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Description  |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an armature winding for a dynamoelectric machine
having a double-layer concentric-wound coil arrangement or a lap winding
arrangement and a method of making such an armature winding.
2. Description of the prior art
FIG. 62 is a development diagram of a conventional arrangement of a
concentric-wound type armature winding of AC machinery, particularly,
three-phase induction motors. The shown armature winding is of a
three-phase, four-pole, 48-slot type. FIG. 63 shows an arrangement of
coils of the armature winding disposed in slots. Each dotted line in FIG.
62 shows a coil side which is inserted into the coil to overlap with the
upper side (open side) thereof. Each solid arc in FIG. 63 shows an coil
end of the coil and each black dot shows the coil side. Numerals 1 to 48
designate slot numbers, which will be hereinafter presented as #1 to #48.
Reference symbols U1, U2, U3 and U4 designate pole windings of a phase U,
reference symbols V1, V2, V3 and V4 pole windings of a phase V, and
reference symbols W1, W2, W3 and W4 pole windings of a phase W.
Only one coil is inserted in each of slots #1 and #12 in the first pole
winding U1 of the phase U so that concentric-wound coils are composed,
whereas a coil is inserted in each of slot pairs of #2 and #11, and #3 and
#10 together with another coil of another phase (coils of windings V4 and
W1 respectively) so that concentric-wound coils are composed. Usually, the
coils inserted in the slot pair of #2 and #11 and in the slot pair of #3
and #10 have the same number of turns, which number is a half of that of
the coil inserted in the slot pair of #1 and #12. All the other
concentric-wound coils also have the above-mentioned double-half turns
relation in the number of turns.
Publication No. 51-28125 (1976) of a Japanese examined patent application
discloses an arrangement of the armature winding as shown in FIG. 64.
Publication No. 60-36698 (1985) of a Japanese examined patent application
discloses an arrangement of the armature winding as shown in FIG. 65.
Neither publication describes the number of turns of each coil in detail,
but, usually, the number of turns of the coil when the same is inserted in
the slot together with a coil of another phase is a half of that when only
the coil is inserted in the slot. Thus, all the coils generally have the
double-half turns relation.
The magnetomotive force waveform of an armature winding is nonsinusoidal
when the coils in the respective slots have the double-half turns
relation. The nonsinusoidal magnetomotive force waveform results in a
large number of harmonics, which disadvantageously cause a reduction in
the efficiency and power factor of the motor or an increase in the noise
due to electromagnetic vibration.
For the purpose of overcoming the above-described disadvantage, the prior
art has provided an arrangement of sinusoidal winding wherein the number
of turns of the coil is changed from slot to slot so that the
magnetomotive force distribution approximates a sinusoidal wave. For
example, publication No. 6-261479 (1994) of a Japanese unexamined patent
application discloses an arrangement of armature winding composed into a
sinusoidal, double-layer, concentric-wound winding. Referring to FIG. 67,
the disclosed arrangement will be described. FIG. 67 is a development
diagram of an armature winding of a three-phase, four-pole, 48-slot type
with two parallel electrical paths being formed between external terminals
U and X. When q is the number of slots in each pole in each phase,
q=48/(3.times.4)=4. Each pole winding in each phase comprises four
continuous coils arranged concentrically so that each pole winding is
composed into a double-layer concentric-wound winding. The four coils are
connected to one another so that a pole winding is formed. Thus, as a
whole, the armature winding comprises twelve concentric-wound coils which
are pole windings U1, U2, U3 and U4 of phase U, pole windings V1, v2, V3
and V4 of phase V, and pole windings W1, W2, W3 and W4 of phase W. The
coils are inserted in the slots #5 to #16, and the coil pitches of the
pole windings are 11, 9, 7, and 5 respectively. For example, a first pole
winding U1 of phase U is composed of a coil inserted in the slots #5 and
#16 at the pitch of 11, a coil inserted in the slots #6 and #15 at the
pitch of 9, a coil inserted in the slots #7 and #14 at the pitch of 7, and
a coil inserted in the slots #8 and #13 at the pitch of 5, all the coils
being sequentially laid one upon another. Regarding each of the other
poles of phase U and each of the other phases, four coils are
interconnected at the coil pitches of 11, 9, 7 and 5 in the same manner as
described above.
