BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1A and 1B respectively depict assembled and exploded views of a prior-art, polyphase claw-pole structure wherein the armature magnetic circuit is divided into two parts along the direction of motion and three coils are mounted on the claw base of one part.
FIGS. 2A and 2B respectively depict assembled and exploded views of an alternative assembly of the structure in FIGS. 1A and 1B, wherein the armature magnetic circuit is divided into three sections along the direction of motion and wherein three coils are mounted on the claw base of central section and the two lateral sections of the magnetic circuit are identical.
FIGS. 3A and 3B respectively depict front and assembled views of a polyphase segmented claw pole structure wherein the mechanically assembly of the segmented armature is realized with two annuli flanges and wherein the armature is made with three identical components (segments) based on the present invention which are regularly spaced along the direction of motion and which are magnetically isolated from each other.
FIG. 4A and 4B respectively depict assembled and exploded views of one armature segment based on the present invention wherein the armature magnetic circuit is divided into three sections along the direction of motion and wherein one coil is mounted (or inserted) on the claw base of the central section and the two lateral sections of the magnetic circuit are identical.
FIGS. 5A and 5B respectively depict front and assembled views of a polyphase segmented claw pole structure wherein the mechanically assembly of the segmented armature is realized with a yoke and wherein the armature is made with three identical components (segments) based on the present invention which are regularly distributed along the direction of motion and which are magnetically isolated from each other by a magnetic air gap following a plane perpendicular to the direction of motion.
FIG. 6A and 6B respectively depict assembled and exploded views of one armature segment based on the present invention wherein the magnetic circuit is divided into three sections along the direction of motion and wherein one coil is mounted (inserted) on the claw base of the central section and the two lateral sections of the magnetic circuit are identical.
FIG. 7 is an axial sectional view in a plan that passes by the axis of rotation of a cylindrical structure made with a segmented claw pole stator with interlaced claws according to this invention and a surface mounted permanent magnet rotor split in two parts along the direction of motion, that are separated by an axial air gap.
FIG. 8 is an axial sectional view in a plan that passes by the axis of rotation of a cylindrical machine made with a segmented claw pole stator according to this invention with non-interlaced claws and with a rotor made of three rows of permanent magnets, which are separated by two axial air-gaps and mounted on the surface of a single rotor yoke.
FIG. 9 is an axial sectional view in a plan that passes by the axis of rotation of a cylindrical structure made with a segmented claw-pole stator with non-interlaced claws according to this invention and a surface mounted permanent magnet rotor split in two parts along the direction of motion, that are separated by an axial air gap and respectively equipped with two rows of permanent magnets.
FIG. 10 is an axial sectional view in a plan that passes by the axis of rotation of a cylindrical structure made with a segmented claw pole stator with interlaced claws according to this invention and a hybrid rotor split into two independent sections which are magnetically isolated by an axial air gap, following the direction of motion wherein the first section is a surface mounted permanent magnet rotor structure and the second section is a rotor made with electromagnets.
FIG. 11 is an axial sectional view in a plan that passes by the axis of rotation of a cylindrical structure made with a segmented claw pole stator with interlaced claws which is split into two magnetically isolated parts following the direction of motion, and is associated to a hybrid rotor structure.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The embodiments of the present invention will be described with reference to FIGS. 3A through 11.
According to this invention, an electrical machine armature is realized with several identical segments that are uniformly distributed around the cylindrical air-gap surface between the stator and rotor in the case of a rotational motion, or along the planar air-gap surface between the stator and rotor in the case of a linear motion and are always separated by a magnetic air-gap surface that is in a plane perpendicular to the cylindrical air-gap surface between the stator and rotor in the case of a rotational motion as shown on FIGS. 3 and 5, or perpendicular to the planar air-gap surface between the stator and rotor in the case of a linear motion.
