Patent Publication Number: US-9419486-B2

Title: Housing less transverse flux electrical machine

Description:
CROSS-REFERENCES 
     The present invention relates to, claims priority from and is a non-provisional patent application of U.S. Provisional Patent Application No. 61/704,793, filed Sep. 24, 2012, entitled MODULAR TRANSVERSE FLUX ELECTRICAL MACHINE, these documents are incorporated herein by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to transverse flux electrical machines. The present invention more specifically relates to transverse flux alternators and motors assembly. 
     2. Description of the Related Art 
     Alternators and motors are used in a variety of machines and apparatuses to produce electricity from mechanical movements. They find applications for energy production and transportation, to name a few. Alternators and motors can use Transverse Flux Permanent Magnet (TFPM) technologies. 
     Transverse flux machines with permanent magnet excitation are known from the literature, such as the dissertation by Michael Bork,  Entwicklung und Optimierung einer fertigungsgerechten Transversalfluβmaschine  [Developing and Optimizing a Transverse Flux Machine to Meet Production Requirements], Dissertation 82, RWTH Aachen, Shaker Verlag Aachen, Germany, 1997, pages 8 ff. 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 pole pitch. The open ends of these U-shaped cores are aimed at an air gap between the stator and rotor and form the poles of the stator. Facing them, permanent magnets and concentrators are disposed in such a way that the 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 intermittently located between the poles of the stator and have no ferromagnetic short circuit, short-circuit elements are disposed in the stator. 
     Put otherwise, transverse flux electrical machines include a circular stator and a circular rotor, which are separated by an air space called air gap, that allows a free rotation of the rotor with respect to the stator, and wherein the stator comprises soft iron cores, that direct the magnetic flux in a direction that is mainly perpendicular to the direction of rotation of the rotor. The stator of transverse flux 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 machine. In this type of machine, the rotor comprises a plurality of identical permanent magnet parts, which are disposed so as to create an alternated magnetic flux in the direction of the air gap. This magnetic flux goes through the air gap with a radial orientation and penetrates the soft iron cores of the stator, which directs this magnetic flux around the electrical conductors. 
     In the transverse flux electrical machine of the type comprising a rotor, which is made of a plurality of identical permanent magnet parts, and of magnetic flux concentrators, the permanent magnets are oriented in such a manner that their magnetization direction is parallel to the direction of rotation of the rotor. Magnetic flux concentrators are inserted between the permanent magnets and redirect the magnetic flux produced by the permanent magnets, radially towards the air gap. 
     The transverse flux electrical machine includes a stator, which comprises horseshoe shaped 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 mainly perpendicular to the axis of rotation of the rotor. 
     The perpendicular orientation of the magnetic flux in the cores of the stator, with respect to the rotation direction, gives to transverse flux electrical machines a high ratio of mechanical torque per weight unit of the electrical machine. 
     It is therefore desirable to produce an electrical machine that is easy to assemble. It is also desirable to provide an electrical machine that is economical to produce. Other deficiencies will become apparent to one skilled in the art to which the invention pertains in view of the following summary and detailed description with its appended figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an isometric view of a TFEM in accordance with at least one embodiment of the invention; 
         FIG. 2  is an isometric view of a TFEM in accordance with at least one embodiment of the invention; 
         FIG. 3  is a right side elevational view of a TFEM in accordance with at least one embodiment of the invention; 
         FIG. 4  is a left side elevational view of a TFEM in accordance with at least one embodiment of the invention; 
         FIG. 5  is a top plan view of a TFEM in accordance with at least one embodiment of the invention; 
         FIG. 6  is a bottom plan view of a TFEM in accordance with at least one embodiment of the invention; 
         FIG. 7  is a rear elevational view of a TFEM in accordance with at least one embodiment of the invention; 
         FIG. 8  is a front elevational view of a TFEM in accordance with at least one embodiment of the invention; 
         FIG. 9  is an isometric semi-exploded view of a TFEM illustrating a stator portion and a rotor portion in accordance with at least one embodiment of the invention; 
         FIG. 10  is an isometric semi-exploded view of a portion of a TFEM illustrating a rotor portion in accordance with at least one embodiment of the invention; 
         FIG. 11  is an isometric semi-exploded view of a TFEM illustrating multiple phase modules of a stator portion in accordance with at least one embodiment of the invention; 
         FIG. 12  is a magnified section of an isometric semi-exploded view of a TFEM in accordance with at least one embodiment of the invention; 
         FIG. 13  is a section view of a TFEM illustrating multiple phase modules in accordance with at least one embodiment of the invention; 
         FIG. 14  is a section view of a TFEM illustrating cores pairs in a stator portion in accordance with at least one embodiment of the invention; 
         FIG. 15  an isometric view of a core in accordance with at least one embodiment of the invention; 
         FIG. 16  an isometric semi-exploded view of a phase module of a stator portion in accordance with at least one embodiment of the invention; 
         FIG. 17  an isometric semi-exploded view of a phase module of a stator portion in accordance with at least one embodiment of the invention; 
         FIG. 18  an isometric partial assembly of a phase module in accordance with at least one embodiment of the invention; 
         FIG. 19  an isometric partial assembly of cores with a coil in accordance with at least one embodiment of the invention; 
         FIG. 20  a front elevational view of a phase module illustrating relative angles thereof in accordance with at least one embodiment of the invention; 
