Note: Descriptions are shown in the official language in which they were submitted.
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DYN~MO-ELECTRIC M~CHINE LAMINATION CONSTRUCTION
BAC~GROUND OF THE INVENTION
FIELD OF THE INVENTION
The pre~ent invention relates generally to eore
laminations or punchin~s ror use ~n dynamo-electric
machines, and ~ore particularly to a lamination
construction in which teeth and yoke portions of the
laminations have relative dimensions such as to provide
improved output for a given ~ize machine.
DESC~IPTION OF THE ~NOWN ART
Arrangements are known for improYing the efficiency
or power output of dynamo-electric machines through the
provi~ion of certain ~lot di~tributions in either a stator
or rotor core element of the machine, e.g. U.S. Patent
4,566,179 (January 28, 1986) or by creating a prescribed
variation of magnetic flux through a pole o~ the ~achine
QtatOr relative to the ampere-turns of the pole such as in
U.S. Patent 4,209, 720 (Ju~e 24, 1 gBo) . Howe~er, there
ha~ not been di~closed a machine lamination construction
by which the operating efficiency of a dynamo-electric
machine having a ~tacked laminated stator and/or rotor is
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lmproYed by a prescribed ratio of inner diameter to outer
dia~eter ror the lamination. Also, thPre has been no
disclosure Or a lamination cons'cruction by which the rat~ o
of flux density in a tooth portion o~ the lamination to
flux density in a yoke portion of ~he lamination can be
increased over that obtained conventionally, and, as a
result, yield greater output or operating efficiency ~or
the mach~ne.
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SUMMARY OF THE INVENTION
An object of the invention i to provide a dynamo-
electric ~achine lamination eonstruct~on in which
improvement is obtained through a greater ~mount of
lamlnation material and les~ winding conductors than used
previously.
Another ob~ect o~ the invention is to provide a
dynamo-eleo~ric ~achine in which leakage rlux from end
turns of a winding embedded in slots of a la~inated core,
i substantially reduced.
A further object of the invention is to provide a
dynamo-electric machine having a greater horsepower to
volume ratio than that previously obtained.
The variou~ ~eatures o~ novelty which characterize
the lnvention are pointed out with particularity ln the
claimq annexed to and forming a part of the present
disclosure. For a better understanding o~ the invention,
its operating adYantages and specific ob~ects attained by
it3 use, re~erence ~hould be had to the accompanying
drawing and descrlptive matter in whlch there are
illu~trated and de~cribed preferred e~bodiment3 of the
lnven'cion .
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BRIEF DESCRIPTION OF THE DR~WINGS
In the drawings:
Figure 1 is a side view, partly in section, of a
dynamo-electric machine in which the present invention
may be embodied;
Figure 2 is a front view of the machine in Figure
2;
Figure 3 is a plan view of a plate lamination for
forming a stator in the machine of Figures 1 and 2;
Figure ~ is an enlarged view of a part of the
lamination in Figure 3;
Figure 5 is a plan view of another plate lamination
for forming a stator in the machine of Figures 1 and 2;
Figure 6 is an enlarged view of a part of the
lamination in Figure 5;
Figure 7 is a table showing preferred ranges and
specific values of physical relationships and ratios
associated with the laminations of Figures 3 and 5 when
dimensioned for different frame sizes and designed for
different numbers of poles;
Figure 8 is a table showing comparative data for
physical relationships and ratios associated with the
laminations of Figures 3 and 5 (when of a NEMA 1~0 Frame
size and designed for 2 (two), 4 (four)/ and 6 (six)
pole operation) in relation to those of known
laminations for a certain machine frame size;
Figure 9 is a table showing comparative data on-
physical relationships and ratios associated with the
laminations of Figures 3 and 5 (when of a NEMA 210 Frame
size and designed for 2 (two) or 4 (four) pole
operation) in relation to those of the known laminations
for another machine frame size; and
Figure 10 is a plan view of a plate lamination for
forming a slotted rotor.
