Note: Descriptions are shown in the official language in which they were submitted.
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1 CORE FOR TRANSVERSE FLUX ELECTRICAL MACHINE
2
3 BACKGROUND OF THE INVENTION
4 1. Field of the Invention
[01] This invention relates generally to transverse flux electrical
machines. The
6 present invention more specifically relates to a core for transverse flux
alternators
7 and assembly thereof.
8
9 2. Description of the Related Art
[02] Alternators and motors are used in a variety of machines and
apparatuses
11 to produce electricity from mechanical movements. They find applications
for
12 energy production and transportation, to name a few. Alternators and motors
can
13 use Transverse Flux Permanent Magnet (TFPM) technologies.
14 [03] Transverse flux machines with permanent magnet excitation are
known
from the literature, such as the dissertation by Michael Bork, Entwicklung und
16 Optimierung einer fertigungsgerechten Transversalflugmaschine
[Developing and
17 Optimizing a Transverse Flux Machine to Meet Production Requirements],
18 Dissertation 82, RWTH Aachen, Shaker Verlag Aachen, Germany, 1997, pages
8
19 if. The circularly wound stator winding is surrounded by U-shaped soft
iron cores
(yokes), which are disposed in the direction of rotation at the spacing of
twice the
21 pole pitch. The open ends of these U-shaped cores are aimed at an air
gap
22 between the stator and rotor and form the poles of the stator. Facing
them,
23 permanent magnets and concentrators are disposed in such a way that the
24 magnets and concentrators that face the poles of a stator core have the
opposite
polarity. To short-circuit the permanent magnets, which in the rotor rotation
are
26 intermittently located between the poles of the stator and have no
ferromagnetic
27 short circuit, short-circuit elements are disposed in the stator.
28 [04] Put otherwise, transverse flux electrical machines include a
circular stator
29 and a circular rotor, which are separated by an air space called air
gap, that allows
1
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1 a free rotation of the rotor with respect to the stator, and wherein the
stator
2 comprises soft iron cores, that direct the magnetic flux in a direction that
is mainly
3 perpendicular to the direction of rotation of the rotor. The stator of
transverse flux
4 electrical machines also comprises electrical conductors, defining a toroid
coil,
which is coiled in a direction that is parallel to the direction of rotation
of the
6 machine. In this type of machine, the rotor comprises a plurality of
identical
7 permanent magnet parts, which are disposed so as to create an alternated
8 magnetic flux in the direction of the air gap. This magnetic flux goes
through the air
9 gap with a radial orientation and penetrates the soft iron cores of the
stator, which
directs this magnetic flux around the electrical conductors.
11 [05] In the transverse flux electrical machine of the type comprising
a rotor,
12 which is made of a plurality of identical permanent magnet parts, and of
magnetic
13 flux concentrators, the permanent magnets are oriented in such a manner
that
14 their magnetization direction is parallel to the direction of rotation
of the rotor.
Magnetic flux concentrators are inserted between the permanent magnets and
16 redirect the magnetic flux produced by the permanent magnets, radially
towards
17 the air gap.
18 [06] The transverse flux electrical machine includes a stator, which
comprises
19 horseshoe-shaped like soft iron cores, which are oriented in such a
manner that
the magnetic flux that circulates inside these cores, is directed in a
direction that is
21 mainly perpendicular to the axis of rotation of the rotor.
22 [07] The perpendicular orientation of the magnetic flux in the cores
of the
23 stator, with respect to the rotation direction, gives to transverse flux
electrical
24 machines a high ratio of mechanical torque per weight unit of the
electrical
machine. Eddy currents influence the magnetic efficiency.
26 [08] Eddy currents (also called Foucault currents) are circular
electric currents
27 induced within conductors by a changing magnetic field in the conductor,
due to
28 Faraday's law of induction. Eddy currents flow in closed loops within
conductors, in
29 planes perpendicular to the magnetic field. They can be induced within
nearby
stationary conductors by a time-varying magnetic field created by an AC
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1 electromagnet or transformer, for example, or by relative motion between a
2 magnet and a nearby conductor. The magnitude of the current in a given
loop is
3 proportional to the strength of the magnetic field, the area of the loop,
and the rate
4 of change of flux, and inversely proportional to the resistivity of the
material.
