Abstract:
Wireless power transfer systems comprising of special arrangements of magnetic field generating materials within the wireless power transmitter and the wireless power receiver. The arrangement enables a greater amount of the magnetic field to be contained within the air gap between the wireless power transmitter and the wireless power receiver than outside of the air gap.

Description:
RELATED APPLICATIONS 
       [0001]    This application is:
       a continuation of PCT application No. PCT/CA2015/050327 which was filed on 20 Apr. 2015 and which is hereby incorporated herein by reference; and   claims priority from, and the filing date benefit of, U.S. Provisional Application No. 61/984,771, filed on Apr. 26, 2014, which is also hereby incorporated herein by reference.       
 
     
    
     TECHNICAL FIELD 
       [0004]    This application pertains to an arrangement of magnetic field generating elements comprising permanent magnets or coils or combinations thereof that enables the magnetic field to be stronger and concentrated in the air gap between the wireless power transmitter and the wireless power receiver in wireless power transfer systems. 
       BACKGROUND 
       [0005]    It is well known that power can be wirelessly conveyed from one place to another using the Faraday effect, whereby a changing magnetic field causes an electrical current to flow in an electrically isolated secondary circuit. Magnetic inductive charging is the most popular form of wireless power transfer currently in use. The basic form of magnetic inductive charging uses two coils in close proximity where one coil acts as the wireless power transmitter and the other acts as the receiver of wireless power. A time-varying current flows in the transmitter coil, which produces a time-varying magnetic field. This time-varying magnetic field induces current in the nearby receiver coil (Faraday&#39;s law), which can then be used to charge various devices. 
         [0006]    Magnetic-coupling technology has also been described as a viable wireless power transfer solution. The technology may make use of a strong magnetic coupling whereby a rotating magnet in a wireless power transmitter couples onto another nearby magnet in the wireless power receiver. The transfer of energy is via rotational magnetic coupling rather than direct magnetic induction mechanism. The time-varying magnetic field generated by the rotating magnets typically has a lower frequency compared to magnetic induction systems. 
         [0007]    There are health and safety concerns of stray magnetic fields in wireless power transfer systems. Additionally, stray magnetic fields also induce eddy currents in nearby metallic objects creating heat which results in a loss of power transfer efficiency. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0008]    In drawings, which depict non-limiting embodiments of the invention: 
           [0009]      FIG. 1  is a cross-sectional view of a wireless power transfer system according to an example embodiment; 
           [0010]      FIG. 2  is a cross-sectional view of a wireless power transfer system according to an example embodiment; 
           [0011]      FIG. 3  is a cross-sectional view of a wireless power transmitter or receiver magnet comprising a plurality of coils as the individual magnetic field generating units according to an example embodiment; 
           [0012]      FIG. 4  is schematic view of a wireless power transmitter or receiver magnet according to an example embodiment; 
           [0013]      FIG. 5  is a cross-sectional view of a wireless power transmitter or receiver magnet according to an example embodiment; 
           [0014]      FIG. 6  is a cross-sectional view of a wireless power transmitter or receiver magnet according to an example embodiment; 
           [0015]      FIG. 7  is a cross-sectional view of a wireless power transfer system comprising individual magnetic field generating units, some of which comprise both permanent magnets and stationary coils according to an example embodiment; 
           [0016]      FIG. 8  is a cross-section of a wireless power transfer system comprising a combination of a plurality of moveable permanent magnets in a Halbach array and stationary coils according to an example embodiment; and 
           [0017]      FIG. 9  is a cross-section of a wireless power transfer system comprising a combination of a plurality of moveable permanent magnets and stationary coils according to an example embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    One aspect of the invention provides a magnetically coupled wireless power transfer system having a rotating wireless power transmitter magnet and a rotating wireless power receiver magnet. In some embodiments, the wireless power transmitter and receiver magnets each comprise a plurality of magnetic field generating units. 
         [0019]      FIG. 4  depicts a wireless power transmitter magnet  402  that is part of a wireless power transfer system  400  according to a particular embodiment. Wireless power transfer system  400  may comprise a power receiver magnet (not shown in the  FIG. 4  view) which has features similar to those of transmitter magnet  402 . Wireless power transmitter magnet  402  (or the corresponding wireless power receiver) of the  FIG. 4  embodiment is generally cylindrically shaped having a cylindrical axis  170  and comprises a plurality of quasi-pie-shaped magnetic field generating units  408 . Wireless power transmitter magnet  402  (or the corresponding receiver magnet) is described herein as having an axial direction  170 , a generally circular magnetization-variation direction  150  and generally radial uniform-magnetization directions  160 . Each magnetic field generating unit  408  exhibits predominantly a single magnetization direction  420 . The magnetization direction  420  of each field generating unit  408  may be orthogonal to a corresponding uniform-magnetization direction  160 , as depicted in  FIG. 4 . As can be seen from  FIG. 4 , magnetization-variation direction  150  extends circumferentially about axis  170  and uniform-magnetization directions  160  extend radially from axis  170 . 
         [0020]    Each magnetic field generating unit  408  exhibits predominantly a single magnetization direction  420 , which may vary between magnetic field generating units  408  along magnetization-variation direction  150 . The magnetization directions  420  of magnetic field generating units  408  adjacent to one another in magnetization-variation direction  150  may be different from one another. 
         [0021]    For convenience, additional embodiments herein are depicted using various types of quasi-cross-sectional illustrations. For example,  FIG. 1  is a quasi-cross-sectional view of a magnetically coupled wireless power transfer system  100  according to an example embodiment having a transmitter  102  and a receiver  104 , each of which is cylindrically shaped similar to power receiver/transmitter magnet  402  depicted in  FIG. 4 . The quasi-cross-sectional view of transmitter  102  is taken along transmitter magnetization-variation direction  150 A and in an axial direction  170  and the quasi-cross-sectional view of receiver  104  is taken receiver magnetization-variation direction  150 B in an axial direction  170 . In other words,  FIG. 1  is not a true cross-section, but instead depicts a quasi-cross-sectional (i.e. circumferentially unraveled) view of a cylindrical power transmitter magnet  102  unraveled along magnetization variation direction  150 A and a quasi-cross-sectional (i.e. circumferentially unraveled) view of a cylindrical power receiver magnet  104  unraveled along magnetization variation direction  150 B. For brevity, further unraveled views shown in the drawings may be referred to herein as “cross-sections”. 
         [0022]    The  FIG. 1  wireless power transfer system  100  comprises a wireless power transmitter magnet  102  and wireless power receiver magnet  104  in close proximity and separated by an air gap  106 . In the  FIG. 1  embodiment, the wireless power transmitter magnet  102  and wireless power receiver magnet  104  each comprise individual magnetic field generating units  108 . In particular, wireless power transmitter magnet  102  comprises individual transmitter magnetic field generating units  108 A and wireless power receiver magnet  104  comprises individual receiver magnetic field generating units  108 B. For brevity, transmitter magnetic field generating units  108 A and receiver magnetic field generating units  108 B may be referred to more generally herein as magnetic field generating units  108  which may refer to one or both of transmitter magnetic field generating units  108 A and receiver magnetic field generating units  108 B. 