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DETAILED DESCRIPTION OF THE INVENTION
Flg. 1 ~hows a ~ide view, in section, o~ a dynamo
~lectric machine 10 in which khe present invention may be
embod~ed. A ~ront view o~ the machine 10 i~ ~hown in Fig~ -
2.
Ba~ically, the ~achine 10 lncludes a generally
cylindrical outer casing 12, and a generally cyl~ndrical
stator 14 f~xed coaxially within the outer casing 12 and
having a coaxial qtator bore 16. A rotor 18 i s supported
by suitable bear~ngs 20a, 20~ at the fron~ and back of
casing 12, to extend axially within the stator bore 16 and
~or rotational ~ovement about the bore axis. In the
particular example shown a shaft part 22 of the rotor 18
extends axially from a ~ront end shield 24 of the ~ach~ne
10, and has a key 26 pro~ecting radially outward from a
recess cut axially a certain distance ~rom the front of
the ~haft part 22. Key 26 serves to lock the shaft part
22 into a corresponding key way cut in a load member (not
shown), e.g.1 a ~an1 to which rotational mot~ve power ~s
1;o be supplied by the macbirle 10.
A b~ck end shield 28 (Fig. 1~ together with the
casiDg 12 and the rront end shield 24 serve to contain and
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protect the stator 14, rotor 18 and associated
conductive windings~ In the example shown, a machine
cooling fan 30 is mounted on a rotor stub part 32
which extends outside the back end shield 28, and
directs an air current flow over the casing.
As shown in Fig. 1, the stator 14 is comprised
of a stack of plate laminations 34 of ferromaynetic
material. The laminations 34 are stacked face-to-face
and are held together to form a core by any of the
various means well known in the art. ~ number of
slots extend along the axial length of the stator 14,
and extend radially from the stator bore 16. These
slots accommodate stator windings that have end turns
36, parts of which are shown in Fig. 1. Details of
individual plate laminations embodying the invention
in preferred forms are given below.
As shown in Fig. 1, the shaft part 22 of the
rotor 18 extends axially from the machine casing or
housing 12 and has a stack of rotor laminations 40
fixed coaxially on the shaft part 22 intermediate the
~ront and back bearings 20a, 20b. Sets of conductive
bars 42 pass through a number of axially extending
slots formed in the rotor 18 near the outer periphery
of each of the laminations 40O The bars 42 are
shorted to one another at the axial ends 44a, 44b of
the rotor laminations 40 by a set of end rings.
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In Fig. 1, the stator winding end turns 36
at axial end faces 48a, 48b, of the stator 14, are a
source of stator -flux leakage i.e. magnetic flux
produced by the stator winding which dses not
interface with the conductiYe bars 42 in the rotor
laminations 40. Inasmuch as stator flux leakage
does not contribute to the resultant torque exerted
on the rotor 18 when the stator winding or windings
ar~ energized, such flux leakage adversely effects
the operating efficiency of the machine 10. It will
therefore be understood that any means by which
potential sources of stator flux leakage can be
reduced or eliminated, are of great importance in
dynamo-electric machine construction.
Certain machine construction standards are
known in the industry, particularly those set out by
~NSI/NEMA Standards Publications No. MGl-1978(R1981).
The present invention aims to provide a dynamo-
electric machine construction which conEorms with
industry standards, particularly with respect to the so-
called 180 and 210 frame size constructions. It will be
understood, however, that although dimensions for machine
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laminations disclosed herein will apply to the 180 and
210 frame sizes, the invention can be embodied with
advantage in machines of various sizes and proportions.