[09] By Lenz law, an eddy current creates a magnetic field that opposes the
6 magnetic field that created it, and thus eddy currents react back on the
source of
7 the magnetic field. For example, a nearby conductive surface will exert a
drag
8 force on a moving magnet that opposes its motion, due to eddy currents
induced
9 in the surface by the moving magnetic field. This effect is employed in
eddy
current brakes, which are used to stop rotating power tools quickly when they
are
11 turned off. The current flowing through the resistance of the conductor
also
12 dissipates energy as heat in the material hence having an adverse effect on
13 electrical machines efficiency. Thus eddy currents are a source of
energy loss in
14 alternating current (AC) inductors, transformers, electric motors and
generators,
and other AC machinery, requiring special construction such as laminated
16 magnetic cores to minimize them.
17 [10] Cores made of a stack of sheet material radially laminated and
angularly
18 stacked along the coil of the TFEM is channeling the flux therein while
producing
19 circular eddy currents in the lamination plane that are not restrained
in the
thickness of the lamination. The purpose of stacking laminated sheet material
is to
21 decrease the eddy current losses, which is not the case when the motor is
in the
22 unaligned positon. The coil needs to be more massive to compensate the
lower
23 global efficiency of the TFEM by reducing the Joules losses (conducting
losses).
24 The cores housing, that is not laminated, is also more complex to
manufacture and
assemble to hold each core stack together during the assembly of the stator
and
26 part of the magnetic flux is loss to the housing when the magnetic
concentrators
27 are in the unaligned position. Other detrimental issues are occurring when
honing
28 the stator's interior like a separation of the laminated sheets cores.
29 [11] It is therefore desirable to provide a core design that is
minimizing eddy
currents. It is desirable to produce a core for an electrical machine that is
easy to
31 assemble. It is also desirable to provide a core for an electrical
machine that is
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1 economical to produce. Other deficiencies will become apparent to one
skilled in
2 the art to which the invention pertains in view of the following summary and
3 detailed description with its appended figures.
4
BRIEF DESCRIPTION OF THE DRAWINGS
6 [12] Figure 1 is an isometric view of a TFEM, in accordance with at
least one
7 embodiment of the invention;
8 [13] Figure 2 is an isometric view of a TFEM, in accordance with at
least one
9 embodiment of the-invention;
[14] Figure 3 an isometric exploded view of a TFEM in accordance with at
least
11 one embodiment of the invention;
12 [15] Figure 4 is an isometric view of a prior art core;
13 [16] Figure 5 is an isometric view of an illustration of the magnetic
flux of a
14 prior art core;
[17] Figure 6 is an isometric view of an illustration of the Eddy currents
flow of
16 a prior art core;
17 [18] Figure 7 is an isometric view of a core, in accordance with at
least one
18 embodiment of the invention;
19 [19] Figure 8 is an isometric view of the magnetic flux in a core, in
accordance
with at least one embodiment of the invention;
21 [20] Figure 9 is an isometric view of the Eddy currents flow in a
core, in
22 accordance with at least one embodiment of the invention;
23 [21] Figure 10 is a side elevation view of a core, in accordance with
at least
24 one embodiment of the invention;
[22] Figure 11 is an isometric view of a core, in accordance with at least
one
26 embodiment of the invention;
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1 [23] Figure 12 is an isometric view of a core, in accordance with at
least one
2 embodiment of the invention;
3 [24] Figure 13A is an isometric view of a first core manufacturing
step, in
4 accordance with at least one embodiment of the invention;
[25] Figure 13B is an isometric view of a second core manufacturing step,
in
6 accordance with at least one embodiment of the invention;
7 [26] Figure 130 is an isometric view of a third core manufacturing
step, in
8 accordance with at least one embodiment of the invention;
9 [27] Figure 14 is an isometric view of a core, in accordance with at
least one
embodiment of the invention;
11 [28] Figure 15 is an isometric semi-exploded view of a TFEM phase
assembly
12 in accordance with at least one embodiment of the invention;
13 [29] Figure 16 is an isometric semi-exploded view of a TFEM phase
assembly,
14 in accordance with at least one embodiment of the invention;
[30] Figure 17 is an isometric semi-exploded view of a TFEM phase assembly,
16 in accordance with at least one embodiment of the invention;
17 [31] Figure 18 is a top plan view of a portion of a TFEM phase
assembly, in
18 accordance with at.least one embodiment of the invention;
19 [32] Figure 19 is a top plan view of a portion of a TFEM phase
assembly, in
accordance with at least one embodiment of the invention;
21 [33] Figure 20 is a side elevation view of a portion of a TFEM phase
assembly,
22 in accordance with at least one embodiment of the invention;
23 [34] Figure 21 is an isometric view of a portion of a TFEM phase
assembly, in
24 accordance with at least one embodiment of the invention;
[35] Figure 22 is an isometric view of a portion of a TFEM phase assembly,
in
26 accordance with at least one embodiment of the invention;
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1 [36] Figure 23 is a side elevation view of a portion of a TFEM phase
assembly,
2 in accordance with at least one embodiment of the invention; and
3 [37] Figure 24 is a side elevation view of a portion of a TFEM phase
assembly,
4 in accordance with at least one embodiment of the invention.
