Note: Descriptions are shown in the official language in which they were submitted.
1~982~
Bac ro~nd of the Invention
This invention relates to a reversing permanent split
capacitor (PSC) motor design, and in particular, to a reversing -
PSC motor finding application in a drive system for an agitator
of an automatic washing machine. While the invention is
described with particular detail in respect to such application,
those skilled in the art will recognize the wider applicability
of the inventive principles disclosed hereinafter.
This application, being a division of Canadian
application Serial No. 590,598 filed February 9, 1989, claims
only certain features of the invention disclosed herein below in
its entirety.
PSC motors have been used to drive washing machines for
a long time. ~he motors themselves have ~een known since nearly
the birth of induction motors.
Likewise, washing machines are not new. Over the years,
many attempts have been made to ~implify drive mechanisms
em~loyed to drive the agitator and spin wash basket of automatic
wahers. Many motor types have been employed for this purpose,
including a both induction motors and direct current motors of
various constructions. More recently, brushless permanent magnet
motors, and electronically controlled motors having unusual
winding configurations in the form of winding stages have been
suggested ~or use in washing machines. See for example, the U.S.
Patent No. 4,390,826 to Erdman et al. Motors having winding
stage6 are expensive to manufacture and difficult to control.
~hat ls to say, they require expensive and sophisticated
01ectronic control circuitry for operation. While conventional ;
brushless permanent magnet motors employing conventional
windings, as opposed to the stages used in the Erdman patent, for
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111(141./11~1~777/07/~ n . ,.
., " . ' .
132982~
example, have long been suggested for washing machine
applications, they too require relatively complicated control
circuitry for operation.
The motor and method of design disclosed hereinafter
utilizes a specifically designed reversible split capacitor motor
capable of reversing 120 times a minute to provide the agitation
motion for a washing machine. In order to achieve this high
reversability, numerous design criteria needed to be met. The
criteria to my knowledge, could not be met with conventionally
constructed PSC motors.
With respect to any PSC motor where reversing is
important, rotor inertia must be kept as low as possible so that
the rotor does not develop a tendency to nfly wheeln in the
lnitial direction o~ rotation instead of reversing as required by
the application. The motor also must not have third quadrant
torque. This means that when running in a negative speed mode,
the motor must not develop any negative torque. If negative
torque i5 developed during operation, the motor may not reverse
upon reversal of the power connections. Most importantly, the
motor must provide equivalent electrical and mechanical output in
both directions. The washing machine performance characteristic
necessarily depends on essentially eguivalent motor output in
each direction of rotation to enable the washing machine to
deliver equal washing motions in each direction of motor rotation.
As can be appreciated, the most relevant factor in
determining the rotor's inertia is rotor weight. Rotor weight is
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Ol~lL/DI1~777l07/lll/80
':' ' '
132982~
directly related to its overall diameter. However, if rotor
diameter is too small, then the motor is incapable of developing
sufficient torque in various drive applications in general and in
a washing matching application in particular. On the other hand,
if a large bore or diameter design is employed, fourth quadrant
torque to overcome inertia is difficult to attain. Under
conventional motor design criteria, the motor secondary
resistance, that is to say, the resistance of the rotor, is
chosen so that it is less than or equal to total stator
impedance. The design of the motor described hereinafter employs
a high resistance rotor. The secondary resistance, i.e. the ~;
resistance of the rotor in the preferred embodiment is
approximately 1.4 times the impedance of the stator. In any
case, acceptable resistances are in a range between 1.25 to 1.55
times the impedance of the stator. The motor construction
described hereinafter achieves certain design criteria not met
with conventional techniques. First, it enables the locked rotor
torque in each direction of motor rotation to remain high, i.e.
approximately 60% of breakdown torque. It also insures that no
third quadrant torque will be produced. I have found that when
reversible PSC motors designs deviate from these ratios, the
result iB a motor design that either costs too much, or fails to
meet the instant reversability or peak torque requirements of the
particular application.
The conventional method for manufacturing a four pole
rever~ing PSC motor is to employ two windings having equal turn
03~1./D113777/07/11~/ffff ",,
- 132982~
counts and wire sizes for the motor stator. The windings then
are placed at so electrical degrees (45 mechanical degrees) apart
in a suitable stator core lamination design. A capacitor is
placed between the two windings, and power is applied to one side -;
or the other of the winding/capacitor configuration. Functional
use of each winding depends upon which side of the capacitor has
power applied to it. With one connection method, the first
winding acts as the motor main winding and the second winding
acts as an auxiliary winding. On reversal, the winding functional
aspects also are reversed. Equal winding turns means that the
turns ratio or K ratio of the windings, conventionally defined
as the number of auxiliary winding effective turns divided hy the
nu~ber of ~ain winding effective turns, is one.