         FIG. 21  a front elevational view of a phase module illustrating relative angles thereof in accordance with at least one embodiment of the invention; 
         FIG. 22  is an isometric view of a portion of a coil and cores assembly in accordance with at least one embodiment of the invention; 
         FIG. 23  is isometric view of a portion of a phase module assembly in accordance with at least one embodiment of the invention; 
         FIG. 24  is isometric view of a portion of a phase module assembly in accordance with at least one embodiment of the invention; 
         FIG. 25  is a section view of a core module in accordance with at least one embodiment of the invention; 
         FIG. 26  is a section view of a coil in accordance with at least one embodiment of the invention; 
         FIG. 27  is an isometric view of a phase module assembly in accordance with at least one embodiment of the invention; 
         FIG. 28  is an isometric view of a phase module assembly in accordance with at least one embodiment of the invention; 
         FIG. 29  is an isometric view of a phase module assembly in accordance with at least one embodiment of the invention; 
         FIG. 30  is an isometric view of a phase module assembly in accordance with at least one embodiment of the invention; 
         FIG. 31  is an isometric view of a phase module assembly in accordance with at least one embodiment of the invention; 
         FIG. 32  is an isometric view of a phase module and jig assembly in accordance with at least one embodiment of the invention; 
         FIG. 33  is an isometric view of a phase module and jig assembly ready for resin injection in accordance with at least one embodiment of the invention; 
         FIG. 34  is a side elevational view of a resin-injected stator module before being machined and/or honed in accordance with at least one embodiment of the invention; 
         FIG. 35  is flow chart representative of assembly steps in accordance with at least one embodiment of the invention; and 
         FIG. 36  is flow chart representative of resin injection steps in accordance with at least one embodiment of the invention. 
     
    
    
     SUMMARY OF THE INVENTION 
     It is one aspect of the present invention to alleviate one or more of the shortcomings of background art by addressing one or more of the existing needs in the art. 
     The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. It is not intended to identify key/critical elements of the invention or to delineate the scope of the invention. Its sole 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. 
     Generally, an object of the present invention provides a modular Transverse Flux Electrical Machine (TFEM), which can also be more specifically appreciated as Transverse Flux Permanent Magnet (TFPM), which includes phase modules thereof. 
     An object of the invention is generally described as a modular electrical machine including a plurality of phase modules adapted to be axially assembled. 
     Generally, an object of the invention provides a TFEM including a plurality of phase modules assembled together with an intervening phase shift generally set at 120° [electrical] to provide standard symmetrical electric current overlapping over a complete 360° electrical cycle. A two-phases electrical machine would have a 90° phase shift and would use a similar logic and is also encompassed by the present invention. 
     One object of the invention provides at least one phase module including cooperating halves. 
     At least one object of the invention provides at least one phase module including a plurality of cores, and associated poles, angularly spaces apart from one another with different angular distances therebetween. 
     At least one aspect of the invention provides at least one phase including at least three adjacent cores, and associated poles, angularly distanced apart with a substantially similar angular distance therebetween and each at least three adjacent cores being further angularly spaced apart from an adjacent at least three adjacent cores, and associated poles, with a different angular distance thereof. 
     At least one aspect of the invention provides at least two adjacent cores, and associated poles, angularly radially separated with an angle of 10.8° and angularly radially separated from adjacent cores with at least one significantly different angle. 
     At least one object of the invention provides a set of poles, and intervening angular distance therebetween, that is repeated at least two times in a phase to locate the poles in the phase module. 
     At least one object of the invention provides a modular TFEM including a plurality of phase modules axially secured together by opposed support portions. 
     At least one aspect of the invention provides a phase module including a plurality of identical angular portions thereof. 
     At least one aspect of the invention provides a plurality of angular portions having intervening locating mechanism thereof adapted to locate and secure adjacent angular portions together. 
     At least one aspect of the invention provides an angular portion including a wire opening thereof adapted to receive therein coil wires extending outside the phase module. 
     At least one object of the invention provides a TFEM including a stator skewing angularly locating cores therein in respect with the rotation axis of the TFEM. 
     At least one object of the invention provides a plurality of phase modules including a cooperating positioning mechanism thereof adapted to mechanically angularly locate adjacent phase modules axially assembled together. 
     At least one aspect of the invention provides at least one phase module including a plurality of core-receiving spaces thereof. 
     At least one aspect of the invention provides at least one phase module including a housing including a circumferential cavity adapted to receive therein a cooperating portion of the cores to further mechanically radially locate and secure the cores to the phase module housing. 
     At least one object of the invention provides a phase modules including a plurality of angular portions adapted to be sequentially assembled together to allow inserting a coil therein before all the angular portions are assembled together. 
     At least one object of the invention provides a phase module including a plurality of angular portions configured to allow insertion of a coil therein when the assembled angular portions are angularly covering less than 200°. 