6 SUMMARY OF THE INVENTION
7 [38] It is one aspect of the present invention to alleviate one or
more of the
8 shortcomings of background art by addressing one or more of the existing
needs
9 in the art.
[39] The following presents a simplified summary of the invention in order
to
11 provide a basic understanding of some aspects of the invention. This
summary is
12 not an extensive overview of the invention. It is not intended to
identify key/critical
13 elements of the invention or to delineate the scope of the invention.
Its sole
14 purpose is to present some concepts of the invention in a simplified
form as a
prelude to the more detailed description that is presented later.
16 [40] Generally, an object of the present invention provides a core
for a
17 Transverse Flux Electrical Machine (TFEM), which can also be more
specifically
18, appreciated as Transverse Flux Permanent Magnet Machine (TFPMM) although
19 TFEM is going to be used below to facilitate reading of the text.
[41] An object of the invention, in accordance with at least one embodiment
21 thereof, is generally described as a core structure for a TFEM.
22 [42] Generally, .an object of the invention, in accordance with at
least one
23 embodiment thereof, provides a laminated core for assembly in a TFEM that
24 minimizes the eddy current therein.
[43] An object of the invention, in accordance with at least one embodiment
26 thereof, provides a core for a TFEM that is laminated in the direction
parallel to the
27 magnetic field when operatively secured in the TFEM; the flux passes
through the
28 core poles parallel to the laminations plane orientation of the
laminations in the
29 unaligned position.
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1 [44] An object of the invention, in accordance with at least one
embodiment
2 thereof, provides a.core that is laminated in a direction partially circling
the coil
3 when assembled in a TFEM.
4 [45] An object of the invention, in accordance with at least one
embodiment
thereof, provides a core that is laminated in a direction partially circling
the coil
6 when assembled in a TFEM with an angled portion on the core's legs and a
pair of
7 poles of a reduced section.
8 [46] An object of the invention, in accordance with at least one
embodiment
9 thereof, provides a more efficient laminated core that allows for a
smaller coil in
the TFEM that requires less copper thereof.
11 [47] An object of the invention, in accordance with at least one
embodiment
12 thereof, provides a laminated core that avoids a lamination of independent
sheets
13 stack that has to be bent with different radiuses to achieve a
symmetrical sheet
14 stack for the two core poles to have a pole pitch separation distance.
[48] One object of the invention, in accordance with at least one
embodiment
16 thereof, provides a core made from cold electrical strip rolled around a
rectangular
17 tub, then varnished with the mold to prevent the rolled strip to unroll.
The rolled
18 strip is then cut in two symmetrical parts to obtain two cores and each
pole of the
19 core is cut to get the required pole pitch shift between the pair of
poles.
[49] One object.of the invention, in accordance with at least one
embodiment
21 thereof, provides a core for a TFEM that is composed of a laminated steel
sheets
22 and maintains a lower operating temperature when in operation in the
TFEM.
23 [50] An object of the invention, in accordance with at least one
embodiment
24 thereof, provides a core manufactured with a cold electrical steel strip
rolled
around a spacer of a shape and size adapted to accommodate therein a coil.
26 [51] Another object of the invention, in accordance with at least one
27 embodiment thereof, provides a core for a TFEM that is laminated in a "U"
shape
28 with a plurality of superposed "U" shaped sheet portion.
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1 [52] An aspect of the invention, in accordance with at least one
embodiment
2 thereof, provides a core made of rolled sheet material having non-conductive
3 varnished applied on a surface thereof.