In Fig. 3, a stator lamination 34 according to
tha invPntion comprises a flat annular plate of
ferromagnetic material having an outer diameter "OD"
according to the tabular values of Figs. 8 or 9 and a
generally circular bore opening 50 of a certain inner
diameter "ID". The lamination 34 has a number of
equally circumferentially spaced slot openings 52
extending radially from an intermediate circumference 54
to form a number of teeth 56 which extend radially to
the circumference of the bore opening 50. The bore has
a diameter of "ID". In the illustrated embodiment in
Fig. 3, the lamination 34 is a stator lamination so that
the circumference of the bore opening 50 defines one
boundary for a stator-rotor air gap and a bore for
receiving the rotor.
- The slot openings 52 are formed to contain one or
more stator windings which extend axially through the
stator 14 when like ones of the plates 34 are stackPd
face-to-face with corresponding slot openings 52 substan-
tially aligned with one another. In the assembled machine
10 o~ Figs. 1 and 2, the stator windings are arranged to
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correspond to an n (e.g., 2, 4, 6, etc.) pole operating
configuration for the machine 10. When the stator
windings are connected to an outside electrical source,
magnetic flux is produced next to the substantially
aligned air gap peripheries of the stacked laminations
34 to interact with the conductive bars 42 of thP rotor
18.
The annular lamination 34 in Fig. 3 includes a
tooth portion 58 defined by the teeth 56 betw~en the
intermediate circumference 54 and the air gap
peripheryO The remainder of the lamination 34 is
continuous between the intermediate circumference 54
and the outer periphery 59 to define a yoke portion 60
of the lamination 34.
Fig. 4 is an enlarged view of a part of the plate
laminations 3~ in Fig. 3. Specifically, a single slot
opening 52 is shown surrounded by adjacent teeth 56. Lip
parts 61 project circumferentially toward one another from
the adjacent teeth 56, to define a mouth 62 (of width W10)
of the slot opening 52. As is known, mouth 62 should be
sufficiently wide to allow individual conductors 64 forming
the stator winding to be inserted in the opening 52 through
the mouth 62 when the machine 10 is assembled. The lip parts
61 act to seat a winding closure wedge 66 which holds the
conductors 64 of the stator winding firmly in place within
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the stator slots formed by the openings 52. To separate
individual stator windings, an insulating winding
separator 68 may be positioned as shown in Fig. 4 in the
stator slots, and an insulating film 70 positioned
against the walls of the stator slots prevents arcing or
short circuiting of individual conductors 64 with the
material of which the laminations 34 are made.
According to the invention, for a given ratio of
inner diameter ID to outer diameter OD of the lamination
34, the teeth 56 are sufficiently wide relative to the
area of the slot openings 52 so that the ratio of flux
density in the tooth portion 58 (BTl) to flux density in
the yoke portion 60 (BYl) when the stator windings are
energized, as well as electric current is substantially
optimized for a given n pole operation of the stator
windings. The actual number of slot openings is not
critical. For example, the lamination 34 in Fig. 3 is
shown with 24 slots and has relative dimensions suitable
for incorporation in a 1~0 f~ame si2e machine. A
lamination 34' according to the invention as shown in
Fig. 5, has 36 slots and relative dimensions suitable
for use in a 210 frame size machine. Parts of the
lamination 34' which correspond to those of the
lamination 34 in Figs. 3 and 4, are identified with
similar reference numerals.
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An underlying concept of the present invention is to
utilize maximum amounts of ferromagnetic material (e.g., iron)
for the laminations 34 (or 34') and minimum amounts of winding
conductors, e.g., the individual conductor6 64 or 64' in a
dynamo-electric machine having a desired power handling
capability.
In the disclosed embodiments, the ratios of ~he tooth
portions 58 to yoke portions 60 for the lamina~ions 34 substan-
tially differ from known constructions, as does the ratio of
inner diameter to outer diameter of the laminations 34. The lip
parts 61 thus become very small relative to the known structures
as a consequence of the relatively wide teeth 56. Use of less
winding material also results in smaller end turns (e.g., the
stator end turns 36) at the end faces of the lamination stack,
and, thus, undesired flux leakage is significantly reduced from
that in the prior constructions.