         [0023]    Magnetic field generating units  108  (i.e. transmitter magnetic field generating units  108 A and receiver magnetic field generating units  108 B) may comprise permanent magnets such as, but not limited to, NdFeB, samarium cobalt, ferrite, magnetite and alnico magnets made up of combinations of iron, aluminum, nickel, cobalt, titanium and copper and commonly known by trade names such as Alni, Alcomax, Hycomax, Columax, and Ticonal, or combinations thereof. It will be considered in this disclosure that a permanent magnet is an object made from a material that is magnetized and creates its own persistent magnetic field. 
         [0024]    Each magnetic field generating unit  108  may exhibit predominantly a single magnetization direction. In particular, each transmitter magnetic field generating unit  108 A exhibits predominantly a corresponding first magnetization direction  120 A, which may vary between transmitter magnetic field generating units  108 A along transmitter magnetization-variation direction  150 A. Transmitter variation direction  150 A may comprise a circumferentially oriented magnetization-variation direction  150 , as shown in  FIG. 4 . The first magnetization directions  120 A of transmitter magnetic field generating units  108 A adjacent to one another in transmitter magnetization-variation direction  150 A may be different from one another. Each first magnetization direction  120 A may also be orthogonal to a corresponding transmitter uniform-magnetization direction  160 A, as depicted in  FIG. 1 . Each transmitter uniform-magnetization direction  160 A may comprise a radially oriented uniform-magnetization direction  160  as shown in  FIG. 4 . First magnetization direction  120 A of each transmitter magnetic field generating unit  108 A may be constant along its corresponding transmitter uniform-magnetization direction  160 A. In some embodiments, first magnetization direction  120 A of each transmitter magnetic field generating unit  108 A may be constant within each transmitter magnetic field generating unit  108 A. 
         [0025]    Similarly, each receiver magnetic field generating unit  108 B exhibits predominantly a corresponding second magnetization direction  120 B which may vary between receiver magnetic field generating units  108 B along receiver magnetization-variation direction  150 B. Receiver variation direction  150 B may comprise a circumferentially oriented magnetization-variation direction  150 , as shown in  FIG. 4 . The second magnetization directions  120 B of receiver magnetic field generating units adjacent to one another in receiver magnetization-variation direction  150 B may be different from one another. Each second magnetization direction  120 B may be orthogonal to a corresponding receiver uniform-magnetization direction  160 B, as depicted in  FIG. 1 . Each receiver uniform-magnetization direction  160 B may comprise a radially oriented uniform-magnetization direction  160  as shown in  FIG. 4 . Second magnetization direction  120 B of each receiver magnetic field generating unit  108 B may be constant along its corresponding receiver uniform-magnetization direction  160 B. In some embodiments, second magnetization direction  120 B of each receiver magnetic field generating unit  108 B may be constant within each receiver magnetic field generating unit  108 B. 
         [0026]    In some embodiments, transmitter magnetization-variation direction  150 A is orthogonal to each of transmitter uniform-magnetization directions  160 A and receiver magnetization-variation direction  150 B is orthogonal to each of receiver uniform-magnetization directions  160 B, as is the case in the cylindrical embodiment shown in  FIG. 4 , where magnetization-variation directions  150  are circumferentially oriented and uniform-magnetization directions  160  are radial. In some embodiments, transmitter magnetization-variation direction  150 A and receiver magnetization-variation direction  150 B may be located in planes which are parallel to one another. In some embodiments, these planes are not precisely parallel and may have normal vectors oriented at an angle between 0° and 15° relative to one another. 
         [0027]    In some embodiments, transmitter  102  and receiver  104  are co-axial along cylinder axis  170 . In some embodiments, transmitter uniform-magnetization directions  160 A are distributed circumferentially about cylinder axis  170  ( FIG. 4 ) of the wireless power transmitter and extend from cylinder axis  170  in radial directions and receiver uniform-magnetization directions  160 B are distributed circumferentially about cylinder axis  170  of the wireless power receiver and extend from cylinder axis  170  in radial directions. In some embodiments, transmitter magnetization-variation direction  150 A extends circumferentially about cylinder axis  170  and the receiver magnetization-variation direction  150 B extends circumferentially about cylinder axis  170  of the wireless power receiver (i.e. as depicted in  FIG. 4  in respect to uniform-magnetization direction  160  and magnetization-variation direction  150 ). 
         [0028]    In some embodiments, the variation of first and second magnetization directions  120 A,  120 B may exhibit a spatially periodic pattern. In particular, the variation of first magnetization directions  120 A of transmitter magnetic field generating units  108 A may exhibit a first spatially periodic pattern along transmitter magnetization-variation direction  150 A. The first spatially periodic pattern may have a first period comprising a number, λ 1 , of transmitter magnetic field generating units  108 A. The variation of second magnetization directions  120 B of receiver magnetic field generating units  108 B may exhibit a second spatially periodic pattern along receiver magnetization-variation direction  150 B. The second spatially periodic pattern may have a second period comprising a number, λ 2 , of receiver magnetic field generating units  108 B. 
         [0029]    In some embodiments, the angular orientations of first magnetization directions  120 A of transmitter magnetic field generating units  108 A adjacent to one another in transmitter magnetization-variation direction  150 A vary about their corresponding transmitter uniform-magnetization directions  160 A by a first angular offset, α 1 . In some embodiments, first angular offset, α 1 , is greater than 0° and varies depending on the number, λ 1  of transmitter magnetic field generating units  108 A in the first period. In some embodiments, the number, λ 1 , of transmitter magnetic field generating units  108 A in the first period multiplied by the first angular offset, α 1 , is equal to 360°. 
         [0030]    Similarly, in some embodiments, the angular orientations of second magnetization directions  120 B of receiver magnetic field generating units  108 B adjacent to one another in receiver magnetization-variation direction  150 B vary about their corresponding receiver uniform-magnetization directions  160 B by a second angular offset, α 2 . In some embodiments, second angular offset, α 2 , is greater than 0° and varies depending on the number, λ 2 , of receiver magnetic field generating units  108 B in the second period. In some embodiments, the number, λ 2 , of transmitter magnetic field generating units  108 B in the second period multiplied by the second angular offset, α 2 , is equal to 360°. As illustrated in the  FIG. 1  embodiment, first angular offsets, α 1 , may be equal to second angular offsets, α 2 , although this is not necessary. In the illustrated embodiments, angular offsets, α 1 , α 2 , are constant within each transmitter magnet  102  and each receiver magnet  104  but this is not strictly necessary. In some embodiments, angular offsets, α 1 , α 2 , may vary within each transmitter magnet  102  and each receiver magnet  104   
         [0031]    In some embodiments, the number, λ 1 , of transmitter magnetic field generating units in the first period comprises three or more transmitter magnetic field generating units. For example, the first period may comprise three transmitter magnetic field generating units  108 A with first angular offsets, α 1 , of approximately 120°. In another example, the first period may comprise four transmitter magnetic field generating units  108 A with first angular offsets, α 1 , of approximately 90°, such as is illustrated in the  FIG. 1  embodiment. Similarly, in some embodiments, the number, λ 2 , of receiver magnetic field generating units in the second period comprises three or more receiver magnetic field generating units. For example, the second period may comprise three receiver magnetic field generating units  108 B with second angular offsets, α 2 , of approximately 120°. In another example, the second period may comprise four receiver magnetic field generating units  108 B with second angular offsets, α 2 , of approximately 90°, such as is illustrated in the  FIG. 1  embodiment. However, it should be understood that the number, λ 1 , of transmitter magnetic field generating units in the first period and the number, λ 2 , of receiver magnetic field generating units in the second period are not limited to three or four but may vary as discussed in more detail herein. 