4 [53] One aspect of the invention, in accordance with at least one
embodiment
thereof, provides a core made of rolled sheet material using non-conductive
6 varnished to secure together the plurality of superposed layers of rolled
sheet
7 material.
8 [54] An aspect of the invention, in accordance with at least one
embodiment
9 thereof, provides a.core for a TFEM that is laminated in a configuration
adapted to
contain the eddy currents in the thickness of the steel sheet when operating
in the
11 TFEM.
12 [55] One other aspect of the invention, in accordance with at least
one
13 embodiment thereof, provides a pair of cores simultaneously manufactured
with a
14 unique rolled strip of cold electrical steel cut in two.
[56] One aspect of the invention, in accordance with at least one
embodiment
16 thereof, provides core that are etched to prevent conductivity between
adjacent
17 layers of steel sheets.
18 [57] One aspect of the invention, in accordance with at least one
embodiment
19 thereof, provides a core having reduced sections abutting operatively
facing
, 20 concentrators when operatively secured in the TFEM.
21 [58] Another aspect of the invention, in accordance with at least one
22 embodiment thereof, provides a core pole pitch shift provided by reduced
sections
23 operatively facing corresponding concentrators when operatively secured in
the
24 TFEM.
[59] Another aspect of the invention, in accordance with at least one
26 embodiment thereof, provides a core with angled surfaces on each leg to
provide
27 a pole pitch shift.
28 [60] An aspect of the invention, in accordance with at least one
embodiment
29 thereof, provides a steel sheet laminating direction that is more
resistant to
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1 delamination when machining and honing the core sections operatively facing
2 corresponding concentrators when operatively secured in the TFEM.
3 [61] One other aspect of the invention, in accordance with at least
one
4 embodiment thereof, provides TFEM halves for receiving, securing and
locating
cores in their respective operating locations in a TFEM.
6 [62] Another aspect of the invention, in accordance with at least one
7 embodiment thereof, provides an assembly using the shape of the core to
radially
8 locate the core in respect with the TFEM's axis of rotation.
9 [63] One aspect of the invention, in accordance with at least one
embodiment
thereof, provides smaller halves for securing and locating a plurality of
cores
11 therein given the lower eddy current generated by the cores.
12 [64] One aspect of the invention, in accordance with at least one
embodiment
13 thereof, provides a transverse flux electrical machine comprising a rotor
portion
14 and a stator portion, the stator portion comprising a plurality of cores
for use in
conjunction with the rotor, each of the plurality of cores comprising a
plurality of
16 ferromagnetic sheet material layers substantially bent in a "U"
configuration and
17 stacked one on top of the other, a surface of each sheet material layer
being
18 substantially parallel with a core axis of the "U" configuration, and a
pair of legs
19 including, respectively, a reduction portion along the legs, toward a
pair of poles
thereof.
21 [65] Embodiments of the present invention each have at least one of
the
22 above-mentioned objects and/or aspects, but do not necessarily have all of
them.
23 It should be understood that some aspects of the present invention that
have
24 resulted from attempting to attain the above-mentioned objects may not
satisfy
these objects and/or may satisfy other objects not specifically recited
herein.
26 [66] Additional and/or alternative features, aspects, and advantages
of
27 embodiments of the present invention will become apparent from the
following
28 description, the accompanying drawings, and the appended claims.
29
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1 DESCRIPTION OF EMBODIMENT(S) OF THE INVENTION
2 [67] Our work is
now described with reference to the Figures. In the following
3 description, for purposes of explanation, numerous specific details are set
forth in
4 order to provide a thorough understanding of the present invention by way of
embodiment(s). It may be evident, however, that the present invention may be
6 practiced without these specific details. In other instances, when
applicable, well-
7 known structures and devices are shown in block diagram form in order to
8 facilitate describing the present invention.
