Patent Publication Number: US-9906108-B2

Title: Sensorless electric machine

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This Continuation-In-Part (C.I.P.) application claims the benefit of the Nov. 1, 2012 filing of U.S. application Ser. No. 13/666,283 (Entitled: SENSORLESS ELECTRIC MACHINE). The aforementioned application is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to electric machines and more particularly to a sensorless electric machine, a component thereof, vehicles that employ the component and electric machine, and methods of making and operating the same. 
     With an electric machine, be it an interior permanent magnet (IPM) machine, permanent magnet (PM) assisted synchronous reluctance machine (SRM), or an SRM, position is a critical informational element for torque control at and near zero excitation frequency. Typically, an encoder, tachometer, or resolver is used with electric machines as the position sensor. 
     However, the position sensor (e.g., encoder) along with its cabling and interface electronics contributes a significant portion of the motor drive system cost and overall complexity and is often a major reliability concern. Since the advent of the high frequency injection method for zero frequency encoderless control, encoderless controls have seen great improvements but none have found success in recovering the full, or near full, torque capability of the machine. This is due to loss of small signal saliency at high-load levels for the machine. 
     Accordingly, there is an ongoing need for improvement of current electric machine technologies that address complexity, cost, efficiency, and/or performance. 
     BRIEF DESCRIPTION 
     The present invention overcomes at least some of the aforementioned drawbacks by providing improvements that allow electric machines, such as IPM motors to operate with full torque control without the need for any positions sensor (e.g., encoder). More specifically, the present invention is directed to a machine component and a machine that, when employing the component, is able to operate as a sensorless electric machine. A vehicle that uses one or more electric machines and methods of making and operating such an electric machine is/are also disclosed. 
     Therefore, in accordance with one aspect of the invention, a rotor component comprises a rotor circuit configured for use with one of an interior permanent magnet (IPM) machine and a synchronous reluctance machine (SRM), the rotor circuit comprising: at least one pole circuit, wherein the at least one pole circuit are made of a conductive, non-magnetic material. 
     In accordance with another aspect of the invention, an electric machine comprises a rotor core comprising magnetic steel; a stator configured with a plurality of stationary windings therein; a plurality of openings disposed within or on the rotor core; and a rotor circuit configured to introduce saliency based on an orientation of a portion of the rotor circuit in relationship to a pole location of the electric machine, said rotor circuit made of a conductive, non-magnetic material. 
     In accordance with another aspect of the invention, an electric machine comprises: a rotor core; a stator configured with a plurality of stationary windings therein; a plurality of openings disposed within the rotor core; and a rotor circuit structure comprising at least one pole circuit disposed in a predetermined location, wherein said predetermined location is in range that extends from about a q-axis to about a d-axis of the electric machine. 
     In accordance with another aspect of the invention, an electric machine comprising: a rotor core; a stator configured with a plurality of stationary windings therein; a plurality of openings disposed within the rotor core; a rotatable shaft therethrough; and a rotor circuit structure comprising at least one loop or ring of a conductive, non-magnetic material, wherein said at least one loop or ring is substantially concentric about a d-axis of the electric machine. 
     In accordance with another aspect of the invention, an interior permanent magnet (IPM) machine comprises a means for converting electrical energy to rotational energy; and a means for providing increased magnetic saliency at high frequency excitation. 
     Various other features and advantages of the present invention will be made apparent from the following detailed description and the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: 
         FIG. 1  is a perspective view of a rotor circuit structure component according to an embodiment of the present invention. 
         FIG. 2  is a perspective view of rotor core of an electric machine incorporating a rotor circuit structure component according to an embodiment of the present invention. 
         FIG. 3A  is a top view of a portion of a rotor lamination and rotor circuit structure component according to an embodiment of the present invention. 
         FIG. 3B  is a schematic perspective diagram of the rotor circuit structure component in  FIG. 3A  according to an embodiment of the present invention. 
         FIG. 4A  is a top view of a portion of a rotor lamination and rotor circuit structure component according to another embodiment of the present invention. 
         FIG. 4B  is a schematic perspective diagram of the rotor circuit structure component in  FIG. 4A  according to an embodiment of the present invention. 
         FIG. 5A  is a top view of a portion of a rotor lamination and rotor circuit structure component according to another embodiment of the present invention. 
         FIG. 5B  is a schematic perspective diagram of the rotor circuit structure component in  FIG. 5A  according to an embodiment of the present invention. 
         FIG. 6A  is a top view of a portion of a rotor lamination and rotor circuit structure component according to another embodiment of the present invention. 
         FIG. 6B  is a schematic perspective diagram of the rotor circuit structure component in  FIG. 6A  according to an embodiment of the present invention. 
         FIG. 7A  is a top view of a portion of a rotor lamination and rotor circuit structure component according to another embodiment of the present invention. 
         FIG. 7B  is a schematic perspective diagram of the rotor circuit structure component in  FIG. 7A  according to an embodiment of the present invention. 
         FIG. 8A  is a top view of a portion of a rotor lamination and rotor circuit structure component according to another embodiment of the present invention. 
         FIG. 8B  is a schematic perspective diagram of the rotor circuit structure component in  FIG. 8A  according to an embodiment of the present invention. 
         FIG. 9A  is a top view of a portion of a rotor lamination and rotor circuit structure component according to another embodiment of the present invention. 
         FIG. 9B  is a schematic perspective diagram of the rotor circuit structure component in  FIG. 9A  according to an embodiment of the present invention. 
         FIGS. 10A, 10B, and 10C  are schematic diagrams showing perspective views of a rotor circuit structure component according to embodiments of the present invention. 
         FIG. 11  is a schematic diagram of a top view of a portion of a rotor circuit structure component according to an embodiment of the present invention. 
         FIG. 12A  is a schematic diagram of a top view of a portion of a rotor circuit structure component according to an embodiment of the present invention. 
         FIG. 12B  is top view of a portion of a rotor lamination and the rotor circuit structure component of  FIG. 12A  according to another embodiment of the present invention. 
         FIG. 13  is a schematic diagram of a top view of a portion of a rotor circuit structure component according to an embodiment of the present invention. 
         FIG. 14A  is a schematic diagram of a top view of a portion of a rotor circuit structure component according to an embodiment of the present invention. 
         FIG. 14B  is top view of a portion of a rotor lamination and the rotor circuit structure component of  FIG. 14A  according to another embodiment of the present invention. 
         FIG. 15  is top view of a portion of a rotor lamination and the rotor circuit structure component according to another embodiment of the present invention. 
         FIG. 16  is top view of a portion of a rotor lamination and the rotor circuit structure component according to another embodiment of the present invention. 
         FIG. 17A  is schematic diagram showing a perspective view of a partial installation of a portion of a rotor circuit structure component in a rotor portion of a machine according to an embodiment of the present invention. 
         FIG. 17B  is schematic diagram showing a perspective view of a completed installation embodiment shown in  FIG. 17A . 
         FIG. 18  is schematic diagram showing a perspective view of a completed installation of a portion of a rotor circuit structure component in a rotor portion of a machine according to another embodiment of the present invention. 
         FIG. 19  is schematic diagram showing a perspective view of a completed installation of a portion of a rotor circuit structure component in a rotor portion of a machine according to another embodiment of the present invention. 
         FIG. 20  is a schematic diagram showing a perspective view of a rotor circuit structure component according to another embodiment of the present invention. 
         FIG. 21  is a graph illustrating small signal saliency for electric machine of the related art. 
         FIG. 22  is a graph illustrating small signal saliency for an electric machine with a rotor circuit structure, according to an embodiment of the present invention. 