         [0032]    In some embodiments, the number of transmitter magnetic field generating units  108 A in a wireless power transmitter is a positive integer multiple of the number, λ 1 , of transmitter magnetic field generating units  108 A in a first period. Similarly, the number of receiver magnetic field generating units  108 B in a wireless power receiver may be a positive integer multiple of the number, λ 2 , of receiver magnetic field generating units  108 B in a second period. 
         [0033]    In some embodiments, at least one of the plurality of transmitter magnetic field generating units  108 A comprises a permanent magnet and/or at least one of the receiver magnetic field generating units  108 B comprises a permanent magnet. In some embodiments, at least one of the plurality of transmitter magnetic field generating units  108 A comprises an electromagnetic coil and/or at least one of the receiver magnetic field generating units  108 B comprises an electromagnetic coil. 
         [0034]    In some embodiments, the first magnetization directions  120 A, the first angular offsets, α 1 , and the number, λ 1 , of transmitter magnetic field generating units 108 A in the first period, may be such that transmitter magnetic field generating units  108 A comprise a Halbach array. Similarly, in some embodiments, the second magnetization directions  120 B, the second angular offsets, α 2 , and the number, λ 2 , of receiver magnetic field generating units  108 B in the second period may be such that receiver magnetic field generating units  108 B comprise a Halbach array. 
         [0035]    In the Halbach array embodiment depicted in the magnetically-coupled wireless power transfer system  100  in  FIG. 1 , a plurality of magnets or magnetic field generating units  108  are arranged in such a way that adjacent magnetic field generating units  108  (from left to right in the  FIG. 1  view) of wireless power transmitter  102  have magnetization directions  120  offset by about α 1 =−90° (about their corresponding uniform-magnetization directions  160 ). The adjacent magnetic field generating units  108  (from left to right in the  FIG. 1  view) of the wireless power receiver  104  have magnetization directions  120  offset by about α 2 =90° (about their corresponding uniform-magnetization directions  160 B). The magnetic field generating units  108  directly aligned with each other across the air gap  106  within the wireless transmitter magnet  102  and wireless receiver magnet  104  and which have magnetization directions  120  oriented in axial directions  170  have such magnetization directions  120  oriented in the same direction along axis  170  (see vertical direction  110  of the  FIG. 1  illustration). The magnetic field generating units  108  directly aligned with each other across the air gap  106  within the wireless transmitter magnet  102  and wireless receiver magnet  104  and which have magnetization directions  120  oriented in magnetization-variation directions  150  have such magnetization directions  120  oriented opposite to one another along their respective magnetization-variation directions  150  (see horizontal direction  112  of the  FIG. 1  illustration). 
         [0036]    As can be seen in the resulting magnetic flux lines in this  FIG. 1  embodiment, where each of the transmitter magnet  102  and receiver magnet  104  comprise Halbach arrays, the strongest magnetic fields are depicted by the bold dotted lines  114  and are located within the air gap  106  between transmitter magnet  102  and receiver magnet  104 . The weakest magnetic fields are located in the regions  116  on the opposite sides of the transmitter magnet  102  and receiver magnet  104  from the air gap  106 . As a result, this Halbach arrangement of the  FIG. 1  embodiment enhances the magnetic field between transmitter magnet  102  and receiver magnet  104 . The enhanced magnetic field between transmitter magnet  102  and receiver magnet  104  increases the efficiency of the wireless power transfer while limiting the intensity of stray magnetic fields on the outside of the transmitter and receiver magnets. 
         [0037]    In an embodiment, the wireless power transmitter or the wireless power receiver in the magnetically-coupled wireless power transfer system  100  in  FIG. 1  is equipped with a rotor (not expressly shown in  FIG. 1 ) to allow the wireless power receiver or transmitter to rotate about a corresponding axis  170 . In another embodiment the wireless power transmitter is equipped with a rotor and the wireless power receiver is equipped with a rotor in the magnetically-coupled wireless power transfer system  100  in  FIG. 1 . In some embodiments, such rotors permit the wireless power transmitter and receiver to be rotatable about a common axis  170 . Such rotors may comprise a rotary assembly having an axle (as shown in  FIG. 4 ) or the like, allowed to rotate by, for example, a bushing or a bearing. 
         [0038]      FIG. 2  is a cross-sectional view of a magnetically coupled wireless power transfer system  200  according to an example embodiment. System  200  is substantially similar to system  100  except that first and second magnetization directions  220 A and  220 B corresponding to field-generating units  208  have each been reversed. In other respects, system  200  exhibits similar or identical features as described above in relation to system  100  and such similar or identical features would be apparent to those skilled in the art upon reading the description and understanding the figures herein. For example, and without limitation, system  200  may comprise a plurality of transmitter magnetic field generating units  208 A and a plurality of receiver magnetic field generating units  208 B (similar to transmitter magnetic field generating units  108 A and receiver magnetic field generating units  108 B). Each transmitter magnetic field generating unit  208 A may exhibit predominantly a corresponding first magnetization direction  220 A and each receiver magnetic field generating unit  208 B may exhibit predominantly a corresponding second magnetization direction  220 B. The first magnetization directions  220 A may vary in a transmitter magnetization-variation direction  150 A and the second magnetization directions  220 B may vary in a receiver magnetization-variation direction  150 B. Each of the first magnetization directions  220 A may be orthogonal to a corresponding transmitter uniform-magnetization direction  160 A and each of the second magnetization directions  220 B may be orthogonal to a corresponding receiver uniform-magnetization direction  160 B. 
         [0039]    System  200  of the  FIG. 2  embodiment comprises a wireless power transmitter magnet  202  and wireless power receiver magnet  204  in close proximity and separated by an air gap  206 . In the  FIG. 2  embodiment, the plurality of individual magnetic field generating units  208  have magnetization directions  220  oriented in opposite directions to those found in the wireless power transfer system  100  in  FIG. 1  (see magnetization directions  220  having vertical  210  and horizontal  212  orientations in the  FIG. 2  view). 
         [0040]    In the embodiment of a magnetically coupled wireless power transfer system in  FIG. 2 , the strongest magnetic fields are located within the air gap  206  as depicted by the bold dotted magnetic flux lines  214 . This enhances the power transfer efficiency while the weakest magnetic fields are located in the regions  216  on the opposite sides of the transmitter magnet  202  and receiver magnet  204  from the air gap  206 . If permanent magnets such as, but not limited to, NdFeB, samarium cobalt, ferrite, magnetite and alnico magnets comprised of combinations of iron, aluminum, nickel, cobalt, titanium and copper and commonly known by trade names such as Alni, Alcomax, Hycomax, Columax, and Ticonal, or combinations thereof were used to construct the wireless power transfer systems  100  and  200  in  FIGS. 1 and 2 , respectively, the alignment of the individual magnetic field generating units would simply need to be reversed. 