An alternative to the K ratio of one design is disclosed
hereinafter, denominated as an open delta connection. In the
open delta design, a stator is wound with three windings
di~placed ~7y 60 electrical degrees. Typically all three windings
have the ~ame turn counts and wire sizes. In one direction, one
of the windings acts as the main while the combination of the
other two windings and capacitor serve as the auxiliary. In the
reverse direction the third winding acts as the main while the
remaining two windings and capacitor serve as the auxiliary
winding. The resulting K ratio in this design is 1.732. Because
the K ratio is larger than one, a smaller capacitor can be used
ln the open delta design than in the equal turns ratio
I.IPN~777/07/~/RN
132982~ ~
arrangement. Total motor cost may be lower because of the
ability to use the smaller capacitor. ~ -
In general, it is more cost effective to design stator
laminations having silhouettes either in square or in other
parallelogram shapes. From a manufacturing standpoint, these
shapes can be manufactured with less scrap in the lamination
manufacturing operation. I have found that with a square
lamination design, it is important that the lamination be
designed and the winding placement chosen so that each winding
controls approximately identical amounts of lamination material,
so that electrical performance is equal in each direction of ~ ~ -
motor operation. When designed according to the principles ;
disclosed herein, a low cost, highly efficient, small size and
easy to manufacture motor particularly suitable to act in the
drive system of a washing machine is the result.
Thus this invention provides a low cost reversing
PSC motor design.
This invention can also provide a low cost PSC motor
design having applicability in a drive system for a washing
machine.
This invention can also provide a reversible PSC
motor having a high resistance rotor design so that no third
quadrant torque develops during normal motor operation.
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132982~
Also this invention can provide a reversing PSc
motor which includes at least a square or other general~y
parallelogram shape for the lamination silhouette.
In accordance with this invention there is also
provided a lamination design having winding receiving slots
formed in the laminations, the number and arrangement o~
which, in combination with the motor winding placement, is
adapted to provide equal maximum flux densities in each
direction of motor rotation.
This invention can also provide a reversing PSc
motor that obtains higher rates of reversal and superior
motor performance in applicational use than reversing PSC
motors heretofor known.
Other advantages o~ this invention will be apparent
ln view of the following description and accompanying
drawings .
Summarv o~ the Invention
In accordance with this invention, generally stated, a
reversible permanent split capacitor motor is disclosed which
uses a generally parallelogram lamination design. Individual
laminatlons have a central opening and a plurality of radially
extending closed bottom receptacles communicating with the
central opening ~ormed in them. Adjacent receptacles delimit a
~amination tooth, and the inwardly radially directed extensions
o~ the teeth define the central opening.
When ~ormed in a core comprising a plurality of
laminations, the receptacles delimit winding receiving slots and
the central opening defines a rotor receiving bore. The
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lamination preferably has two axis of symmetry, and the sl~ts are
arranged so that each symmetrical axis passes through winding
receiving slot openings. The windings of the motor are
distributed in the slots so that maximum flux density for the
core is approximately equal in each direction of rotation.
Preferably, the rotor design has high resistance, and the
co~bination of rotor inertia and rotor resistance is chosen so
that (i) no third quarter torque exists and (ii) locked rotor :~-
torque always will enable the motor to start in either direction. -
Brief Description of the Drawins
In the drawings, Figure 1 is a view in perspective
partially broken away, depicting an automatic washing machine
ut~l~z~ng the motor of the present invention:
Figure 2 is a cross sectional view of a portion of the
automatic washer shown in Figure 1:
Figure 3 ~s a view in perspective of the motor employed
in connection with the wash~ng machine of Figure l;
Figure 4 i8 a speed torque curve representation of the
motor design o~ the present invention as compared with a
conventional reversible ~plit capacitor motor:
Figure Sa i6 a diagra~matic view, labeled prior art,
showing a ~irst conventional winding for a reversible PSC motor
acting as a main winding in one direction of rotation,
illustratlng a ~irst yoke area o~ maximum flux density.