         FIG. 23  is a graph illustrating small signal saliency angle for electric machine of the related art. 
         FIG. 24  is a graph illustrating small signal saliency angle for an electric machine with a rotor circuit structure, according to an embodiment of the present invention. 
         FIG. 25  is a schematic graph comparing motor speed and torque for a related art machine (without a rotor structure) and a machine with a rotor circuit structure, according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Unless defined otherwise, technical and scientific terms used herein have the same meaning as is commonly understood by one of ordinary skill in the art with respect to the presently disclosed subject matter. The terms “first”, “second”, and the like, as used herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The terms “a”, “an”, and “the” do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item, and the terms “front”, “back”, “bottom”, and/or “top”, unless otherwise noted, are used for convenience of description only, and are not limited to any one position or spatial orientation. 
     If ranges are disclosed, the endpoints of all ranges directed to the same component or property are inclusive and independently combinable (e.g., ranges of “up to about 25 wt. %,” is inclusive of the endpoints and all intermediate values of the ranges of “about 5 wt. % to about 25 wt. %,” etc.). The modified “about” used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., includes the degree of error associated with measurement of the particular quantity). Accordingly, the value modified by the term “about” is not necessarily limited only to the precise value specified. 
     As used herein, the term “Pole Circuit” means one or more circuits that is affiliated with one pole of the electric machine. The one or more circuits may comprise one ring/loop, multiple rings/loops, one loop/ring of a cage, or one loop/ring of a cage with one or more inner rings/loops. The cage may be a shifted or non-shifted cage. Rings/loops may be shifted or non-shifted. 
     As used herein, the term “Shifted Cage” means one or more connected rings or loops wherein a rotor conductor (or if more than one rotor conductor are adjacent, then a midpoint between the plurality of adjacent rotor conductors) is not aligned with a q-axis of the machine, but instead is shifted by a distance from the q-axis. Contrastingly, a cage that is not shifted has a rotor conductor (or if more than one rotor conductor are adjacent, then a midpoint between the plurality of adjacent rotor conductors) that is aligned with the q-axis of the machine. Alternatively stated, a midpoint of the loop of a pole circuit (or loops in the embodiments having multiple loops in a single pole circuit) does not align with the d-axis in a shifted cage embodiment. 
     As used herein, the terms “D-axis”, “d-axis”, or “direct axis” of the rotor means the axis that is aligned with the center of the magnetic pole of the rotor. 
     As used herein, the terms “Q-axis”, “q-axis”, or “quadrature axis” of the rotor means the axis that is aligned with the mid-point of the two magnetic poles of the rotor. 
     Aspects of the present invention have been shown to offer advantages over previous electric machine constructs. Aspects of the present invention provide design features for an electric machine (e.g., IPM motor) that enables full torque control without the use of any position sensor. An aspect of the present invention includes the use of a component, termed herein a special rotor structure that introduces magnetic saliency for high frequency excitation, wherein this high frequency excitation can be used for sensorless (e.g., encoderless) motor control. The rotor structure introduces electrical circuits (shorted circuit, closed circuit with passive or active elements) to specific orientation of the rotor so that it couples with the stator winding magnetically. The position of the rotor is measured by applying high frequency carrier voltage to the stator and by indirectly measuring the current of the rotor, by measuring the (reflected) high frequency carrier current response in the stator. If the rotor circuit is aligned in phase with the high frequency injection the impedance of the motor is reduced. This variation of impedance is used to track rotor position. As a result, small signal saliency up to necessary loading level is introduced and maintained without impact on electric machine performance, efficiency, and reliability. 
     Under aspects of the present invention, the motors have q-axis inductance, L q , and a d-axis inductance, L d . Saliency is defined as L q /L d . Aspects of the present invention have been shown to lower L d , thereby effectively increasing saliency. Further, in certain embodiments having multiple rings with different pitch per pole circuit (see e.g.,  FIGS. 12A, 12B, 14A, 14B, 15 ) will further reduce the inductance and increase the saliency even further than single loop embodiments. An additional benefit of the multiple ring embodiments is even if one ring breaks open, the remaining rings will support the increase of saliency. 
     Referring to  FIG. 1  a rotor circuit or electrical component  10  incorporating aspects of the present invention is shown. The component  10  may comprise one or more rotor conductors (e.g., rotor bars  14 ) connected to one or more connection elements  16 . As shown, the rotor bars  14  are substantially longitudinal in configuration. As will be discussed herein the component  10  and the rotor bars  14  and connection elements  16  are configured so as to substantially surround permanent magnets  40  located in an electric machine  100  ( FIG. 2 ). In this manner two or more rotor bars  14  are connected to two or more connection elements  16  such that they define a loop or ring  12 . While the embodiment in  FIG. 1  clearly shows a quantity of four rings  12  each ring  12  comprising two rotor bars  14  and two connection elements  16 , other quantities and configurations of elements of the component  10  are suitable without departing from the present invention. For example, the component  10  may comprise four rotor bars  14  and a plurality of connection elements  16  are either end of the component  10 , thereby defining a cage  13 . Similarly, in another embodiment, the component  10  may comprise a plurality of loops or rings  12 , wherein each ring  12  comprises four rotor bars  14  and two connection elements  16 . In still other embodiments, the ring(s)  12  and/or cage  13  may comprise virtually any quantity of conductors and/or connection elements. 
     The embodiment shown in  FIG. 1  is a non-shifted configuration having four pole circuits  200 , wherein each pole circuit comprises a loop  12 , wherein each loop  12  comprises two connection elements  16  and two rotor bars  14 . 
     Magnets are shown and described throughout portions of this document. It should be noted that while rectangular magnets  40  are often depicted in the figures, other shapes of magnets are available without departing from the invention. For example and not by limitation, the magnets  40  may be trapezoidal, curved, or other shapes, or combination of shapes to suitably fit within the openings  22  of the stack of laminations  10 . 
     The rotor bars  14  and connection elements  16  may be made of any suitable conductive, non-magnetic material, or combinations thereof. By example but not limitation, the rotor bars  14  and connection elements  16  may be castings made of aluminum, copper, alloys of copper or aluminum, or other suitable material or combination of materials. 
     It should be noted that although several of the embodiments discussed herein discuss the use of rotor bars, other conductive elements may be used in the component  10  without departing from the invention. For example, any suitable rotor conductor may be substituted in lieu of the rotor bars  14  that are discussed herein for the various embodiments. Other conductive elements for use in lieu of the rotor bars  14  and/or the connection elements  16  include, but are not limited to, one or more of multistranded bars, multi-stranded wire, litz wire, and combinations thereof. 
     Similarly, the rotor bar  14  has a cross-sectional shape that is suitable to address design factors including skin effect, cooling surface, structural strength, EM fitness, and the like. Suitable shapes for the cross-section of the rotor bar include a circle, square, rectangle, and the like. 
     The end perspective view of another embodiment of the component  10  located in rotor portion of a motor  100  is shown in  FIG. 2 . The motor  100  includes a plurality of rotor core laminations  20  stacked so as to form a rotor core  90 . As shown, in the end view where a cover plate is omitted for illustrative purposes only so as to allow a first rotor core lamination  20  to be viewed. The rotor core lamination  20  includes a plurality of openings  22 . Permanent magnets  40  may be located within the plurality of openings  22 . For illustrative purposes only the permanent magnets  40  are shown disposed in only one set (e.g., at one pole) of openings  22 . The other three sets of openings  22  (i.e., four-pole machine) are shown without permanent magnets  40  therein. At the center of the rotor core lamination  20  is a shaft opening  94  configured to receive a rotatable shaft (not shown). As depicted, the component  10  is similar to the embodiment shown in  FIG. 1  and comprises a quantity of four rings or loops  12 , each comprising two rotor bars  14  connected to two connection elements  16 . In this manner, two of the rotor bars  14  and the two connection elements  16  are interconnected so as to form a rotor ring or loop  12 . Four rotor rings or loops  12  are formed as part of the component  10  in this manner so as to match the quantity of poles (i.e., four) in the embodiment of the motor shown  100 . The stator surrounding the rotor core  90  is omitted for illustrative purposes only. 