         [0041]    The Halbach arrays in the wireless power transfer systems illustrated in  FIGS. 1 and 2  may be constructed using permanent magnets such as, but not limited to, NdFeB, samarium cobalt, ferrite, magnetite and alnico magnets comprised of combinations of iron, aluminum, nickel, cobalt, titanium and copper and commonly known by trade names such as Alni, Alcomax, Hycomax, Columax, and Ticonal, or combinations thereof. Another embodiment may be envisioned where the permanent magnets may be replaced by coils. Using coils in the place of permanent magnets may offer at least three distinct advantages. Firstly, rare earth magnets can be rather expensive in cost. A low cost alternative to permanent magnets would be preferred to keep manufacturing costs low. Secondly, rare earth magnets are denser and heavier in weight than coils. Thirdly, it is much easier to change the magnetization direction in coils than permanent magnets by simply reversing the current flow within the coils. 
         [0042]    In an embodiment, the wireless power transmitter or the wireless power receiver in the magnetically-coupled wireless power transfer system  200  in  FIG. 2  is equipped with a rotor (not expressly shown in  FIG. 2 ) to allow the wireless power receiver or transmitter to rotate about a corresponding axis  170 . In another embodiment the wireless power transmitter is equipped with a rotor and the wireless power receiver is equipped with a rotor in the magnetically-coupled wireless power transfer system  200  in  FIG. 2 . In some embodiments, such rotors permit the wireless power transmitter and receiver to be rotatable about a common axis  170 . Such rotors may comprise a rotary assembly having an axle (as shown in  FIG. 4 ) or the like, allowed to rotate by, for example, a bushing or a bearing. 
         [0043]      FIG. 3  is a cross-sectional view of a wireless power transmitter magnet  303 , where each field generating unit  308 A comprises one or more corresponding coils  302  according to a particular embodiment.  FIG. 3  shows power transmitter magnet  303  in a first state  304  and a second state  310 . The Fig. power transmitter magnet  303  may comprise part of a wireless induction-based power transfer system  300 , wherein alternating the current in the coils  302  of power transmitter magnet  303  induces corresponding current in one or more proximate receiver coils (not shown in  FIG. 3 ). Power transmitter magnet  303  of system  300  exhibits some similarities to the power transmitter magnet  102  of the  FIG. 1  embodiment. For example, and without limitation, power transmitter magnet  303  may comprise a plurality of transmitter magnetic field generating units  308 A. Each transmitter magnetic field generating unit  308 A may exhibit predominantly a corresponding first magnetization direction  320 A (which may vary depending on the direction of current flow through its corresponding coil  302 ). The first magnetization directions  320 A may vary in a transmitter magnetization-variation direction  150 A. Each of the first magnetization directions  320 A may be orthogonal to a corresponding transmitter uniform-magnetization direction  160 A. In some embodiments, the one or more receiver coils of system  300  may be arranged in a manner similar to that of transmitter magnet  303  with receiver coil units corresponding to the field generating units  308  of transmitter magnet  303 , although this is not necessary. While  FIG. 3  depicts a wireless power transmitter  303 , a wireless power receiver could be provided with field generating units arranged in a manner similar to the field generating units  308  of transmitter magnet  303   
         [0044]    In some embodiments, coils  302  of transmitter  303  may be electrically connected in series. In some embodiments, coils  302  may be fabricated from a single wire. In the  FIG. 3  embodiment of wireless power transmitter  303  (or a similarly configured wireless power receiver), the electrical current-carrying coils  302  may be arranged such that current flow through coils  302  in a first direction causes the magnetization directions  320 A of transmitter  303  to have the Halbach arrangement  304  (shown at the top of  FIG. 3 ) and such that current flow through coils  302  in a second (opposing) direction causes the magnetization directions  320 A of transmitter  303  to have the Halbach arrangement  310  (shown at the bottom of  FIG. 3 ). Alternating the current flow between these first and second directions creates magnetic field flux which is concentrated on one side of transmitter  303  and which varies between the  FIG. 3  configurations  304 ,  310 . This concentrated and varying magnetic field can induce current in the receiver coils of system  300 . 
         [0045]    The magnetic induction wireless power transfer system  300  of the  FIG. 3  embodiment may comprise a wireless power transmitter  303  having a plurality of field generating units  308 A, each of which may further comprise one or more electrical current-carrying coils  302 . A wireless power receiver (not shown in  FIG. 3 ) may comprise one or more receiver coils. In some embodiments, a wireless power receiver may comprise a plurality of magnetic field generating units, each of which may further comprise one or more electrical current-carrying coils, and which may have an arrangement similar to that of transmitter  303 . An air gap may separate the wireless power transmitter  303  and wireless power receiver. The plurality of electrical current-carrying coils  302  in wireless power transmitter  303  and the wireless power receiver may be arranged in an array such that the magnetic field strength is greater in the air gap between the wireless power transmitter and wireless power receiver than the magnetic field strength outside of the air gap separating the wireless power transmitter and wireless power receiver. 
         [0046]    The coils  302  in transmitter  303  and the receiver may be arranged such that the magnetization directions of adjacent field-generating units (in the transmitter and/or the receiver) are angularly offset from one another. In the particular case of the illustrated embodiment, adjacent field-generating units  308 A exhibit angular offsets, α, of about 90° about their corresponding uniform-magnetization directions  160 A. The alternating current going into each coil  302  in transmitter  303  may be phased relative to the current in other coils  302  to ensure that the magnetic field directions  320 , which may be 306 (vertical in the illustrated view) and  308  (horizontal in the illustrated view) produced by the transmitting coils  302  achieve strong magnetic field (depicted by bold dotted lines) on one side compared to the magnetic field (depicted by thin dotted lines) on the other (similar to as shown in  FIG. 1 ). This can be achieved, for example, by connecting the ends of each adjacent coil  302  in series such that either state  304  or  310  is achieved when the current reverses direction in the transmitter as shown in  FIG. 3 . In system  300 , the strongly one-sided time varying magnetic field produced by transmitter  303  induces a time-varying current in one or more receiver coils (which may comprise a set of receiver coils having an arrangement similar to the coils  302  of transmitter  303 ) and which are located on the side of transmitter  303  having the stronger field and potentially separated from transmitter  303  by an air gap. Other magnetization patterns may be possible than those listed in  FIG. 3  such as where the angular offset, α, may range from about 1° to about 90° or more. 
         [0047]      FIG. 4  is a schematic view of a wireless power transmitter or receiver magnet according to an example embodiment.  FIG. 4 . depicts an exemplary non-unraveled view of a wireless power transmitter magnet  402  or receiver magnet. Any of the transmitter and/or receivers of the embodiments described in connection with  FIGS. 1-3 and 5-8  may have the non-unraveled configuration shown in  FIG. 4 , although this is not necessary. System  400  represents an exemplary embodiment of a wireless power transmitter magnet  402  or receiver magnet that could exhibit any of the properties described above or below in relation to a wireless power transmitter magnet (i.e. magnet  104  or any other transmitter magnet or coil herein) or a wireless power receiver magnet (i.e. magnet  102  or any other receiver magnet or coil herein). System  400  may be substantially similar to system  100  (or  200  or any other embodiment herein), although shown from a different perspective. In other respects, system  400  may exhibit similar or identical features as described above in relation to system  100  and such similar or identical features would be apparent to those skilled in the art upon reading the description and understanding the figures herein. For example, and without limitation, power transmitter magnet  402  of system  400  comprises a plurality of magnetic field generating units  408  (similar to transmitter magnetic field generating units  108 A and receiver magnetic field generating units  108 B). Each magnetic field generating unit  408  may exhibit predominantly a corresponding magnetization direction  420 . The magnetization directions  420  may vary in a magnetization-variation direction  150 . Each of the magnetization directions  420  may be orthogonal to a corresponding uniform-magnetization direction  160 . 
