the
distance or pitch of a pole from one another. Each axial conducting piece is
completely and independently insulated. The several coils are connected in series,
and both ends of any desired number of series-connected coils are short-circuited
with one another. Usually, the number of the short-circuited groups of coils
amounts to at least three, and the groups are also insulated from one another.
With this arrangement of winding, the induced currents must circulate in an
exactly analogous manner as the inducing currents. In the several short-circuited
groups of coils there are produced currents that are proportional to the electro-
motive forces that are induced in each group. The secondary rotary field is just
as regular as the primary one.
The construction becomes very simple in the case where the cross-sectional areas
of the conductors are so small that the winding of the continuously connected
coils can be effected with a continuous length of wire so as to avoid connexions
or joints as much as possible. But this winding has, on the other hand, the
disadvantage that the insulated conductors or wires of small cross section capable
of being coiled require a comparatively large space for the insulating covering.
It has, now, been found by experiment that the efficiency and the attractive
force of an induction-motor with a phase-armature remains the same whether the
conductors are insulated from the iron body or from one another, or are not
insulated, and that, which is particularly important, the distribution and the
intensity of the inducing currents in the conductors remain the same when the
conductors consist of wound insulated or bare copper wire of equal cross sectional
area of copper.
This is a result similar to that which was found by the inventor of closed
armatures, Herr von Dolivo Dobrowolsky, in respect of the conductors of
the closed armatures, where insulation of the couductors from the iron also re-
mains without influence upon the efficiency of the motor.
According to this invention, therefore, there is a continuous winding with bare
copper wire. The essential features of this winding with bare wire are that for
all the elements of construction of the closed armature with the numerous con-
nexions there is substituted a single continuous length of wire with a few
connexions at the ends, and that, in place of an irregular distribution of current
in the closed armature, all the properties of the phase-armature with insulated
conductors are preserved. Further, the requisite cross-sectional area of the con-
ductor in a groove or hole in the iron body is produced by arranging that so many
coils of bare copper wire of a cross sectional area suitable for convenient winding
are wound one after another through the same hole until the total cross-sectional
area of all the wires is equal to the desired cross sectional area of the conductor.
Now, although the wire coils are wound mechanically in series, they can act as
conductors connected in parallel. The coiling itself is effected in exactly the
same manner as in phase-armatures with insulated wire, after the fashion of a
known continuous-current armature-winding with short-circuiting of a number of
groups of coils or windings.
There is now a further essential property of the new winding, viz., that no
attention need be paid either to the insulating of the conductors from one another
as in the phase-armature, or to the contact of the conductors with one another as
in the closed armature. The main path of the current obviously follows the
mechanical connexion of the wire and any accidental more or less intimate contact
of the copper with the iron or the conductors of the various groups of coils one
with another, will offer such a considerable resistance to the passage of the current
as compared with that of the normal conducting path, that contacts of that kind
will have scarcely any appreciable influence upon the distribution of the current.
The connexion of the continuous length of wound wire and the short circuiting

page_text: of a group of coils or windings insure a distribution of current which is most
favourable for the operation of the motor.
Although the winding can be effected as in the phase-armature in accordance
with any known scheme of winding, it is preferred to employ the scheme of wind-
ing illustrated in the accompanying drawing. In the case specially illustrated,
the armature has four poles; and the coils or windings are bedded in 24 holes, in
each of which are two wires situated side by side. The coils or windings of each
pair of holes of each pole are short-circuited on each other at K to form a group
or phase. The winding is a sort of drum-winding with bobbins or coils of un-
equal section.
The great advantages in constructing a winding of this kind will be readily
understood. The winding can withstand any heating because there are no sen-
sitive insulating parts employed. In the case of the breakage of wire, the passage
of the current is not interrupted, because in such a case the contacts of the wires
and bobbins or coils situated upon one another are sufficient to maintain the
passage of the current. The mechanical connexion of the conductors, and there-
fore also the electrical connexion of the same, is the very strongest conceivable
because the conductors consist of one piece or length of wire.