Figure 5b is a diagrammatic view showing a second
conventional winding for a reversible PSC motor acti~g as a main
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0164L/DI~3777/07/14/88
~329825
winding in a second direction of rotation~ i~lustrating a second
yo~e area of maximum flux density, the first and second yoke
areas being substantially different from one another.
Figures 6a and 6~ are diagrammatic views showing first
and second axes of symmetry for the lamination, further
illustrating respective first (Figure 6a) and second (Figure 6b)
windings of the motor of figure 5 shifted 15' respectively, also
illustrating first (Dl) and second (D2) yoke portions of
maximum flux density for the laminations there illustrated.
Figures 7a and 7b are diagrammatic views of the
lamination design o~ the present invention for a X ratio of one
design in which the axes of symmetry of the lamination are chosen
to extend through a winding recei~ing receptacle or slot, the
wlndings being positioned in the slots so that the area of
~aximum flux density (D) is the ~ame in each direction o
rotation.
Figure 8a i8 a diagrammatic view of a X ratio equal to
one design for a first illustrative embodiment of motor of this
inventi~n.
Figure 8b is a diagrammatic view of an opened delta
design for a second illustrative embodiment of motor of this
invention;
Figure 9a is a diagrammatic view of a connection diagram
~or the motor shown in Figure 8b.
Figure 9b is a phasor diagram illustrating the operation
oP the motor shown in Figure 8b and 9;
0~641./DN~777/071~/BB
1~2982~
Figures lOa and lOb are diagrammatic views showing
respective first (9a) and third (9b~ windings acting as main
windings for an open delta arrangement in a prior art lamination
design, further illustrating first and second yoke areas of
maximum flux density: ~
Figures lla and llb are diagrammatic views of first ~ .
(lOa) and third (lOb) windings acting as main windings for an ~:
open delta arrangement of the motor of this invention,
illustrating the availability of yoke portions having
approximately equal flux densities in each direction of motor
rotation employing the motor design of this invention;
Figu-re 12a is an end ~iew of one illustrative embodiment
of the motor of this invention:
Figure 12b is a second end view of the motor of this ..
invention; .
Figure 12c is a view in side elevation of the motor of :
this invention; and
Figure 13 is an enlarged sectional view o~ the motor of
this invention.
De cri~tion o~ the Preferred ~mbodiment
Re~erring now to the Figure 1, reference numeral 10
indicates generally a vertical axis agitator type washing machine
having preselectable controls for automatically operating the
machine through a programmed series o~ washing, rinsing and .
spinning ~teps. The machine 10 includes a frame 12 carrying
panel~ l~ forming th~ sides, top, ~ront and bacX o~ a cabinet
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03641./DN3777/07/14/8a
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132982~
1. A hinged lid 18 is provided in the usual manner for access
to the interior of the washing ~achine 10. In the e~bodiment
illustrated, the washing machine 10 has a rear conso7e 20 in
which is disposed setable control means, including a timer dial
22 and a temperature selector 24. Other controls may be
provided, if desired.
Internal to the washing machine 10 there is disposed a
perforated fluid containing tub 26 within which is rotably
mounted a perforated basket 28 for rotation about a vertical :
axis. A vertically disposed agitator 30 is connected for
operation to a motor 32 through a drive mechanism 34.
Referring to Figure 2, the agitator 30 is linked by a
shaft 36 to the drive 34, which in turn is driven by a suitable
pulley arrangement 38 by the motor 32. The motor 32 is mounted
in an arrangement 40 and 42 which connects to the ~rame 12 of the
wa6her 10. In the embodiment illustrated, the motor 32 is linked
by a pulley arrangement 38, that arrangement including a drive
pulley 44 and a driven pulley 46 connected by a belt 48 to a
drive 34. The drive 34, in the embodiment illustrated, also .
includes a planetary gear drive having a spring clutch 50 in a
planetary housing 52 mounted in a reduction drive frame 54 that
connects to the ~rame 12. While a planetary reduction drive has
been shown in the drawings and disclosed herein for use with the
motor 32 o~ the present invent$on, those skilled of the art will
recognize that a variety o~ other driver arrangements can be
utllized with the motor 32. It is also contemplated that the
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03~4L/D113777/07~ 30
132982~
motor ~2 may be directly attached to the agitator in operation of
the washing machine lo. As will be appreciated by those skilled
in the art, the washing machine 10 being described here for
background information and detail, may comprise any of a variety
of commercially available devices.