     At least one object of the invention provides a TFEM stator including resin therein for securing the coil and the cores inside the angular portions and also to maintain them in their respective locations when the internal portion of the phase module is machined, bored or honed. 
     At least one object of the invention provides a TFEM stator including injected resin therein for securing the angular portions together with the coil. 
     At least one object of the invention provides a housingless rotatable transverse flux electrical machine (TFEM) comprising a stator including at least one phase module comprising a pair of opposed halve members respectively including a plurality of core-receiving spaces sized and designed to receive, locate and secure therebetween a plurality of cores; and a coil operatively disposed in respect with the cores inside each phase modules, the pair of opposed halves being the exterior housing of the stator allowing the TFEM to be used without further housing. 
     At least one object of the invention provides a housingless stator adapted to be used in a rotatable transverse flux electrical machine (TFEM), the housingless stator comprising at least one phase module comprising a pair of opposed halve members respectively including a plurality of core-receiving spaces sized and designed to receive, locate and secure therebetween a plurality of cores; and a coil operatively disposed in respect with the cores inside each phase modules, the pair of opposed halves being the exterior housing of the stator allowing the TFEM to be used without further housing. 
     At least one object of the invention provides a kit for assembling a phase in a rotatable transverse flux electrical machine (TFEM), the kit comprising a pair of halves; a plurality of cores adapted to be located between the halves; a coil adapted to be located between the halves in operating position in respect with the plurality of cores; and resin to secure the coil and the plurality of cores with the pair of halves. 
     Embodiments of the present invention each have at least one of the above-mentioned objects and/or aspects, but do not necessarily have all of them. It should be understood that some aspects of the present invention that have resulted from attempting to attain the above-mentioned objects may not satisfy these objects and/or may satisfy other objects not specifically recited herein. 
     Additional and/or alternative features, aspects, and advantages of embodiments of the present invention will become apparent from the following description, the accompanying drawings, and the appended claims. 
     DESCRIPTION OF EMBODIMENT(S) OF THE INVENTION 
     Our work is now described with reference to the Figures. In the following description, for purposes of explanation, numerous specific details are set forth in 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 practiced without these specific details. In other instances, when applicable, well-known structures and devices are shown in block diagram form in order to facilitate describing the present invention. 
     The embodiments illustrated below depict a TFEM  10  with thirty-two (32) pairs of poles and a 510 mm diameter at the air gap and a 100 mm length of the magnets. The configuration of the TFEM  10 , an external rotor instead of an internal rotor, the number of phases can change in accordance with the desired power output, torque and rotational speed without departing from the scope of the present invention. 
     A TFEM  10  is illustrated in  FIG. 1  through  FIG. 8 . The TFEM  10  includes a stator portion  14  and a rotor portion  18 . The stator portion  14  is adapted to remain fixed while the rotor portion  18  is located within the stator portion  14  and is adapted to rotate in respect with the stator portion  14  about rotation axis  22 . The TFEM of the illustrated embodiments has a modular construction. Two axial side members  26  are secured together to assemble three electrical phases  30  together, each being provided by a phase module  32 . Each phase module  32  is adapted to individually provide an electrical phase  30  of alternating current. The present embodiment illustrates three phases  30  axially coupled together to provide tri-phased current when the TFEM  10  is rotatably actuated. The pair of axial side members  26  interconnects and axially secures together the three phases  30 . Proper tension is applied to each of the plurality of axial securing members  34  to ensure the phase modules  32  remain fixedly secured together. In the present embodiment, each axial side member  26  is provided with a series of extending axial securing member receiving portions  38  adapted to receive the axial securing members  34  therein while the axial securing members  34  extends axially outside the phase modules  32 . The axial securing members  34  could alternatively pass through the phase modules  32 , provided with axial openings therein, in another unillustrated embodiment. 
     Still referring to  FIG. 1  through  FIG. 8 , the axial side members  26  can be made of steel or other suitable material providing sufficient mechanical strength for the required purpose. Each axial side members  26  is optionally provided with a lifting link  42  sized and designed to receive therein, for example, a crane hook (not illustrated) to lift and move the TFEM  10 . The axial side members  26  are further equipped with a support portion  46  adapted to secured thereto a pair of feet  50  configured to interconnect both axial side members  26  together and to further facilitate securing the TFEM  10  to a base chassis (not illustrated). For instance, the base chassis can be a nacelle when the TFEM  10  is installed in a windmill or alternatively any other chassis provided by the equipment the TFEM  10  is operatively connected to. 
     Each axial side member  26  is configured to receive and secure thereto an axial rotor support member  54 . The axial rotor support member  54  is recessed in a circular cavity  56  (visible in  FIG. 9 ) defined in its associated axial side member  26  to concentrically locate the rotor portion  18  in respect with the stator portion  14 . The axial rotor support member  54  is further removably secured to its associated axial side member  26  with a plurality of fasteners  58 . The actual configuration of the embodiment illustrated in  FIG. 9  allows removal of the rotor portion  18  in one axial direction  60  when both axial rotor support members  54  are unsecured from their respective axial side member  26  because the circular cavities  56  are both located on the same side of their respective axial side member  26 . This allows for easy maintenance of the TFEM  10  once installed in its operating configuration with its external mechanism. 