Although it is preferred to employ a regular winding, progressing according
to the number of poles of the field, yet it is obvious that the winding may be irregn-
larie, one having induced currents which do not pass mainly along the
mechanical connexion of the wires, which do not follow any definite division of
poles, but pass through contact-pieces between the wires. In other words, what is
essential to the invention is that the wire is bare, but the conductors neither are
necessarily all connected with one another, nor are they necessarily partly insulated
from one another, or from the iron, and only every two axial conductors are
mechanically and directly connected together.
Dated this 22nd dox of December 1907
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C., Chartered Patent Agent.
Improvements in the Armatures of Induction-motors.
A communication from abroad from the MASCHINENFABRIK OERLIKON, of Oerlikon,
Switzerland
I, WILLIAM LLOYD WISE, of 46, Lincoln's Inn Fields, in the County of
London, Consulting Engineer and Chartered Patent Agent, 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:-
The winding-arrangements heretofore employed in the inducing-system (short
circuited on itself) of induction-motors for polyphase and monophase currents are:
(1) The so-called short-circuited armature of Dolivo-Dobrowolsky consisting of
two copper rings or copper discs at the ends of the armature-cylinder and a
number of copper bars imbedded in the iron body in an insulated or uninsulated
manner, and arranged parallel to the axis, all the ends of the said copper bars
being directly electrically connected together by means of the copper rings or
plates; and
(2) A so-called phase-armature, with coils of copper wire or copper bars insulated
from the iron body and progressing according to the manner of the drum-winding

page_text: or gramme winding of continuous-current armatures, the arrangement being such
that a definite number of compartments of these coils are short-circuited on
themselves.
The
It is essential to the first arrangement that there be a good conductive con-
nexion of the ends of all the bars together at the ends of the armature, so that
each end of each rod is connected electrically in a direct, and therefore as a rule
mechanical, manner with the adjacent end and with each following one.
connexion is direct because the current can pass from each end to each other end
without having to pass through a bar or conductor. In the best-known form of
construction, this connexion is effected at each side or end by means of the copper
ring into which all the ends of the bars are soldered, screwed, or riveted. This
arrangement of the conductors has the well-known disadvantages that the cur-
rents induced in the bars accumulate in the connecting pieces between the bars,
and that in consequence of the resistance of these connexions between two
adjacent bars, a uniform distribution of the current-potentials in the bars pro-
portional to the induced electro-motive forces, is prevented, and thus the regularity
of the secondary rotary field is disturbed. This construction is also attended, when
carried into practice, by the great difficulty that a good conducting connexion
with a ring must be made for each conductor at two places. The resistance to
the passage of the current between the bars and the connecting rings may easily
constitute a considerable fraction of the total resistance of the effective current-
circuit.
These disadvantages are obviated by the arrangement of the phase-armature,
in which the insulated conductors form coils which are connected after
the manner of the drum-winding or
continuous
the ring-winding of
current armatures. In the drum-winding only those longitudinally arranged con-
ductors are connected directly with one another that are situated almost at the distance
or pitch of adjacent poles from one another. Each longitudinal conducting piece is
completely and independently insulated. The several coils are connected in series,
and both ends of any desired number of series-connected coils are short-circuited
with one another. Usually, the number of the short-circuited groups of coils
amounts to at least three, and the groups are also insulated from one another.
With this arrangement of winding, the induced currents must circulate in an
exactly analogous manner as the inducing currents. In the several short-circuited
groups of coils there are produced currents that are proportional to the electro-
motive forces that are induced in each group. The secondary rotary field is just
as regular as the primary one.
The construction becomes very simple in the case where the cross-sectional areas
of the conductors are so small that the winding of the continuously connected
coils can be effected with a continuous length of wire so as to avoid connexions
or joints as much as possible. But this winding has, on the other hand, the
disadvantage that the insulated conductors or wires of small cross section capable
of being coiled require a comparatively large space for the insulating covering.