Fig. 7 is a table which shows preferred ranges and spe-
cific values for physical constants, relationships, and ratios
associated with both stator and rotor laminations having a num-
ber of slots ~ according to the invention. Assuming, e.g.,
that a machine conforming to a standard frame size is to be
cons~ructed, the NEa~A Standards will limit ~he maximum outside
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dimensions of the motor in which the stator lamination size is
optimized. Typical outer diameters ~O.D.) for both stator and
rotor laminations for use in the 180 and 210 frame size stand-
ard, are represented in Fig. 7. Fig. 7 also provides specific
values as well as ranges for various ratios which are used to
define the improved stator lamination. The ratio ID/OD repre-
sents the ratio of the inner diameter of the stator lamination
to the outer diameter and gives an indication of the larger
amount of ferromagnetic material than copper which is used in
the present laminations. The ratio Tl/Ts represents a ratio of
the tooth width (Tl) of the stator lamination to the bore
circumference divided by the number of stator slots Sl, (TS =
x ID/Sl). This effectively provides an indication of the
tooth width. The value Btl/Byl can be used to represent the
flux density in the tooth to the flux density in the yoke if it
is assumed that the flux in the tooth and yoke is the same,
which is a close approximation. This ratio yives an indication
of tooth to yoke ratio. This ratio is also determinable geomet-
rically from a stator lamination by the relationship Btl/Byl =
(qr x n x Yl)/(Sl x Tl~ where n is the number of poles, Yl is
the dimension shown in Figs. 3 and 5, and Sl and Tl are as
defined hereinabove.
The final column in Fig. 7 is a ratio of the inter-
action of the stator to the rotor, where S represents the number
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of siots, T represents the width of the tooth, 1 represents the
stator and 2 represents the rotor. The chart of Fig. 7 sets
forth the values and ranges for 2, 4 and 6 pole machines (n).
For the 4 pole, 180 frame and 210 frame, two embodiments are
shown.
Fig. 8 is a table in whicn physical constants, relation-
ships, and ratios associated with the laminations dimensioned
according to the invention as shown in Fig. 7 are compared with
the closest known prior configuration, for 2, 4 ~nd 6 pole AC
induction tors for a 180 frame size. For comparison with
known values, the specific measurements have been converted into
inches. Of course, the ranges still remain the same as was
shown in Fig. 7. Included in this chart is a value of the net
and gross area of the slots in the stator multiplied by the
number of slots in the stator (Sl). The net slot area
(ASLOT-NET) equals the gross slot area (ASLOT-GROSS, see Fig. 3)
less the area occupied by the slot liners, separators, and
wedges and less the area A3 at the mouth not available for
insertion of windingQ (see Fig. 4).
Fig. 9 is a table similar to that of Fig. 8, in which
laminations configured according to the invention as shown in
Fig. 7, are compared with the closest known prior laminations
for two and four pole AC induction motors with a ~10 frame size.
Ayain specific values have been converted to inches.
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It will be seen from Figs. 8 and 9 that in
addition to having a lower inner diameter to outer
diameter ratio and a higher ratio of flux density
between the tooth and yoke portions than in the prior
corresponding laminations, the teeth width of the
present laminations is generally greater. It should be
remembered that the present improved laminations are the
result of an interaction of the various values. Thus,
not each and every one of the values is consistently
changed for each embodiment. The result, however, is
consonant with the underlying concept of the present
invention which, as mentioned, is to utilize maximum
amounts of lamination material and minimum amounts of
winding (i.e., copper) material.
Machines employing laminations configured
according to th~ invention have yielded greater
horsepower to volume ratios when compared with known
corresponding machines. Of course, variations occur
depending on efficiency. However, Tables 1, 2 and 3
below show a comparison of efficiency and volume
measurements for 2, 4 and 6 pole AC induction motors
with laminations according to the present invention and
corresponding motors according to the prior art.
