Note: Descriptions are shown in the official language in which they were submitted.
CA 02234488 2006-06-30
1
'MODULAR MOTOR'
TECHNICAL FIELD
The present invention relates to functionally modular motors.
BACKGROUND ART
Brushless D.C. motors of various types are known wherein torque is produced by
the interaction of a pennanent magnet rotor with stationary windings carrying
pulses of
d.c. current. An example of such a prior art motor is disclosed in the
applicant's published
Canadian Patent Application 2005807. This reference discloses a functionally
modular
motor having a torque-producing module, a sha$ and bearing module and a rotor
parameter-sensing module, embodied in a motor having a dual-disc permanent
magnet
rotor and a stator separated by an axially oriented air gap. This type of
motor will be
referred to hereinbelow as a 'modular' motor. While the modular motors
described in the
prior art are capable of operating in a satisfactory manner, their compact
size makes them
dependent on conductive heat transfer for cooling, which to. date has placed
certain
limitations on their capacity.
It is, thus, an object of the present invention to provide a novel modular
motor
It is another object of the present invention to provide a motor with improved
interrrnal heat transfer characteristics, thereby to improve torque operating
ranges
relatively independent of motor RPM.
CA 02234488 1998-04-09
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DISCLOSURE OF THE INVENTION
Briefly stated, the invention involves a modular motor
comprising a discoidal stator unit and a discoidal rotor unit
rotatable about an axis of rotation under a torque established
therein, said stator unit being supported by a frame
arrangement and having a winding assembly within in a matrix
of polymer material, said winding assembly including a number
of winding elements, each of said winding elements having a
pair of radially disposed portions, wherein at least one of
said radially disposed portions of each winding element is
spaced from a radially disposed portion of another winding
element to form a cooling region therein, said cooling region
being arranged for the location therein of thermally
conductive materials having a thermal conductance of at least
1.5 w=cm/(cm2='C), thereby to transfer heat from said stator
unit and toward said frame arrangement during operation of
said motor.
In another aspect of the present invention, there is
provided a method of cooling a modular motor of the type
having a discoidal stator unit and a discoidal rotor unit
rotatable about an axis of rotation under a torque established
therein, said stator being supported by a frame arrangement
and having a winding assembly encased in a matrix of polymer
material, said winding assembly including a number of winding
elements, each of said of said winding elements having a pair
of radially disposed portions, said method comprising the
steps of:
spacing at least one of said radially disposed portions
of each winding element from a radially disposed portion of
another winding element to form a cooling region therein;
CA 02234488 2006-06-30
3
locating in said cooling region; a thermally conductive material having a
thermal
conductance of at least 1.5w,cm/(cm2'0C.), thereby to transfer heat from said
stator unit
toward said frame arrangement during operation of said motor.
In still another aspect of the present invention, there is provided a
discoidal
winding assembly for an electric motor, comprising a plurality of winding
elements, said
winding elements being arranged so'as to form a plurality of cooling regions
between
adjacent winding elemenEs, said cooling regions containing thermally
conductive
materials arranged to transfer heat radially outwardly therefrom, said
thermally
conductive materials being further arranged to suppress eddy current losses
therein.
In still another aspect of the present invention, there is provided a method
of
improving conductive heat transfer in a discoidal stator unit for an electric
motor,
comprising steps of
providing a plurality of winding elements,
forming a plurality of cooling regions between adjacent winding elements,
locating said winding elements in a matrix of polymer material; and
arranging each of said cooling regions to receive a thermally conductive
material,
to transfer heat radially outwardly toward an adjacent frame structure, said
thermally
conductive materials being further arranged to suppress eddy
CA 02234488 2007-02-09
4
current losses therein.
Still another alternative embodiment provides a,modular
motor having a discoidal stator unit.and a discoidal rotor unit
rotatable about an axis of rotation.under a torque established.
therein, said stator unit being supported by a frame arrangement;
said stator.unit having a winding assembly integrally forrned
within a matrix of polymer material, said winding assembly
further including a number of winding elements, each o.f said
. , .
winding elements having a pair of radial portions which are
arranged radially relative to said- axis of rotation, said winding
elements being arranged in three winding sets, the radial .