9 [68] A TFEM 10
is illustrated in Figure 1 through Figure 3. The TFEM 10
includes a stator portion 14 and a rotor portion 18. The stator portion 14 is
adapted
11 to remain fixed while the rotor portion 1, located within the stator
portion 14, is
12 adapted to rotate .in respect with the stator portion 14 about rotation
axis 22
13 thereof. The illustrated stator portion 14 is equipped with an array of
fins 16
14 radially protruding from the housing 26 to help increase the heat exchange
between the housing 26 and the environment. The embodiments illustrated below
16 depict a TFEM 10 with an exemplary number of pairs of poles and an
exemplary
17 635 mm (25 inches) diameter at the air gap is for illustrative purposes in
the
18 context of the invention. The configuration of the illustrated TFEM 10
includes an
19 internal rotor portion 18 and an external stator portion 14. An alternate
embodiment could use an external rotor portion 18 instead of an internal rotor
21 portion 18. The number of phases can change in accordance with the specific
22 application, the desired power output, torque and rotational speed could
vary
23 without departing from the scope of the present invention.
24 [69] The TFEM.
of the illustrated embodiments includes a housing 26 adapted
to receive therein, for example, three phase modules 30. An axial side member
34
26 is secured to the housing 26 to hold therein the three assembled electrical
phase
27 modules 30 inside the housing 26. Each phase module 30 is adapted to
28 individually provide an electrical phase of alternating current. The
present
29 embodiment illustrates three phases 30 axially coupled together to provide
tri-
phased current when the TFEM 10 is rotatably actuated. In the present
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1 embodiment, the axial side member 34 is secured to the housing 26 with a
series
2 of fasteners (not illustrated) engaging threaded holes 38.
3 [70] The axial side member 34 and the housing 26 are configured to
receive
4 and secure thereto a bearing assembly 42. The bearing assemblies 42
rotatably
secure and concentrically locate the rotor portion 18 in respect with the
stator
6 portion 14. The actual configuration of the embodiment illustrated in Figure
1
7 throughout Figure 3 allows removal of the rotor portion 18 in one axial
direction 46
8 when the axial side member 34 is unsecured from the housing 26. This allows
for
9 easy maintenance of the TFEM 10 once installed in its operating
configuration.
[71] As it is also possible to appreciate from the embodiment illustrated
in
11 Figure 1 throughout Figure 3 a solid drive member 50 of the rotor portion
18 that
12 rotatably engages and extends through the axial side member 34, on one
axial
13 side, and rotatably extends through the housing 26 on the opposite axial
side. The
14 solid drive member 50 could alternatively be a hollowed drive member in
other
unillustrated embodiments. The drive member 50 is adapted to transmit
rotatable
16 motive power from an external mechanism (not illustrated) to the TFEM 10.
The
17 external mechanism (not illustrated) could, for example, be a windmill
rotatable
18 hub (not illustrated) to which the rotor blades (not illustrated) are
secured to
19 transmit rotational. motive power to the TFEM 10. The external mechanism
expressed above is a non-limitative example and other external mechanisms
21 adapted to transmit rotational motive power to the TFEM 10 are considered
to
22 remain within the scope of the present application.
23 [72] Focusing now on Figure 3 that is illustrating a semi-exploded
view of the
24 TFEM 10 where a skilled reader can appreciate the rotor portion 18 is
axially
extracted from the .stator portion 14. The rotor portion 18 is axially
extracted from
26 the stator portion 14 by removing the axial side member 34 from the housing
26. It
27 can be appreciated that the rotor portion 18 of the exemplary embodiment
has
28 three distinct axial phase modules 30, each providing an electrical phase,
adapted
29 to axially align and operatively cooperate with the three phase modules 30
of the
exemplified stator portion 14. The rotor portion 18 includes a plurality of
alternated
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1 magnets 54 and concentrators 58 that are disposed parallel with the rotation
axis
2 22. Pluralities of Cores 62 are held and located between a pair of aluminum
3 support halve members 66 from which a plurality of pairs of poles 118 are
radially
4 and proximally extending therefrom.
[73] As indicated
above, the rotor portion 18 is adapted to rotate in respect with
6 the stator portion 14. The speed of rotation can differ depending of the
intended
7 purpose. Power remains function of the torque and the rotation speed of the
rotor
8 portion 18. Therefore, the TFEM is going to produce more power if the TFEM
9
rotates rapidly as long as its operating temperature remains in the operating
range
of its different components to prevent any deterioration thereof (e.g. magnet
11 demagnetization or insulating vanish deterioration, to name a few). The
axial side
12 member 34 is adapted to be unsecured from the housing 26 for inspection and
13 maintenance. Figure 3 also illustrates that each phase module 30 of the
rotor 18
14 uses a sequence of individual alternated permanent magnet 54 and
concentrator
58. Strong permanent magnets 54 can be made of Nb-Fe-B as offered by Hitachi
16 Metals Ltd and NEOMAX Co. Ltd. Alternatively, suitable magnets can be
obtained
17 by Magnequench Inc. and part of this technology can be appreciated in
patents
18 US 5,411,608, US 5,645,651, US 6,183, 572, US 6,478,890, US 6,979,409 and
19 US 7,144,463.
[74] Each phase
module 30 is going to be discussed in more details below.