My correspondents have found by experiment that the efficiency and the starting
torque of an induction-motor with a phase-armature remains the same whether
the conductors are insulated from the iron body or from one another,
or are not insulated, and that, which is particularly important, the distri-
bution and the intensity of the inducing currents in the conductors remain the
same when the conductors consist of wound insulated or bare copper wire of equal
cross sectional area.
This is a result similar to that which was found by the inventor of closed
armatures, Herr von. Dolivo-Dobrowolsky, in respect of the conductors of
the closed armatures, where insulation of the conductors from the iron also re-
mains without influence upon the efficiency of the motor.
According to this invention, therefore, there is a continuous winding with hare
copper wire. The essential features of this winding with bare wire are that for
all the elements of construction of the closed armature with the numerous con-

page_text: nections there is substituted a single continuous length of wire with a few
connexions at the ends, and that, in place of an irregular distribution of current
in the closed armature, all the properties of the phase-armature with insulated
conductors are preserved. Further, the requisite cross-sectional area of the con-
ductor in a groove or hole in the iron body is produced by arranging that so many
coils of bare copper wire of a cross-sectional area suitable for convenient winding
are wound one after another through the same hole until the total cross-sectional
area of all the wires is equal to the desired cross sectional area of the conductor.
Now, although the wire coils are wound mechanically in series, they can act as
conductors connected in parallel. The coiling itself is effected in exactly the
same manner as in phase-armatures with insulated wire, after the fashion of a
known continuous-current armature-winding with short-circuiting of a number of
groups of coils.
There is now a further essential property of the new winding, viz. that no
attention need be paid either to the insulating of the conductors from one another
as in the phase-armature, or to the contact of the conductors with one another as
in the closed armature. The main path of the current obviously follows the
mechanical connexion of the wire and any accidental more or less intimate contact
of the copper with the iron or the conductors of the various groups of coils one
with another will offer such a considerable resistance to the passage of the current
as compared with that of the normal conducting path, that contacts of that kind
will have scarcely any appreciable influence upon the distribution of the current.
The connexion of the continuous length of wound wire and the short circuiting
of a group of coils insure a distribution of current which is most favourable for the
operation of the motor.
Although the winding can be effected as in the phase-armature in accordance
with any gnown scheme of winding, it is preferred to employ the scheme of wind-
ing illustrated in the drawing filed with my provisional specification. In the case
specially illustrated, the armature has four poles, and the coils or windings are
are situated side by
bedded in 24 holes, in each of which two wires
each pole are
side. The coils or windings of each pair of holes of
short-circuited on each other at K to form a group or phase. The winding is a
sort of drum-winding with bobbins or coils of unequal section.
The great advantages in constructing a winding of this kind will be readily
understood. The winding can withstand any heating because there are no sen-
sitive insulating parts employed. In the case of the breakage of a wire, the passage
of the current is not interrupted, because in such a case the contacts of the wires
and bobbins or coils situated upon one another are sufficient to maintain the
passage of the current. The mechanical connexion of the conductors, and there-
fore also the electrical connexion of the same, is the very strongest conceivable,
because the conductors consist of one piece or length of wire.
Although it is preferred to employ a regular winding, progressing according
to the number of poles of the field, yet it is obvious that the winding may be irregu-
larie, one having induced currents which do not pass mainly along the
mechanical connexion of the wires, which do not follow any definite division of
poles, but pass through contact-pieces between the wires. In other words, what is
essential to the invention is that the wire is bare, but the conductors neither are
necessarily all connected with one another, nor are they necessarily partly insulated
from one another, or from the iron, and only every two longitudinal conluctors
are mechanically and directly connected together.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed I declare that what
I claim is;-
-
1. Armature winding for induction motors, wherein the current conductors are
5 wound in the grooves or holes of the iron body in the form of coils of bare wire of

page_text: convenient cross section for winding, the coils being drawn side by side through
each hole and the number thereof being such that the sum of the cross-sectional
areas of the several wires in each hole will be equal to the desired cross sectional
area, of conductor as set forth.
2. The improved armature winding for induction motors described and shown.
Dated this 20th day of September 1898.
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C., Chartered Patent Agent.