=portions of each winding set being arranged in radial pairs,
wherein the radial pairs of said winding sets are spaced equally
around said winding assembly with each radial pair from a first
= of said winding sets positioned between one radial:pair from a
second of said winding sets,to form one cooling region and one
radial pair from a third of said winding sets to form another
cooling region, a plurality of thermally conductive elements,
each of said thermally conductive elements being positioned in a
-corresponding one of said cooling regions, each of said
. .
thermally conductive elements being formed from thermally
conductive materials having a thermal conductance of at least
1.5 w-cm/(cm2= C), and including a plurality of laminated heat
conductive strip segments, said thermally conductive elements being arranged
to 'transfer heat from said stator unit_and toward
said frame arrangement during operation of said motor.
Still another alternative embodiment provides a modular
motor ha-ving a discoidal stator unit and a discoidal rotor unit
rotatable about an axis of rotation under a torque established
, .
. _ .
CA 02234488 2007-02-09
4a
therein, said stator unit being supported by a frame arrangement,
said stator unit having a winding assembly integrally formed
within a matrix of polymer material, said winding assembly
further including a number of winding elements, each of said
winding-elements having a pair of radial portions which are.,
-arranged radially relative to said axis of rotation, the radial
portions of each winding set being arranged in 'radial pairs; said
winding elements being arranged in three winding sets, wherein
the radial pairs.of said winding sets are spaced equally around
10. said winding assembly with each radial pair from a first of said
winding sets positioned between one radial pair from a second of
said winding sets to form one cooling region and one radial.pair
from a third of said winding sets to form another cooling region,
a plurality of thermally conductive elements, each of said
thermally conductive elements being positioned in a
. . .
corresponding one of said cooling regions, each of said
thermally.conductive elements being formed from thermally
conductive materials having ~a thermal conductance of at least
1.5 w=cm!(cm2=C), said thermally conductive elements being
arranged to transfer heat from said stator unit and toward said
frame arrangement during operation of said motor, wherein said cooling region
includes an inlet passage for the transfer of
, . .
coolant fluids into said cooling region and an outlet passage for
the transfer of coolant fluids out of said cooling region.
In yet another alternative embodiment provides a modular
motor as a discoidal stator unit and a discoidal rotor unit
rotatable about an axis of rotation under a torque -established
therein, said stator unit being supported by a frame arrangemerit;
said stator unit having a winding assembly integrally formed
within a matrix of polymer material, 'said winding assembly
. -
.. . ~
CA 02234488 2007-02-09
4b
further including a number of winding elements, each of said
winding elements having a pair of radial portions which are
arranged radially relative to said axis of rotation, the radial
f= =
portions of each winding set being arranged in radial pairs; said
winding elements being arranged in three winding sets, wherein
, . .
the radial pairs of said winding sets are spaced equally around
said winding assembly with each radial pair from a first of said
winding sets positioned between one radial pair from a second of
said winding sets to form one cooling region and one radial pair
from a third of said winding sets to form another cooling region,
each of said thermally conductive elements being formed from
thermally conductive materials having a thermal conductance of
at least 1.5 w=cm/(cm2='C), said thermally conductive elements
being arranged,.to transfer heat from said stator unit and toward
-.15 said frame. arrangement during operation of said motor, wherein
said polymer material has an outer surface coinciding with the
outer surface of said stator unit, further comprising a layer of
reinforcing.material located within said matrix and immediately
adjacent said outer surface, said reinforcing material being
sufficient to inhibit the progression of microcracks through said
polymer material.
Still another alternative embodiment provides a modular
motor having a discoidal stator unit and a discoidal rotor unit
'25 rotatable about an axis of rotation under a'torque established
therein, said stator unit being supported by a frame arrangement,
said stator unit having a winding assembly integrally formed
within a matrix of polymer material, said winding assembly
having a peripheral region for engagement with said frame
arrangement, said winding assembly further including a number
of winding elements, each of said winding elements having a
. .
