Note: Descriptions are shown in the official language in which they were submitted.
1~3~ '45
03-HM-5246
BACKGROU~D OF THE INVENTION
.
The present invention relates generally to polyphase
multi-speed alternating current winding arrangements and more
particularly to such winding arrangements as might be used in
5 an induction motor. Even more specifically, the present
invention relates to polyphase induction motors of the speed
changing variety and techniques for fabricating such motors
to meet certain specified design requirements.
The classical polyphase alternating current dynamo-
electric machine ha~ a slotted magnetic core in which threeseparate phase windings are lap-wound with the individual
phase windings being wye or delta connected to a three-phase
source of alternating current. Such a lap-wound stator is
not, however, easily adapted to automated production techniques
since each coil of that lap-winding has one side turn portion
disposed in the bottom ~radially outermost) part of the stator
core slot while another side turn portion is disposed in the
top area of another stator core slot. ThUS, each coil has
one of its side turn portions covered by a side turn portion
of another coil and with this requirement the several coils
are generally hand-placed in their respective slots.
In recent years, the use o~ concentric winding arrange-
ments has become quite popular since for any qiven lap-winding
arrangement there is an equivalent concentric winding arrange-
ment and the concentric winding arrangement is rather ~asilyadapted to mass production techniques by forming the concentric
winding~ external of the stator core and then simultaneously
or sequentially machine inserting those concentric windings
into the appropriate stator core slots. It should be noted
that there are concentric winding arrangements having no equiv-
alent la~-winding arranaement.
It is frequently desirable to provide an induction motor
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03-HM-S246
which may have its windin~ appropriately interconnected to
operate at a selected one of, for example, two different
operating speeds. Such multi-speed or pole changing motors,
while not unknown in the polypllase induction motor art,
S are often found in single phase motor designs. These
arrangements for changing the operating speed of an induction
motor may include windings operable in either speed mode and
additional windings which are not operable in all of the speed
modes, thereby giving an effective number of poles which differs
from mode to mode. Also known is the provision of a specified
number of wound poles which are interconnected in one operating
mode to be of alternatin~ magnetic polarity while in another
operating mode these wound poles have their interconnections
such that consecutive wound poles are of the same magnetic
polarity, thereby inducing between each pair of such wound
poles, a consequent pole of an opposite magnetic polarity,
thereby effectively doubling the number of poles when the
stator connections are such as to induce the corresponding
consequent poles.
For many multi-speed motor installations it is important
to be able to design the motor so as to give a torque ratio
tailored to the particular environment. This is especially
important in hermetic motor~, such as employed to drive com-
pressors of the type employed in refrigerating and air condition-
ing systems. In a sinqle-phase two-speed motor of the consequent-
pole variety, this tailoring of the motor torque ratio to suit
the needs of the particular installation is frequently accomplished
by providing a so-called extended main winding which is used only
in one of the pole configurations to red~e the torque in that
pole configuration while not detrimentally affecting motor opera-
tion in the other pole configuration, in which that extended main
winding is idle. Such an approach is not, however, easily adapted
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1~3~ 5
- 03-HM-5246
to polyphase motor winding arrangments.
The typical consequent pole polyphase winding arrangement
has the wound poles of either lap or concentric configuration of
full pitch for the lower speed mode of operation and therefore
of fifty percent pitch for the higher speed mode of operation.
Such a winding arrangement of a type made and sold by the
assignee of the present invention is illustrated in concentric
form in Fig. 4. The pitch factors for this arrangement become
apparent when the equivalent lap-winding is sketched.
To modify the torque of a motor such as depicted in Fig.
4, in one of its pole number operating modes, without deleteriously
affecting the motor performance in the other of its pole number
operating modes, is not easily accomplished. Merely decreasing
number of turns gives an increased flux density in the stator
and increased I2R losses deteriorating both efficiency and power
factor in the other of the pole number operating modes. Known
winding arrangements including the one illustrated in Fig. 4,
due in part to the large number of teeth spanned by the outermost
of the concentric coils, experience substantial end turn in-
sulating problems which while not insurmountable do increase bothinsulating material requirements and fabrication time thereby
leading to an increased overall cost for the motor, Also,with
a Fig. 4 winding configuration, the latitude of achievable tor-
que ratios within allowable current density and flux density
2S limitations is quite limited.
SUMMARY OF THE INVENTION
Among the several objects of the present invention may
be noted the provision of an integrated technique for the
.. . . .