     As it is also possible to appreciate from the embodiment illustrated in  FIGS. 1 through 8 , the rotor portion  18  extends through the axial rotor support members  54  and rotatably engages both axial rotor support member  54 . A solid rotor drive member  62  further extends from one axial rotor support members  54 . The solid drive member  62  could alternatively be a hollowed drive member in another unillustrated embodiment. The drive member  62  is adapted to transmit rotatable motive power from an external mechanism (not illustrated) to the TFEM  10  and includes a drive securing mechanism  66  adapted to rotatably couple the drive member  62  of the TFEM  10  to a corresponding rotatable drive element from the external mechanism (not illustrated). The external mechanism (not illustrated) could, for example, be a windmill rotatable hub (not illustrated) to which the rotor blades (not illustrated) are secured to transmit rotational motive power to the TFEM  10 . The external mechanism expressed above is a non-imitative example and other external mechanisms adapted to transmit rotational motive power to the TFEM  10  are considered to remain within the scope of the present application. 
     The TFEM  10  is further equipped with a protective plate  70  adapted to store and protect electrical connectors and electrical wires that extends from the TFEM  10  through an electrical outlet  74 . 
     Turning now to  FIG. 9  illustrating a semi-exploded TFEM  10  where a skilled reader can appreciate the depicted rotor portion  18  is axially extracted  60  from the stator portion  14 . The rotor portion  18  is axially extracted  60  from the stator portion  14  by removing the plurality of fasteners  58  and unsecuring the axial rotor support members  54  from their respective associated axial side member  26 . It can be appreciated that the rotor portion  18  of the exemplary embodiment has three distinct modular phases  36 , each providing an electrical phase  30 , adapted to axially align and operatively cooperate with the three phase modules  32  of the exemplified stator portion  14 . The rotor portion  18  includes a plurality of magnets  94  and concentrators  98  that are disposed parallel with the rotation axis  22 . An alternate unillustrated embodiment uses skewed magnets  94  and concentrators  98  that are disposed non-parallel (at an angle) with the rotation axis  22 . 
       FIG. 10  illustrates a further exploded view of the rotor portion  18 . As indicated above, the rotor portion  18  is adapted to rotate in respect with the stator portion  14 . The speed of rotation can differ depending of the intended purpose. Power remains function of the torque and the rotation speed of the rotor portion  18  therefore the TFEM is going to produce more power if the TFEM rotates rapidly as long as its operating temperature remains in the operating range of its different parts to prevent any deterioration (e.g. magnet demagnetization or insulating vanish deterioration, to name a few). The axial rotor support members  54  are adapted to be unsecured from the bearing holder  78  by removing the plurality of fasteners  82 . A sequence of assembled seal  86 , bearing  90  and bearing holder  78  is used on the front side of the rotor portion  18  while the same type of assembly is used on the opposite axial side of the rotor portion  18  to rotatably secure the rotor  80  to the axial rotor support members  54 .  FIG. 10  also illustrates that each phase module  36  of the rotor  80  uses a sequence of alternating permanent magnets  94  and concentrators  98 . Strong permanent magnets  94  can be made of Nb—Fe—B as offered by Hitachi Metals Ltd and NEOMAX Co. Ltd. Alternatively, suitable magnets can be obtained by Magnequench Inc. and part of this technology can be appreciated in U.S. Pat. No. 5,411,608, U.S. Pat. No. 5,645,651, U.S. Pat. No. 6,183,572, U.S. Pat. No. 6,478,890, U.S. Pat. No. 6,979,409 and U.S. Pat. No. 7,144,463. 
     A semi-exploded stator portion  14  is illustrated in  FIG. 11 . The axial side members  26  are exploded from the illustrative three (3) phase modules  32 . Each phase module  32  is going to be discussed in more details below. However, a positioning mechanism  102  is provided to polarly locate each phase module  32  in respect with its adjacent phase module  32  so that proper phase shift is maintained. Generally, the phase shift is set at 120° electrical to provide standard symmetrical electric current overlapping over a complete 360° electrical cycle. The 120° phase shift allows to, in theory, eliminate harmonics that are not multiples of three (3). The 120° phase shift illustrated herein is a preferred embodiment and is not intended to limit the angular phase shift of the present invention. 
     The illustrative embodiment of  FIG. 11  includes three (3) phase modules  32 . Another possible embodiment includes a multiple of three (3) phases modules  32  mechanically secured together, like the three (3) phase modules of  FIG. 11 , and electrically connected by phase  30  to increase the capacity of the TFEM  10  by simply increasing the axial length of the TFEM  10 . Thus, a nine (9) phase modules  32  would be coupled three-by-three for a three-phased 30 TFEM  10 . Another embodiment is a one-phase  30  TFEM  10  including only one phase module  32 . One other embodiment could be a two-phased 30 TFEM  10  electrically coupled together in a one-phase  30  configuration and with a phase shift of 90° in a two-phase  30  configuration. 