. ; . . . .
CA 02234488 2007-02-09
_ ,..__....__, . ............
4c
pair of radial portions which are arranged radially relative to
said axis of rotation, wherein at least one of said radial portions
of each winding element is spaced from a radial portion of
another winding-element to form a cooling region therein which
5. extends radially through said winding assembly to said
peripheral region, a thermally conductive element being located
in said cooling region-and being formed from thermally
-conductive materials having a thermal conductance of at least
1.5 w=cm/(cm2= C), said thermally conductive element being
arranged to transfer heat from said stator unit and toward said
frame arrangement during operation of said motor; said winding
. elements being formed with a fill factor ranging from about 30
to about 35 percent, said windings being formed from an
electrically conductive filament, wherein said conductive
filament is formed from a copper alloy material having a
diameter of about 0.020 inches. , .
Still another alternative embodiment provides a discoidal
winding assembly for an electric motor, having a plurality of
winding elements, said winding elements being arranged so as to
form a plurality of cooling regions between adjacent winding
elements, 'said cooling regions containing thermally conductive
materials arranged to transfer heat radially outwardly therefrom,
said thermally conductive materials being further arranged to
.25 suppress eddy curreint losses therein, wherein said each of
winding elements includes a pair of radial portions, each of said
radial portions of one winding element being engaged with a
radial portion of an adjacent winding element to form a radial
pair, each of said cooling regions being located between adjacent
' -
= 30 radial pairs, wherein said winding sets are located within a
, -_
matrix of polymer inaterial, wherein said thermally conductive
.
CA 02234488 2007-02-09
4d
materials have a thermal conductance .at least 1.5 w=cm/(cm2='C) and include a
plurality of thermally conductive elements, each of
said thermally conductive elements being positioned in a
- corresponding one of said cooling regions, wherein each
5'thermally conductive element includes a plurality of laminated_
heat conductive strip segments.
=
~. .
. .
Still another alternative embodiment provides a discoidal
winding assembly for an electric motor, having a plurality of
winding elements, said winding elements being arranged so as to
form a plurality of cooling regions between adjacent winding
elements, said cooling regions containing thermally conductive
materials arranged to transfer heat radially outwardly therefrom,
wherein said each of winding elements includes a pair of radial
portions, each o.f said radial portions of -one winding element
being engaged with a radial portion of an'adjacent winding
element to form a radial pair; each of said cooling regions being
located between adjacent radial pairs; wherein said winding sets
are located within a matrix of polymer.material, wherein said
thermally conductive materials have a thermal conductance of at
least 1.5 w=cm/(cm2 C) and include a plurality of thermally
conductive elements, each of said thermally conductive elements
being positioned in a corresponding one of said cooling regions,
wherein said cooling region includes an inlet passage for the
transfer of coolant fluids into said cooling region and an outlet
passage for the transfer of coolant fluids out of'said cooling
region.
. _
. , . . _ = .
.
.'. .
CA 02234488 2007-02-09
=
4e
BRIEF DESCRIPTION OF THE DRAWINGS
" . - -
Several preferred embodiments of the present, invention
will now be described, by way of example only, with reference
. - .
to the appended drawings in which:
Figure 1 is a sectional view of a modular motor;
Figure 2 is a fragmentary axial view of a winding
assembly, portion of the motor of figure 1;
Figurq 2a is a fragmentary view of a portion illustrated in
Figure 2=;
Figure 3 is a sectional view taken on line 3--3 of figure 2;
= .
- .
Figure 4 is a sectional view taken on line 4-4 of figure 2;
Figure' 5 is a schematic view taken on line 5--5 of Figure 3
showing one step in the fabrication of the winding assembly
=
portion figure 2;
Figure 6 is another schematic-view of another step in the
- - . .
fabrication of the winding assembly portion figure 2;
.
Figure 7 is another axial view of the winding assembly
portion of figure 2 following a subsequent forming step;
" . .
Figure 8 is a sectional view taken on line 8--8 of figure
.