     Referring respectively to  FIGS. 3A and 3B , a top view of a portion of a rotor lamination  20  portion of an electric machine  100  with a component  10  and the corresponding schematic diagram of a perspective view of the component  10  from  FIG. 3A  are shown respectively.  FIG. 3A  depicts a rotor lamination  20  of a single layer, four-pole IPM  100  having straight permanent magnets  40  therein.  FIG. 3B  depicts a rotor component  10  that may be termed a four-loop configuration. As shown, the rotor lamination  20  includes a plurality of openings  22  that, depending on the particular embodiment, may have disposed therein one or more permanent magnets  40 . Once the permanent magnets  40  are disposed within the openings  22  there typically remains adjacent to either end of the permanent magnets  40  an opening, or remaining opening,  24 . For illustrative purposes only, the stator and/or stator windings are not shown that substantially surround the rotor component. 
     The plurality of rotor bars  14  are disposed in the plurality of openings  24  longitudinally through the stack of rotor laminations  20 . At or near either end of the stack of rotor laminations  20  are connection elements  16  that are connected to both ends of the rotor bars  14 . In this manner, the component  10  embodiment in  FIG. 3B  has four rotor loops  12  each constructed of two rotor bars  14  and two connection elements  16 , thereby matching the quantity of poles (i.e., four) for the particular machine  100 . As depicted there are four pole circuits  200  in the embodiment. As the center (or midpoint) of the four loops  12  align with the d-axis, this is a non-shifted embodiment. As shown, the plurality of rotor bars  14  is co-located in the plurality of openings  22  with the plurality of magnets  40 . By placing the plurality of rotor bars  14  in the unused cavity  24  portion of the openings  22 , the pole circuit  200  can be implemented without compromising the electromagnetic performance of the motor  100 . 
     Referring respectively to  FIGS. 4A and 4B , a top view of a portion of a rotor lamination  20  portion of an electric machine  100  with a component  10  and the corresponding schematic diagram of a perspective view of the component  10  from  FIG. 4A  are shown respectively.  FIG. 4A  depicts a rotor lamination  20  of a single layer, four-pole IPM  100  having straight permanent magnets  40  therein.  FIG. 4B  depicts a rotor component  10  that may be termed a four-loop, shifted-ring configuration. As shown and known in the art, the rotor lamination  20  includes a plurality of openings  22  that, depending on the particular embodiment, may have disposed therein one or more permanent magnets  40 . Once the permanent magnets  40  are disposed within the openings  22  there typically remains adjacent to either end of the permanent magnets  40  an opening, or remaining opening,  24 . For illustrative purposes only, the stator and/or stator windings are not shown that substantially surround the rotor component. 
     The plurality of rotor bars  14  are disposed in some of the plurality of openings  24  longitudinally through the stack of rotor laminations  20 . In this embodiment two adjacent rotor bars  14  are co-located in a single opening  24  while the opening  24  at the other end of the magnet  40  is left unfilled. At or near either end of the stack of rotor laminations  20  are connection elements  16  that are connected to both ends of the rotor bars  14 . In this manner, the component  10  embodiment in  FIG. 4B  has four rotor loops  12  each constructed of two rotor bars  14  and two connection elements  16 , thereby matching the quantity of poles (i.e., four) for the particular machine  100 . By co-locating the two rotor bars  14  from adjacent poles, the four loops  12  are effectively connected to each other, thereby forming shifted rings  13 . As depicted there are four pole circuits  200  in the embodiment. As the center (or midpoint) of the four loops  12  do not align with the d-axis, this is a shifted cage embodiment. As shown, the plurality of rotor bars  14  is co-located in the plurality of openings  22  with the plurality of magnets  40 . By placing the plurality of rotor bars  14  in the unused cavity  24  portion of the openings  22 , the pole circuit  200  can be implemented without compromising the electromagnetic performance of the motor  100 . 
     Referring respectively to  FIGS. 5A and 5B , a top view of a portion of a rotor lamination  20  portion of an electric machine  100  with a component  10  and the corresponding schematic diagram of a perspective view of the component  10  from  FIG. 5A  are shown respectively.  FIG. 5A  depicts a rotor lamination  20  of a single layer, four-pole IPM  100  having straight permanent magnets  40  therein.  FIG. 5B  depicts a rotor component  10  that may be termed a four-loop, shifted-cage configuration, similar to the embodiment shown in  FIGS. 4A and 4B . As shown and known in the art, the rotor lamination  20  includes a plurality of openings  22  that, depending on the particular embodiment, may have disposed therein one or more permanent magnets  40 . Once the permanent magnets  40  are disposed within the openings  22  there typically remains adjacent to either end of the permanent magnets  40  an opening, or remaining opening,  24 . For illustrative purposes only, the stator and/or stator windings are not shown that substantially surround the rotor component. 
     The plurality of rotor bars  14  are disposed in some of the plurality of openings  24  longitudinally through the stack of rotor laminations  20 . In this embodiment instead of co-locating two adjacent rotor bars  14  in a single opening  24  (as done in  FIG. 4A ), the two adjacent rotor bars  14  are combined (or “shared”) into a single rotor bar  14 . Again, the opening  24  at the other end of the magnet  40  is left unfilled. At or near either end of the stack of rotor laminations  20  are connection elements  16  that are connected to both ends of the rotor bars  14 . In this manner, the component  10  embodiment in  FIG. 5B  has four rotor loops  12  each constructed of two rotor bars  14  and two connection elements  16 , thereby matching the quantity of poles (i.e., four) for the particular machine  100 . However, the quantity of total rotor bars  14  is less due to the effective “sharing” of rotor bars  14  from the adjacent loops  12  (and poles). The component  10  has eight connection elements  16  but four rotor bars  14  for use in a four pole machine  100 . By cross connecting adjacent loops  12  with the connection elements  16  from adjacent poles, the four loops  12  are effectively connected to each other, thereby forming a cage, or shifted cage  13 . As depicted there are four pole circuits  200  in the embodiment. As the center (or midpoint) of the four loops  12  do not align with the d-axis, this is a shifted cage embodiment. As shown, the plurality of rotor bars  14  is co-located in the plurality of openings  22  with the plurality of magnets  40 . By placing the plurality of rotor bars  14  in the unused cavity  24  portion of the openings  22 , the pole circuit  200  can be implemented without compromising the electromagnetic performance of the motor  100 . 
     Referring respectively to  FIGS. 6A and 6B , a top view of a portion of a rotor lamination  20  portion of an electric machine  100  with a component  10  and the corresponding schematic diagram of a perspective view of the component  10  from  FIG. 6A  are shown respectively.  FIG. 6A  depicts a rotor lamination  20  of a spoke-type, four-pole IPM  100  having straight permanent magnets  40  therein.  FIG. 6B  depicts a rotor component  10  that may be termed a four-loop configuration. As shown and known in the art, the rotor lamination  20  includes a plurality of openings  22  that, depending on the particular embodiment, may have disposed therein one or more permanent magnets  40 . Once the permanent magnets  40  are disposed within the openings  22  there typically remains adjacent to either end of the permanent magnets  40  an opening, or remaining opening,  24 . For illustrative purposes only, the stator and/or stator windings are not shown that substantially surround the rotor component. 