~ design and fabrication of a wide variety of multi-speed poly-
phase motors to meet certain design specifications; the pro-
vision of a design and fabrication technique as suggested by
the previous object wherein predetermined torque ratios may
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03-HM-5246
be achieved by changing the winding pitch; the provision of
a stator assembly for a polyphase multi-speed motor having
short pitch windings and characterized by its compact end
turn arrangement; the provision of a two speed three-phase
S motor design which meets predetermined design requirements
such as a desired torque ratio for the respective speed modes;
and the provision of a design and fabricating technique for
multi-speed polyphase motors which obviate the somewhat haphazard
prior art approach to such motor design. These as well as other
objects and advantageous features of the present invention will
be in part apparent and in part pointed out hereinafter.
In general, a stator assembly for use in a pole chang-
ing motor which provides a predetermined torque ratio for spec-
ified pole number operating modes is fabricated by selecting a
stator core having a rotor accepting bore with a plurality of
winding accepting core slots communciating with the bore, deter-
mining the number of turns of a selected wire size which may be
placed in selected core slots, determining the number of effec-
tive turns per pole in each of the specified pole number opera-
ting modes, determining by, for example, bench tests, a torqueratio for the motor in the specified pole number operating modes
and changing the winding distribution in the core slots to change
the number of effective turns per pole in each of the specified
pole number operating modes to bring the torque ratio into closer
conformity with the predetermined torque ratio. The winding
distribution may be changed by changing the pole pitch or by
changing the number of turns in certain ones of the concentric
coils forming the coil groups. The winding distribution may,
for example, be changed by changing the number of core slots
spanned by each of the concentric coils in each of the plurality
of pole groups by a li~e amount. The foregoing sequence of
s~eps subsequent to the selection of a stator core may in some
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03-HM-5246
cases be repeated until the difference between the predetermined
torque ratio and the determined or measured torque ratio is less
in magnitude than some predetermined value.
Also in qeneral and in one form of the invention, a
polyphase induction motor has a stator including a primary core
member with end faces, a yoke section, and a number of teeth
sections forming coil accommodating slots, and a bore with
first, second and third winding phases displaced in phase
from one another carried by the core and each of the winding
phases including at least two pole groups each formed by at
least two concentric coils with an outermost coil in each pole
group spanning the most teeth sections for that pole group.
The three winding phases may be delta connected to a polyphase
source with the two pole groups of each phase connected in
series to be of the same magnetic polarity for inducing a
like number of consequent poles for each phase when operating
the motor in a lower speed mode and the three winding phases
wye connected to a polyphase source with the two pole groups
of each phase connected in parallel to be of opposite magnetic
polarity for operating the motor in a higher speed mode. The
three winding phases may, alternatively, be wye connected to a
polyphase source with the two pole groups of each phase connected
in series to be of the same magnetic polarity for inducing a
like number of consequ2nt poles for each phase for operating
the motor in a lower speed mode and the three winding phases
delta connected to a polYphase source with the two pole groups
of each phase connected in series to be of opposite magnetic
polarity for operating the motor in a higher speed mode. In
either of these alternative arrangements, each winding phase
may consist of two pole groups each formed by~four concentric
coils with adjacent coil side turn portions separated by but
a single stator tooth, and in each arrangement the pole pitch
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03-HM-5246
in the higher speed mode is less than one while the pole pitch
in the lower speed mode is also less than one in the first
alternative arrangement and is less than one in the second
alternative arrangement.
S BRIEF DESCRIPTION OF THE DRAWING
Fig. 1 is an end view of a stator according to the present
invention illustrating schematically the positioning of the several
wlndings;
Figs. 2-3 are schematic diagrams illustrating the inter-
connection of the windings of Fig. 1 for low speed and high speed
modes of operation respectively;
Fig. 4 is an end view of a stator similar to Fig. 1 but
illustrating schematically a known arrangement of the several
windings;
Fig. 5 is a schematic diagram illustrating the inter-
connection of the windings of Fig. 4 for a low speed mode of opera-
tion; ~
Fig. 6 is a schematic diagram illustrating the interconnec-
tion of the windings of Fig. 4 for a high speed mode of operation;
Fig. 7 is an end view of a stator similar to Figs. 1 and
4 but illustrating schematically another variation on the position-
ing of the several windings according to the present invention;
Fig. 8 is a schematic diagram illustrating the interconnec-
tion of the windings of Fig. 7 for a low speed mode of operation;
Fig. 9 is a schematic diagram illustrating the interconnec-
tion of the windings of Fig. 7 for a high speed mode of operation; and
Figs. 10 and 11 illustrate magnetomotive force diagrams for
the motor of Figs. 1-3 in the higher and lower speed modes
respectively.