! , . . . ' ' . ..- .
' ' . - ' . . . : . . . , . . .
. ' . . ' . . .. . . .
I. ,
- ' . . , . - . = - . . . -
=
' . ' . . . . . . . .
CA 02234488 1998-04-09
7;
Figure 9 is a side view of a winding set used in the
fabrication of the winding assembly portion of figure 2;
5
Figure 10 is a view taken on arrow 10 of figure 9;
Figure 11 is a view taken on arrow 11 of figure 10;
Figure 12 is front view of one winding element of the
winding set of figure 9 following a subsequent forming step;
Figure 13 is a top plan view of the winding element of
figure 12;
Figure 14 is a bottom plan view of the winding element of
figure 12;
Figure 15 is a sectional view taken on line 15-15 of
figure 12;
Figure 16 is a side view of a thermally conductive
element used in the formation of the winding assembly portion
shown in figure 2;
Figure 16a is a magnified fragmentary assembly view of a
portion of the thermally conductive element shown in figure
16;
Figure 17 is a side view taken on arrow 17 of figure 16;
Figure 18 is a fragmentary perspective view of another
modular motor;
CA 02234488 1998-04-09
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Figure 18a is a sectional view taken on line 18a-18a of
figure 18;
Figure 18b is a sectional view taken on line 18b-18b of
figure 18;
Figure 19 is an end view of an element to form one
component of the motor shown in figure 18;
Figure 20 is a sectional view taken on line 20-20 of
figure 19;
Figure 21 is a top plan view of the element illustrated
in figure 19;
Figure 22 is a side view of the element illustrated in
figure 19; and
Figure 23 is a top plan view of the element as
illustrated in figure 22.
BEST MODE FOR CARRYING OUT THE INVENTION
The term 'winding element' herein is intended to refer to
a coil of wire formed according to predetermined dimensional
tolerances.
The term 'winding set' is intended to refer to a number
of winding elements.
The term 'winding assembly' is intended to refer to an
assembly of a number of winding sets to form one component of
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7
a stator unit.
Referring to the figures, particularly figure 1, there is
provided a modular motor 10 having an inner rotor disc
arrangement 12 and an outer rotor disc arrangement 13, each of
which include a disc plate 12a and a number of permanent
magnets 12b attached thereto, or alternatively a permanent
magnet ring structure axially magnetized in a pattern of north
and south magnetic poles. The magnets 12b are arranged to
provide a plurality of alternating north and south poles, 'N'
and 'S' respectively, on opposite sides of a stator unit 14.
A frame arrangement, in the form of a stator ring member 16,
supports the stator unit 14 in position and this includes a
mounting flange 16a to mount the motor 10 to an adjacent frame
member as shown at 'M' . This adjacent frame member M may, for
example, be part of a machine that the motor 10 is to drive.
The disc arrangements 12, 13 are positioned relative to
the stator unit 14 by way of an axle 20 which has a pair of
bearing regions 20a, 20b with substantially the same diameter,
along with an outer end 20c adjacent one of the bearing
regions 20a, 20b to serve as a torque output shaft for the
motor 10.
The axle 20 has a pair of inner regions 20d, 20e
relatively larger in diameter than the bearing regions and a
central region 20f is located between the inner regions 20d,
20e with a still larger diameter. The diameter difference
between the inner regions 20d, 20e and central region 20f
presents two outwardly facing abutment faces 20g, 20h. Each
of the outer and inner rotor discs are positioned adjacent to
and are fixed with a corresponding abutment face by way of
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8
threaded fasteners not shown.
An inner bearing support bracket 30 is fixed to the
stator ring member 16 by way of threaded fasteners 32 and has
an aperture 30a with a bearing 31 therein which is engaged
with the axle 20 at one bearing region thereof. Similarly,
an outer bearing support bracket 34 is fixed to the stator
ring member 16 opposite to the inner bearing support bracket
30 and by way of the same threaded fasteners 32. The outer
bearing support bracket 34 has an aperture 34a with a bearing
36 therein which is engaged with the axle 20 at the bearing
region 20b. An end plate 38 is also provided adjacent the
inner bearing support bracket 30 and fixed thereto by way of
a number of threaded fasteners shown at 40. The end plate 38
and the inner bearing support bracket 30 provide therebetween
a chamber 42 for locating electronic circuitry to operate the
motor, as shown in phantom at 33.