     As best seen from  FIG. 12 , each positioning mechanism  102  is embodied as a protruding portion  106  and corresponding cavity  110  sized and designed to mate together to polarly locate two adjacent phase modules  32  together. Additionally, each phase module  32  further includes a circular ridge  114  on one axial side and corresponding circular groove  118  on the opposite axis side. Engagement of the circular ridge  114  and circular groove  118  ensures concentric positioning of adjacent phase modules  32  along the rotation axis  22  of the TFEM  10 . Other shapes, designs and/or mechanical elements suitable to locate the phase modules  32  and the axial side members  26  together could be used without departing from the scope of the present application. Additionally, the recessed portion  104  is further defined in the phase modules  32  and the axial side members  26  to facilitate separation of adjacent assembled phase modules  30  and cooperating axial side members  26  by inserting a tool therein and prying to separate the two adjacent phase modules  32 . 
     A section view of the TFEM  10  is illustrated in  FIG. 13 . The rotor portion  18  includes a cylindrical frame  122  preferably removably secured to the rotatable drive member  62  with a series of fasteners  128  via two plates  124  radially extending from the drive member  62 . As explained above, the cylindrical frame  122  is sized and designed to accommodate three electrical phases  30 , each provided by a phase module  36  including its alternate series of magnets  94  and concentrators  98  secured thereon. The circular stator portion  14  and the circular rotor portion  18  are separated by an air space called “air gap”  126  that allows an interference-free rotation of the rotor portion  18  with respect to the stator portion  14 . Generally, the smallest is the air gap  126  the most performance the TFEM is going to provide. The air gap  126  is however limited to avoid any mechanical interference between the stator portion  14  and the rotor portion  18  and 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 stator portion  14  comprises soft iron cores (cores)  130  that direct the magnetic flux in a direction that is mainly perpendicular to the direction of rotation of the rotor portion  18 . The stator portion  14  of TFEM  10  also comprises in each phase module  32  electrical conductors defining a toroid coil  134  that is coiled in a direction that is parallel to the direction of rotation of the TFEM  10 . In this embodiment, the rotor portion  18  comprises a plurality of identical permanent magnets  94 , which are disposed so as to create an alternated magnetic flux in the direction of the air gap  126 . This magnetic flux goes through the air gap  126  with a radial orientation and penetrates the soft iron cores  130  of the stator portion  14 , which directs this magnetic flux around the toroid coil  134 . 
     In the TFEM  10  of the type comprising a rotor portion  18  including a plurality of identical permanent magnets  94  and of magnetic flux concentrators  98 , the permanent magnets  94  are oriented in such a manner that their magnetization direction is parallel to the direction of rotation of the rotor portion  18 , along rotation axis  22 . Magnetic flux concentrators  98  are disposed between the permanent magnets  94  and redirect the magnetic flux produced by the permanent magnets  94  radially towards the air gap  126 . In contrast, the stator portion  14  comprises “horseshoe-shaped” soft iron cores  130 , which are oriented in such a manner that the magnetic flux that circulates inside these cores  130  is directed in a direction that is mainly perpendicular to the direction of rotation of the rotor portion  18 . The perpendicular orientation of the magnetic flux in the cores  130  of the stator portion  14 , with respect to the rotation direction, gives to TFEM a high ratio of mechanical torque per weight unit of the electrical machine. 
     The rotor portion  18  has been removed in  FIG. 14  illustrating an encumbrance-free section view of the stator portion  14 . One can appreciate a plurality of pole faces  138  extending from each core&#39;s  130  legs  142  (as best seen in  FIG. 15 ). The pole faces  138  are disposed at an angle α from the rotation axis  22  of the TFEM  10 . The angle α of the pole faces  138  is called stator skew and is one of a plurality of elements that can be acted upon to reduce or cancel the ripple torque and the cogging torque. The stator skew allows for progressive electromagnetic interaction between the cores  130  and the magnets  94  and the concentrators  98 . 
     Focusing on the stator skew element, in reference with  FIG. 14  through  FIG. 18 , a plurality of cores  130  are disposed in each phase module  32  of the stator portion  14 . Yet another element to consider is the number of pairs of poles n. The number of pairs of poles n is equal to the number of cores  130  given that there are two poles  138  per core  130 . The number of magnets  94  is equal to the number of concentrators  98  and their number is twice the number of pairs of poles n and consequently also twice the number of cores  130 . The number of pairs of poles n is preferably thirty-two (32) as exemplified in the present application. 