Corresponding reference characters indi-cate corresponding
parts throughout the several views of the drawing.
The exemplifications set out herein illustrate a preferred
embodiment of the invention in one form thereof and such exem-
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03-HM-5246
plifications are not to be construed as limiting the scope of
the disclosure or the scope of the invention in any manner.
DESCR~PTION OF T B PREFERRED EMBODIMENT
Referring now to the drawing generally, a stator assembly
11 or 15, for use in a pole changing motor, is fabricated to have
a predetermined torque ratio for specified pole number operating
modes by first selecting a stator core 17 or 21 having a rotor
acce~ting bore 23 or 27, and a plurality of winding accepting
core slots, such as 29 or 33, with each slot communicating with
the bore. As illustrated, the stator cores 17 and 21 happen to
be identical so-called forty frame cores with twenty-four stator
core slots and these cores are illustrated at about 85 percent
of their actual size.
The core slots, such as slot 29 in Fig. 1, are peripher-
ally determined by the stator core yoke section 35 and the ad-
jacent stator teeth 37 and 39 and by the bore 23 periphery with
some minor clearance being allowed between the tooth tip ends
near the bore to accommodate bore insulating wedges, if desired.
For a selected wire size, the number of turns which may
be placed in a selected core slot may be determined either ex-
perimentally or graphically or by known empirical relationships
determined by the technique of placing the coils in the slots.
The number of effective turns per pole in each of the
specified pole number operating modes is next determined by
summing for each coil within a pole group the product of the
number of turns in that coil and the sine of 90 times the ratio
of the number of teeth spanned by that coil to the number of
teeth per pole for the given stator configuration. Thus, for
example, in the twenty-four slot stator illustrated in Fig. 1,
in its two pole configuration, there are twelve slots per pole,
or equivalently a maximum of twelve teeth which could be spanned
by the outermost coil in a pole group. Thus, if coil 41 has
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03-EIM-5246
Nl turns and spans eight stator teeth, while 43 has N2 turns
spanning six coil teeth, coil 45 has N3 turn-q spanning four coil
teeth, and coil 47 spanning a pair of coil teeth has N4 turns,
the number of effective turns per pole in the two pole mode
would be given by:
N - Nl sin(t8/12) 90)+ N2 sin((6/12) 90)+ N3 sin
(4/12) 90)+ N4 sin((2/12) 90~
This result may of course be appropriately scaled depend-
ing upon the specific number of phases to get a representative
value for the entire motor winding.
A torque ratio for the motor in the specified pole number
operating modes may now be determined by actual bench testing of
the motor employing known textbook techniques, by creating a
mathematical model for the motor, or more simply, but only
approximately, by the known approximation that the tor~ue is
inversely proportional to the square of the number of effective
turns. If this determined torque ratio does not meet the desired
design parameters for the motor, the winding distribution in the
core slots may be changed to change the number of effective turns
per pole in each of the specified pole number operating modes to
bring the torque ratio into closer conformity with a predetermined
ratio. This change in the winding distribution may be accomplished
either by changing the specific number of turns in given coils or
by changing the numbers of teeth spanned by various coils or by
some combination of these two techniques. In some cases it
may be desirable to repeat the foregoing sequence of determina-
tions to better fit the resulting design to the initially est-
ablished design parameters.
Referrin~ now specifically to Fig. 1, the stator 11 has
one end face thereof visible and is seen to includ~ a primary
core member 17 having a number of teeth sections, such as 37
and 3~, extending radially inwardly from the stator core yoke
1139;~45
03-HM-5246
section 35 with adjacent teeth sections formin~ coil accommoda-
ting slots~ such as 29 and 53, as well as defining the rotor
accepting bore 23. A first windin~ phase including the con-
centric coils 41, 43, 45 and 47, as one pole group thereof,
and the pole group interconnecting leads 61 and 63, is located
radially intermediate to other winding phases, with the phases
being displaced in phase one from the other. The outermost
coil in each pole group, such as coil 41, is seen to span the
greatest number of teeth sections for that pole group while
having less than full pole pitch. This may perhaps be most
easily seen by sketchin~ the equivalent lap-winding which has
a throw from slots 1 to 6, thereby encompassing five of the
twelve teeth per pole in the illustrated two-pole configuration.