21 However, a positioning mechanism is provided to angularly locate each phase
22 module 30 in respect with its adjacent phase module 30 so that proper phase
shift
23 is maintained. Generally, the phase shift is set at 120 electrical to
provide
24 standard symmetrical electric current overlapping over a complete 360
electrical
cycle. The 120 phase shift allows to, in theory, eliminate harmonics that are
not
26 multiples of three (3). The 120 phase shift illustrated herein is a
preferred
27 embodiment and is not intended to limit the angular phase shift of the
present
28 invention.
29 [75] The
illustrative embodiment of Figure 3 includes three (3) phase modules
30. Another possible embodiment includes a multiple of three (3) phase modules
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1 30 mechanically secured together and electrically connected by phase to
increase
2 the capacity of the TFEM 10 by simply increasing the axial length of the
TFEM 10.
3 Thus, a nine (9) phase modules 30 would be coupled three-by-three for a
"triple"
4 three-phased 30 TFEM 10. Another possible embodiment is a one-phase 30
TFEM 10 including only one phase module 30. One other possible embodiment
6 could be a two-phased TFEM 10 electrically coupled together in a one-phase
30
7 configuration and with a phase shift of 90 electrical in a two-phase 30
8 configuration.
9 [76] The rotor portion 18 includes a cylindrical support frame 70
preferably
removably secured to the rotatable drive member 50. As explained above, the
11 cylindrical support frame 70 is sized and designed to accommodate three
electrical
12 phases, each provided by a phase module 30 including its alternate series
of
13 magnets 54 and concentrators 58 secured thereon. The circular stator
portion 14
14 and the circular rotor portion 18 are separated by an air space called "air
gap" 74
that allows an interference-free rotation of the rotor portion 18 with respect
to the
16 stator portion 14. Generally, the smallest is the air gap 74 the most
performance
17 the TFEM is going to provide. The air gap 74 is however limited to avoid
any
18 mechanical interference between the stator portion 14 and the rotor portion
18 and
19 is also going to be influenced by manufacturing and assembly tolerances in
addition to thermic expansion of the parts when the TFEM 10 is actuated. The
21 stator portion 14 comprises soft iron cores 62 (C-cores) that direct the
magnetic
22 flux in a direction that is mainly perpendicular to the direction of
rotation of the
23 rotor portion 18. The stator portion 14 of TFEM 10 also comprises in each
phase
24 module 30 electrical conductors defining a toroid coil 78 that is coiled in
a direction
that is parallel to the direction of rotation of the TFEM 10. In this
embodiment, the
26 rotor portion 18 comprises a plurality of identical permanent magnets 54,
which
27 are disposed so as to create an alternated magnetic flux in the direction
of the air
28 gap 74. This magnetic flux goes through the air gap 74 with a radial
orientation
29 and penetrates the soft iron cores 62 of the stator portion 14, which
directs this
magnetic flux around the toroid coil 78.
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1 [77] In the
TFEM 10 of the type comprising a rotor portion 18 including a
2 plurality
of identical permanent magnets 54 and of magnetic flux concentrators 58,
3 the permanent magnets 54 are oriented in such a manner that their
magnetization
4 direction
is parallel=to the direction of rotation of the rotor portion 18, along
rotation
axis 22. Magnetic flux concentrators 58 are disposed between the permanent
6 magnets 54 and redirect the magnetic flux produced by the permanent magnets
7 54 radially towards the air gap 74. In contrast, the stator portion 14
comprises
8 "horseshoe-shaped" soft iron cores 62, which are oriented in such a manner
that
9 the
magnetic flux that circulates inside these cores 62 is directed in a direction
that
is mainly perpendicular to the direction of rotation of the rotor portion 18.
The
11
perpendicular orientation of the magnetic flux in the cores 62 of the stator
portion
12 14, with
respect to the rotation direction, gives to TFEM a high ratio of mechanical
13 torque per weight unit of the electrical machine.