The motor 32, ~s shown in Figures 12 and 13 t includes a
first end shield a 200 and a second end shield a 201 which axe
attached to a stator assembly 202 in any conventional manner.
Threaded fasteners work well, for example. The end shields 200
and 201 respectively include a central hub 204 which houses
suitable bearings 206 for rotably supporting a rotor assem~ly
205. The rotor assembly 205 is mounted to a ~haft 210. The
shaft 210 in turn is journaled in the bearings 206, which, as
indicated, are positioned the respective hubs 204. The rotor
assemb~y 205 is mou~ed on the shaft 210 by any convenient
method. ShrinX or press fits work well, for example. The
attachment of the motor 32 to the washing machine 10 is described
in particular detail in U S Patent No. 4,947~539. Likewise,
certain related constructional features of the motor 32, not
forming a part of the invention disclosed herein are descLi~ed
in U.S Patent No. 5,035,043.
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. :
-" 13~982~
T~le rotor assembly 205 preferably is a laminated
str~cture having a squirrel cage design. The assembly 205
includes end rings 207 and 208. In the embodiment illustrated,
the end ring Z08 has an integrally cast fan 209 formed with it,
for purposes of cooling the motor. A fan assembly 220 also is
provided on the opposite rotor end for rotation with the shaft
210 for the purposes of additional cooling of the motor 32.
Details of the cooling functions and construction of the fan
assembly 220 may be found in U.S, Patent No. 4,833,049. Power
is supplied to the motor through conventional lead wire 222
which may be terminated in any suitable way. Conventional
connector plugs work well, for example. -
As indicated above, electrically the motor 32 may take
two ~orm8. Equivalent circuits for the motor windings are shown
in Figures 8a and 8b. As shown in Figure 8a, the equal K ratio
design, a lead wire 300 is connected to one side of a first
winding 301. A 8econd side o~ winding 301 is connected to a lead
302. The lead 300 also is connected to a first side of a winding
303. A second side of the winding 303 is connected to a lead
304~ A capacitor 305 is connected between the leads 302 and
304. A switch means 310 is provided to connect an input
¢onductor or line 311 either to the lead 302 or the lead 304,
depending upon the direction of rotation desired.
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0301~ DN377710711~
1329~2~
The open delta design is shown in Figure 8b. Like
reference numerals are employed, where appropriate. In the
embodiment shown, the input lead 300 again is connected to one
side of a winding 301 and a winding 303. The second side of
winding 301 is connected to a conductor or lead 302 and a
capacitor 305. A second side 308 of the capacitor 305 is
connected to a first side of a third winding 309. A second side
of winding 309 is connected to the lead 304 and to a second side
of the winding 303. The leads 302 and 304 again are connected to -
the switch means 310 and through the switch means to the other
input power conductor 311, movement of the switch means 310
between either a terminal 320 or a terDinal 321 will cause -
alternate rotation of the rotor in either a clockwise or a
counter-clockwise direction, respectively.
~ he circuit design in Figure 8a is a somewhat more
convent~onal ~ethod of producing a reversing PSC type motor. For
exa~ple, in the embodiment of Figure 8a, the windings 301 and 303
pre~erably have the same wire sizes and turn count. Those
sXilled in the art will appreciate that the windings 301 and 303
comprise a number of poles. ~hat is to say, the winding 301 may
be constructed from any desired number o~ poles. The number of
poles determines the maximum operating motor speed and for most
washing mach~ne applications, 2, 4, 6 and 8 pole con~igurations
are ~ound to be adequate. Other variations will be apparent to
those sXilled in the art. As indicated above, the drawings
indicate a ~our pole configuration.
03~1./DN~777/07/1~/11~ , ,
1329~2~
I~ Figure 8b, each of the windings 301, 303 and 309
preferably h~ve the same turn counts and wire sizes. In one
direction of rotation, winding 301 will act as the main while the
combination of windings 303 and 30g serve as the auxiliary
winding. In the other direction of rotation, winding ~03 acts as
the main winding, while windings 301 and 309 serve as the
auxiliary winding. Again, the individual windings may be wound
in a variety of pole configurations.
As previously indicated, the largest single factor in ~ ~ -
determlning a rotor's inertia is its weight. Rotor weight is
dirèctly related to its outer diameter. For the washing machine
application described herein, the optimum stator bore diameter
was derived to be at 70mm or 2.756 inches. The outer diameter
dimension ~or the stator lamination was chosen at approximately
4.2 inches. This combination of size factors enables the motor
o~ my invention to have the lowest material cost for the
per~ormance reguired in the washing machine application described.