FIG. 68 illustrates the number of turns of the coil in each slot. It is
noted that FIG. 68 shows only the arrangement of the coils inserted in the
respective slots but shows nothing as to which coils serve as the upper or
lower coils. The number of turns of each slot-inserted coil in the shown
arrangement is the same as in the prior art, but the number of coils in
each phase is twice as large as that in the prior art. For example, as
shown in FIG. 68, the first pole winding U1 of the phase U is distributed
in slots #5 to #8 and in slots #13 to #16, and the number of turns is
changed sequentially from 28 in slot #5 to 21 in slot #6, 13 in slot #7
and 5 in slot #8 and from 5 in slot #13 to 13 in slot #14, 21 in slot #15
and 28 in slot #16, whereby the winding U1 is composed into a
concentric-wound winding. Further, the second pole winding U2 of the phase
U is distributed in slots #17 to #20 and in slots #25 to #28, and the
number of turns is changed sequentially from 28 in slot #17 to 21 in slot
#18, 13 in slot #19 and 5 in slot #20 and from 5 in slot #25 to 13 in slot
#26, 21 in slot #27 and 28 in slot #28, whereby the winding U2 is composed
into a concentric-wound winding. Thus, the numbers of turns of the coils
are changed sequentially from 5 in slot #1 to 13 in slot #2, 21 in slot
#3, 28 in slot #4, 28 in slot #5, 21 in slot #6, 13 in slot #7 and 5 in
slot #8 so that the magnetomotive force can be rendered approximately
sinusoidal.
Since the above-described arrangement is composed into the double-layer,
concentric-wound type, the total numbers of turns of upper and lower coils
inserted in slots #1 to #4 in FIG. 68, for example, are 33, 33, 34 and 34.
Thus, the total number of turns of coils inserted in each slot is
approximately uniform, which shows that the sectional area of each slot is
effectively utilized.
The number of turns of each coil inserted in each slot is determined so
that the magnetomotive force produced by the winding is rendered
approximately sinusoidal and so that the high frequency winding factor
approximates zero. For example, this is described in detail in "Study on
the theory of abnormal phenomena in induction motors," by Chukichi Okawa
in "Shibaura Review" Volume 8, 1934. FIG. 69 illustrates an arrangement of
upper and lower coils and the number of turns of each coil in the armature
winding as shown in FIG. 68.
FIGS. 70A and 70B show distribution of the magnetomotive force in the case
of the sinusoidal winding and in the case of a nonsinusoidal winding
respectively. FIG. 71 shows winding factors of the sinusoidal winding
shown in FIG. 70A and those of the nonsinusoidal winding shown in FIG.
70B. As obvious from these figures, the sinusoidal winding can render the
magnetomotive force approximately sinusoidal and reduce the high frequency
winding factor to a large extent.
FIG. 72 illustrates the arrangement of upper and lower coils inserted in
each slot and the number of turns of each coil with respect to the winding
arrangement shown in FIG. 68. First, all the pole windings U1 to U4 of
phase U are inserted into the slots to serve as lower coils. All the pole
windings V1 to V4 of phase V are then inserted into the slots to serve as
lower coils. Finally, all the pole windings W1 to W4 of phase W are
inserted into the slots to serve as upper coils, so that the double-layer,
concentric-wound winding is provided. Since all the windings of each phase
can be simultaneously inserted into the slots, the inserting work can be
simplified and the windings can be inserted into the slots by a coil
inserting machine. Consequently, the above-described winding arrangement
can achieve the same effect of sinusoidal winding as in a lap winding, and
insulators can be mechanically inserted into the slots. Thus, in the
above-described arrangement, the numbers of turns of the coils inserted in
each slot is changed so that the magnetomotive force produced by the
winding is rendered approximately sinusoidal, whereby the motor
characteristics can be improved.
In the conventional concentric-wound windings as shown in FIGS. 62 and 66,
however, all the coils inserted in each slot have the double-half turns
relation in the number of turns. Accordingly, since the magnetomotive
force cannot be rendered sinusoidal, a large number of harmonics result in
reduction in the efficiency and power factor of the motor or an increase
in the noise due to electromagnetic vibration.