14 [78] Figure 4
illustrates a prior art core 62 manufactured with a plurality of
superposed sheets of metal 82 that are bent and separated with insulating
layers
16 86. The sheets of metal 82 are stacked in a plane adapted to be parallel
with the
17 axis of rotation 22 when the core 62 is operatively assembled in the TFEM.
The
18 magnetic flux 90 exits from the concentrator 58.1 in a direction orthogonal
to the
19 surface
of the plurality of superposed sheets of metal 82 as illustrated in Figure 5.
The Eddy currents 94 flow in closed loops within the conductors, in planes
21 perpendicular to the magnetic field 90 and perpendicular to the surfaces of
the
22 sheets of metal 82. In contrast, Figure 6 further illustrates the Eddy
currents 94 in
23 closed loops in a plane perpendicular to the magnetic field 90 and planar
with the
24 surfaces of the sheets of metal 82.
[79] A core 62
manufactured with a plurality of superposed bent sheets of
26 metal 82 about core axis 104, separated with insulating layers 86 stacked
in a
27 plane perpendicular with the axis of rotation 22 when the core 62 is
operatively
28 assembled in the TFEM, is illustrated in Figure 7. Each leg 114 includes a
leg 114
29 section reducing portion 120 embodied as an inclined portion 116 that is
progressively reducing the section of each of the legs 114 to provide a pair
of
31 poles 118
that is smaller than the section of the legs 114. The inclined portion 116
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1 is alternated on opposed sides of the legs 114 thus angularly offsetting the
poles
2 118 of a same core 62 to allow magnetic interaction with adjacent
concentrators
3 58 when operatively assembled with the rotor portion 18. The reducing
portion 120
4 can be adjusted to allow even offset, a distanced offset or partial overlap
of the
legs' poles 118 in respect with corresponding concentrators 58. The inclined
6 portion 116 is embodied beginning on the core's leg 114, after the bent in
the core
7 62. Alternatively, the inclined portion 116 could be embodied beginning next
to the
8 bent in the core's leg 114. In another non-illustrated embodiment, in order
to
9 radially reduce the height of the core 62 and get a more compact core 62,
the
inclined portion 116 is beginning on the core's leg 114, before the bent in
the core
11 62. The inclined portion 116 is illustrated with a rectilinear or planar
surface
12 however, a curved surface 120 could alternatively be embodied without
departing
13 from the scope of the present invention. Shape variations in the core 62,
using the
14 inclined portion 116, can be adjusted to manage the magnetic flux 90
therein. The
magnetic flux 90 exits from the concentrator 58.1 to a first leg 114 of the
core 62 in
16 a direction orthogonal to the surface of the plurality of superposed sheets
of metal
17 82, as illustrated in Figure 8. The magnetic flux 90 exits the same leg 114
from the
18 opposed leg's surface back to the adjacent concentrator 58.2. This magnetic
flux
19 90 path occurs when the concentrators 58 are not radially aligned with the
cores'
62 legs 114. Otherwise when the concentrators 58 are aligned with the core's
62
21 legs 114, the magnetic flux 90 enter one leg 114 of the core 62 and exits
through
22 the second leg 114 of the core 62. In both positions the magnetic flux 90
path is
23 parallel to each sheet of metal 82 of the core 62. The Eddy currents 94
flow in
24 closed loops within the conductors in planes perpendicular to the magnetic
field
90. Figure 9 further illustrates the Eddy currents 94 in closed loops in a
plane
26 perpendicular to the magnetic field 90 and perpendicular with the surfaces
of the
27 sheets of metal 82. The Eddy currents 94 are contained in the thickness of
the
28 sheets of metal 82 hence producing a plurality of reduced Eddy currents 94
and
29 increasing the efficiency of the core 62.