         [0048]    In some embodiments of magnetic coupling wireless power transfer charging systems, rotation of coupled magnets creates a current whereby power can be transferred from a power transmitter to a receiver.  FIG. 4  is an illustration of an embodiment of a wireless power transmitter magnet  402  or receiver magnet in a disk-like (or cylindrical) shape constructed of a plurality of individual petal-shaped, pie-shaped or wedge-shaped magnetic field generating units  408 , which may comprise permanent magnets or coil-based magnets. In this embodiment, petal-shaped individual magnetic field generating units  408  each with a specific magnetization direction  420  are linked together or otherwise abut one another. Lines  404  denote the location of demarcation where the individual magnetic field generating units  408  are linked side-by-side. 
         [0049]    Additionally in the  FIG. 4  embodiment, the magnets are linked to an optional inner core  406  for further stabilization, although core  406  is not necessary. System  400  may further comprise a rotor  418  operative connected to transmitter magnet  402  by which transmitter magnet  402  may be rotated about axis  170  (e.g. with a motor or some other mover). Additionally or alternatively, the transmitter  402  may be rotated in the magnetic-variation direction  150  by coils carrying alternating current (AC) placed behind the magnets (e.g. coils similar to coils  706  in  FIG. 7 ). Although the embodiment in  FIG. 4  shows the transmitter magnet  402  being depicted as a disk, other non-limiting shapes may be used such as, for example, cylindrical or spherical. The magnetic field generating units  408  may be comprised of permanent magnets such as, but not limited to, NdFeB, samarium cobalt, ferrite, magnetite and alnico magnets made up of combinations of iron, aluminum, nickel, cobalt, titanium and copper and commonly known by trade names such as Alni, Alcomax, Hycomax, Columax, and Ticonal, or combinations thereof. In the  FIG. 4  system  400 , a receiver magnet (not shown) may be provided and may have properties similar to transmitter magnet  402  (except that the receiver magnet is not drivingly rotated). 
         [0050]      FIG. 5  is a cross-sectional view of a wireless power transmitter or receiver magnet  502  according to an example embodiment which may form part of a wireless power system  500  according to an example embodiment. System  500  is substantially similar to system  100  except that the angular offset, α, of the magnetization directions  520  is smaller than in system  100 . In other respects, system  500  exhibits similar or identical features as described above in relation to system  100  and such similar or identical features would be apparent to those skilled in the art upon reading the description and understanding the figures herein. For example, and without limitation, system  500  comprises a plurality of magnetic field generating units  508  (similar to transmitter magnetic field generating units  108 A and receiver magnetic field generating units  108 B). Each magnetic field generating unit  508  may exhibit predominantly a corresponding magnetization direction. The magnetization directions  520  may vary in a magnetization-variation direction  150 . Each of the magnetization directions  520  may be orthogonal to a corresponding uniform-magnetization direction  160 . The magnetization directions  520  may exhibit a spatially periodic pattern having a number, λ, of magnetic field generating units  508  in each period. 
         [0051]    It may be envisioned that other Halbach arrangement embodiments may be used that differ from those described in  FIGS. 1 and 2  that may also lead to enhancement of the magnetic field on one side of a transmitter or receiver magnet while minimizing or substantially reducing the magnetic field on the opposite side of the transmitter or receiver. The embodiment illustrated in  FIG. 5  is a depiction of a cross-section (i.e. an unraveled view) of a wireless transmitter or receiver magnet  502  comprised of a plurality of individual magnetic field generating units  508  in an arrangement similar to that found in  FIG. 4  (the rotor is not shown). The magnetization directions  520  between adjacent individual magnetic field generating units  508 , comprising permanent magnets or coils or combinations thereof, within the wireless power transmitter or receiver exhibit angular offsets, α, of about −45° about their corresponding uniform-magnetization directions. The magnetic field generating units  508  may be comprised of permanent magnets such as, but not limited to, NdFeB, samarium cobalt, ferrite, magnetite and alnico magnets made up of combinations of iron, aluminum, nickel, cobalt, titanium and copper and commonly known by trade names such as Alni, Alcomax, Hycomax, Columax, and Ticonal, or combinations thereof. The wireless power transmitter or receiver magnet embodiment  502  depicted in  FIG. 5  may further comprise a rotor. The rotor may comprise a rotary assembly having an axle or the like, allowed to rotate by, for example, a bushing or a bearing. 
         [0052]      FIG. 6  is a cross-sectional view of a wireless power transmitter or receiver magnet  602  according to an example embodiment which may form part of a wireless power system  600  according to an example embodiment. System  600  is substantially similar to system  100  except that the angular offset, α, of the magnetization directions  620  is smaller than in system  100 . In other respects, system  600  exhibits similar or identical features as described above in relation to system  100  and such similar or identical features would be apparent to those skilled in the art upon reading the description and understanding the figures herein. For example, and without limitation, system  600  comprises a plurality of magnetic field generating units  608  (similar to transmitter magnetic field generating units  108 A and receiver magnetic field generating units  108 B). Each magnetic field generating unit  608  may exhibit predominantly a corresponding magnetization direction. The magnetization directions  620  may vary in a magnetization-variation direction  150 . Each of the magnetization directions  620  may be orthogonal to a corresponding uniform-magnetization direction  160 . The magnetization directions  620  may exhibit a spatially periodic pattern having a number, λ, of magnetic field generating units  608  in each period. 
         [0053]    Another Halbach array embodiment may be envisioned as illustrated in  FIG. 6  for use in a wireless power transfer system.  FIG. 6  is a depiction of a cross-section of a wireless transmitter or receiver magnet  602  comprised of a plurality of individual magnetic field generating units  608  in an arrangement similar to that found in  FIG. 4  (the rotor is not shown). The magnetization directions  620  between adjacent individual magnetic field generating units  608  comprised of permanent magnets or coils or combinations thereof within the wireless power transmitter or receiver exhibit angular offsets, α, of about −30° about their corresponding uniform-magnetization directions. The magnetic field generating units  608  may be comprised of permanent magnets such as, but not limited to, NdFeB, samarium cobalt, ferrite, magnetite and alnico magnets made up of combinations of iron, aluminum, nickel, cobalt, titanium and copper and commonly known by trade names such as Alni, Alcomax, Hycomax, Columax, and Ticonal, or combinations thereof. The wireless power transmitter or receiver magnet embodiment  602  depicted in  FIG. 6  may further comprise a rotor. The rotor may comprise a rotary assembly having an axle or the like, allowed to rotate by, for example, a bushing or a bearing. 
         [0054]    In the Halbach array embodiments for wireless power transfer systems described herein, they have been limited to angular offsets, α, of about 30°, 45° and 90° about their corresponding uniform-magnetization directions (i.e. uniform-magnetization directions  160 ). This has been for purposes of description only and should not be considered limitative. In principle there could be an infinite number of angular offsets, α, in magnetization directions from about ±1° to about ±120° but for practical reasons these may be limited. Furthermore, the magnetization directions aren&#39;t required to be vertical or horizontal. It is desired that the magnetization directions “rotate” in different directions for the transmitter and receiver, thereby causing the magnetic field in the gap to become more sinusoidal and hence the induced current in the coil becomes more sinusoidal. 