FIGS. 4A, 4B and 6A, 6B show detailed views of one armature segment according to this invention. Each segment comprises a magnetic circuit component having one or more pieces and a winding made with one or several coils (FIGS. 4A, 4B and 6A, 6B). This magnetic circuit is equipped with several rows of claws following the direction of motion and the magnetic flux circulates in the three dimensions inside them. The magnetic circuit of one armature segment is preferably made from an iron-powder based composite soft Magnetic material formed by pressing, molding, or machining. Some parts of the magnetic circuit components where the magnetic flux is circulating in two dimensions (i.e. in a plain or a bi-dimensional surface) can also be made of stacked sheets, or laminations of soft magnetic material. The mechanical assembly of the magnetic circuit components can be accomplished by gluing, screwing, or pressing the parts together or other suitable mechanical fixation processes.
The number of segments in an armature is equal to or is a multiple of the number of phases of the electrical machine. Each magnetic circuit segment can be equipped with two rows of claws only, but generally it is better to use three rows of claws, as presented in FIGS. 4A, 4B and 6A, 6B. These rows of claws are parallel one in relation to the other, and each row follows the direction of motion. The top surfaces of the claws face the air gap between the stator and the rotor. The base of a claw forms a part of the magnetic circuit that is perpendicular to the air-gap surface like a tooth in a conventional slotted machine. All the claws in an armature segment are connected to a magnetic yoke common to each row of claws (FIGS. 4A, 4B and 6A, 6B). One or several non-overlapped coils are wound around the base of certain claws. In an armature segment according to this invention, the distribution of the claws along the direction of motion can be either regular or irregular and it is possible to use various widths of claws in a same segment (see the widths of the claws 412 and 414 in FIG. 4B).
Generally, the area of the top surface of each claw, adjacent to the air-gap surface between the stator and rotor, is greater than the cross-sectional area of the base of the claw. This allows each claw to cover a larger surface of the air gap between the stator and rotor, while at the same time reducing the size of the magnetic field sources of the rotor on the other side of the air-gap surface. The axial length of the claws of each segment of magnetic circuit, along the axis perpendicular to the direction of motion is always greater than the axial length of the claw bases in the same axis as shown in FIGS. 4A, 4B and 6A, 6B. The claw can be also enlarged symmetrically on each side of the base of the claw along the axis parallel to the direction of motion. This modification assists the mechanical seating of the winding and can simplify the mounting of the coils.
Normally, the claws of two adjacent rows are interlaced, or interspaced, to minimize the total axial length of the motor, whilst still covering a greater air-gap surface (see the arrangement of claws 412, 414, and 422 in FIGS. 4A and 4B). However, when the distance between the claws becomes too small, the magnetic flux leakage between them can become significant. It is therefore preferable to reduce the axial length of the claws along the axis perpendicular to the direction of motion to minimize the flux leakages between them. In this case, the claws are not really interlaced in the axial direction along the axis perpendicular to the direction of motion but the distribution of the claw positions along the direction of motion is not modified in comparison to the previous case.
Normally, the claws of the lateral rows placed on both sides of the central row are aligned in the direction perpendicular to the rows of claws (see the arrangement of claws 412 and 432 in FIGS. 4A and 4B). Consequently their magnetic potential are identical and their axial tip along an axis perpendicular to the direction of motion can touch themselves or be separated by a small air gap without creating any magnetic flux leakage between them as shown in FIGS. 6A and 6B with claws 612, 632 and 614, 634.
As indicated above, an armature segment of the present invention can incorporate one or more wire coils, connected either in series or in parallel, to generate the magnetic field in the claws and/or to embrace the magnetic flux that is circulating. Each coil is wound directly around the base of one claw (FIGS. 6A and 6B) or it can also encircle several claws (FIGS. 4A and 4B). The coils are always regularly distributed around the cylindrical air-gap surface between the stator and rotor in the case of a rotational motion, or along the planar air-gap surface between the stator and rotor in the case of a linear motion and they are not interlaced. The axes of the coils are always perpendicular to the surface of the air-gap between the stator and rotor and the plane defined by the coils is always parallel to the direction of motion and the air-gap surface between the stator and rotor. In the case of embodiments employing a number of claw rows higher than two, the coils are mounted entirely on the bases of the even rows, or the odd rows, but not intricate or intermixed.