Each of the bearing assemblies and the stator ring member
16 are arranged to seal the operating components of the motor
10 from its external ambient environment. This means that the
motor 10 is particularly useful in applications where the
motor 10 must be able to withstand hostile environments.
It can be seen from figure 1 that the outer diameter of
the axle's central region is also arranged to provide a
minimum air gap between the outer surface thereof and an inner
surface presented by the stator unit 14. Furthermore, the
outer surfaces of the disc arrangements 12, 13 are also
arranged to provide a minimum air gap with the adjacent
surfaces of the bearing assemblies and the stator unit 14. It
can thus be seen that the motor 10 can be formed in a manner
that requires minimal air spacing therein and therefore
CA 02234488 1998-04-09
9
presents a compact size for a given torque rating.
Referring to f igures 2 to 8, the stator unit 14 has a
winding assembly 50, which includes a number of winding
elements 52, and molded into a polymer matrix shown at 53. In
addition, cooling is provided by heat conductive material
which is placed in intimate heat transfer relationship to the
winding elements 52 as will be described.
As shown in figures 9 to 15, the winding elements 52 are
preferably formed with a 'fill factor' ranging from about 30
to about 35 percent. The term 'fill factor' refers to the
proportion of the total overall volume occupied by the winding
element 52 that is in fact occupied by the wire of the winding
element 52, the balance being occupied by other materials such
as insulating tape and polymer matrix as will be described.
In other words, the higher the fill factor, the greater the
density of wire in the winding element 52.
The winding elements 52 are formed into winding sets as
shown in figure 9, each containing a number of winding
elements 52, three in this particular case. The winding sets
are formed from a conductive filament having a diameter
ranging from about 0.020 to 0.008 inches, preferably a copper
alloy material having a diameter of about 0.020 inches. This
small diameter is chosen to minimise eddy current losses.
More preferably, the winding elements 52 making up each of the
three phases are formed from a single strand of the filament.
The winding elements 52 take the shape as shown in
figures 12 to 15 after a forming step, each having a pair of
portions 56 which are positioned radially in the winding
assembly as will be described, an outer end portion 58 and an
CA 02234488 1998-04-09
inner end portion 60. The outer and inner end portions 58, 60
are offset relative to a plane in which the two radial
portions 56 are located.
5 Referring to figure 2, three winding sets 54a, 54b and
54c are used in the winding assembly 50, to correspond to one
phase of multiple phase, in this case three phase, power
switching system, which is conventionally used to reduce the
pulse torquing that would otherwise occur with a single phase.
10 Each winding set is formed by coupling, such as for example by
way of mylar tape, adjacent pairs of radial portions of the
winding elements, thereby to form radial pairs.
In the winding assembly 50 as shown in figures 2 to 6,
the outer and inner end portions 58, 60 of the first phase
winding elements 52 are arranged to face into the page while
the outer and inner end portions 58, 60 of the third phase
winding elements 52 are arranged to face out of the page, as
shown in figure 2. The second phase is different from the
first and third phases in that the outer end portion 58 of
each winding element 52 is split with a first portion bent
over to engage the outer portions of the first phase winding
elements 52 and a first portion bent over to engage the outer
portions of the third phase winding elements 52 as shown in
figures 5 and 6. The inner end portions 58, 60 are also split
into two portions and bent over the respective inner end
portions 60 of the first and third phase winding elements 52.
Looking more particularly at the winding assembly 50 as
viewed in figure 3, the first, second and third phase winding
sets are arranged so that they are each offset from the other.
For example, each adjacent radial pair of the second phase
winding elements has, on its left, a radial pair of the third
CA 02234488 1998-04-09
11
phase winding elements and, on its right, a radial pair of the
first phase winding elements. Furthermore, these alternating
radial pairs from the first, second and third phases are
spaced from one another to form a repeating series of cooling
regions 70 therein.