When this same winding is employed in a consequent-pole mode,
the equivalent lap-winding would encompass five of the six
teeth associated with each pole, so it is clear that in either
pole configuration the winding arrangement illustrated in Fig.
1 is a short pitch winding.
Fig. 3 illustrates the manner of interconnecting the
winding leads of the Fig. 1 stator assembly to operate as a
two-speed three-phase motor in a two-pole mode where every
motor pole is a wound pole. Identifying pole groups by their
end lead numbers, it will be seen that one phase winding includes
two ~ole groups connected to be of opposite magnetic polarity.
Thus, pole group 57-59 and pole group 75-77 form the two poles
for one phase, and are connected as at 79 to one phase of a
three-phase source. The other two phases of this three-phase
source are connected to leads 81 and 83 which are in turn con-
nected to a parallel arrangement of each pair of pole groups for
the corresponding phase. Thus, the Fig. 3 interconnection
provides a high-speed wye-connected winding arrangement.
Fig. 2 illustrates the three winding phases in a delta
113~4S 03-l~M-5246
connection to the same polyphase source 79, 81, 83 but here
each phase of two pole groups i9 series connected to create
like magnetic poles and to therefore induce a similar number
of consequent poles for operating the motor in a lower speed
mode. Thus, comparing Figs. 3 and 2, it will be noted that
the current flow at some instant of time will be for one pole
group from lead 57 to lead 59, while the current flow for the
other pole group of that same phase will be from line lead 75
to lead 77. As noted earlier, this arrangement creates wound
poles of opposite ~agnetic polarity. However, when the current
flow is from lead 57 to lead 59, in the winding connection of
Fig. 2, the current flow through the other coil group for this
phase is from lead 77 to lead 75, thereby effectively creating
two like magnetic poles for this phase. The other pole groups
are similarly interconnected as is easily followed by comparing
the lead identification numbers 72, 65, 67, 69, 71, 73, 63, 61,
77, 75, 57, 59 in Figs. 1 through 3. The particular scheme
in which the several pole group leads are interconnected for
higher and lower speed operating modes has been used as illus-
trated by the corresponding sequence of lead interconnectionsin Fig. 5, where beginning at the three phase source terminal
79, leads 87, 93, 99, 105 join one phase winding in a delta
configuration to three phase source terminal 81, while leads
95, 101, 107 and 89 in that order connect a second phase
across three phase terminals 81 and 83, with the delta inter-
connection being completed by the third phase in order 103,
85, 91, 97. The corresponding wye configuration for a higher
speed mode of operation is illustrated in Fig. 6.
Fig. 4 illustrates a known winding arrangement on the
same stator core configuration as depicted in Fig. 1, and tests
have been run comparina these two winding arrangements when
applied to substantially the same stator core. It will be noted
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03-1~M-5246
that the span of each coil in a pole group, as illustrated in
Fig. 4, is one stator tooth greater than the corresponding
span of coils in the pole groups as depicted in Fig. 1. The
Fig. 4 span of the several coils corresponds to a pitch factor
of one in the four pole mode of operation, and a pitch factor
of 0.5 in the two pole running mode. Again, this can be most
easily seen by sketching the equivalent lap-winding and noting
that each coil thereof spans six stator teeth or equivalently
has a throw of 1-7. A ta~ulation of experimental verification
of the torque ratios achievable with the stator arrangement as
exemplified by Figs. 1 and 7, as compared to the known winding
arrangement of Fig. 4, is tabulated as follows:
Fia. 1 Fig. 4 Fig. 6
coil throw for equiv-
alent lap winding 1 - 6 1 - 7 1 - 8
pitch
2 pole 41.7 50 5B.3
4 pole 83.3 100 83.3
break-down torque
in oz. ft.
2 pole 455 391 821
4 pole 440 476 436
4 pole/2 pole .97 1.22 .53
maximum running torque
in oz. ft.
2 pole (3000 rpm; 60 Hz) 390 330 607
4 pole (1500 rpm; 60 Hz) 355 373 362
4 pole/2 pole .91 1.13 .60
locked rotor current
in amps.