As explained above, the embodiments described herein generally have a cylindrical geometry for the use in a cylindrical machine armature. For convenience of reference, the direction co-linear with the axis of revolution of the structures described herein shall be referred to as the axial direction; the direction defined by a point rotating about the axis of revolution shall be referred to as the circumferential direction; and the direction normal to the axis of revolution shall be referred to as the radial direction. To simplify the description, only outer-segmented armatures of cylindrical machines are presented. However, it must be evident that the embodiments described above also can be applied to an inner armature.
FIGS. 3A and 3B show a cylindrical segmented armature 30 of an electrical machine with an internal rotor structure (which is not represented in these figures). It is a three-phase armature that is divided in three identical segments 320, 330, 340. These segments are regularly distributed around the cylindrical surface of the air gap between stator and rotor, following the direction of motion and they are separated by a magnetic air-gap in a plane perpendicular to the cylindrical air-gap surface between the stator and rotor.
The segments are mechanically assembled and correctly positioned by two annular flanges 310, 350 that are fixed on the lateral parts of the magnetic circuit of each segment.
The magnetic circuit of each segment has a number of claws (discussed below) that extend in a radially inward direction from the yoke. Each segment includes one or several coils. These coils are generally mounted on the central row of claws and there are two other rows of claws which encircle the coils and are used to channel and distribute the magnetic flux in the air gap between the stator and the rotor as presented in FIGS. 4A, 4B and 6A, 6B
Generally, the magnetic circuit of each segment can be divided into three parts, following three rows of claws (FIGS. 4B, 6B). This division is defined by a plane perpendicular to the cylindrical air-gap surface and following the direction of the motion. As shown in FIGS. 4A and 6A, a coil can be easily wound or easily mounted on the central part of the magnetic circuit. In the case of FIG. 4B, this central part 420 of the magnetic circuit has two claws 422, 424. There are two identical magnetic parts 410, 430 with three claws 412, 414, 416 and 432, 434, 436 (FIG. 4B). These identical lateral parts are mechanically connected on both sides of the yoke of the central magnetic part 420 without any magnetic air gap. This magnetic circuit arrangement encircles the coil 440 that is mounted on the central part 420 (FIGS. 4A and 4B).
In the embodiments of FIGS. 4A and 4B and 6A and 6B, a row of claws which supports a winding is adjacent to rows of claws without windings.
It is also possible to make different types of modifications to the magnetic circuit component affecting the cogging torque, such as slots or grooves with lower depths on the top surface of the claws facing the air-gap surface between the stator and rotor, or special profiling of the claws to increase in frequency of the cogging torque pulsations, thus helping to reduce its amplitude. One can also adapt the harmonic content of the emf by using rectangular, triangular, or trapezoidal shapes of claw.
It is also possible to split in the radial direction one or several claws which belong to a same row of claws of the segment, in order to define a new air gap between its parts. This split can be radially extended up to the yoke. However, in the following description, we consider that this kind of division process of the claw does not change the total number of claws in a segment because both parts of this divided claw are not interspaced by another claw placed in another row of claws of the segment. The general structural variables of a polyphase claw-pole segmented armature according to the present invention are the number of phases Mph, the number of segments Nseg, the total number of coils per segment Nb, and two specific numbers of claws G1 and G2 in each magnetic segment which are defined below. According to the present invention, these variables must satisfy the following relationships:
Mph>1
Nseg=k1×Mph k1 is an integer greater than 0;
G2=G1+1 or G2=G1−1
G2>0
Nb=k2 k2 is an integer greater than 0 but lower than G1+2;
where:
- Mph is the number of phases; Mph being higher than 1;
- Nseg is the total number of identical segments regularly distributed along the direction of motion;
- Nb is the total number of coils distributed along the length of a row in each armature segment;
- G1 is the number of claws in each armature segment, which are in a row of claws which supports the coils ;and
- G2 is the number of claws in each armature segment, which are in a row of claws which does not support any coil.