         [0055]    For magnetically coupled wireless power transfer systems, the transmitter magnet rotor may be driven by a motor and rotated to create a first time-varying magnetic field. This induces rotation in a receiver magnet across a gap to produce a second time-varying magnetic field. The transfer of power across the gap is through magnetic coupling. The second time varying magnetic field induces electrical current in coils around the receiver magnets. An alternative wireless power transfer system that reduces or even eliminates the need for a motor which in turn would lead to a lower cost system with lower maintenance is described below. 
         [0056]      FIG. 7  is a cross-sectional view of a wireless power transfer system  700  comprising individual magnetic field generating units made up of both permanent magnets and stationary coils according to an example embodiment. System  700  is substantially similar to system  100  except that coils  706  and  712  have been added, as described below. In other respects, system  700  exhibits similar or identical features as described above in relation to system  100  and such similar or identical features would be apparent to those skilled in the art upon reading the description and understanding the figures herein. For example, and without limitation, system  700  may comprise a plurality of transmitter magnetic field generating units  708 A and a plurality of receiver magnetic field generating units  708 B (similar to transmitter magnetic field generating units  108 A and receiver magnetic field generating units  108 B). Each transmitter magnetic field generating unit  708 A may exhibit predominantly a corresponding first magnetization direction  720 A and each receiver magnetic field generating unit  708 B may exhibit predominantly a corresponding second magnetization direction  720 B. The first magnetization directions  720 A may vary in a transmitter magnetization-variation direction  150 A and the second magnetization directions  720 B may vary in a receiver magnetization-variation direction  150 B. Each of the first magnetization directions  720 A may be orthogonal to a corresponding transmitter uniform-magnetization direction  160 A and each of the second magnetization directions  720 B may be orthogonal to a corresponding receiver uniform-magnetization direction  160 B. 
         [0057]    The embodiment illustrated in  FIG. 7  is a cross-section of a wireless power transfer system  700  comprises a combination of a plurality of permanent magnets in a Halbach array and stationary coils. The wireless power transfer system comprises a wireless power transmitter  702  that further may comprise a plurality of transmitter magnetic field generating units  708 A aligned in the form of a Halbach transmitter magnet (rotor not shown) where the horizontal and vertical magnetization directions  720 A of the individual transmitter magnetic field generating units  708 A exhibit angular offsets, α, of about −90° about their corresponding uniform-magnetization directions  160 A. Placed below the plurality of transmitter magnetic field generating units  708 A is a plurality of stationary electrical current-carrying coils  706 . An alternating electrical current may be passed through stationary electrical current-carrying coils  706  to induce rotational motion in the transmitter magnetic field generating units  708 A. 
         [0058]    The wireless power transfer system  700  further comprises a wireless power receiver  704  that comprises a plurality of receiver magnetic field generating units  708 B aligned in the form of a Halbach receiver magnet (rotor not shown). The horizontal and vertical magnetization directions  720 B of the individual receiver magnetic field generating units  708 B are offset by an angular offset, α, of about +90° about their corresponding uniform-magnetization directions, or opposite to that found in the Halbach transmitter magnet. The vertical magnetization directions of the Halbach receiver and transmitter magnets are aligned in the same direction while the horizontal magnetization directions of the Halbach transmitter and receiver magnets are in opposite directions. Placed between the plurality of receiver magnetic field generating units  708 B in the Halbach receiver magnet (rotor not shown) of the wireless power receiver and the plurality of transmitter magnetic field generating units  708 A in the Halbach transmitter magnet (rotor not shown) of the wireless power transmitter is a plurality of stationary electrical current-carrying power receiver coils  712  in which an alternating current is induced by the enhanced magnetic field caused by rotation of the receiver and transmitter magnetic arrays around an axis (i.e. axis  170 , not shown). It is preferred that the stationary receiver coils  712  are located in close proximity to the Halbach receiver magnet as the magnetic field is strongest. The wireless power transmitter  702  and wireless power receiver  704  are separated by an air gap  714 . Within the air gap  714  are located the strongest magnetic fields of the Halbach transmitter and receiver magnets. In the regions  716  on the opposite sides of the Halbach transmitter and receiver magnets from the air gap  714  is located the area where the magnetic field is substantially reduced relative to the magnetic fields within the air gap  714 . This Halbach arrangement embodiment substantially reduces stray magnetic fields and enhances the magnetic fields within the air gap  714  in order to enhance the efficiency of the power transmission. 
         [0059]    Other Halbach arrangement embodiments may be envisioned for use in wireless power transfer systems using combinations of permanent magnets and coils as explained herein and illustrated in the non-limiting example in  FIG. 7 . For example, magnetization directions of the individual magnetic field generating units within the Halbach transmitter and receiver magnets may exhibit angular offsets, α, of about −45° to about −30° about their corresponding uniform-magnetization directions as described in  FIGS. 5 and 6 , respectively. Other angular offsets, α, of varying angles may be used from about ±1° to about ±90° or more. The magnetic field generating units  708 A,  708 B may be comprised of permanent magnets such as, but not limited to, NdFeB, samarium cobalt, ferrite, magnetite and alnico magnets made up of combinations of iron, aluminum, nickel, cobalt, titanium and copper and commonly known by trade names such as Alni, Alcomax, Hycomax, Columax, and Ticonal, or combinations thereof. 
         [0060]    In an embodiment, the wireless power transmitter in the wireless power transfer system  700  in  FIG. 7  further comprises a rotor. In another embodiment, the wireless power receiver in the wireless power transfer system  700  in  FIG. 7  further comprises a rotor. In another embodiment, both the wireless power transmitter comprises a rotor and the wireless power receiver comprises a rotor in the wireless power transfer system  700  depicted in  FIG. 7 . The rotor may comprise a rotary assembly having an axle or the like, allowed to rotate by, for example, a bushing or a bearing. 
         [0061]    The wireless power transfer system  700  embodiment shown in  FIG. 7  may be operated as follows. Changing the current in the stationary transmitter coils  706  creates a magnetic field that induces the rotation/movement of the Halbach transmitter magnetic field generating units  708 A which produces a strong first time-varying magnetic field. This first magnetic field couples with the Halbach receiver magnetic field generating units  708 B which rotate/move and produce a second time varying magnetic field that in turn induces a time-varying current in the stationary receiver coils  712  located in the air gap  714  where the magnetic field is the strongest. This results in power being transferred from the wireless power transmitter  702  to the wireless power receiver  704 . 