Figure 4 is a speed torque curve for the conventional
xeversing PSC motor design sometimes used in washing machine
applications. As shown in Figure 4, with conventional or
standard (STD) motor designs, third guarter torque can ~ave a
negative value. This is highly undesirable in cituations where a
large number o~ rever~als per minute ~or the motor are required.
Indeed, this condition is not desirable in applications requiring
any number o~ reversals. By ~ollowing the design criteria set
~orth herein, the ~econd speed torgue characteristic shown in
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O~O~I/DN3777/ D7/ ~ 8
132982~
F~:~ re 4 was obtained. Significantly, no third quarter torque is
present in the design; high locked rotor torque or starting
torque is obtained; breakdown torque is equivalent to the
standard motor; and the operating range of the motor on the speed
torq~e curve is roughly equivalent. More importantly, the
operational performance can be repeated in either direction of
rotation.
Figures Sa and 5b show conventional winding and slot
configurations in known reversing PSC motors. For purposes of
description, a lamination 500, which is a generally a
parallelogram shape, is shown in a known winding and slot
design. The parallelogram shape found most convenient to use is
a ~quare. The lamination 500 includes certain constructional
details not forming part of the present invention in the form of
mounting bolt openings 501 adjacent a plurality of cleat notches
502, The cleat notches 502 are utilized to interlock the
laminations in a predetermined core height as is ~nown in the
art. The lamination 502 has, for purposes oS describing the
pre5ent invention, an X axis o~ ~ymmetry 503 and a Y axis of
symmetry S04, as re~erenced to Figure 5a. As there shown, each
lamination 500 has a central bore opening 514. ~he opening 514
has a plurality o~ radially extending close bottom receptacles
505 communicating with the central opening 514. Ad~acent
receptacles 505 de~ine teeth 506 having tips 507, the inwardly
extending ends o~ which de~ine the opening 514.
036~L/DN3777107/1~
1329825
In their assembled relationship, the individual
laminations 500, delimit a core 509 (shown in Figure 13), while
the receptacles 505 delimit winding receiving slots 520. The
central opening 514 defines a rotor receiving bore 521. In the -
embodiment illustrated, there are twenty-four (24) slots 520,
which are numbered for description in a clockwise direction, as
referred to in Figures 5a and 5b, by the notations Sl through
S24. Conventionally in prior art designs, one tooth 506 lies
along each respective one of the axes of symmetry 503 and 504.
As can be seen in Figure 5, the number of teeth equal the number
of slots and each tooth centerline axis represents 15~ of a
conventional compass measurement.
Figures 5a and 5b illustrate diagrammatically the
respective w~ndings 301 and 303 acting as main windings.
Conventionally, during motor construction one of the windings is
placed in the slots first, and the second winding is placed
radlally inwardly o~ the first winding, and the winding may share
~lots with one another. For ease Or description, however, the
w~ndings 301 and 303 are shown separately in Figures 5a and Sb.
Maximum ~lux density in the lamination 500 occurs in the
area~ where the respective windings are split, as between the
slot S3 and S4 in Figure 5a and slot S24 and Sl in Figure 5b.
Flux density i~ determined by ~irst deriving the total motor flux
'~ ~rom the ~ormula:
= V~M6 (4-54 x 10~)(.95)
...... . . ;::
~f)(C~
- 17 -
0361l1,/DN3777/07/l~
~f,,~ ",, ,, ,' ,,, " ~ ,,' ,-'" ,,~ '," ;,' ~ "~ ', "~ ,; "",,'~", `'"~ ;';~''
- 1~2982~
Where VR ~ 5 = the root mean square value of the
terminal voltage applied to the motor; :
f = frequency of the voltage ~o~rce; :
CXu= T~tal number of effective cond~ctor of ;
the motor; where c is the total actual
mot~r turns and X~ is a winding factor
to obtain effective turns.
F1UX is expressed in K lines. Once total flux is
determined F1UX density is determine~ from the formula:
Flux Density = ~/A
Where A = the cross-sectional area of the core structure ~
of concern. Generally, the ~tooth~ density and core density are ;
calculated. For the core structure, flux density is determined
in practice by the distance between the slot bottom, times the
core stack height. RMS values of flux density are obtained by
dividing the flux density obtained from the above calculation by
the i6quare root of 2.