In the embodiments of this invention, each armature segment has only one phase winding which can be realized with one or several coils. However, it is also possible to connect the winding of different segments in series or in parallel to realize a complete armature phase winding. The armature segments associated with each phase are distributed in the phase order around the circumference of the stator. The same sequence of segment distribution is repeated several times when a phase winding is using more than one segment. For example, in the case of a three-phase machine, with identified phases A, B, and C, the order of the coil segments is A, B, C if its segmented polyphase claw-pole armature is made with three segments. The order of the coils segments becomes A, B, C, A, B, C if the armature is made with six segments and A, B, C, A, B, C, A, B, C in the case of nine segments. The coils of each phase winding can be connected either in series or in parallel, in accordance to the specific application and design.
The polyphase claw pole segmented armature presented in FIGS. 6A and 6B preferably is associated with a rotor with 8 or 10 poles. In this example, the assembly of the three armature segments is realized with a cylindrical external yoke made of non-magnetic material. The top side of each armature segment which is in contact to the cylindrical external non-magnetic yoke can be mechanically assembled to it by gluing, screwing, or pressing techniques. It is also possible to use a massive magnetic material for the realization of the yoke presented in FIGS. 6A and 6B. In this case, the cross section of this yoke must be small enough to obtain a magnetic saturation of the material and to minimize the magnetic flux leakage between two adjacent armature segments.
As in the case of a conventional laminated motor structure, the modification of the magnetic circuit axial length is used to adapt the power of the motor by adjusting the number of identical laminations to stack. This approach has the advantage of optimizing the production process by using identical magnetic parts for the design of a large power range of motors. One can apply the same approach in the case of the claw-pole armature segments presented in this invention. By example, one can directly stack two identical armature segments along the axis of rotation, without separating them by an air gap. This transformation doubles the length of the complete segmented armature and doubles the power of the machine. The assembly of both armature segments can be realized with a common yoke or between two flanges. Optionally, a slight shift can be introduced between the two segmented structures in the direction of motion, to reduce the cogging torque, for example.
The armature segments, according to this invention, can be completely insulated by a conventional tightness method in order to let a cooling fluid circulate inside them. In this case, the winding is directly in contact with the cooling fluid and heat dissipation is improved.
Another way to improve heat dissipation is to equip each armature segment with a cooling system, using water or any kind of cooling fluid circulation, with forced or natural convection. The cooling system can be integrated as a part of the magnetic circuit. It is then possible to compact the cooling system integrated in the magnetic circuit in a single part, made with the same magnetic material. One can equip the outer surface of each segment with cooling fins to increase the surface in contact with the ambient air. These fins can form an integral part of the magnetic circuit component, where the magnetic flux can also circulate. With such an arrangement, the heat dissipation is improved, without increasing the weight, the total size and weight of the electrical machine is minimized, the power and torque-to-weight ratio are increased, and the machine production process is simplified.
The segmented claw-pole stator armatures can be used with classic structures of cylindrical, axial, or planar rotors of synchronous machines, variable reluctance machines, and induction machines. However, in the case of an armature segment according to this invention, which is divided in three parts, following the direction of motion and with two adjacent rows of claws interlocked (or interspaced), it can be interesting to split the rotor in two parts, as in the example shown in FIG. 7. This figure shows a cross-sectional view of a segmented claw-pole armature 70 in a plan that passes by the axis of rotation of the rotor. This segmented claw-pole armature 70 is associated to a cylindrical rotor structure divided in two identical parts 72, 74 that are separated by an axial air gap. These rotor parts 72, 74 have several magnetic poles, alternatively magnetized along the direction of the rotor motion. In the example of FIG. 7, permanent magnets are mounted on the surface of annular magnetic yokes 724, 744 which can be mechanically assembled on a same shaft (not shown in this figure). Each rotor part must be correctly positioned in relation to the stator claws. In this case, the claws of the central and lateral parts can have an identical radial thickness. This division of the rotor into several rows can also be used to smooth the cogging torque if the magnet rows are slightly shifted with a suitable angle.