     The plurality of rotor bars  14  are disposed in the plurality of outboard openings  24  longitudinally through the stack of rotor laminations  20 . At or near either end of the stack of rotor laminations  20  are connection elements  16  that are connected to both ends of the rotor bars  14 . In this manner, the component  10  embodiment in  FIG. 6B  has four rotor loops  12  each constructed of two rotor bars  14  and two connection elements  16 , thereby matching the quantity of poles (i.e., four) for the particular machine  100 . As depicted there are four pole circuits  200  in the embodiment. As the center (or midpoint) of the four loops  12  align with the d-axis, this is a non-shifted embodiment. As shown, the plurality of rotor bars  14  is co-located in the plurality of openings  22  with the plurality of magnets  40 . By placing the plurality of rotor bars  14  in the unused cavity  24  portion of the openings  22 , the pole circuit  200  can be implemented without compromising the electromagnetic performance of the motor  100 . 
     Referring respectively to  FIGS. 7A and 7B , a top view of a portion of a rotor lamination  20  portion of an electric machine  100  with a component  10  and the corresponding schematic diagram of a perspective view of the component  10  from  FIG. 7A  are shown respectively.  FIG. 7A  depicts a rotor lamination  20  of a spoke-type, four-pole IPM  100  having straight permanent magnets  40  therein.  FIG. 7B  depicts a rotor component  10  that may be termed a four-loop, rotor cage configuration, similar in aspects to the embodiment shown in  FIGS. 6A and 6B . As shown and known in the art, the rotor lamination  20  includes a plurality of openings  22  that, depending on the particular embodiment, may have disposed therein one or more permanent magnets  40 . Once the permanent magnets  40  are disposed within the openings  22  there typically remains adjacent to either end of the permanent magnets  40  an opening, or remaining opening,  24 . For illustrative purposes only, the stator and/or stator windings are not shown that substantially surround the rotor component. 
     The plurality of rotor bars  14  are disposed in the outboard plurality of openings  24  longitudinally through the stack of rotor laminations  20 . In this embodiment instead of co-locating two adjacent rotor bars  14  in a single opening  24  (as done in  FIG. 6A ), the two adjacent rotor bars  14  are combined into a single rotor bar  14 . At or near either end of the stack of rotor laminations  20  are connection elements  16  that are connected to both ends of the rotor bars  14 . In this manner, the component  10  embodiment in  FIG. 7B  has four rotor loops  12  each constructed of two rotor bars  14  and two connection elements  16 , thereby matching the quantity of poles (i.e., four) for the particular machine  100 . However, the quantity of total rotor bars  14  is less due to the effective sharing of rotor bars  14  from the adjacent loops  12  (and poles). The component  10  thus comprises eight connection elements  16  but four rotor bars  14  total for use in a four pole machine  100 . By cross connecting adjacent loops  12  with the connection elements  16  from adjacent poles, the four loops  12  are effectively connected to each other, thereby forming a cage  13 . As depicted there are four pole circuits  200  in the embodiment. As the center (or midpoint) of the four loops  12  align with the d-axis, this is a non-shifted cage embodiment. As shown, the plurality of rotor bars  14  is co-located in the plurality of openings  22  with the plurality of magnets  40 . By placing the plurality of rotor bars  14  in the unused cavity  24  portion of the openings  22 , the pole circuit  200  can be implemented without compromising the electromagnetic performance of the motor  100 . 
     Referring respectively to  FIGS. 8A and 8B , a top view of a portion of a rotor lamination  20  portion of an electric machine  100  with a component  10  and the corresponding schematic diagram of a perspective view of the component  10  from  FIG. 8A  are shown respectively.  FIG. 8A  depicts a rotor lamination  20  of a multi-layer, four-pole IPM  100  having straight permanent magnets  40  therein.  FIG. 8B  depicts a rotor component  10  that may be termed a four-loop configuration. As shown and known in the art, the rotor lamination  20  includes a plurality of openings  22  that, depending on the particular embodiment, may have disposed therein one or more permanent magnets  40 . Once the permanent magnets  40  are disposed within the openings  22  there typically remains adjacent to either end of the permanent magnets  40  an opening, or remaining opening,  24 . For illustrative purposes only, the stator and/or stator windings are not shown that substantially surround the rotor component. As with multi-layer IPM, there is typically a plurality of rows of openings  22  and permanent magnets  40  therein located for each pole. 
     The plurality of rotor bars  14  are disposed in the plurality of openings  24  longitudinally through the stack of rotor laminations  20 . At or near either end of the stack of rotor laminations  20  are connection elements  16  that are connected to both ends of the rotor bars  14 . In this manner, the component  10  embodiment in  FIG. 8B  has four rotor loops  12  each constructed of two rotor bars  14  and two connection elements  16 , thereby matching the quantity of poles (i.e., four) for the particular machine  100 . In this particular embodiment, the rotor bars  14  are located in the furthest inboard openings  24  of the multi-layer rotor lamination  20 . It should be apparent, that the rotor bars could be located in other openings  24  of the lamination  20 . As depicted there are four pole circuits  200  in the embodiment. As the center (or midpoint) of the four loops  12  align with the d-axis, this is a non-shifted embodiment. As shown, the plurality of rotor bars  14  is co-located in the plurality of openings  22  with the plurality of magnets  40 . By placing the plurality of rotor bars  14  in the unused cavity  24  portion of the openings  22 , the pole circuit  200  can be implemented without compromising the electromagnetic performance of the motor  100 . 
     Referring respectively to  FIGS. 9A and 9B , a top view of (an entire) portion of a rotor lamination  20  portion of an electric machine  100  with a component  10  and to the corresponding schematic diagram of a perspective view of the component  10  from  FIG. 9A  are shown respectively.  FIG. 9A  depicts a rotor lamination  20  of a multi-layer, four-pole IPM  100  having straight permanent magnets  40  therein.  FIG. 9B  depicts a rotor component  10  that may be termed a four-loop, cage or shifted-cage configuration. As shown and known in the art, the rotor lamination  20  includes a plurality of openings  22  that, depending on the particular embodiment, may have disposed therein one or more permanent magnets  40 . Once the permanent magnets  40  are disposed within the openings  22  there typically remains adjacent to either end of the permanent magnets  40  an opening, or remaining opening,  24 . For illustrative purposes only, the stator and/or stator windings are not shown that substantially surround the rotor component. As with multi-layer IPM, there is typically a plurality of rows of openings  22  and permanent magnets  40  therein located for each pole. 
     The plurality of rotor bars  14  are disposed in the plurality of openings  24  longitudinally through the stack of rotor laminations  20 . In this configuration only a single rotor bar  14  is placed in an opening  24  in each pole (See  FIG. 9A ). At or near either end of the stack of rotor laminations  20  are connection elements  16  that are connected to both ends of the rotor bars  14 . The connection element  16  connects a rotor bar  14  from a first pole to the rotor bar  14  of an adjacent pole, thereby shifting the element  10 . In this manner, the component  10  embodiment in  FIG. 9B  has four rotor loops  12  each constructed of two rotor bars  14  and two connection elements  16 , thereby matching the quantity of poles (i.e., four) for the particular machine  100 . However, due to the shifted-cage configuration of the embodiment, only four rotor bars  14  total and eight connection elements  16  are required for a four-pole machine  100  such as that depicted. In this particular embodiment, the rotor bars  14  are located in the furthest inboard openings  24  of the multi-layer rotor lamination  20 . It should be apparent, that the rotor bars could be located in other openings  24  of the lamination  20 . As depicted there are four pole circuits  200  in the embodiment. As the center (or midpoint) of the four loops  12  do not align with the d-axis, this is a shifted cage embodiment. As shown, the plurality of rotor bars  14  is co-located in the plurality of openings  22  with the plurality of magnets  40 . By placing the plurality of rotor bars  14  in the unused cavity  24  portion of the openings  22 , the pole circuit  200  can be implemented without compromising the electromagnetic performance of the motor  100 . 