     Therefore, each core  130  includes a pair of poles  144  extending from respective core&#39;s legs  142  (not visible in  FIG. 14  but illustrated in  FIG. 15 ). Each core  130  ends with two poles  136  having respective pole faces  138  thereof that can be seen inside the stator module  14  illustrated in  FIG. 14 . Each pole  136  of a pair of poles  144  is offset  132  to locate each pole  136  from a pair of poles  144  at a distance thereof that is generally equivalent to a distance of two adjacent concentrators  98  on the rotor portion  18  (commonly referred to as “pole pitch”). The core  130  of the illustrated embodiment includes a pair of opposed locating portions  148  adapted to locate the core  130  in the phase module  32 . The locating portions  148  are embodied in the illustrative core  130  in  FIG. 15  as protrusions  160  extending from the opposed sides of the core  130 . The skewed pole faces  138  of an embodiment are a projection toward the rotation axis  22  of the angled core&#39;s legs  142 . Each pair of pole faces  138  can be skewed, or angled, to more or less progressively engage the electromagnetism of the magnets  94  and the concentrators  98  on the rotor portion  18 , on the other side of the air gap  126 , when the rotor portion  18  is operatively assembled with the stator portion  14 . The angle α of the pole faces  138  of the illustrated embodiment is provided by the angle of the core&#39;s legs  142  that is dictated by the design and the shape of the core-receiving spaces  140  in the phase module  32  assembly as illustratively embodied in  FIG. 16  and  FIG. 17 . 
     In the present embodiment, as shown in  FIG. 16 , each stator phase module  33  is built with a sufficiently mechanically resistant material machined to form proper shapes therein and includes four angular portions  146  (for instance, four angular portions  146  of 90° [mechanical] each=360° [mechanical] once assembled together for a complete stator phase module  32 ) that are assembled together to locate and secure the cores  130  and the coil  134  within the phase module  32 . The embodiment illustrated in  FIG. 16  uses four (4) angular portions  146  and could alternatively use a different number of angular portions  146  as long as they complete 360° [mechanical] without departing from the scope of the present application; an embodiment including a modular phase  32  with two angular portions  146  is illustrated in  FIG. 17 . A three angular portions  146  embodiment is also contemplated and within the scope of the present invention. The angular portion  146  illustrated in  FIG. 18  includes two halves  150  secured together with fasteners  154  and further respectively located with pins  158 . The halves  150  are sized and designed to receive therein a predetermined number of cores  130  with a precise stator skew angle α (identified in  FIG. 19 , inter alia). One can appreciate that the distances between the angular sides of the angular portion  146  and their first respective adjacent core  130  is not the same on each halve  150  because of the core  130  skewing. This could have an influence on reference locations of the angles indicated in  FIG. 20  and  FIG. 21  depending of the reference point used to locate the cores  130 . 
     The phase module  30  can alternatively be constructed with an alternated halves  150  disposition to prevent having halves  150  evenly angularly disposed on each side of the phase module  30 . The alternate layout of the halves  150  over the circumference of a complete phase module  30  thus increases the mechanical strength of the phase module  30  because the junction between two adjacent angular portions  146  (on one side of the phase module  30 ) is going to be mirrored (on the opposite side of the phase module  30 ) by a continuous portion of the counterpart opposed halve  150 . In this embodiment, the fact that the halves  150  are not angularly evenly disposed along the circumference of a phase module  30  on each side thereof, implies that the angular portions  146  are overlapping each other. 
       FIG. 19  depicts some isolated cores  130  and associated coil  134  sub-assemblies to more clearly illustrate the angle α of the stator skew. The cores  130  and the coil  134  are in the same relative position as if they were within their angular portion  146  (not illustrated), both halves  150  (not illustrated) of the angular portion  146  however, has been removed so that a reader can better appreciate the relative position of the cores  130  and the coil  134  in the assembly. From  FIG. 19 , the skilled reader can appreciate that the cores  130  are collectively disposed precisely at angle α to provide the desired stator skew and also respectively disposed at predetermined angular distances from each other. 
     Moving now to  FIG. 20  and  FIG. 21 , a skilled reader can appreciate the angles about which are respectively polarly located the cores  130  in a phase module  32 . The angles are applied to four (4) angular portions  146  of the embodiment (as indicated above, the illustrated embodiment has four (4) angular portions of 90° each). The relative angles are to be considered between a same reference point on each core  130 . More specifically,  FIG. 20  depicts an angular portion  146  including eight (8) cores  130  respectively identified C1-C8. In this embodiment, cores C1-C4 form a set  148  of poles  136  where the intervening angles (10.781° [mechanical]) between the repeated angular sequences of poles A, B, C, D is constant. The intervening angle (10.781° [mechanical]) could be different and remain constant if the number of cores  130  present in a set  148  of poles  136  is different without departing from the scope of the present application. 
     A set  148  of poles  136  is repeated with intervening radial angle  152  that has a value adapted to complete an angle of 45° [mechanical]  156  in the present illustrative embodiment. The actual intervening angle  152  of the illustrated embodiment is 12.656° [mechanical] and this angle, required to complete the angle of 45° of the embodiment, could be different should another configuration of set  148  of poles  136  be desirable. In other words, a new set of poles  148  begins each 45° [mechanical] and is repeated a number of times in the present configuration. The number of sets  148  in the illustrative embodiment is eight (8), two per angular portion  146  of 90°. The angle of 45° of the embodiment is 360° [mechanical]/8 and could alternatively be 30°, 60° or 90° and fit in the angular portion  146  of 90° in the illustrated embodiment. 