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Through the use of relatively wider teeth in
the present laminations, flux density saturation for a
given size and power machine can be achieved with a
shorter lamination stack than in the prior
constructions. Hence, the electromagnetic volume
(OD L for machines according to the invention is
generally lower than the volumes in the prior machines
for the same efficiency. The use of wider or fatter
teeth also produces a relatively higher flux density
in the air gap between stator and rotor lamination
stacks in machines according to the invention. Thus,
more torque is produced on the rotor for a given
machine size.
Fig. 10 illustrates a rotor lamination, more
fully described in the Canadian Application Serial No.
561,099, Gandhi et al, filed March 10, 1988. Fig. 10
clearly illustrates the width T2 of the rotor teeth,
and it will be understood that a fabricated rotor as
shown in Fig. 1 would include a number S2 of rotor
slots, and the same number S2 of rotor teeth each
having a width T2 such that the various ratios
involving S2 and T2, or the value of S2 in the tables
of Figs. 7, 8 and 9 are determinable in motors wherein
principles of the present invention are applied.
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TABLE 1
-2-POLE AC ~ MOTORS
% EFFICIENCY VOLUME ~OD)2L
~( LO ~ F~ ) ~2 ~1~ ~7
5 (HI EFF) 89~3 91 2 3 67 4 74
7 . 5 (LO EFF) 8r.5 87 .1 3 21 2 47
7.~ (HI EFF) 90.6 91.1 4 12 3 30
TABLE 2
4 -POL E AC ~TION MOTORS
S ~ VOLUME tOD ) 2L
HP PRIOR NEW PRIOR NE~ ~
~(LO EFF) ~ ~0 86.7 ~ ~6-2.27
3 (HI EFF) 89.9 90.6-90.9 3 21 3 09
(LO EFF) 85 . 3 87. 4-88 . 2 2 75 2 68-3 30
(HI EFF) 90.6 90.8-91.5 1~ 37 3 30-3 92
TABLE 3
6-POLE AC ~ MOTORS
S EFFICIENCY YOLUME (OD ) 2L
~(LO EFF)~E~W7 ~RIOR NEW
2 (HI EFF)B8.7 B9.8 4 35 3 71
3 )~
~MM x 1~ Thus, tabular value of 2.75 means 2.75 (106? MM3;
tabular value 2.27 means 2.27 (106) MM3; etc.
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Terminology used herein includes the words "generally
cylindrical", "essentially round" and "annular". When these
terms are used herein with reference to or in connection with
laminations (or plates) or structures made from such laminations
(e.g., "cores", stators, etc.), such texms will ba inclusivély
descriptive of laminations, cores, etc. that do not have "true
round" configurations due to the pxesence of peripherally
located "key slots", marker notches, flats resulting from
production processes (such as occur from zig-zag punch lines,
for example)~ and so forth.
/
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RELATION~IP TO OTHER APPLICATION~
This application has been filed on March 17,
1988 as well as commonly assigned Canadian Application
Serial No. 561,117 - BASE ASSEMBLY FOR DYN~O-ELECTRIC
MACHINE in the name of Robert L. Sieber, filed March 10,
1988, Canadian Application Serial No. 561,099 - CLOSED
SLOT ROTOR CONST~UCTION in the names of Deepakkumar J.
Gandhi et al, filed March 18, 1988; and Canadian
Application Serial No. 561,100 - LIP STRUCTURE FOR A
STATOR IN ~ DYNAMO-E~ECTRIC MACHINE in the names of
Deepakkumar J. Gandhi et al, filed March 10, 1988.
While the concept of the invention has generally
been described in connection with a stator lamination,
it should be appreciated that the same concept of
increasing the amount of ferromagnetic material as
compared to the amount of copper, or conductive
material, can also be applied to a rotor lamination.
Similar concepts would be applied by making the teeth
wider on the rotor and the slots smaller.
While the foregoing description represents
preferred embodiments of the present invention, it will
be obvious to those skilled in the art that various
changes and modifications may be mad~, without departing
from the true spirit and scope of the present invention.