The cooling regions 70 are arranged to permit heat
conductive material to be placed in close heat transfer
relationship with the winding elements 52 to maximize the
cooling thereof.
The cooling region is preferably arranged for the
location therein of thermally conductive materials having a
thermal conductance of at least 1.5 w=cm/(cm2= C), thereby to
transfer heat from the stator unit and toward the frame
arrangement during operation of the motor. More preferably,
the cooling regions extend radially across the stator unit and
the thermally conductive elements are thermally coupled with
the frame arrangement for heat transfer thereto.
For example, the conductive material may be in the form
of a cooling fluid, such as water, a glycol-based or other
coolant, or a solid material such as copper. For example, a
thermally conductive element 80, as shown in figures 16 and
17, may be provided in each of these cooling regions 70 for
transferring heat therefrom.
The thermally conductive element 80 is arranged to fit
within a corresponding one of the cooling regions 70. Each
thermally conductive element 80 includes a laminate structure
formed by a plurality of heat conductive strip segments. In
this case, the thermally conductive element 80 is formed from
a number of laminated conductive strips 82 which are formed
CA 02234488 1998-04-09
12
with two convergent side surfaces, each to lie adjacent a
corresponding radial pair. The thermally conductive element
80 generally takes the shape of an inverted tear drop with a
single layer of self-adhesive mylar tape 85 to isolate each
strip from an adjacent strip as shown at 86, as shown in
figure 16a.
To form the thermally conductive element 80, first an
anchor pin 84 is arranged as a mandrel. A number of copper
strips, preferably nine, are then bent over the mandrel to
form a pair of leg portions on either side thereof with a
bight portion therebetween. In this case, the mandrel defines
a central axis and the bight portions are aligned relative to
the central axis. The leg portions on one side are also
provided with a slight jog 87 which improves the alignment of
the so-formed leg portions with a single longitudinal axis as
shown at 89. As mentioned above, each of the strips 82 is
insulated on one side so that the strips 82 are electrically
isolated from one another and this may be done with a single
layer self-adhesive mylar tape. Once the strips 82 are in
place, the thermally conductive element 80 can be completed by
applying one layer of glass cloth 83 to both sides of the
assembly with epoxy adhesive.
More preferably, there are three groups of three strips
82 of equal length, including three inner strips, three middle
strips which are relatively longer than the inner strips and
three outer strips which are relatively longer than the middle
strips.
Referring again to figures 2 and 8, another feature of
the stator unit 14 is the provision of a layer of reinforcing
material 90 which is located on the winding assembly 50 so
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13
that it is immediately adjacent the outer peripheral surface
of the so-formed stator unit 14. The reinforcing material is
selected so that it is capable of inhibiting the progression
of microcracks through the polymer material, as may occur at
the outer surface due to temperature gradients and
fluctuations thereof during operation. Preferably, the
reinforcing material is glass cloth material.
The stator unit 14 is formed in the following manner.
The winding elements 52 are first wound on a winding form to
adopt the shape as shown in figures 9 to 11. The winding
elements 52 for phases 1 and 3 are then formed by a forming
tool to provide the offset outer and inner end portions 58, 60
as shown in figures 12 to 16. The winding sets for all phases
are then assembled as discussed above to form the winding
assembly 50 shown in figure 2.
A thermally conductive element 80 is then located in each
of the cooling regions 70 in the manner described above. The
winding assembly 50 is then wrapped with the layer of
reinforcing material 90 and tacked thereon with beads of
adhesive material. The winding assembly 50 is brought to
required dimensions and the winding connections are made to
allow three phase switching of the stator unit 14.
The winding assembly 50 is then placed in a mold and is
filled with a matrix of polymer material to form the stator
unit, wherein the polymer material has an outer peripheral
surface corresponding to the outer surface of the stator unit
14. Desirably, the polymer material is a low viscosity epoxy
material to allow the polymer material to seep into the
interstitial spaces between the winding elements 52 themselves
and between the winding elements 52 and the thermally
conductive elements 80. Preferably, the polymer material has
CA 02234488 1998-04-09
14
a viscosity in the range of about 210 to 260 centipoise
seconds. The stator unit is then assembled with the other
components of figure 1 to complete the motor.
In use, multiple phase, in this case three phase, D.C.
power pulses are delivered to the stator unit 14, resulting in
currents flowing through each of the three winding sets and
torque being generated at the torque output shaft. As a
result, each of the winding sets generates heat. As shown in
figure 2a, this heat is transferred radially outwardly toward
the adjacent frame structure along two paths, first through
the winding sets themselves as shown by arrows 'Ha', that is
along the radially disposed portions. The heat is also
transferred tangentially across the polymer boundary
separating the radially disposed portions with the adjacent
thermally conductive element 80, as shown by arrows 'Hb' and
continues in a radial direction toward the adjacent frame
structure through the thermally conductive element 80 as shown
by arrows 'Hc'. The heat is then transferred to the stator
ring member 16, and thereafter out to the frame via the
mounting flange 16a. This means that the motor 10 is capable
of transferring heat from winding losses to the motor's
mounting arrangement essentially by thermal conduction, into
the ad j acent frame structure by way of the frame member ' M' on
which the motor is mounted.
Thus, the motor 10 provides an improved heat transfer
regime by the use of two heat conduction paths, the first
through the radial portions of the winding elements themselves
and the second through the cooling regions located between
adjacent radial pairs. In this first case, the radial
portions of the winding sets transfer heat while at the same
time generate heat through ohmic resistance losses therein.
CA 02234488 1998-04-09
On the other hand, the cooling regions transfer heat while
eddy current losses are suppressed, thereby minimizing ohmic
resistance losses therein. In the case of the thermally
conductive element 80, the eddy current losses are suppressed
5 by the use of a laminated structure.
The modular motor 10 is highly compact with substantially
improved cooling characteristics which are based on a
principle that heat transferred due to winding losses is
10 transferred out of the motor by radial thermal conduction to
the periphery of the stator unit where it is in contact with
a stator ring, through the windings themselves as well as
through the cooling regions. For this conductive heat
transfer through the cooling regions to be efficient, the
15 cooling regions themselves should have a sufficient quantity
of thermally conductive material, itself having a sufficiently
high thermal conductance, such as for example a minimum
thermal conductance of 1.5 w=cm/(cm2= C).
Typical unit thermal conductances (w=cm/(cm2= C)} are as
follows:
Resin: 0.008
Copper: 3.5
Steel: 0.67
Aluminum: 2.0
The motor provides improved heat transfer characteristics
through the motor by locating the cooling regions between the
radial pairs of the windings, that is in regions of the stator
unit which would otherwise be occupied by the resin matrix
which has a relatively poor conductance as above noted. It is
estimated that as much as a 30 percent improvement in radial
CA 02234488 1998-04-09
16
winding loss heat transfer can be achieved by adding the
thermal conductive elements in the cooling regions as above
described.
The thermally conductive elements 80 should be
dimensioned so that they extend, to the extent possible,
substantially the entire length of the adjacent radial
portions 56 of each winding element 52 and be intimately
associated therewith. However, there should be sufficient
spacing between the thermally conductive elements 80 and the
radial portions 56 to enable the polymer material to flow
therebetween to maintain the integrity of the molded assembly
and winding insulation.
Thus, the above motor construction provides for the
effective removal of internal heat from operating losses by
thermal conduction from the winding elements to the adjacent
supporting frame structures. This motor construction produces
torque relatively independent of motor RPM and maximizes the
heat conduction in an axial air-gap electric motor for a given
frame size.