     Referring collectively to  FIGS. 10A, 10B, and 10C , schematic diagrams of perspective views of components  10  according to aspects of the present invention are shown. The figures are provided to show various schematic embodiments to show the general positional relationship between various elements of the component  10  and a d-axis and q-axis of a machine (not shown in its entirety) that may employ the component  10 . The d-axis (direct axis) and the q-axis (quadrature axis) are denoted by arrows labeled “d” and “q”, respectively. As shown in  FIG. 10A , a component  10  includes four rotor loops or rings  12 . Each ring  12  comprises two rotor bars  14  connected at each end to a connector element  16 . Rotor bars  14  are effectively shared by adjacent rings  12  so that all four rings  12  are connected. There are a total of four rotor bars  14  for the element  10 . Because the rotor bars  14  are effectively shared by adjacent poles or the component  10 , only four rotor bars  14  are needed by the component  10  for use with a four-pole machine (not shown). In this manner, the four loops  12 , being interconnected, effectively define a cage  13 . As shown, the approximate midpoint of the loop  12  aligns with the d-axis. In other words, a loop  12  is substantially concentric with the d-axis. Similarly, the q-axis may substantially align with a rotor bar  14 . As depicted there are four pole circuits  200  in the embodiment. As the center (or midpoint) of the four loops  12  align with the d-axis, this is a non-shifted cage embodiment. As shown in  FIG. 10B , the four rings  12  are not interconnected as in the embodiment shown in  FIG. 10A . Each ring  12  comprises two rotor bars  14  and two connector elements  16 . As shown, and as with the embodiment in  FIG. 10A , the approximate midpoint of the loop  12  aligns with the d-axis. In other words, a loop  12  is substantially concentric with the d-axis. Similarly, the q-axis may substantially align with a conceptual line or axis between two adjacent rotor bars  14 . As depicted there are four pole circuits  200  in the embodiment. As the center (or midpoint) of the four loops  12  align with the d-axis, this is a non-shifted embodiment. 
     Referring to the embodiment shown in  FIG. 10C , the element  10  comprises four rotor loops or rings  12 . Each ring  12  comprises two rotor bars  14  connected at each end to a connector element  16 . Rotor bars  14  are effectively shared by adjacent rings  12  so that all four rings  12  are connected, effectively defining a shifted cage  13  configuration. Thus, there are a total of four rotor bars  14  for the element  10 . As shown, and as with the embodiments in  FIGS. 10A and 10B , the approximate midpoint of the loop  12  aligns with the d-axis. In other words, a loop  12  is substantially concentric with the d-axis. However, in the embodiment shown in  FIG. 10C , the rotor bar  14  does not align with the q-axis but is shifted by a certain angle (or distance) from the q-axis. As depicted there are four pole circuits  200  in the embodiment. As the center (or midpoint) of the four loops  12  do not align with the d-axis, this is a shifted cage embodiment. 
     As shown in  FIGS. 10A-10B , each embodiment is configured such that the d-axis aligns about with the midpoint of connector element  16 . That is a loop  12  or plurality of inner loops may be substantially concentric with the d-axis. However, depending on the embodiment the rotor bar  14  or an equidistant axis between adjacent rotor bars  14  may align with the q-axis a shown in  FIGS. 10A and 10B , respectively. Contrastingly, as shown for example in  FIG. 10C , the rotor bar  14  or an equidistant axis between adjacent rotor bars  14  may be offset, or shifted, from being aligned with the q-axis. The embodiments shown are configured for use in a four-pole machine  100 . It should be apparent to one skilled in the art that other configurations of elements  10  are allowed without departing from aspects of the present invention. For example, an element  10  configured for use in an eight-pole machine  100  would contrastingly have at least eight rotor bars  14 . In embodiments of the present invention, the quantity of rotor bars  14  would equal the quantity of poles of the machine  100  (see e.g.,  FIGS. 10A and 10C ). Contrastingly, in other embodiments, such as the element  10  shown in  FIG. 10B , the quantity of rotor bars  14  (e.g., eight) may be double the quantity of poles (e.g., four) of the machine  100 . Clearly, other configurations of elements  10  that have differing quantities of rotor bars  14  in view of quantity of poles of the machine  100  in which the element  10  is configured for are available under aspects of the present invention without departing from the intent of the invention. 
     Referring to  FIGS. 11 and 12A , schematic diagrams of top views of a portion of a rotor structure component  10  according to embodiments of the present invention are shown. (These schematic views are such that effectively it is as if a portion of the component  10  were opened and rolled out flat, in a planar fashion, on the plane of the page). The component  10  comprises a plurality of rotor bars  14  connected to a plurality of connection elements  16 . The component  10  in  FIG. 11  comprises a single ring  12  per pole of the machine  100  (not shown). The two adjacent rotor bars  14  align with the q-axis and the approximate midpoint of the ring  12  aligns with the d-axis. That is the ring  12  on the right side in the  FIG. 11  is substantially concentric with the d-axis. Each pole circuit comprises a ring  12 . While only two pole circuits  200  are depicted, the component would have four pole circuits  200  in the embodiment. As the center (or midpoint) of the loops  12  align with the d-axis, this is a non-shifted embodiment. Alternatively, the component  10  of  FIG. 12A  comprise multiple rings  12  per pole of the machine  100  (not shown in its entirety). Multiple concentric rings  12  in each pole circuit  200  can further assist in further increasing saliency. Having multiple rings  12  (vs. a single ring  12 ) with different pitch in a pole circuit  200  results in further decreased inductance in the d-axis, L d , over L d  of a machine having single rings. This reduction of inductance along the d-axis causes a desired increase in saliency of the machine. An additional benefit is if, for example, one ring  12  breaks open, the remaining rings will support the increase of saliency. There are three rings  12  per pole on the component  10  shown. The outermost two adjacent rotor bars  14  of the rings  12  align with the q-axis and the approximate midpoints of the multiple rings  12  align with the d-axis. That is the rings  12  on the right side in the  FIG. 12A  are substantially concentric with the d-axis. It should be apparent that although three rings  12  are depicted, other configurations and quantities are allowable without departing from aspects of the present invention. Each pole circuit  200  comprises a plurality of concentric rings  12 . While only two pole circuits  200  are depicted, the component would have four pole circuits  200  in the embodiment. As the center (or midpoint) of the loops  12  align with the d-axis, this is a non-shifted embodiment. 