The double-layer concentric-wound winding employing the sinusoidal winding
as shown in FIG. 67 overcomes the above-described drawbacks. However, the
coils belonging to different phases are inserted in all the slots #1 to
#48 although the differences in the number of coil turns among the slots
are small, as is obvious from FIG. 72. Accordingly, the insulators need to
be inserted into all the slots so that the coils belonging to the
different phases are insulated from each other, which results in increase
in the number of steps in the assembly of the winding.
Furthermore, in some slots, the number of turns of the upper coil quite
differs from that of the lower coil in the armature winding shown in FIG.
67. These slots include slots #1, #4, #5, #8, #9, #12, #13, #16, #17, #20,
#21, #24, #25, #28, 29, #32, #33, #36, #37, #40, #41, #44, #45 and #48. In
each of these slots, one coil is wound five turns, whereas the other coil
is wound 28 turns. Accordingly, since the dimensions of the insulator
inserted into each slot need to be varied, a large number of different
types of insulators need to be provided. Furthermore, the coil and the
insulator are sometimes settled improperly in the slot when the number of
turns of the coil first inserted into the slot is smaller. Consequently,
the subsequent manual or mechanical inserting of the coil is rendered
difficult or the insulator having inserted in the slot is displaced,
whereupon the quality of products is lowered. Additionally, since the pole
windings have different dimensions respectively, coil formers the number
of which is equal to that of the pole windings are disadvantageously
required.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a method of
making an armature winding of dynamoelectric machines having a
double-layer concentric-wound winding or a lap winding arrangement,
wherein a magnetomotive force produced by windings constituting one of
poles has a high approximation to a sinusodial wave, the number of coils
constituting each pole can be reduced, the number of types and the number
of insulators inserted into the slots can be reduced, and the coils can be
mechanically inserted into the slots readily.
The present invention provides a method of making an armature winding for a
three phase four pole dynamoelectric machine, comprising the steps of
setting a number q of slots per phase per pole at or above four and
setting a number of coils of one winding corresponding to one pole at or
above two and to be smaller than the number q, setting a number of turns
and a coil pitch of each of the coils at different values from each other
and setting a minimum coil pitch at or above q and at or below 2q,
arranging the coils into an integral-slot winding having a
concentric-wound winding distribution wherein the number of turns of each
coil is increased or decreased sequentially from an outermost coil to an
innermost coil, winding the coil with a maximum number of turns in the
concentric-wound winding into a single-layer winding and each of the other
coils into a double-layer winding, simultaneously inserting into the slots
a first set of windings including three windings corresponding to first
poles of three phases and three windings corresponding to fourth poles of
the three phases, and simultaneously inserting into the slots a second set
of windings including three windings corresponding to third poles of the
three phases and three windings corresponding to second poles of the three
phases, the steps being sequentially executed.
According to the above-described method, the number of coils of each pole
winding is smaller than the number of slots per pole, whereupon the number
of coil formers can be reduced. The number of slots into which coils of
different phases are inserted can be reduced. The difference between the
numbers of turns of two coils inserted into one slot can be reduced. The
coils can be mechanically inserted into the slots readily.
The number of turns of each coil may be set at a value different among the
slots per phase per pole so that a magnetomotive force produced by the
winding is rendered approximately sinusoidal.
The invention also provides a method of making an armature winding for a
three phase four pole dynamoelectric machine, comprising the steps of
setting a number q of slots per phase per pole at or above four and
setting a number of coils of one winding corresponding to one pole at or
above two and to be smaller than the number q, setting a number of turns
and a coil pitch of each of the coils at different values from each other
and setting a minimum coil pitch at or above q and at or below 2q,
arranging the coils into an integral-slot winding having a
concentric-wound winding distribution wherein the number of turns of each
coil is increased or decreased sequentially from an outermost coil to an
innermost coil, winding the coil with a maximum number of turns in the
concentric-wound winding into a single-layer winding and each of the other
coils into a double-layer winding, simultaneously inserting into the slots
a first set of windings including three windings corresponding to first
poles of three phases and three windings corresponding to third poles of
the three phases, and simultaneously inserting into the slots a second set
of windings including three windings corresponding to fourth poles of the
three phases and three windings corresponding to second poles of the three
phases, the steps being sequentially executed.