It is possible to realize a synchronous machine by using a segmented claw-pole armature, according to this invention, with a hybrid rotor excitation system: the first rotor part is equipped with permanent magnets and the second rotor part is equipped with claw or teeth and one or several coils to realize several electromagnets supplied by a direct current. An example of such a hybrid rotor is presented on FIG. 10. In such a machine, the magnetic flux produced by each rotor excitation part respectively circulates inside the magnetic circuit of the armature segments and along different flux paths if the two rotor parts 1010, 1020 are separated by an axial magnetic air gap, as shown in FIG. 10. This specific arrangement permits control of the total flux inside the coils mounted on the central part of an armature segment by using the excitation direct current of the electromagnets mounted on the second part of the rotor. Such a machine structure with a hybrid rotor associated to a segmented claw-pole armature, according to this invention, can be advantageously used for a vehicle alternator or an electrical vehicle motorization.
Different arrangements of a hybrid rotor structure can be associated to the segmented claw-pole armature presented in this invention. For example, one can realize a hybrid rotor with a first part equipped with permanent magnets and a second part equipped with a squirrel cage or wound rotor structure used in asynchronous motors. This kind of machine can be used as a line-start permanent magnet motor. By using the same approach, it is also possible to associate a segmented claw-pole armature presented in this invention to a hybrid rotor with a first part equipped with permanent magnets and a second part equipped with a variable reluctance structure. This arrangement can be interesting for traction applications where a flux weakening control is necessary for high-speed operation.
In the case of an armature segment according to this invention, which is divided in three parts, following the direction of motion and with two adjacent rows of claws non interlocked, it can be interesting to use the configuration of permanent magnet rotor presented in FIG. 8. FIG. 8 shows an axial view of a segmented claw-pole armature 80 associated to a cylindrical rotor structure 82 with a single magnetic yoke 820 and three rows of permanent magnets rows 822, 824, 826. A permanent magnet row 824 is positioned in regard to the claws of central part of the armature segment 80. The other permanent magnet rows 822, 826 are positioned in regard to the claw of the lateral parts of magnetic segments. The respective widths of these two lateral magnet rows are equal to one half of the central magnet row. It can be noticed that it is also possible to smooth the cogging torque if the three magnet rows are slightly shifted with a suitable angle.
In the case of a synchronous machine or a permanent magnet machine using a polyphase claw-pole segmented armature according to this invention, the performance of the machine depends on the selected combination of number of rotor poles pair and number of claws of the segmented armature. Higher performances are obtained when the following relationship is satisfied:
2P=Nseg×(G1+G2)+K
where:
- P is the number of pole pairs on the rotor;
- Nseg is the total number of identical armature segments which are regularly distributed along the direction of motion;
- G1 is the number of claws in each armature segment, that are in a row of claws which supports the coils;
- G2 is the number of claws in each armature segment that are in a row of claws which does not support any coil; and
- K is an integer equal to −3 or −2, or −1 or 1 or 2 or 3.
The polyphase claw-pole segmented armature structures according to this invention can also be used for electrical traction and propulsion systems, electrical generation systems, robotics and machine tools, domestic appliances, mechatronic systems, rotating and linear electromechanical actuators, automotive, aeronautics and aero-space applications.
While only some embodiments of the present invention are described above, it is obvious that several modifications or simplifications are possible without departing from the spirit or the scope of the present invention.
Patent Application
20080093950