         [0062]      FIG. 8  is a cross-section of a wireless power transfer system  800  comprising a combination of a plurality of moveable permanent magnets in a Halbach array and stationary coils according to an example embodiment. System  800  is substantially similar to system  100  except that rotating wireless power transmitter  102  has been replaced with a stationary wireless power transmitter  802  (similar to that of  FIG. 2 ). In other respects, system  800  exhibits similar or identical features as described above in relation to system  100  and such similar or identical features would be apparent to those skilled in the art upon reading the description and understanding the figures herein. For example, and without limitation, system  800  may comprise a plurality of transmitter magnetic field generating units  808 A and a plurality of receiver magnetic field generating units  808 B (similar to receiver magnetic field generating units  108 B). Each transmitter magnetic field generating unit  808 A may exhibit predominantly a corresponding first magnetization direction  820 A and each receiver magnetic field generating unit  808 B may exhibit predominantly a corresponding second magnetization direction  820 B. The first magnetization directions  820 A may vary in a transmitter magnetization-variation direction  150 A and the second magnetization directions  820 B may vary in a receiver magnetization-variation direction  150 B. Each of the first magnetization directions  820 A may be orthogonal to a corresponding transmitter uniform-magnetization direction  160 A and each of the second magnetization directions  820 B may be orthogonal to a corresponding receiver uniform-magnetization direction  160 B. 
         [0063]    The wireless power transfer system  800  in  FIG. 8  is comprised of a wireless power transmitter  802  that is further comprised of a plurality of stationary electrical current-carrying coils  804  through which a time-varying current may be passed to create a first time varying magnetic field in a Halbach manner where the resulting horizontal and vertical magnetization directions exhibit angular offsets, α, of about −90° about their corresponding uniform-magnetization directions. The wireless power transfer system  800  further comprises a wireless power receiver  806  that is comprised of a plurality of magnetic field generating units  808 B aligned in the form of a Halbach receiver magnet (rotor not shown) where the horizontal and vertical magnetization directions  820 B of the individual receiver magnetic field generating units  808 B exhibit angular offsets, α, of about +90° about their corresponding uniform-magnetization directions, or opposite to that found in the Halbach transmitter magnet. The vertical magnetization directions of the Halbach receiver magnet and magnetic field generated by the stationary transmitter coils may be aligned in the same direction while the horizontal magnetization directions are in opposite directions. The magnetic field generating units  808 B may be comprised of permanent magnets such as, but not limited to, NdFeB, samarium cobalt, ferrite, magnetite and alnico magnets made up of combinations of iron, aluminum, nickel, cobalt, titanium and copper and commonly known by trade names such as Alni, Alcomax, Hycomax, Columax, and Ticonal, or combinations thereof. 
         [0064]    Placed between the plurality of magnetic field generating units  808 B in the Halbach receiver magnet of the wireless power receiver and the plurality of stationary coils  804  in the Halbach transmitter of the wireless power transmitter  802  is a plurality of stationary power receiver coils  810  where a current is induced. It is preferred that the stationary receiver coils  810  are located close to the magnetic field generating units  808  as the magnetic field is strongest. The wireless power transmitter  802  and wireless power receiver  806  are in close proximity and separated by an air gap  812 . Within the air gap  812  is located the strongest magnetic fields (represented by bold dotted lines) of the Halbach power transmitter  802  and receiver  806 . In the regions  814  on the opposite sides of the power transmitter and receivers from the air gap  812  are located in the area where the magnetic field is substantially reduced relative to the fields within the air gap  812 . This Halbach arrangement embodiment substantially reduces stray magnetic fields and enhances the magnetic fields within the air gap  812  in order to enhance the efficiency of the power transmission. Other Halbach arrangement embodiments may be envisioned to use in wireless power transfer systems using combinations of permanent magnets and coils as explained herein and illustrated in the non-limiting example in  FIG. 8 . For example, magnetization directions  820  of the individual magnetic field generating units within the Halbach transmitter and receiver may exhibit angular offsets, α, of about −45° to about −30° about their corresponding uniform-magnetization directions as described in  FIGS. 5 and 6 , respectively. Other angular offsets, α, of varying angles may be used. In an embodiment, the wireless power receiver further consists of a rotor in the wireless power transfer system  800  depicted in  FIG. 8 . 
         [0065]    The wireless power transfer system  800  embodiment shown in  FIG. 8  may be operated as follows. Applying a current, such as an alternating current, in the stationary electrical current-carrying transmitter coils  804  creates a first time varying magnetic field in a Halbach arrangement where each individual coil has an angular offset, a. This first time varying magnetic field magnetically couples onto the Halbach magnetic field generating units (permanent magnets)  808 B (rotor not shown) in the wireless power transfer receiver  806 . This induces motion/rotation of the magnetic field generating units  808 B. This motion/rotation generates a secondary time-varying magnetic field resulting in electrical current being induced in the coils  810  adjacent to the magnetic field generating units  808 B. 
         [0066]    In another embodiment related to wireless power transfer system  800  in  FIG. 8 , the wireless power transmitter consists of stationary electrical current-carrying coils and a plurality of moveable permanent magnets in a Halbach array and a rotor. The wireless power receiver comprises stationary current-carrying coils only. Applying a current to the stationary coils in the transmitter creates a first time varying magnetic field in a Halbach arrangement which induces motion/rotation of the magnetic field generating units in the transmitter. This motion/rotation generates a secondary time-varying magnetic field resulting in electrical current being induced in the coils in the wireless power receiver. 
         [0067]      FIG. 9  is a cross-section (taken in a plane orthogonal to uniform-magnetization directions  960 A,  960 B) of another embodiment of a wireless power transfer system  900  comprising a combination of a plurality of moveable permanent magnets and stationary coils according to an example embodiment. System  900  comprises a cylindrical transmitter magnet  908 A with an axial transmitter magnetization-variation direction  950 A about which magnets  908 A are rotated. System  900  also comprises a cylindrical receiver magnet  908 B with an axial receiver magnetization-variation direction  950 B about which magnets  908 B are rotated. Rotating magnets  908 A and  908 B may be magnetically coupled. System  900  is similar to system  100  except as described herein. In other respects, system  900  exhibits similar or identical features as described above in relation to system  100  and such similar or identical features would be apparent to those skilled in the art upon reading the description and understanding the figures herein. For example, and without limitation, system  900  may comprise a plurality of transmitter magnetic field generating units  908 A and a plurality of receiver magnetic field generating units  908 B (similar to transmitter magnetic field generating units  108 A and receiver magnetic field generating units  108 B, although different in shape). Each transmitter magnetic field generating unit  908 A may exhibit predominantly a corresponding first magnetization direction  920 A and each receiver magnetic field generating unit  908 B may exhibit predominantly a corresponding second magnetization direction  920 B. The first magnetization directions  920 A may vary in a transmitter magnetization-variation direction  950 A and the second magnetization directions  920 B may vary in a receiver magnetization-variation direction  950 B. Each of the first magnetization directions  920 A may be orthogonal to a corresponding transmitter uniform-magnetization direction  960 A and each of the second magnetization directions  920 B may be orthogonal to a corresponding receiver uniform-magnetization direction  960 B. 
         [0068]    The wireless power transfer system comprises a wireless power transmitter  902  that further may comprise a plurality of transmitter magnetic field generating units  908 A. Magnetic field generating units  908 A comprised of permanent magnets  906  interleaved with stationary electrical current-carrying coils  918 A. The permanent magnets  906  may be comprised of permanent magnets such as, but not limited to, NdFeB, samarium cobalt, ferrite, magnetite and alnico magnets made up of combinations of iron, aluminum, nickel, cobalt, titanium and copper and commonly known by trade names such as Alni, Alcomax, Hycomax, Columax, and Ticonal, or combinations thereof. 