     Referring to  FIG. 12B , a top view of a portion of a rotor lamination  20  portion of an electric machine  100  with a component  10  and a schematic diagram of a perspective view of the component  10  from  FIG. 12A  is shown.  FIG. 12B  depicts a rotor lamination  20  of a multi-layer, four-pole IPM  100  having straight permanent magnets  40  therein. Some attributes of the embodiment shown are similar to the embodiment shown in  FIG. 8A . As shown and known in the art, the rotor lamination  20  includes a plurality of openings  22  that, depending on the particular embodiment, may have disposed therein one or more permanent magnets  40 . Once the permanent magnets  40  are disposed within the openings  22  there typically remains adjacent to either end of the permanent magnets  40  an opening, or remaining opening,  24 . For illustrative purposes only, the stator and/or stator windings are not shown that substantially surround the rotor component. As with multi-layer IPM, there is typically a plurality of rows of openings  22  and permanent magnets  40  therein located for each pole. 
     The plurality of rotor bars  14  are disposed in the plurality of openings  24  longitudinally through the stack of rotor laminations  20 . At or near either end of the stack of rotor laminations  20  are connection elements  16  that are connected to both ends of the rotor bars  14 . In this manner, the component  10  embodiment in  FIG. 12B  has four rotor loops  12  each constructed of two rotor bars  14  and two connection elements  16 , thereby matching the quantity of poles (i.e., four) for the particular machine  100 . However, there are two inner rings or loops  12  for each ring or loop  12  (See  FIG. 12A ). As shown, the rotor bars  14  for each of the two inner rings or loops  12  also are inserted into the openings  24  adjacent to magnets  40 . Each pole circuit  200  comprises the plurality of concentric rings  12 . While only two pole circuits  200  are depicted, the component would have four pole circuits  200  in the embodiment. As the center (or midpoint) of the loops  12  align with the d-axis, this is a non-shifted embodiment. As shown, each of the plurality of rotor bars  14  of a loop  12  is co-located in the plurality of openings  22  with the plurality of magnets  40 . By placing the plurality of rotor bars  14  in the unused cavity  24  portion of the openings  22 , the pole circuit  200  can be implemented without compromising the electromagnetic performance of the motor  100 . 
     Referring to  FIGS. 13 and 14A , schematic diagrams of top views of a portion of a rotor structure component  10  according to embodiments of the present invention are shown. (These schematic views are such that effectively it is as if a portion of the component  10  were opened and rolled out flat, in a planar fashion, on the plane of the page). The component  10  comprises a plurality of rotor bars  14  connected to a plurality of connection elements  16 . The rotor bars  14  are shared by adjacent loops or rings  12 . As such the rings  12  collectively form a cage  13 . The component  10  in  FIG. 13  comprises a cage  13  with a single loop  12  per pole of the machine  100  (not shown). The single, shared rotor bar  14  aligns with the q-axis and the approximate midpoint of the loops  12  of the cage  13  aligns with the d-axis. That is the ring  12  of the cage  13  on the right side in the  FIG. 13  is substantially concentric with the d-axis. Each pole circuit  200  comprises a ring  12 . While only two pole circuits  200  are depicted, the component would have four pole circuits  200  in the embodiment. As the center (or midpoint) of the loops  12  align with the d-axis, this is a non-shifted cage embodiment. Alternatively, the component  10  of  FIG. 14A  comprise a cage  13  also having multiple inner rings  12  per pole of the machine  100  (not shown). The additional multiple rings  12  can further assist in further increasing saliency over embodiments having only single rings per pole circuit  200 . There are two inner rings  12  per pole on the component  10  in addition to the cage  13 . The shared rotor bar  14  of the cage  13  aligns with the q-axis and the approximate midpoints of the multiple inner rings  12  and the cage  13  align with the d-axis. That is the rings  12  and the cage  13  on the right side in the  FIG. 14A  is substantially concentric with the d-axis. Each pole circuit  200  comprises a plurality of concentric rings  12 . While only two pole circuits  200  are depicted, the component would have four pole circuits  200  in the embodiment. As the center (or midpoint) of the three loops or rings  12  align with the d-axis, this is a non-shifted cage embodiment. It should be apparent that although two rings  12  are depicted in addition to the cage  13 , other configurations and quantities are allowable without departing from aspects of the present invention. 
     Referring to  FIG. 14B , a top view of a portion of a rotor lamination  20  portion of an electric machine  100  with a component  10  and a schematic diagram of a perspective view of the component  10  from  FIG. 14A  is shown.  FIG. 14B  depicts a rotor lamination  20  of a combination multi-layer/spoke-type, four-pole IPM  100  having straight permanent magnets  40  therein. Some attributes of the embodiment shown are similar to the embodiments shown in both  FIG. 7A  and  FIG. 8A . As shown and known in the art, the rotor lamination  20  includes a plurality of openings  22  that, depending on the particular embodiment, may have disposed therein one or more permanent magnets  40 . Once the permanent magnets  40  are disposed within the openings  22  there typically remains adjacent to either end of the permanent magnets  40  an opening, or remaining opening, 24. For illustrative purposes only, the stator and/or stator windings are not shown that substantially surround the rotor component. As with multi-layer IPM, there is typically a plurality of rows of openings  22  and permanent magnets  40  therein located for each pole. As shown, the spoke-type aspect of the IPM  100  also includes magnets  40  that are radially disposed in a plurality of openings  22 . Once the permanent magnets  40  are disposed within the openings  22  there typically remains adjacent to either end of the permanent magnets  40  an opening  24 . 
     The plurality of rotor bars  14  are disposed in the plurality of openings  24  longitudinally through the stack of rotor laminations  20 . At or near either end of the stack of rotor laminations  20  are connection elements  16  that are connected to both ends of the rotor bars  14 . As shown in  FIG. 14A , the outer rings  12  share common rotor bars  14 , thereby defining a cage  13 . In this manner, the component  10  embodiment in  FIG. 14B  has four rotor loops  12  each constructed of two rotor bars  14  and two connection elements  16 , thereby matching the quantity of poles (i.e., four) for the particular machine  100 . The four rotor loops  12  sharing common rotor bars  14  thereby defines a cage  13 . Thus, the cage  13  may be formed of four rotor bars  14  and eight total connector elements  16 . However, there are also two inner rings or loops  12  for each outer ring or loop  12  (See  FIG. 14A ). As shown, the rotor bars  14  for each of the two inner rings or loops  12  also are inserted into the openings  24  adjacent to magnets  40 . The rotor bars  14  for the cage  13  may be inserted in the openings  24  adjacent to the spoke-type magnets  40 . The rotor bars  14  for the two inner loops or rings  12  may be inserted in the openings  24  adjacent to the multi-layer type magnets  40 . Each pole circuit  200  comprises a plurality of concentric rings  12 . While only two pole circuits  200  are depicted, the component would have four pole circuits  200  in the embodiment. As the center (or midpoint) of the three loops  12  align with the d-axis, this is a non-shifted cage embodiment. As shown, each of the plurality of rotor bars  14  of a loop  12  is co-located in the plurality of openings  22  with the plurality of magnets  40 . By placing the plurality of rotor bars  14  in the unused cavity  24  portion of the openings  22 , the pole circuit  200  can be implemented without compromising the electromagnetic performance of the motor  100 . 
     Referring to  FIG. 15 , a top view of (an entire) portion of a rotor lamination  20  portion of an electric machine  100  with a component  10  is shown.  FIG. 15  depicts a rotor lamination  20  of a multi-layer, four-pole IPM  100  having straight permanent magnets  40  therein. As discussed herein, the magnets  40  are not limited to only straight-shaped magnets. This embodiment is similar in some aspects to the embodiments illustrated in  FIGS. 9A and 9B  and the  FIGS. 14A and 14B . The rotor component  10  may be termed a shifted-cage with inner rings or loops configuration. As shown and known in the art, the rotor lamination  20  includes a plurality of openings  22  that, depending on the particular embodiment, may have disposed therein one or more permanent magnets  40 . Once the permanent magnets  40  are disposed within the openings  22  there typically remains adjacent to either end of the permanent magnets  40  an opening, or remaining opening, 24. For illustrative purposes only, the stator and/or stator windings are not shown that substantially surround the rotor component. As with multi-layer IPM, there is typically a plurality of rows of openings  22  and permanent magnets  40  therein located for each pole. 