2 pole 102 86.3 177
4 pole 53 S7.4 51.2
efficiency
2 pole rated load 86.3 85.3 90.0
2 pole peak value 89.5 90.7 90.9
4 pole rated load 84.3 84.9 83.8
4 pole peak value 85.5 85.6 84.7
power factor
2 pole rated load 92.5 92.6 88.6
2 pole peak value 93.0 92.6 90.7
4 pole rated load 70.5 69.9 69.0
4 pole peak value 71.0 75.0 75.0
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03-~M-5246
Fi~. 1 Fig. 4 Fig. 6
wire diameter .0453 .0453 .0605
in inches (bare diameter)
number of turns
Phase 1 29-30-30-30 29-28-29-28 16-17-17-17
Phase 2 29-30-30-30 29-28-29-28 16-17-17-17
Phase 3 2~-30-30-31 2~-28-29-29 16-17-17-18
line to line
resistance in
ohms
2 pole .938 .985 .463
4 pole 1.251 1.307 1.403
effective turns
2 pole 34.85 38.51 51.15
4 pole 48.23 47.56 27.04
relative harmonic
voltage levels
2 pole
3rd .604 .462 .250
5th .027 .145 .204
7th .156 .111 .020
9th .10~ .191 .250
4 pole
3rd .500 .707 .500
5th .067 .259 .067
7th .067 .259 .067
9th .500 .707 .500
Numerous salient features of the present invention~are
apparent from the foregoing tabulation. Thus, for example,
a designer faced with the problem of increasing, for eY.ample,
the two pole torque in his motor design would, with the
Fig. 4 arrangement, merely decrease the number of turns
in the several windings, thereby increasing substantially
the flux density in the core, giving a new motor design
with increased two pole torque and increased four pole
torque with the ratio of the four pole to two pole maximum run-
ning torques remaining about 1.13 as tabulated. This design
change would, however, substantially increase the losses
in the motor and deteriorate the power factor. If,
however, the designer approached the problem according to
the teachings of the present invention, he would, at least in
concept, increase the two pole torque while decreasing the four
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03-HM-5246
pole torque, which while providing him with the needed two pole
torque, would not deleteriously effect the efficiency or power
factor to a significant degree. Thus, a four pole to two
pole torque ratio of .91 would be achieved in the Fig. 1 con-
figuration with the listed design parameters, while a four poleto two pole torque ratio of .6 would be achieved in the Fig. 7
configuration, all while maintaining the other operating para-
meters within acceptable limits. Similarly, note that the
efficiencies in the two pole configuration for the winding
arrangement of Fig. 7 have been improved while not substantially
diminishing the four pole efficiencies as compared to the known
Fig. 4 winding arrangement, while the efficiency figures between
the Fig. 1 and Fig. 4 configurations are substa~tially identical.
Another significant advantage in the configuration of
Fig. 1 as compared to that illustrated in Fig. 4 does not appear
from the tabulated values. Either winding arrangement could
be and is,as shown in the afore-mentioned table, wound as a
graded winding arrangement. This simply means that the two
pole groups of the outermost phase have longer end turn portions
than those of the intermediate phase, while the innermost phase
has the end turn portions of its coil groups shorter than either
of the other phases. This is done both to save material and
to obviate any buckling in the end turn portions of the inner
positioned phase windings due to excessive material therein.
To balance the reactance between the several phases, an additional
turn or two is sometimes added in the outermost coil of that
radially innermost pole group and this additional turn shows up
in each of the three configurations compared in the tabulation
in Phase 3. Ilowever, since the winding arrangement of Fig. 1
is short pitched, grading of the windings is particularly effective
to separate the several phases, one from another, without the need
for additional insulation between the several phase winding
1~9~45
03-t~M-5246
end turn portions. This advantage which saves both material
and assembly time is peculiar to the configuration of Fig. 1.
The winding arrangement illustrated in Fig. 7 and its
two depicted operating modes, as illustrated in Figs. 8 and 9,
are unique, not only in providing the unusually low four pole
to two pole torque ratio illustrated in the table, but also
that both winding interconnection schematics ha~e the pole
groups for each phase connected in series.