The invention further provides a method of making an armature winding for a
three phase six pole dynamoelectric machine, comprising the steps of
setting a number q of slots per phase per pole at or above four and
setting a number of coils of one winding corresponding to one pole at or
above two and to be smaller than the number q, setting a number of turns
and a coil pitch of each of the coils at different values from each other
and setting a minimum coil pitch at or above q and at or below 2q,
arranging the coils into an integral-slot winding having a
concentric-wound winding distribution wherein the number of turns of each
coil is increased or decreased sequentially from an outermost coil to an
innermost coil, winding the coil with a maximum number of turns in the
concentric-wound winding into a single-layer winding and each of the other
coils into a double-layer winding, simultaneously inserting into slots a
first set of windings including three windings corresponding to a first
phase of three phases and having a same polarity and three windings
corresponding to a third phase of the three phases and having a polarity
opposed to the polarity of the windings corresponding to the first phase,
simultaneously inserting into the slots a second set of windings including
three windings corresponding to a second phase of the three phases and
having a same polarity and three windings corresponding to the first phase
of the three phases and having a polarity opposed to the polarity of the
windings corresponding to the second phase, and simultaneously inserting
into slots a third set of windings including three windings corresponding
to the third phase of the three phases and three windings corresponding to
the second phase of the three phases, the steps being sequentially
executed.
The invention further provides a method of making an armature winding for a
three phase dynamoelectric machine, comprising the steps of setting a
number q of slots per phase per pole at or above four, setting a number of
coils of one winding at 2.times.(q-1) which is at or above two, and
setting coil pitches of the respective coils at different values from one
another, setting a minimum coil pitch in the plurality of coils
corresponding to the one winding at or above q and at or below 2q, setting
a number of turns of each of the coils corresponding to the one winding so
that the number is minimum at an outermost slot and an innermost slot and
so that the number is maximum at a central slot and arranging the coils
into a concentric distribution, setting outermost coils of two windings
belonging to the same phase in the concentric winding distribution so that
the outermost coils are apart from each other by a pitch equal to the
minimum coil pitch, winding the coil with a maximum number of turns in the
concentric-wound winding distribution into a single-layer winding and each
of the other coils into a double-layer winding, and simultaneously
inserting into slots a first set of windings corresponding to all pole
windings of a first phase, simultaneously inserting into slots a second
set of windings corresponding to all pole windings of a second phase, and
simultaneously inserting into slots a third set of windings corresponding
to all pole windings of a third phase, the steps being sequentially
executed.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects, features and advantages of the present invention will become
clear upon reviewing the following description of made by a method
preferred embodiments thereof, made with reference to the accompanying
drawings, in which:
FIG. 1 is a development diagram of an armature winding of a first
embodiment in accordance with the present invention;
FIG. 2 shows the numbers of turns of coils inserted in slots;
FIGS. 3A and 3B are graphs of distributions of winding magnetomotive force;
FIG. 4 is a graph comparatively showing winding factors in sinusoidal and
nonsinusoidal windings;
FIG. 5 illustrates an arrangement of upper and lower coils and the number
of turns of each coil in the armature winding of the first embodiment;
FIG. 6 illustrates an arrangement of coils of the armature winding of the
first embodiment;
FIG. 7 illustrates the numbers of turns of coils inserted in the slots;
FIG. 8 is a development diagram of the armature winding of a modified form
of the first embodiment;
FIG. 9 illustrates an arrangement of made by a method upper and lower coils
and the number of turns of each coil in the armature winding of a second
embodiment in accordance with the present invention;
FIG. 10 illustrates a coil arrangement of the armature winding of the
second embodiment as an example as viewed from the end winding side;
FIG. 11 illustrates an arrangement of coils of the armature winding as
another example;
FIG. 12 is a development diagram of made by a method the armature winding
of a third embodiment in accordance with the invention;
FIG. 13 is a development diagram of the armature winding of made by a
method a fourth embodiment in accordance with the invention;