         [0069]    The permanent magnets  906  may be in a cylindrical shape (with an axis parallel to magnetic variation direction  950 A) interconnected by a common shaft (not shown) that passes through the stationary coils  918 A. The permanent magnets  906  may rotate about the magnetization-variation direction  950 A and are further surrounded by coils  940 . Magnet rotation is induced by application of a current in the coils  940  surrounding the permanent magnets  906 . The wireless power transfer system  900  further comprises a wireless power receiver  912  that further comprises a plurality of receiver magnetic field generating units  908 B comprised of permanent magnets  916  interleaved with stationary coils  918 B. The permanent magnets  916  may be in a cylindrical shape interconnected by a common shaft (not shown) that passes through the stationary electrical current-carrying coils  918 B. The magnets may rotate about magnetization-variation direction  950 B and are further surrounded by coils  930 . The wireless power transmitter  902  and receiver  912  are further separated by an air gap  922 . 
         [0070]    In the example in  FIG. 9 , the magnetization directions of the plurality of magnetic field generating units  908 A of the wireless power transmitter  902  exhibit angular offsets, α, of about −90° about their corresponding uniform-magnetization directions  960 . The magnetization directions  920  of the magnetic field generating units  908 B of the wireless power receiver  912  exhibit angular offsets, α, of about +90° about their corresponding uniform-magnetization directions. Other angular offsets, α, of magnetization directions of various angles may be used. The permanent magnets  916  may be comprised of permanent magnets such as, but not limited to, NdFeB, samarium cobalt, ferrite, magnetite and alnico magnets made up of combinations of iron, aluminum, nickel, cobalt, titanium and copper and commonly known by trade names such as Alni, Alcomax, Hycomax, Columax, and Ticonal, or combinations thereof. 
         [0071]    In an embodiment, the wireless power transmitter in the wireless power transfer system  900  in  FIG. 9  further comprises a rotor. In another embodiment, the wireless power receiver in the wireless power transfer system  900  in  FIG. 9  further comprises a rotor. In another embodiment, both the wireless power transmitter comprises a rotor and the wireless power receiver comprises a rotor in the wireless power transfer system  900  depicted in  FIG. 9 . The rotor may comprise a rotary assembly having an axle or the like parallel with magnetization-variation directions  950 A,  950 B, allowed to rotate by, for example, a bushing or a bearing. 
         [0072]    The wireless power transfer system  900  embodiment shown in  FIG. 9  may be operated as follows. The stationary coils  918 A and  940  in the wireless power transmitter  902  are energized by alternating current to produce a time varying magnetic field that rotates the permanent magnets  906  connected by a common shaft on an axis parallel to magnetization-variation direction  950 B. The coils  918 A and  940  are interconnected and electrical current through the adjacent coils  918 A will flow in a way to maintain a Halbach magnetic field with magnetic flux directed towards the wireless power receiver as much as possible. This forms the first time-varying magnetic field with magnetic field focused towards the receiver  912 . The permanent magnets  916  linked by a common shaft in a direction parallel to magnetization-variation direction  950 A with interleaved coils  918 B on an axis parallel to magnetization-variation direction  950 A in the wireless power receiver  912  rotates through magnetic coupling with the first time-varying magnetic field. This motion generates a second time-varying magnetic field which induces electrical current through the coils  930  around the permanent magnets  916 . These coils  930  are connected to the adjacent (interleaved) coils  918 B, which produces a third time-varying magnetic field that cancels and reinforces the second time-varying magnetic field such that a second Halbach magnetic field is formed at the receiver. The magnetic flux is focused towards the wireless power transmitter with the highest magnetic fields within the air gap  922 . In the regions  924  on the opposite sides of the power transmitter and receivers from the air gap  922  are located in the area where the magnetic field is substantially reduced relative to the fields within the air gap  922 . This Halbach arrangement may substantially reduce stray magnetic fields and enhances the magnetic fields within the air gap  922  in order to enhance the efficiency of the power transmission. 
         [0073]    The invention described herein may be used in wireless power transmission systems based on the Faraday effect and Halbach arrays to increase the efficiency of the power transmission and make safer for consumers by reducing stray magnetic fields. Said wireless power transmission systems may be used in applications such as, but not limited to, boats, automobiles, trucks, delivery vehicles, transit buses, ships, aircraft, motorcycles, electric bicycles, consumer devices and medical implants and other devices. A further advantage of the invention described may be the reduction in cost and in weight by eliminating the need for soft-iron cores in the coils. Lastly, the systems described herein may be scalable to more magnets and/or coils to produce different power ranges. 
         [0074]    As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the spirit or scope thereof. For example:
       Various embodiments described herein (e.g. systems  100 ,  200 ,  300 , etc.) may each include a variety of features. It should be understood that this description and the accompanying claims include additional embodiments that comprise combinations of any of the features of any of the embodiments herein.   In some instances, this description and the accompanying claims use terms generally to describe directions, orientations, shapes, relationships (e.g. equalities) and/or the like. For example, transmitter magnetic field generating unit may have a first magnetization direction that is orthogonal to a transmitter magnetization-variation direction. Such directions, orientations, shapes, relationships and/or the like should be considered to accommodate the specified directions, orientations, shapes, relationships and/or the like and/or relatively small deviations (from an operational or engineering perspective) from the specified directions, orientations, shapes, relationships and/or the like.   In some instances, this description and the accompanying claims refer to transmitter magnetic field generating units using the reference numerals  108 A,  208 A,  308 A etc. and to receiver magnetic field generating units using the reference numerals  108 B,  208 B,  308 B etc. It should be understood from this description that magnetic field generating units  408 ,  508 ,  608  and like reference numerals may refer to transmitter magnetic field generating units or receiver generating units generally. Similarly, magnetization-variation directions  150  and like reference numerals may refer to transmitter magnetization-variation directions or receiver magnetization-variation directions. Similarly, this naming principle may apply to magnetization directions (e.g. magnetization directions  420 ,  520 ,  620  and like reference numerals), uniform-magnetization directions (e.g. uniform-magnetization directions  160  and like reference numerals) and generally herein.   In some instances, this description may refer to horizontal and vertical magnetization directions in the figures. This is done for convenience. It should be understood that a horizontal magnetization direction is any magnetization direction that, when broken down into horizontal (in the page) and vertical (in the page) components, exhibits a horizontal component of magnitude greater than zero and vertical magnetization directions are magnetization directions that are substantially vertical (in the page).   In some instances, this description and the accompanying claims refer to the horizontal and vertical directions. This is done for convenience and refers merely to the horizontal and vertical directions in  FIGS. 1 to 9 . It should be understood that entire systems (e.g. systems  100 ,  200 ,  300  etc.) may be rotated such that what is horizontal or vertical in the figures is no longer horizontal or vertical in practice.   In some instances, this description and the accompanying claims refer to receiver magnetic field generating units. Where the receiver field generating units comprise coils, this reference is a matter of nomenclature and doesn&#39;t necessarily mean that the receiver magnetic field generating units are driven to generate corresponding magnetic fields. In practice, the receiver magnetic field generating units may instead have currents induced therein, which induced currents may in turn create corresponding magnetic fields.       
 
         [0081]    While a number of exemplary aspects and embodiments have been discussed above, those of skill in the art will recognize certain modifications, permutations, additions and sub-combinations thereof. It is therefore intended that the following appended aspects or claims and aspects or claims hereafter introduced are interpreted to include all such modifications, permutations, additions and sub-combinations.