     Another unillustrated embodiment of sets  148  includes two (2) cores  130  with a predetermined intervening angular distance (or angle thereof). The set  148  of two cores  130  is separated from the next set  148  of two cores  130  with a different intervening angular distance. This alternate repetitive arrangement of sets  148  is used to build a complete phase module  32 . One can appreciate from the illustrated embodiment that the cores  130  are identical and their respective locations dictate the respective locations of their associated poles  136 . Other possible embodiment could use cores  130  that are not all identical and the location the poles  136  in the stator module  14  should prevail to ensure proper function of the TFEM. 
     In reference now with  FIG. 22  is illustrated an angled portion  146  subassembly where a plurality of cores  130  are inserted in their respective core-receiving space  140  defined in one halve  150 . Each core-receiving space  140  is machined or shaped in the halve  150  at a precise angular position to properly locate each core  130  thereof. The core-receiving space  140  extends to a circumferential cavity  164  sized and designed to receive therein the locating portion  148  of each core  130 . The circumferential cavity  164  is axially deeper than the depth of the core-receiving space  140  to define an edge adapted to abut the locating portion  148 , and appended edge  166 , and therefore radially locates the core  130  in the phase module  32 . The circumferential cavity  164  can be continuous around each halves  150  or be discontinuous as illustrated in  FIG. 22  and  FIG. 23 . A discontinuous circumferential cavity  164  allows for less material removal and increased mechanical strength of the phase module  32 . A protrusion  168  is radially proximally located between core-receiving spaces  140  to further support the cores  130  and to create a proximal wall portion when two cooperating halves  150  are assembled together to form an angular portion as it is illustrated in  FIG. 24 . Similarly, a radial edge  192 , circumvently defined in a distal wall portion  196 , further axially locates the two assembled halves  150  and creates an external wall of the phase module  32 . Thus, two assembled halves  150  create a solid housing surrounding self-localized cores  130  secured therein. Each halve  150  is further provided with internal pillar members  172  adapted to mirror with corresponding internal pillar members  172  of the other cooperating halve  150  and prevent, inter alia, deformation of the halves  150  when they are secured together with fasteners through openings  176  disposed in some of the pillar members  172 . A skilled reader can understand that the core-receiving spaces  140  of two cooperating halves  150  are not mirroring each other because they are intended to receive therein cores  130  that have poles offset  132  and also because of the angle α of the stator skew, as described above. 
     Still referring to  FIG. 22 ,  FIG. 23  and  FIG. 24 , each halve  150  includes a unification mechanism  180  adapted to unite and locate two adjacent angular portions  146 . The unification mechanism  180  illustrated in the embodiments includes a male portion  184  and a corresponding female portion  188 . The male portion  184  is sized and designed to match the female portion  188  and ensures proper mechanical connection between the angular portions  146 . 
       FIG. 25  depicts a section view of a phase module  32  with two assembled halves  150 . It is possible to appreciate the position of the core  130  enclosed in the phase module  32 , however, the circular phase module  32  and the skewed core  130  render a little non-obvious the interpretation of  FIG. 25 . 
       FIG. 26  represents a section view of an isolated coil  134  including a plurality of conductive wire  200  windings covered with a layer of insulating resin  204 . It can be noted the illustrated embodiment includes a plurality of conductive wire  200  windings although other unillustrated embodiments can use a single or multiple conductive wires to form the coil  134 . The conductive wire  200  illustrated in the embodiment has a rectangular, or oblong, section to maximize the conductive wire  200  density in the coil  134  (less empty space). An additional insulating layer  208 , made of fabric in the embodied illustration, is added over the coil  134  to protect the conductive wires  200  and the insulating resin  204  to be damaged by mechanical contacts with the halves  150  during installation. 
     Moving now to the angular portions  146  assembly illustrated in  FIG. 27  through  FIG. 31 . A first assembled angular portion  146  is secured to a first jig plate  212 . The angular portion  146  is located with locating rings  224  disposed on the jig plate  212  to mechanically position the angular portions  146  thereof. The coil  134  is introduced between the legs  142  of the cores  130  disposed in the angular portion  146  once the first angular portion  146  is installed on the first jig plate  212 . The first angular portion  146  to be installed on the jig plate  212  is preferably the angular portion  146  including a wire opening  216  adapted to pass through the connecting wires  220  extending from the coil  134 . It might be more difficult to assemble the angular portions  146  if one does not begin the assembly with the angular portion  146  including the wire opening  216 . A second angular portion  146  is assembled as illustrated in  FIG. 28  and  FIG. 29  adjacent to the angular portion  146  already installed on the jig plate  212 . A third and a fourth angular portions  146  are simultaneously assembled to complete the angular portions  146  assembly as it can be appreciated in  FIG. 30 . The final angular portion  146  assembly is preferably made with a 180° angular portion  146  sub-assembly to ensure the male portions  184  and the female portions  188  of the angular portions  146  are easily engaging.  FIG. 31  illustrates four (4) angular portions  146  assembled together and supported by the jig plate  212  in accordance with an illustrative embodiment of the invention. Another possible unillustrated embodiment encompassed by the present invention includes only two halves  150  to build a phase module  32 , one on each side of a phase module  32 , each halve  150  radially covering 360° of the phase module  32 , about the rotation axis  22 , to enclose the cores  130  and the coil  134  therein. 