[80] Figure 10, Figure 11 and Figure 12 depict an exemplary core 62
31 manufactured with a plurality of layers of sheets metal 82. From these
Figures,
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1 one can appreciate the pattern created by the sheets of metal 82 circling
around
2 the central opening 98 configured to receive therein the coil 78 (not
illustrated in
3 Figure 10, Figure 11 and Figure 12).
4 [81] A possible manufacturing method for producing a core 62 consists
in
rolling a strip of sheet metal around a central jig that is sized and designed
to
6 leave an opening in the center of the rolled strip of metal 102 forming a
double-
7 core 106. The rolled strip of ferromagnetic metal 102 is exemplified in
Figure 13 a)
8 after a first manufacturing step rolling the strip of sheet metal around the
central
9 jig. The double-core 106 is then cut in two along its middle plan 110. The
result is
depicted in Figure 13 b) showing one half of the double core 106 of Figure 13
a)
11 that is becoming a core 62. A third step is performed to the core's legs
114 at an
12 angle a as illustrated in Figure 13 c). The portions of the legs 114
that are cut on
13 opposite sides of the core 62 to form and locate a pair of poles 118
that are axially
14 offset 122, thus not axially aligned. The pair of poles 118 is axially
offset 122 to
face different concentrators 58 (not illustrated in Figure 13) and allows
movement
16 of the magnetic flux 90 (not illustrated in Figure 13) through the core 62.
The
17 cuttings of the core 62 can be used to adjust the polar offset of the pair
of poles
18 118 and the stator overlap, if desirable. Cutting the core 62 should be
made in
19 such a way that no. metal residue remains between two layers of sheet of
metal 82
hence preventing magnetic shortcuts in the core 62. The core 62 can be etched
21 (etching process) as part of the manufacturing process to ensure no
shortcuts are
22 present in the core 62. As mentioned above, a layer of dielectric
material, such as
23 electrically insulating resin or varnish, on the faces of the sheets of
metal 82 are
24 preventing shortcuts therebetween. An example of a core 62 in its final
configuration is depicted in Figure 14. The cores 62 could be further cut to
reduce
26 their width and/or their length to build a more compact TFEM. The strip of
sheet
27 metal could be stretched, beyond its elastic deformation domain, to change
its
28 thickness in specific region of the core 62. Thickness variations of the
sheet metal
29 of the layers of the core 62 can be used to modify, alter and/or adjust
the magnetic
behavior of the cores 62.
16
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1 [82] A
circular array of cores 62 is illustrated in Figure 14, Figure 15 and Figure
2 16 in a predetermined angular array about the axis of rotation 22. The
respective
3 positions of each core 62 is determined by corresponding core-receivers 126
4 disposed in each of the pair of support halve members 66.1 and 66.2. The
cores
62 are radially located and secured and their pairs of poles 118 are
substantially
6 facing the axis of rotation 22. The toroid coil 78 is assembled in the
central
7 openings 98 of the cores 62 and connection wires 130 are extending outside
the
8 illustrated assembly to be electrically connected. It can be appreciated the
cores
9 62 are held by the pair of support halve members 66.1 and 66.2 at an angle
13
thereof, hence providing progressive interaction with the concentrators 58
when
11 operatively assembled with the rotor portion 18 and rotating about the axis
of
12 rotation 22.
13 [83] The
angle a and angle 13 are illustrated with more details in Figure 17
14 throughout Figure 19. Again, the angle a is dictated by the cut section on
each leg
of the core 62 while the angle [3 is defined by the shape of the core
receivers 126
16
located in the pair of support halve members 66.1 and 66.2. The core receiver
126
17 comprises an angled portion 134 adapted to match the corresponding angled
18 portion 138 in each of the legs 114 of the core 62. The angled portion 134
of the
19 core receiver 126 and the corresponding angled portion 138 of the legs 114
are
fixing the radial distance of each core 62 in respect with the axis of
rotation 22.
21 The final distance of the pair of poles 118 in respect with the rotor
portion 18 is
22 going to be determined by the final adjustment of the air gap 74, which
could be
23 made by honing the central portion of the assembled stator 14 with a boring
24
machine tool. Figure 20 throughout Figure 23 show a partial assembly of a core
62
with the toroid coil 78 and in cooperation with a set of magnets 54 and
26
concentrators 58. One can appreciate with the partial assembly of the core 62
that
27 the pair of poles 118 is not simultaneously facing a same concentrator 58
because
28 of the opposite cuts with angle a. The angle 13 ensures a progressive
interaction
29 between the pair of poles 118 and the concentrators 58.
[84] The
description and the drawings that are presented above are meant to
31 be illustrative of the present invention. They are not meant to be limiting
of the
17
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=
MTC-102-005-001-CA1
1 scope of the present invention. Modifications to the embodiments described
may
2 be made without departing from the present invention, the scope of which is
3 defined by the following claims:
=
18