Assuming other factors being equal, flux density
depends, in the lamination des~gn shown in Figures Sa and Sb, on
the di~tace between the slot bottoms and any particular end
point of the lamination SOO. As can be seen in Figure 5b, the
dlstance Dl is ~ubstantially smaller than the distance D2, 80
that the prior art motor depicted in Figures 5a and Sb cannot
pos~ibly ha~e equivalent performance in each direction of
rotation. Since motor electrical performance decreases as flux
density increases, motor operation in the Figure ~b arrangement is
demon~tratably wor~e than in the Figure 5a mode of operation.
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0~641./DN~777/07/14/00
: " '. '
:S ' ., . " ~. , s , ~,~. ... ...... .
132982~ ~
Figures 6a and 6b depict a conventio~al way to improve
m~t~r performance. Where the motor is intended to operate in a
single direction, performance improvement sometimes can be
accomplished by shifting the winding one slot in either direction
from the associated symmetry axis. When this is done with a
reversible motor, however, performance in both directions of
rotation does not improve. As can again ~e seen, t~e distance
D1, while increased with the shifted winding, is still
substantially different from the distance D2 shown in Figure 6b.
Again, motor performance will not approach equivalency in each
direction of motor rotation.
Figures 7a and 7b illustrate the final configuration for
a lamination 580 used for the motor 32. Like numerals are
employed, where appropriate. As there shown, the lamination
de~ign itself has been rearranged so that the axes 503 and 504
now pa~s through a slot of the lamination rather than a tooth.
When 80 arranged, each winding split occurs 22.5 from the one o~
the axe8 o~ symmetry 503 and 504, regardless of which winding is
utllized as the main winding. Consequently, maximum flux density
o~ necessity is the same in each direction of rotation and
equivalent ~odes o~ electrical performance, and consequently
equAl washing performance, i5 obtained. Equivalent performance
occur~ regardless o~ the time spent in either direction of
rotation during washing operation.
Figure 9 ~s a connection diagra~ for the open delta
deslgn described above. Again, each winding comprises ~our
- 19 - ,;,':
03~L/ON3777/0711~/ss
,: ,
i3298~
p ~s, each pole having two sets of wire turns forming the pole.
The radially extending lines represent tooth axes, and the wire
turn sets are wound to span three and fi~e teeth, respectively.
The winding configuration and coil placement are diagramatically
illustrated in Figure 9. Also shown in 9 are the connections
between poles, the leads, and a protector employed with the motor
32 of this invention, regardless of the winding configuration
used.
Figure 9b represents a phasor diagram for the open delta
design shown in Figure 8b. The voltage across winding 301,
winding 303, and winding 309 have a resultant phasor in
respective directions of rotation indicated by the reference
numerals 901 and 902. ~he resultants 901 and 902 are equal to
one another.
Performa~ce of the open delta design caused by placement
o~ the winding in the lamination 580, while not exactly equal as
~5 the case of the embodiment shown in Figures 7a and 7b, is
comparable to the improved results obtained by shifting the
winding in the prior art de5igns. Thus, while Figures lOa and
lOb ~how relati~ely large dif~erences in yoke area and
consequently flux densities, the relationship illustrated in
Figures lla and llb tends to minimize the difference. That is to
say, while the distance D~ nis somewhat greater than the
distance D~ n in Figure5 lla and llb respectively, overall motor
cost may justify the difference in performance. I have found
consequently, that either winding design may be employed
- 20 -
03~L/DN3777/07/1~/08
:, ' ' '
`- 132~82~
dd~ntageously with the lamination design 580. With either
embodiment described, it is desirable to attempt to balance the
maximum flux densities in each direction of rotation to ensure
proper washability in washing machine applications, and to ensure
improved electrical performance in other applications.
Uu~erous variations, within the scope of the independent
claims, will be apparent to those ski~led in the art including
the foregoing description and accompanying drawings. Thus, while
cleating was described as the preferred method of core
manufacture, bonding, welding or combinations of the three, or
other methods may be employed if desired. The motor is shown
using a construction in which the end shields are mounted directly
to an end face of a particular lamination. Other constructions ~ -
may be e~ployed. For example, more conventional motor she~ll and
end shield arrangements may be used. Lamination thicknesses and
relative dimensions may change in other e~bodiments of this
invention. A~ indicated, the number of poles and the number of
coils comprising the poles may also vary. These variations are
merely illu~trative.
, ,
; ,,':
-- 21 --
03$~1L/DN~777/07/l~/00