FIG. 14 is a development diagram of the armature winding of a first
modified form of the fourth embodiment;
FIG. 15 illustrates a coil arrangement of the armature winding of the
fourth embodiment as an example as viewed from the end winding side;
FIG. 16 illustrates a coil arrangement of the armature winding of the
fourth embodiment as another example as viewed from the end winding side;
FIG. 17 is a development diagram of the armature winding of a second
modified form of the fourth embodiment;
FIG. 18 is a development diagram of the armature winding of a third
modified form of the fourth embodiment;
FIG. 19 is a development diagram of the armature winding of made by a
method a fifth embodiment in accordance with the present invention;
FIG. 20 is a development diagram of the armature winding of a first
modified form of the fifth embodiment;
FIG. 21 illustrates a coil arrangement of the armature winding of the fifth
embodiment as one example;
FIG. 22 illustrates a coil arrangement of the armature winding of the fifth
embodiment as another example;
FIG. 23 is a development diagram of the armature winding of made by a
method a sixth embodiment in accordance with the present invention;
FIG. 24 is a development diagram of the armature winding of a first
modified form of the sixth embodiment;
FIG. 25 illustrates a coil arrangement of the armature winding of the sixth
embodiment;
FIG. 26 is a development diagram of the armature winding of a second
modified form of the sixth embodiment;
FIG. 27 is a development diagram of the armature winding of a third
modified form of the sixth embodiment;
FIG. 28 illustrates a coil arrangement of the armature winding of the sixth
embodiment as one example;
FIG. 29 illustrates a coil arrangement of the armature winding of the sixth
embodiment as another example;
FIG. 30 is a development diagram of the armature winding of made by a
method a seventh embodiment in accordance with the present invention;
FIG. 31 is a development diagram of the armature winding of a first
modified form of the seventh embodiment;
FIG. 32 illustrates a coil arrangement of the armature winding of the
seventh embodiment;
FIG. 33 is a development diagram of the armature winding of made by a
method an eighth embodiment in accordance with the present invention;
FIG. 34 is a development diagram of the armature winding of a first
modified form of the eighth embodiment;
FIG. 35 illustrates a coil arrangement of the armature winding of the
eighth embodiment;
FIG. 36 is a development diagram of the armature winding of made by a
method a ninth embodiment in accordance with the present invention;
FIG. 37 is a development diagram of the armature winding of a first
modified form of the ninth embodiment;
FIG. 38 illustrates a coil arrangement of the armature winding of the ninth
embodiment;
FIG. 39 illustrates a coil arrangement of the armature winding of made by a
method a tenth embodiment;
FIG. 40 illustrates a coil arrangement of the armature winding of made by a
method an eleventh embodiment;
FIG. 41 illustrates a coil arrangement of the armature winding of method by
a method a twelfth embodiment;
FIG. 42 illustrates a coil arrangement of the armature winding of made by a
method a thirteenth embodiment;
FIG. 43 is a development diagram of the armature winding of a fourteenth
embodiment in accordance with the present invention;
FIG. 44 illustrates the numbers of made by a method turns of coils inserted
in the slots in the fourteenth embodiment;
FIG. 45 illustrates an arrangement of upper and lower coils and the number
of turns of each coil in the armature winding of the fourteenth
embodiment;
FIG. 46 illustrates a coil arrangement of the armature winding of the
fourteenth embodiment;
FIG. 47 illustrates the numbers of turns of coils inserted in the slots in
the armature winding of the fourteenth embodiment;
FIG. 48 is a development diagram of the armature winding of a modified form
of the fourteenth embodiment;
FIG. 49 is a development diagram of an armature winding of made by a method
a fifteenth embodiment in accordance with the present invention;
FIG. 50 illustrates the numbers of turns of coils inserted in the slots in
the fifteenth embodiment;
FIG. 51 illustrates an arrangement of upper and lower coils and the number
of turns of each coil in the armature winding of the fifteenth embodiment;
FIG. 52 illustrates a coil arrangement of the armature winding of the
fifteenth embodiment;
FIG. 53 illustrates a coil arrangement of the armature winding of a first
modified form of the fifteenth embodiment;
FIG. 54 is a development diagram of the armature winding of a second
modified form of the fifteenth embodiment;
FIG. 55 illustrates a coil arrangement of an armature winding of made by a
method a sixteenth embodiment in accordance with the present invention;
FIG. 56 illustrates a coil arrangement of the armature winding of a
modified form of the sixteenth embodiment;
FIG. 57 illustrates a coil arrangement of an armature winding of made by a