In the low speed four pole configuration illustrated in
Fig. 8, one source phase terminal 79 connects to the series
combination of the fir-qt phase winding defined by leads 119,
125, 131 and 113. The central or neutral connections of the
wye configuration is then coupled to another source phase ter-
minal by leads 121, 115, 109 and 127, while the third source
lS phase is connected to the third phase winding by leads 111,
117, 123 and 129, which again terminates at the neutral center
connection. This arrangement provides two consequent poles
for each pair of wound poles, so current flow fromlead 119 to
lead 125 provides the same magnetic polarity of a wound pole
a~s does current flow from lead 131 to lead 113. It will be
noted, however, that current flow from lead 119 to lead 125
necessitates that same current flow from lead 113 to lead 131
in the connection illustrated in Fig. 9, and hence the two
magnetic poles associated with that phase are unlike and the
Fig. 9 interconnection provi~es a high speed or two pole mode
of operation.
Figs. 10 and 11 are magnetomotive force diagrams for the
winding arrangement illustrated in Fig. 1, with Fig. 10 corres-
ponding to the two pole high speed winding interconnection of
Fig. 3, while Fig. 11 illustrates the four pole consequent pole
lower speed interconnection of these windings, as depicted in
Fig. 2. Before proceed~ng with a discussion of these magneto-
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03-HM-5246
motive force diagrams, it should be recalled that a three phase
voltage soùrce may be depicted as three superimposed sinusoidal
wave forms each displaced from its predecessor by 120 electrical
degrees. If time is "frozen" when one of these sinusoidal wave
forms is at a maximum, the other two phase wave forms will be
at one-half this maximum magnitude and in an opposite sense.
Therefore, in the circuit diagram of Fig. 3, if one ampere were
exiting terminal 81, one-half ampere would be entering each of
terminals 79 and 83 at this instant. It is the magnetomotive
wave form which occurs at this time which is depicted in Figs.
10 and 11.
The stator core of Fig. 1 has been cut along a slot
adjacent to slot 53, uncurved and laid out in a straight line
to aid understanding of these magnetomotive force wave forms.
Thu~, a single conductor representing coil 41 and a single
conductor representing coil 55 are depicted in a first slot,
coil 43 depicted in a second slot and the remaining coils of
one pole group from Fi~. 1 identified by their corresponding
reference numerals 45 and 47. Further, the conductor exem-
plifying a coil of a particular phase, say phase 1, is illus-
trated as being circular, while phase 2 is depicted as a
triangular conductor and phase 3 as a square conductor, all
merely for ease of understanding. At the aforementioned
frozen instant of time, current flowing in the direction toward
the observer from the drawing is illustrated by a dot within
each conductor, while current flow in the direction away from
the observer is depicted b~ a cross within each conductor.
The cumulative effect of these current flows gives rise to
the north and south poles of the illustrated somewhat stepped
increasing and decreasing air gap mmf at this instant of time.
When the several phase pole groups are interconnected
as illustrated in Fig. 2, the slot positioning of the individual
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03-aM-5246
coil indicating conductors remains unchanged, however, the
direction of current flow in certain ones of those conductors
changes and the contribution of each is again summed, this time
giving the magnetomotive force diagram illlustrated in Fig. 11.
Of course, the designation of phases as being Phase 1,
Phase 2, and Phase 3 is completely arbitrary and as discussed
may not correspond to the mechanical order of placing the coils
in the core slots. However, interchanging two phases, as is
well known, merely results in a reversal of the direction of
motor operation and is not significant to the present invention.
In summary then, the series-delta two-pole, series-wye
four-pole arrangement of Figs. 7 through 9 pro~ides good two-
pole and four-pole performance since typically the higher torque
requirement is in the two pole configuration and this basic
design may be "tuned" by slight modification of the numbers of
turns to provide torque ratios of the four-pole to the two-
pole configuration in the range of .5 to 1. The parallel-wye
two-pole and series-delta four-pole arrangement of Figs. 1
through 3 has a short (1-6) pitch with a very desirable end
turn configuration and requires the interconnection of only six
leads to accomplish switching between its two pole number
operating modes. This Fig. 1 through 3 configuration provides
reasonably good two pole and four pole performance without
excessive losses and with acceptably low harmonic content in
each of the pole configurations, providing an overall desirable
motor design.
From the foregoing it is now apparent that a novel method
of fabricating a stator assembly for use in a pole changing motor
as well as novel polyphase induction motor stator arrangements
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1139~4~
03-HM-5246
have been disclosed meeting the objects and advantaseous features
se~ out hereinbefore as well as others and that modifications as
to the precise configurations, shapes and details may be made by
those having ordinary skill in the art without departing from the
S spirit of the invention or the scope thereof as set out by the
claims which follow.
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