     The plurality of rotor bars  14  are disposed in the plurality of openings  24  longitudinally through the stack of rotor laminations  20 . In this configuration only a single rotor bar  14  is placed in an opening  24  in each pole (See  FIG. 9A ). At or near either end of the stack of rotor laminations  20  are connection elements  16  that are connected to both ends of the rotor bars  14 . The connection element  16  connects a rotor bar  14  from a first pole to the rotor bar  14  of an adjacent pole, thereby shifting the element  10  creating a shifted cage  13  configuration. In this manner, the component  10  embodiment has four rotor loops  12  each constructed of two rotor bars  14  and two connection elements  16 , thereby matching the quantity of poles (i.e., four) for the particular machine  100 . However, due to the shifted-cage configuration of the embodiment, only four rotor bars  14  total and eight connection elements  16  are required for a four-pole machine  100  such as that depicted. In this particular embodiment, the rotor bars  14  are located in the furthest inboard openings  24  of the multi-layer rotor lamination  20 . It should be apparent, that the rotor bars could be located in other openings  24  of the lamination  20 . In addition, there are two additional inner loops  12  for each pole that are shifted in their configuration as well. Each pole circuit  200  comprises a plurality of concentric rings  12 . As depicted, the component  10  would have four pole circuits  200  in the embodiment. As the center (or midpoint) of the three loops  12  do not align with the d-axis, this is a shifted cage embodiment. As shown, each of the plurality of rotor bars  14  of a loop  12  is co-located in the plurality of openings  22  with the plurality of magnets  40 . By placing the plurality of rotor bars  14  in the unused cavity  24  portion of the openings  22 , the pole circuit  200  can be implemented without compromising the electromagnetic performance of the motor  100 . 
     Referring to  FIG. 16 , a top view of a portion of a rotor lamination  20  portion of an electric machine  100  with a component  10  is shown.  FIG. 16  depicts a rotor lamination  20  of a single layer, four-pole IPM  100  having straight permanent magnets  40  therein. (The embodiment is similar in aspects to the embodiment shown in  FIGS. 3A and 3B ). As shown and known in the art, the rotor lamination  20  includes a plurality of stator windings (not shown) and inboard of the stator windings are disposed one or more permanent magnets  40  located in one or more openings  22  in the rotor lamination  20 . Once the permanent magnets  40  are disposed within the openings  22  there typically remains adjacent to either end of the permanent magnets  40  an opening  24 . 
     The plurality of rotor bars  14  are disposed in the plurality of openings  24  longitudinally through the stack of rotor laminations  20 . At or near either end of the stack of rotor laminations  20  are connection elements  16  that are connected to both ends of the rotor bars  14 . In this embodiment, one or more ring  12  (i.e., rotor bars  14  and connection elements  16 ) is split into two or more rings  12 . As shown, there are two rotor bars  14  placed in the openings  24 , and there are two connection elements  16  connecting the two rotor bars  14 . In this manner, the component  10  embodiment in  FIG. 16  has four rotor loops  12  where each loop  12  is constructed of four rotor bars  14  and four connection elements  16  for the particular machine  100 . By splitting the loops into multiple loops (termed “split rotor bar” configuration) fault tolerance is provided. As long as at least one loop  12  in the plurality of loops  12  remains functional, the ring  12  will be able to introduce the desired ring saliency. It should be apparent that under aspects of the present invention that various configurations of splitting, via design, a connection element  16 , rotor bar  14 , loop  12 , and/or cage  13  into two or more elements other than that shown is possible. For example, the elements may be in other quantities than just two (as depicted in  FIG. 16 ). Each pole circuit  200  comprises the rings, or loops,  12 . While only two pole circuits  200  are depicted, the component would have four pole circuits  200  in the embodiment. As the center (or midpoint) of the loops  12  align with the d-axis, this is a non-shifted embodiment. As shown, each of the plurality of rotor bars  14  of a loop  12  is co-located in the plurality of openings  22  with the plurality of magnets  40 . By placing the plurality of rotor bars  14  in the unused cavity  24  portion of the openings  22 , the pole circuit  200  can be implemented without compromising the electromagnetic performance of the motor  100 . 
     Referring collectively to  FIGS. 17A and 17B  schematic diagrams of perspective views of various embodiments showing the installation of a portion of a component  10  in a machine  100  in accordance with aspects of the present invention. While  FIG. 17A  shows a partial installation of an element, while  FIG. 17B  shows the completed installation of the element from  FIG. 17A . A U-shaped element, which may be pre-formed (e.g., bent), is made of a conductive, non-magnetic material comprising two rotor bars  12  connected via a connection element  16 . The U-shaped element may be inserted into two openings (e.g.,  24 ) in the rotor  90  of the machine  100  (not fully shown). As shown, each of the rotor bars  14  has extensions  15  that extend beyond the length of the rotor core  90  of the machine  100 . The extensions  15  may then be bent and connected together to form a second connection element  16 , thereby forming a completed ring  12 , as shown in  FIG. 17B . The extensions  15  may be connected by any known method including, but not limited to, brazing, welding, mechanically fastening, and the like. 
     Referring to the embodiment shown in  FIG. 18 , a U-shaped element (similar to the embodiment discussed in  FIG. 17A ) comprising element, which may be pre-formed (e.g., bent), is made of a conductive, non-magnetic material comprising two rotor bars  12  connected via a connection element  16 . The U-shaped element may be inserted into two openings (e.g.,  24 ) in the rotor  90  of the machine  100  (not entirely shown). As shown, each of the rotor bars  14  has extensions  15  that extend beyond the length of the rotor  90  of the machine  100 . In a typical embodiment, the extensions  15  of the embodiment in  FIG. 18  do not need to be as long as the extensions  15  of the embodiment in  FIG. 17A . A small U-shaped end piece  18 , made of a conductive material, having extensions  15  may be placed so that the respective extensions  15  of the end piece  18  and the U-shaped element are adjacent to each other. The extensions  15  may be connected by suitable means (e.g., brazing, welding, mechanical fastening, etc.) thereby creating a loop  12 . It should be noted that the end piece need not be U-shaped as discussed above. For example, in another embodiment, a straight element like connection element  16  without extensions  15  may be used in lieu of the U-shaped end piece  18 , wherein the connection element  16  is attached to the U-shaped element and connected thereto. 
     Referring to the embodiment shown in  FIG. 19 , a U-shaped element (similar to the embodiment discussed in  FIG. 18 ) comprising element, which may be pre-formed (e.g., bent), is made of a conductive, non-magnetic material comprising two rotor bars  12  connected via a connection element  16 . The U-shaped element may be inserted into two openings (e.g.,  24 ) in the rotor  90  of the machine  100 . As shown, each of the rotor bars  14  has extensions  15  that extend beyond the length of the rotor  90  of the machine  100 . In a typical embodiment, the extensions  15  of the embodiment in  FIG. 19  do not need to be as long as the extensions  15  of the embodiment in  FIG. 17A . A full-ring connector  17 , made of conductive material, may be placed so that the extensions  15  of the U-shaped element are adjacent to and/or extending through the connector  17 . The extensions  15  and/or rotor bars  14  may be connected to the connector  17  by suitable means (e.g., brazing, welding, mechanical fastening, etc.) thereby creating a loop  12 . 