A segment of another modular motor is shown at 100 in
figure 18, wherein a stator unit 102 is supported by frame
arrangement in the form of a stator ring 104. A cooling
region 106 is located between each radial pair, as described
above. Each cooling region 106 includes an inlet passage 108
for the transfer of coolant fluids into the cooling region 106
and an outlet passage 110 for the transfer of coolant fluids
from the cooling region 106. In this case, the stator unit
102 has an outer surface 102a which engages an inner surface
104a on the stator ring. The stator ring is further provided
with an inlet channel 112 in fluid communication with the each
CA 02234488 1998-04-09
17
inlet passage and an outlet channel 114 in f luid communication
with each outlet passage. The inlet channel 112 has an
aperture 116 to be connected with an inlet fluid coupling
shown in dashed lines at 116a. The outlet channel 114 has an
aperture 118 to be connected with an outlet fluid coupling
118a. It will be seen in figure 18b that the aperture 118 is
formed as an angular extension of the outlet channel through
the body of the stator ring.
The inlet and outlet channels are joined so that the
coolant fluid can be passed through the inlet and outlet
passages to be in intimate heat transfer relationship with the
neighbouring winding elements, not shown. A cooling region of
this type may be formed in a number of ways, including by the
use of a casting technique which provides a core element 120
which is illustrated in figures 19 to 23.
The core element 120 includes a pair of legs 122, 124
which are joined together at one end and which have large
block formations 126, 128 at their other ends, to join the
inlet channel and passage with the outlet channel and passage.
Extending across the two separated block formations 126, 128
is a rigid construction strip shown at 129, the purpose of
which is to hold the ends in position relative to one another
in their final intended position, when this is incorporated
into the resin structure. This strip thereby insures the
proper spacing in maintained during handling and casting
without having to rely on the inherent rigidity of the core
element itself which may otherwise be rather low. The strip
should be of a material compatible with the resin matrix into
which it is finally cast.
The stator unit 102 is formed in the following manner.
CA 02234488 1998-04-09
18
First, a winding assembly is assembled with a core element 120
located in each of the cooling regions as described above.
This is done while ensuring that there is sufficient space
between the outer edge of the core element 120 all adjacent
contact surfaces of the winding element, thereby to ensure
that the polymer will entirely separate the core element 120
from those contact surfaces of the winding elements.
The winding assembly is then wrapped as discussed above
and brought to the required dimensions. The winding
connections are made to allow three phase switching of the
stator unit and thereafter, the winding assembly is placed in
a mold and is filled with a matrix of polymer material as
mentioned above. In this case, the core material is selected
with a melting temperature which exceeds the temperature at
which the matrix of polymer material is formed, but is
sufficiently low to permit the core element 120 to be melted
and substantially all of the material thereof removed. For
example, the core element 120 may be constructed from paraffin
wax or other materials with similar characteristics.
In other words, the core element 120 is formed from a
material that can be safely melted out of the winding assembly
after being filled with polymer and the polymer has
solidified, thus leaving channels in the polymer structure for
fluid flow. The core must be shaped and dimensioned to
conform to the finished shape of the winding assembly and the
winding elements in it. This dictates its particular shape
and the 'block formations' that must fit within the outer
winding region, while providing a fluid path from the
peripheral inlet openings to the radial channels. Once the
winding assembly has been molded and the core element material
subsequently removed, the outer periphery of the winding
CA 02234488 1998-04-09
19
assembly is prepared to be inserted into the stator ring by
aligning each of the inlet and outlet passages with the
corresponding inlet and outlet channels 112, 114 respectively.
As in the case of the motor 10, an improved heat transfer
regime is provided in the motor 100 by the use of two heat
conduction paths, the first through the radial portions of the
winding elements themselves and the second through the cooling
regions located between adjacent radial pairs. In the second
case, the cooling regions transfer heat while eddy current
losses are suppressed. This suppression is achieved by using
a non ferromagnetic coolant materials such as water, glycol-
based or other coolant glycol mixtures, water and the like.
The present invention also concerns a method of cooling
a modular motor comprising the steps of:
providing a discoidal stator unit with a number of
winding elements,
arranging the winding elements with each having a pair of
radial portions, each radial portion of one winding element
being adjacent a radial portion of another winding element,
the adjacent portions being spaced from one another in such a
manner to form a repeating series of cooling regions therein.