method a seventeenth embodiment in accordance with the present invention;
FIG. 58 illustrates a coil arrangement of an armature winding of made by a
method an eighteenth embodiment in accordance with the present invention;
FIG. 59 is a development diagram of an armature winding of made by a method
a nineteenth embodiment in accordance with the present invention;
FIG. 60 is a development diagram of an armature winding of a twentieth
embodiment in accordance with the present invention;
FIG. 61 is a development diagram of an armature winding of made by a method
a twenty-first embodiment in accordance with the present invention;
FIG. 62 is a development diagram of a first conventional armature winding
composed into a concentric-wound type;
FIG. 63 illustrates a coil arrangement of the armature winding as shown in
FIG. 62;
FIG. 64 illustrates a coil arrangement of a second conventional
concentric-wound type armature winding;
FIG. 65 illustrates a coil arrangement of a third conventional
concentric-wound type armature winding;
FIG. 66 is a development diagram of a third conventional concentric-wound
type armature winding;
FIG. 67 is a development diagram of a fifth conventional armature winding
composed into a sinusoidal winding type;
FIG. 68 illustrates the number of turns of coils inserted in slots in the
fifth conventional armature winding shown in FIG. 67;
FIG. 69 illustrates a coil arrangement of the fifth conventional armature
winding shown in FIG. 67;
FIGS. 70A and 70B are graphs of distributions of winding magnetomotive
force in the fifth conventional arrangement shown in FIG. 67;
FIG. 71 is a graph comparatively showing winding factors in sinusoidal and
nonsinusoidal windings in the prior art; and
FIG. 72 illustrates an arrangement of upper and lower coils and the number
of turns of each coil in the fifth conventional arrangement shown in FIG.
68.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A first embodiment of the present invention will be described with
reference to FIGS. 1 to 8. In the figures, reference numerals 1 to 48
designate slot numbers. Reference symbols U1 to U4 designate pole windings
of phase U, V1 to V4 pole windings of phase V, and W1 to W4 pole windings
of phase W.
In the embodiment, the invention is applied to a three-phase, four-pole,
48-slot armature winding. Two parallel electrical paths are formed between
armature winding terminals U and X by pole windings. The number q of slots
per phase per pole is obtained as 48/(3.times.4)=4. Each pole winding of
each phase consists of three (=q-1 concentrically distributed, continuous
coils. Thus, the armature winding is composed into a double-layer,
concentric-wound winding and comprises 12 concentric-wound coils including
pole windings U1, U2 and U3 of phase U, pole windings V1, V2 and V3 of
phase V, and pole windings W1, W2 and W3 of phase W.
Coil pitches of the coils composing each pole winding are set at 11, 9 and
7 respectively. For example, the first pole winding U1 of phase U is
composed of a coil inserted in slots #1 and #12 at coil pitch of 11, a
coil inserted in slots #2 and #11 at coil pitch of 9, and a coil inserted
in slots #3 and #10 at coil pitch of 7, these coils being successively
connected to one another. In each of the other windings of phase U and
each winding of the other phases, three coils with respective coil pitches
11, 9 and 7 are successively connected to one another in the same manner
as described above.
FIG. 2 shows the numbers of turns of the coils inserted in the respective
slots. It is noted that FIG. 2 shows only the arrangement of the coils
inserted in the respective slots but shows nothing as to which of the
coils serves as an upper or a lower coil in the slot. The numbers of turns
of coils inserted in the slots in the embodiment differ from those in the
prior art. For example, in phase U, the first pole winding U1 is
distributed in the slots #1 to #3 and in the slots #10 to #12, and the
number of turns is changed sequentially from 31 in slot #1 to 18 in slot
#2 and 12 in slot #3 and from 12 in slot #10 to 18 in slot #11 and 31 in
slot #12, whereby the winding U1 is composed into a concentric-wound
winding.
Furthermore, the second pole winding U2 is distributed in slots #13 to #15
and slots #22 to #24, and the number of turns is changed sequentially from
31 in slot #13 to 18 in slot #14 and 12 in slot #15 and from 12 in slot
#22 to 18 in slot #23 and 31 in slot #24, whereby the winding U2 is
composed into a concentric-wound winding. On the other hand, the number of
turns of coils of the pole winding U4 is changed from 12 to 18 and 31 and
the number of turns of coils of the pole winding U1 is changed from 31 to
18 and 12 in slots #46, #47, #48, #1, #2 and #3. The degree of change in
the number of turns differs from that in the prior art as shown in FIG.
70A. However, since the number of turns is changed stepwise in the
embodiment, the magnetomotive force distribution can be rendered
approximately sinusoidal as in the prior art.
FIGS. 3A and 3B show distributions | | |