     Referring to  FIG. 20 , a schematic diagram of a perspective view of a component  10  according to an aspect of the present invention is shown. The d-axis (direct axis) and the q-axis (quadrature axis) are denoted by arrows labeled “d” and “q”, respectively. As shown, the component  10  includes four rotor loops or rings  12 . Each ring  12  comprises two rotor bars  14  connected at one end to a connector element  16 . The other ends of the rotor bars  14  are connected to a single full ring connector  17 . In this manner, all rings  12  are effectively connected to the full ring connector  17 , thereby defining a cage  13 . There are a total of eight rotor bars  14  for the element  10 . In this manner, the four loops  12 , being interconnected, effectively define a cage  13 . As shown, the approximate midpoint of a loop  12  aligns with the d-axis. In other words, a loop  12  is substantially concentric with the d-axis. Similarly, the q-axis substantially aligns with a midpoint between two adjacent rotor bars  14 . Each pole circuit  200  comprises rings  12 . The component has four pole circuits  200  in the embodiment. As the center (or midpoint) of the loops  12  align with the d-axis, this is a non-shifted embodiment. 
     While various embodiments discussed herein have general disclosed magnets  40  and openings  22  of specific sizes and configurations, it should be apparent that different quantities, shapes, and configurations that those illustrated may be used without departing from aspects of the present invention. For example, the openings  22  and/or magnets  40  may be other shapes other than straight including, for example, curved, trapezoidal, round, and the like, and combinations thereof. 
     While various embodiments discussed herein have general disclosed rotor conductors (e.g., rotor bars  14 ) disposed in openings  24  adjacent to magnets  40  in the rotor lamination  20 , it should be apparent that under aspects of the present invention that the rotor conductors, in certain embodiments, are disposed in openings and/or voids (e.g., grooves, channels, gaps, etc.) on the outer portion  90  of the rotor. In other words, in embodiments the rotor conductors may be placed in a location such that, at least initially, is not fully surrounded by rotor lamination material. 
     Finite-element analysis based modeling was conducting on various models of machines, both for electric machines not having any rotor circuit structure (i.e., related art) and for electric machines using embodiments of the rotor circuit structures of the present invention. Some results of the modeling are illustrated in  FIGS. 21-24  herein. 
     Small signal saliency and small signal saliency angle is key information used for sensorless control, under aspects of the present invention, and it is defined using small signal impedance. Small signal impedance is defined for a small high frequency variation of current (Δi d , Δi q ) from the operating point current vector (i d , i q ). Small signal impedance varies depending on the orientation of the high frequency current variation (Δi d , Δi q ). Small signal saliency at a given operating point (Δi d , Δi q ) is the ratio of the maximum small signal impedance to the minimum small signal impedance over a full range of orientation of the high frequency current variation. Small signal saliency is greater than or equal to 1, and it is desired to be much larger than 1 for suitable sensorless control performance. Small signal saliency angle is the angular displacement of the maximum small signal impedance orientation from the rotor reference frame, for example the q-axis of the rotor reference frame. The small signal saliency angle is desired to be constant over the operating range, near zero for example, in order to achieve desired encoderless control performance. 
     Referring to  FIG. 21 , a graph showing the small signal saliency on the current vector (i d , i q ) plane for an IPM machine of the related art is depicted as element  300 . Contrastingly,  FIG. 22  shows the contour plots of small signal saliency of an IPM machine incorporating the component in accordance with the present invention as element  350 . As shown in the graph, the resultant saliency is improved and increased as compared to the saliency in the related art machine ( FIG. 21 ). 
     Referring to  FIG. 23 , a graph showing the contour plots of small signal saliency angle on the current vector (i d , i q ) plane an IPM machine of the related art is depicted as element  400 . Contrastingly,  FIG. 24  shows the contour plots of small signal saliency angle of an IPM machine incorporating the component in accordance with the present invention as element  450 . As shown in the graph, the resultant wide angular margin by using the component as compared to the related art machine ( FIG. 23 ) depicting the very tight saliency angle. 
       FIG. 25  shows a graph that depicts speed (%) on a x-axis vs. torque (%) on a y-axis. As shown, when a machine uses the component of the present invention the performance of the machine may reach the upper-left portion (i.e., dark upward pointing arrow) of the graph. That is by employing aspects of the present invention, full torque capability at lower machine speeds is attainable. (For example, an electric machine of the present invention may reach 50% of torque capability at speeds below 10% of the rated speed of the machine. In other embodiments, the electric machine may reach over 75% of torque capability at speeds below 10% of the rated speed of the machine. In still other embodiments, the electric machine may reach over 90% of torque capability at speeds below 10% of the rated speed of the machine. In still other embodiments, the electric machine may reach 100% of torque capability at speeds below 10% of the rated speed of the machine.) 
     Under aspects of the present invention, the components  10  and the electric machines  100  discussed herein may be used as a traction motor for virtually any vehicle. A vehicle support frame connected to the one or more electric machine  100 . Suitable vehicles for use include, but are not limited to, an off-highway vehicle (OHV), a locomotive, a mining vehicle, electric-motorized railcar, automobiles, trucks, construction vehicles, agricultural vehicles, airport ground service vehicles, fork-lifts, non-tactical military vehicles, tactical military vehicles, golf carts, motorcycles, mopeds, all-terrain vehicles, and the like. 
     While the embodiments illustrated and described generally herein have shown that the electric machine  100  to be an interior permanent magnet (IPM) machine, other electric machines than those illustrated herein may employ aspects of the present invention including, for example, PMSRM, SRM, and induction machine, and the like. Various embodiments of the rotor circuit component  10  may be used in these various other types of electric machines. 
     Therefore, in accordance with one aspect of the invention, a rotor component comprises a rotor circuit configured for use with one of an interior permanent magnet (IPM) machine and a synchronous reluctance machine (SRM), the rotor circuit comprising: at least one pole circuit, wherein the at least one pole circuit are made of a conductive, non-magnetic material. 
     In accordance with another aspect of the invention, an electric machine comprises a rotor core comprising magnetic steel; a stator configured with a plurality of stationary windings therein; a plurality of openings disposed within or on the rotor core; and a rotor circuit configured to introduce saliency based on an orientation of a portion of the rotor circuit in relationship to a pole location of the electric machine, said rotor circuit made of a conductive, non-magnetic material. 
     In accordance with another aspect of the invention, an electric machine comprises: a rotor core; a stator configured with a plurality of stationary windings therein; a plurality of openings disposed within the rotor core; and a rotor circuit structure comprising at least one pole circuit disposed in a predetermined location, wherein said predetermined location is in range that extends from about a q-axis to about a d-axis of the electric machine. 
     In accordance with another aspect of the invention, an electric machine comprising: a rotor core; a stator configured with a plurality of stationary windings therein; a plurality of openings disposed within the rotor core; a rotatable shaft therethrough; and a rotor circuit structure comprising at least one loop or ring of a conductive, non-magnetic material, wherein said at least one loop or ring is substantially concentric about a d-axis of the electric machine. 
     In accordance with another aspect of the invention, an interior permanent magnet (IPM) machine comprises a means for converting electrical energy to rotational energy; and a means for providing increased magnetic saliency at high frequency excitation. 
     While only certain features of the invention have been illustrated and/or described herein, many modifications and changes will occur to those skilled in the art. Although individual embodiments are discussed, the present invention covers all combination of all of those embodiments. It is understood that the appended claims are intended to cover all such modification and changes as fall within the intent of the invention.