     A second jig plate  214  is added to the assembled angled portions  146  to secure the phase module  32  between the two jig plates  214  as illustrated in  FIG. 32 . A series of fasteners are engaged through the jig plates  212  and angled portions  146  assembly and secured to the jig plates  212 ,  214  and the phase module  32  together in a tight manner—a seal can be used—preventing leakage between the jig plates  212  and the phase module  32 . The second jig plate portion  214  includes a central wall portion  218  sized and designed to seal the central portion  232  of the phase module  32  between the two jig plates  212 —here again a seal can be used. The assembled jig portions  212 ,  214  and the sealed intervening phase module  32  hence becomes an injection mold in which is injected a resin, or a polymer, adapted to cure and secure all the cores  130  and the coil  134  in the halves  150  of the phase module  32 . 
     Resin or polymer is used to interconnect the parts contained in each phase module  32 . Each phase module  32  is injected separately in the illustrative embodiment however one skilled in the art could understand it is possible to collectively inject all the assembled phase module  32  together with a properly designed assembly process and a jig sized and designed accordingly. The resin  248 , preferably, has to meet two main criteria: 1) sufficient mechanical strength, 2) sufficient thermic conductivity and 3) electrical resistivity. These three requirements ensure all parts of a phase module  32  are adequately maintained together at their respective locations. The injected resin  248  is also a means of filling the gaps and spaces left between the assembled parts to prevent any remaining play due to the tolerances required for manufacturing all the parts and secure all the parts of the assembly together in their operating positions. Sufficient mechanic strength is required to sustain compression mainly due to the torque generated by the operating parts and transferred to the axial members  26  of the TFEM  10 . The selected resin  248  should also be a good vibration damper to protect the cores  130 , the coil  134  and their respective halves  32  and prevent any undesirable contact between the operating parts of the TFEM  10 . Thermal conductivity is another desirable role of the resin  248  that replaces air (empty volumes) in the phase module  32  to cool the internal parts of the TFEM  10  by transferring thermic energy to the environment of the TFEM  10 . The resin  248  should also be tolerant to temperature variations that can reach between −40° C. and 180° C. with minimal changes in its mechanical properties. The resin prevents conducting magnetic flux within the internal parts of the phase module  32  that would prevent proper flux transfer with the cores  130  around the coil  134 . The resin should also prevent creating Foucault current within the internal parts of the phase module  32  and therefore prevent additional energy loss. Finally, the resin  248  should be adapted to be machined to set the final dimensions of the interior of the stator portion  14  to receive therein the rotor portion  18  with minimal airgap  126  therebetween. Epoxy resin is an example of a resin  248  suitable to be used in the present TFEM  10  among other possible choices of resin  248  or other materials adapted to meet the requirements listed above. 
     The second jig module  214  is provided with injection inlets  240 , to inject resin or polymer in the mold, and injection outlets  244  to purge, or vacuum, air from the mold during the injection process. The same process is used with each of the phase module  32  to get, in the context of the present embodiment that is a three-phased alternator, three injected phase modules  32 . Other configurations, other types of mold assembly and mold inlets/outlets can be used without departing from the scope of the exemplified invention. 
     Three injected phase modules  32  are assembled together as explained above and the result is shown in  FIG. 34 . The resin injected in the phase module  32  secures the coil  134 , the cores  130  in the angular portions  146  in addition to secure the angular portions  146  and their respective halves  150  together. The resin thus injected transforms the phase module  34  assembly in a unitary and integral phase module  32 .  FIG. 34  should be viewed in light of  FIG. 14  and from it one can appreciate that the poles  138  of the cores  130  are not shown in  FIG. 34 . This is because the resin injected in the phase module  32  covers the cores  130  and a further step is required to carefully remove a layer of resin inside the assembled core modules  32 . The three (3) assembled phase modules  32  are preferably bored, and optionally honed, once assembled together to remove excess resin and shortens the length of the core&#39;s legs  142  to a desired diameter to ensure tight tolerances can be obtained for the diameter and the concentricity of the multiple core modules  32  assembly in order to minimize the airgap  126  when the rotor portion  18  is assembled with the stator portion  14 . A small airgap increases the magnetic field strength between the stator portion  14  and the rotor portion  18 . One can appreciate that machining all the separate part individually and assembling them thereafter is going to cause an addition of the tolerances that is likely going to increase the final airgap  126  to prevent possible (statistically possible) mechanical interferences. Alternatively, each phase module  32  can individually be bored and honed individually prior to be assembled with adjacent phase modules  32 . The final result, when stator boring is done, is illustrated in  FIG. 14 . 
       FIG. 35  generally illustrates a series of steps adapted to assemble to stator portion in accordance with an embodiment of the invention.  FIG. 36  illustrates illustrative steps for securing the parts of the stator portion together in accordance with at least one embodiment of the invention. 
     The description and the drawings that are presented above are meant to be illustrative of the present invention. They are not meant to be limiting of the scope of the present invention. Modifications to the embodiments described may be made without departing from the present invention, the scope of which is defined by the following claims: