Abstract:
A DC machine for connection to an electrical system may include a stator configured as a portion of the DC machine; a rotor configured as a portion of the DC machine being rotatable with respect to the stator; and a control circuit to control the rotor to allow the rotor to continuously slip with respect to the stator.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to electrical machines and more particularly to a direct current (D C) machine. 
       BACKGROUND 
       [0002]    A DC motor/generator (machine) is any of a class of electrical machines that converts direct current electrical power into mechanical power. The most common types rely on the forces produced by magnetic fields. Nearly all types of DC motors have some internal mechanism, either electromechanical or electronic, to periodically change the direction of current flow in part of the motor. Most types produce rotary motion; a linear motor directly produces force and motion in a straight line. 
         [0003]    DC motors were the first type widely used, since they could be powered from existing direct-current lighting power distribution systems. A DC motor&#39;s speed can be controlled over a wide range, using either a variable supply voltage or by changing the strength of current in its field windings. Small DC motors are used in tools, toys, and appliances. The universal motor can operate on direct current but is a lightweight motor used for portable power tools and appliances. Larger DC motors are used in propulsion of electric vehicles, elevator and hoists, or in drives for steel rolling mills. The advent of power electronics has made replacement of DC motors with AC motors possible in many applications. 
         [0004]    A coil of wire with a current running through it generates an electromagnetic field aligned with the center of the coil. The direction and magnitude of the magnetic field produced by the coil can be changed with the direction and magnitude of the current flowing through it. 
         [0005]    A simple DC motor has a stationary set of magnets in the stator and an armature with one or more windings of insulated wire wrapped around a soft iron core that concentrates the magnetic field. The windings usually have multiple turns around the core, and in large motors there can be several parallel current paths. The ends of the wire winding are connected to a commutator. The commutator allows each armature coil to be energized in turn and connects the rotating coils with the external power supply through brushes. (Brushless DC motors have electronics that switch the DC current to each coil on and off and have no brushes.) 
         [0006]    The total amount of current sent to the coil, the coil&#39;s size and what it&#39;s wrapped around dictate the strength of the electromagnetic field created. 
         [0007]    The sequence of turning a particular coil on or off dictates what direction the effective electromagnetic fields are pointed. By turning on and off coils in sequence a rotating magnetic field can be created. These rotating magnetic fields interact with the magnetic fields of the magnets (permanent or electromagnets) in the stationary part of the motor (stator) to create a force on the armature which causes it to rotate. In some DC motor designs the stator fields use electromagnets to create their magnetic fields which allow greater control over the motor. 
         [0008]    At high power levels, DC motors are almost always cooled using forced air. 
         [0009]    Different number of stator and armature fields as well as how they are connected provide different inherent speed/torque regulation characteristics. The speed of a DC motor can be controlled by changing the voltage applied to the armature. The introduction of variable resistance in the armature circuit or field circuit allowed speed control. Modern DC motors are often controlled by power electronics systems which adjust the voltage by “chopping” the DC current into on and off cycles which have an effective lower voltage. 
         [0010]    Since the series-wound DC motor develops its highest torque at low speed, it is often used in traction applications such as electric locomotives, and trams. The DC motor was the mainstay of electric traction drives on both electric and diesel-electric locomotives, street-cars/trams and diesel electric drilling rigs for many years. The introduction of DC motors and an electrical grid system to run machinery starting in the 1870s started a new second Industrial Revolution. DC motors can operate directly from rechargeable batteries, providing the motive power for the first electric vehicles and today&#39;s hybrid cars and electric cars as well as driving a host of cordless tools. Today DC motors are still found in applications as small as toys and disk drives, or in large sizes to operate steel rolling mills and paper machines. Large DC motors with separately excited fields were generally used with winder drives for mine hoists, for high torque as well as smooth speed control using thyristor drives. These are now replaced with large AC motors with variable frequency drives. 
         [0011]    If external power is applied to a DC motor it acts as a DC generator, a dynamo. This feature is used to slow down and recharge batteries on hybrid car and electric cars or to return electricity back to the electric grid used on a street car or electric powered train line when they slow down. This process is called regenerative braking on hybrid and electric cars. In diesel electric locomotives they also use their DC motors as generators to slow down but dissipate the energy in resistor stacks. Newer designs are adding large battery packs to recapture some of this energy. 
         [0012]    The brushed DC electric motor generates torque directly from DC power supplied to the motor by using internal commutation, stationary magnets (permanent or electromagnets), and rotating electrical magnets. 
         [0013]    Typical brushless DC motors use one or more permanent magnets in the rotor and electromagnets on the motor housing for the stator. 
         [0014]    A homopolar motor has a magnetic field along the axis of rotation and an electric current that at some point is not parallel to the magnetic field. The name homopolar refers to the absence of polarity change. 
         [0015]    A permanent magnet PM motor does not have a field winding on the stator frame, instead relying on PMs to provide the magnetic field against which the rotor field interacts to produce torque. Compensating windings in series with the armature may be used on large motors to improve commutation under load. Because this field is fixed, it cannot be adjusted for speed control. PM fields (stators) are convenient in miniature motors to eliminate the power consumption of the field winding. Most larger DC motors are of the “dynamo” type, which have stator windings. Historically, PMs could not be made to retain high flux if they were disassembled; field windings were more practical to obtain the needed amount of flux. However, large PMs are costly, as well as dangerous and difficult to assemble; this favors wound fields for large machines. 
         [0016]    There are three types of electrical connections between the stator and rotor possible for DC electric motors: series, shunt/parallel and compound (various blends of series and shunt/parallel) and each has unique speed/torque characteristics appropriate for different loading torque profiles/signatures 
       SUMMARY 
       [0017]    A direct current machine for connection to an electrical system, and may include a stator configured as a portion of the direct current machine; a rotor configured as a portion of the direct current being rotatable with respect to the stator; and a control circuit to control the rotor to control a magnetomotive force (mmf) vector about the a face of the rotor. 
         [0018]    The direct current machine may include a first winding group and a second winding group. The first winding group may include at least one first conductor and the second winding group includes at least one second conductor, and the first conductor and the second conductor may be configured in a stair step configuration from slot to slot. 
         [0019]    The stair step configuration may include a first slot and a second slot, and the first slot and the second slot directly adjacent to the first slot includes both first conductor and the second conductor, and the difference in number between the first conductor in the first slot and the first conductor in the second slot is a single first conductor. 
         [0020]    The difference between the second conductor in the first slot and the second conductor in the second slot may be a single second conductor. 
         [0021]    The control circuit may include an angle generator to determine the angle of slip between the rotor and the stator. 
         [0022]    The control circuit may include a magnitude generator to generate a magnitude of slip between the rotor and the stator. 
         [0023]    The control circuit may include an angle summing circuit. 
         [0024]    The control circuit may include a magnitude summing circuit. 
         [0025]    The control circuit may include a first multiplier circuit to connect to the rotor. 
         [0026]    The control circuit may include a second multiplier circuit to connect to the rotor. 
         [0027]    The control circuit controls the rotor to control a magnitude of the magnetomotive force (mmf) vector about the face of the rotor, or about the face of the stator, or about the faces of the rotor and the stator. 
         [0028]    The control circuit controls an angle of the magnetomotive force (mmf) vector about the face of the rotor, or about the face of the stator, or about the faces of the rotor and the stator. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]    The invention may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which, like reference numerals identify like elements, and in which: 
           [0030]      FIG. 1  illustrates a control system for a calibrated slip Direct Current machine of the present invention; 
           [0031]      FIG. 2  illustrates a first slot of the calibrated slip Direct Current machine of the present invention; 
           [0032]      FIG. 3  illustrates a second slot of the calibrated slip Direct Current machine of the present invention; 
           [0033]      FIG. 4  illustrates a third slot of the calibrated slip Direct Current machine of the present invention; 
           [0034]      FIG. 5  illustrates a nineth slot of the calibrated slip Direct Current machine of the present invention; 
           [0035]      FIG. 6  illustrates a cross-sectional view of the stator and rotor of the calibrated slip Direct Current of the present invention; 
           [0036]      FIG. 7  illustrates a cross-sectional view of the stator and rotor of the calibrated slip Direct Current of the present invention; 
           [0037]      FIG. 8  illustrates a cross-sectional view of the stator and rotor of the calibrated slip Direct Current of the present invention; 
           [0038]      FIG. 9  illustrates a cross-sectional view of the stator and rotor of the calibrated slip Direct Current of the present invention; 
           [0039]      FIG. 10  illustrates another control circuit of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0040]    A calibrated slip direct current machine of the present invention as shown in  FIG. 8  may include two winding groups  203 ,  207  on the rotor  103  to positively control the magnitudes and angles of the magnetomotive force (mmf) vectors about the rotor face  103 . The stator  101  of the calibrated slip DC machine  800  of the present invention may be the same as a conventional DC machine stator. As compared to a conventional direct current machine (not shown), the present invention, specifically DC machine  800 , eliminates the need to mechanically commutate the rotor windings to achieve variable direct axes. The DC machine  800  may utilize a salient pole type of stator configuration for direct current machines. The DC machine may also utilize an additional winding group (not shown) in a round stator configuration about the stator  101  to positively control the magnitudes yet establish a fixed angle (fixed direct axes) of the magnetomotive force (mmf) vectors about the stator face. These two configurations should allow the machine  800  to be thermodynamically reversible (operate as a motor or generator depending on shaft torque with respect to shaft rotation) due to Lenz&#39; Law. 
         [0041]    The present invention may also include two or more winding groups  203 ,  207  about the stator to positively control the magnitudes and angles (variable direct axes) of the magnetomotive force (mmf) vectors about the stator face. This configuration allows the machine  800  to be operated in primarily motor mode. 
         [0042]    The calibrated slip rotor can be also utilized. 
         [0043]    Specifically, the DC machine  800  of the present invention may include two winding (or more)  203 ,  207  distributed around the rotor face. Each winding  201 ,  205  may be energized by a dedicated set of slip rings  107  which may be connected to a control circuit  102  as shown in  FIG. 1  to control the current of the first winding group  203  and the second winding group  207 , more particularly the current within the first winding  201  and the second winding  205 . Each winding  201 ,  205  may be positioned together in a single slot and positioned in a plurality of common slots in a stair step fashion where the change in number of the windings  201  of the first winding group  203  and the change in the number of the windings  205  of the second winding group  207  in adjacent slots may be increased (or decreased) of a single winding  201  of the first winding group  203  and a decrease (or increase) of a single winding  205  and a decrease of the second winding group  207 , keeping the total number of windings  201 ,  205  within a single slot the same. The present invention is advantageous for the number of slots on the rotor  103  to be two times the number of poles times an odd integer that is greater than one. An advantage of the present invention is for the number of turns or the number of sets of turns in each slot is to be any integral multiple of this odd integer plus one (1). The two winding groups  203 ,  207  may be continuously stair stepped in the number of winding  201 ,  205  with respect to each other winding groups  203 ,  207  as you move from slot to slot around the rotor face. The present invention distributes an approximate sinusoidal mmf wave around the rotor for any given desired mmf pole position angle, additionally, the present invention makes it easier to mechanically balance the rotor. The sinusoidally distributed mmf wave transitions mostly the fundamental wave pattern of this sinusoidal magnetic field intensity from the rotor face into the air gap; however, due to Gauss&#39; Law the magnetic flux intensity produced by the salient poles of the stator would redistribute the magnetic flux density patterns such that the transitioning flux becomes somewhat evenly concentrated at the stator pole faces. The present invention may soften the torque characteristics of this machine making it adaptable to loads or prime movers with varying torque properties. The torque-speed characteristic of this stator configuration of the calibrated slip direct current machine should allow the machine to operate at moderate speeds while undergoing moderate to severe load or prime mover torque-position disturbances. 
         [0044]    For example, if the odd integer is selected as the odd integer nine (9) for a four-pole machine, the number of slots would be seventy-two (72) and the number of turns of windings  201 ,  205  passing through each slot could be ten (10). The first sequence  801  in stair step arrangement of the conductor/windings  201 ,  205  is to add a single first conductor  201  from winding group one  203  and reduce a single conductor  205  from winding group two  207  and to an adjacent slot starting with a single first conductor  201  from winding group  1   203  and nine second conductors  205  from winding group  2   207  until there is a single conductor  205  from group  2   207  and nine conductors  201  from group  1 . For a seventy-two (72) slot rotor, Slot One (1)  209  as illustrated in  FIG. 2  would have one (1) first conductor  201  positioned in the slot  209  from winding group one (1)  203  and nine (9) second conductors  205  positioned in the slot  209  from winding group two (2)  207 . Slot Two (2)  211  would have two (2) first conductors  201  laid in the slot  211  from winding group one (1)  203  and eight (8) second conductors  205  positioned in the slot  211  from winding group two (2)  207 . Slot Three (3)  213  would have three (3) conductors  201  positioned in the slot  213  from winding group one (1)  203  and seven (7) conductors  205  positioned in the slot  213  from winding group two (2)  207 . The sequence in stair step arrangement would continue, Slot Nine (9)  215  would have nine (9) conductors  201  positioned in the slot  215  from winding group one (1)  203  and one (1) conductor  205  laid in the slot  215  from winding group two (2)  207 . The second sequence  803  in stair step arrangement for the next nine slots is reversed with respect to the above description by reducing the conductors by a single conductor  201  from group  1  (1)  203  and increasing the conductors by a single conductor  205  from group  2  (two)  207  to start from nine conductors  201  from group number one  203  and one conductor  205  from group number two  207  until there are nine conductors  205  from group  2   207  and one conductor  201  from group  1   203 . Slot Ten (10) would be wound the same way as Slot Nine (9) with current flowing in the opposite direction in winding group  2   207  and flowing in the same direction in winding group  1   203 . 
         [0045]    There are four rotor areas per winding group that are equally spaced. The four rotor steel pole center areas of Winding Group One are shifted ninety (90) electrical degrees with respect to the four rotor steel pole center areas of Winding Group Two (2) for this four (4) pole example. The rotor areas between Slots Nine (9) and Ten (10), between Slots Twenty-seven (27) and Twenty-eight (28), between Slots Forty-five (45) and Forty-six (46), and between Slots Sixty-three (63) and Sixty-four (64) are the centers of the four pole faces for Winding Group Two (2). The rotor steel areas between Slot Seventy-two (72) and slot One (1), between Slots Eighteen (18) and Nineteen (19), between Slots Thirty-six (36) and Thirty-seven (37), and between Slots Fifty-four (54) and Fifty-five (55) are the centers of the four pole faces for Winding Group One (1). If Winding Group One (1) is energized through its slip rings with a specific per unit quantity X of current times the Cosine of the desired mmf vector angle k and Winding Group Two (2) is energized through its slip rings with approximately the same specific quantity Y of current times the Sine of the desired mmf vector angle k, the magnetic flux pattern will shift forward by the approximately the a predetermined mmf vector angle k from the zero degree location. Two control loops are established between the rotor shaft speed and position (one input), the machine terminal voltage or reactive power (another input) and the two current sources (two outputs) connected to two sets of slip rings to positively control and calibrate the slip of the rotor. This configuration not only allows the position of the rotor relative to the stator mmf wave to change, this configuration also allows the operation of the rotor at a specific speed with respect to the mmf wave speed of the stator. 
         [0046]    The 72 rotor slot four pole machine example has 36 slots per pole set. The MMF pole distribution and pattern is approximately sinusoidal all of the way around the four pole faces. 
         [0047]    The control circuit  102  is used to control the winding currents. 
         [0048]    The significance of the pole faces define where the direct and quadrature axes lie on the rotor. The characteristic of the direct and quadrature axes is for protection and control and to calculate the transfer of power across the air gap. For a four pole machine example, for winding  1   203  there would be two direct axes  601  and two quadrature axes  603  and for winding  2   207  again there would be two direct axes  603  and two quadrature axes  601 . Under dynamic control you are moving a virtual set of direct and quadrature axes around the rotor face  103  which is a virtual movement as you project it and which is a real movement when you measure it. 
         [0049]      FIG. 1  illustrates a control system for  FIG. 7 ,  FIG. 8  and  FIG. 9  including a control circuit  102  for the calibrated slip DC machine  800  and of the present invention and illustrates a stator  101  which may extend around a rotor  103  which may cooperate with a shaft  105  which may rotate. The calibrated slip DC machine  800  may operate as a generator or may operate as a motor in accordance with the teachings of the present invention. The shaft  105  may be connected to a position sensor  121  which may be an optical wheel to provide an indication of the position such as the rotational position of the shaft and to provide an indication of the slip of the calibrated slip DC and machine  100 .  FIG. 1  additionally illustrates a control circuit for  FIG. 7  and  FIG. 8  which may include a first multiplier circuit  117  and a second multiplier circuit  119  which may be connected to slip rings  107  which may be positioned on the shaft  105  to connect to the first winding group and the second winding group respectively which may be positioned within the rotor  103 . The control circuit for  FIG. 9  and not shown on  FIG. 1  may include a first multiplier circuit  117  and a second multiplier circuit  119  which may be connected to the stator which connect to the first winding group and the second winding group respectively which may be positioned within the stator  101 , and the DC source may be connected to one winding group through one set of slip rings on the rotor. The desired position and slip of the rotor  103  and the output from the position and slip circuit  123  which provides the actual position and slip of the rotor  103  may be input to the summing circuit  113  which may calculate the difference between the two inputs. Alternatively, only one of these two inputs is referenced against desired while the other input may establish an operational bandwidth (set of boundaries). The slip quantity is the time derivative of position quantities and is calculated. When actual position with respect to time is referenced against desired, the error quantity of slip can be “tuned” to optimize controllability to the most narrow bandwidth possible before stability becomes compromised. When slip is referenced against desired, the error quantity of position can be “tuned” to optimize controllability before stability becomes compromised. This makes it possible to apply a soft yet directional starting torque to the rotor when operated as a motor. The output of the summing circuit  113  is input to the angle generator  109  to generate an angle based upon the desired position and desires slip. The magnitude of the desired excitation is input to the magnitude summing circuit  115  and the V where the symbol V may be the symbol for voltage is additionally input to the magnitude summing circuit  115 . The output of the magnitude summing circuit  115  is input to the magnitude generating circuit  111  to generate a magnitude for the first multiplier circuit  117  and the second multiplier circuit  119 , and the output of the angle generator  109  is input to the first multiplier circuit  117  and the second multiplier circuit  119 . The first multiplier circuit  117  multiplies the magnitude by the cosine of the angle and the second multiplier circuit  119  multiplies the magnitude by the sine of the angle. The output of the first multiplier circuit  117  and the second multiplier circuit  119  is input to first winding group and the second winding group of the rotor  103  of  FIG. 7  and  FIG. 8 , and of the stator  101  of  FIG. 9 . 
         [0050]      FIG. 8  illustrates eight groups of rotor slot groups which may be substantially truncated pie shaped and extend around the outer peripheral edge of the rotor  103  and may include an equal number of slots. A first winding group may include the windings in the first group of rotor slots  621  and the windings in the second group of rotor slots  623 . The first group of rotor slots  621  may be adjacent to the second group of rotor slots  623  and may be adjacent to the eighth group of rotor slots  635 . A second winding group may include the winding in the third group of rotor slots  625  and the fourth group of rotor slots  627 . The third group of rotor slots  625  may be adjacent to the second group of rotor slots  623  and may be adjacent to the fourth group of rotor slots  627 ; the first winding group may be repeated and may include the windings in the fifth group of rotor slots  629  and the six group of rotor slots  631 ; the fifth group of rotor slots  629  may be adjacent to the fourth group of rotor slots  627  and the sixth group of rotor slots  631  may be adjacent to the fifth group of rotor slots  629 . The second winding group may be repeated and may include the seventh group of rotor slots  633  and the eighth group of rotor slots  635 . The seventh group of rotor slots  633  may be adjacent to the sixth group of rotor slots  631  and may be adjacent to the eighth group of rotor slots  635 . 
         [0051]    The first group of rotor slots  621  may include the first sequence  801  in stair step arrangement of windings and the second group of rotor slots  623  may include the second sequence  803  in stair step arrangement of windings. The third group of rotor slots  625  may include the first sequence  801  in stair step arrangement of windings. The fourth group of rotor slots  627  may include the second sequence  803  in stair step arrangement. The fifth group of rotor slots  629  may include the first sequence  801  in stair step arrangement of windings and the six group of rotor slots  631  may include the second sequence  803  in stair step arrangement of windings. The seventh group of rotor slots  633  may include the first sequence  801  in stair step arrangement of windings and the eighth group of rotor slots  635  may include the second sequence  803  in stair step arrangement of the windings. The stator  101  may include only the first conductor  201 . 
         [0052]      FIG. 6  illustrates eight groups of rotor slot groups which may be substantially truncated pie shaped and extend around the outer peripheral edge of the rotor  103  and may include an equal number of slots. A first winding group may include the windings in the first group of rotor slots  621  and the windings in the second group of rotor slots  623 . The first group of rotor slots  621  may be adjacent to the second group of rotor slots  623  and may be adjacent to the eighth group of rotor slots  635 . A second winding group may include the winding in the third group of rotor slots  625  and the fourth group of rotor slots  627 . The third group of rotor slots  625  may be adjacent to the second group of rotor slots  623  and may be adjacent to the fourth group of rotor slots  627 ; the first winding group may be repeated and may include the windings in the fifth group of rotor slots  629  and the six group of rotor slots  631 ; the fifth group of rotor slots  629  may be adjacent to the fourth group of rotor slots  627  and the sixth group of rotor slots  631  may be adjacent to the fifth group of rotor slots  629 . The second winding group may be repeated and may include the seventh group of rotor slots  633  and the eighth group of rotor slots  635 . The seventh group of rotor slots  633  may be adjacent to the sixth group of rotor slots  631  and may be adjacent to the eighth group of rotor slots  635 . 
         [0053]    The first group of rotor slots  621  may include the first sequence  801  in stair step arrangement of windings and the second group of rotor slots  623  may include the second sequence  803  in stair step arrangement of windings. The third group of rotor slots  625  may include the first sequence  801  in stair step arrangement of windings. The fourth group of rotor slots  627  may include the second sequence  803  in stair step arrangement. The fifth group of rotor slots  629  may include the first sequence  801  in stair step arrangement of windings and the six group of rotor slots  631  may include the second sequence  803  in stair step arrangement of windings. The seventh group of rotor slots  633  may include the first sequence  801  in stair step arrangement of windings and the eighth group of rotor slots  635  may include the second sequence  803  in stair step arrangement of the windings. 
         [0054]      FIG. 6  additionally illustrates eight groups of stator slot groups which may be substantially truncated pie shaped and extend around the inner peripheral edge of the rotor  103  and may include an equal number of slots. 
         [0055]      FIG. 6  illustrates a first group of stator slots  651  which may be adjacent to an eight group of stator slots  665  and adjacent to a second group of stator slots  653  and illustrates a third group of stator slots  655  which may be adjacent to the second group of stator slots  653  and which may be adjacent to a fourth group of stator slots  657 . A fifth group of stator slots  659  may be adjacent to the fourth group of stator slots  657  and may be adjacent to a sixth group of stator slots  661 . A seventh group of stator slots numerals  663  may be adjacent to the sixth group of stator slots  661  and may be adjacent to the eighth group of stator slots  665 . 
         [0056]    A third winding group may include the windings in the first group of stator slots  651  and the windings in the second group of stator slots  653 . The first group of stator slots  651  may include the first sequence  801  in stair step arrangement of windings and the second group of stator slots  653  may include the second sequence  803  in stair step arrangement of windings. A fourth winding group may include windings in the third group of stator slots  655  and the fourth group of stator slots  657 . The third group of stator slots  655  may include the first sequence  801  of windings. The fourth group of stator slots  657  may include the second sequence  803  in stair step arrangement of the windings and the fifth group of stator slots  659  may include the first sequence  801  in stair step arrangement of windings. The fifth group of stator slots  659  may include the first sequence  801  in stair step arrangement of windings, and the six groups of stator slots  661  may include the second sequence  803  in stair step arrangement of windings. The seventh group of stator slots  663  may include the first sequence  801  in stair step arrangement of windings, and the eighth group of stator slots  665  may include the second sequence  803  in stair step arrangement of windings. 
         [0057]      FIG. 7  illustrates eight groups of rotor slot groups which may be substantially truncated pie shaped and extend around the outer peripheral edge of the rotor  103  and may include an equal number of slots. A first winding group may include the windings in the first group of rotor slots  621  and the windings in the second group of rotor slots  623 . The first group of rotor slots  621  may be adjacent to the second group of rotor slots  623  and may be adjacent to the eighth group of rotor slots  635 . A second winding group may include the winding in the third group of rotor slots  625  and the fourth group of rotor slots  627 . The third group of rotor slots  625  may be adjacent to the second group of rotor slots  623  and may be adjacent to the fourth group of rotor slots  627 ; the first winding group may be repeated and may include the windings in the fifth group of rotor slots  629  and the six group of rotor slots  631 ; the fifth group of rotor slots  629  may be adjacent to the fourth group of rotor slots  627  and the sixth group of rotor slots  631  may be adjacent to the fifth group of rotor slots  629 . The second winding group may be repeated and may include the seventh group of rotor slots  633  and the eighth group of rotor slots  635 . The seventh group of rotor slots  633  may be adjacent to the sixth group of rotor slots  631  and may be adjacent to the eighth group of rotor slots  635 . 
         [0058]    The first group of rotor slots  621  may include the first sequence  801  in stair step arrangement of windings and the second group of rotor slots  623  may include the second sequence  803  in stair step arrangement of windings. The third group of rotor slots  625  may include the first sequence  801  in stair step arrangement of windings. The fourth group of rotor slots  627  may include the second sequence  803  in stair step arrangement. The fifth group of rotor slots  629  may include the first sequence  801  in stair step arrangement of windings and the six group of rotor slots  631  may include the second sequence  803  in stair step arrangement of windings. The seventh group of rotor slots  633  may include the first sequence  801  in stair step arrangement of windings and the eighth group of rotor slots  635  may include the second sequence  803  in stair step arrangement of the windings. The stator  101  may include only the first conductor  201 . 
         [0059]      FIG. 7  illustrates a first group of stator slots  651  which may be adjacent to an eight group of stator slots  665  and adjacent to a second group of stator slots  653  and illustrates a third group of stator slots  655  which may be adjacent to the second group of stator slots  653  and which may be adjacent to a fourth group of stator slots  657 . A fifth group of stator slots  659  may be adjacent to the fourth group of stator slots  657  and may be adjacent to a sixth group of stator slots  661 . A seventh group of stator slots numerals  663  may be adjacent to the sixth group of stator slots  661  and may be adjacent to the eighth group of stator slots  665 . 
         [0060]      FIG. 7  illustrates two sequences  701   703  of a single winding sequence which may be formed in stair step arrangement which may be that the slot may only include a single conductor. Similar to the sequences  801  and  803  the change in the number of conductors either increases or decreases by a single conductor. For example, the slot  711  may have sufficient space for 10 conductors but actually may have only one conductor. Slot  713  which may be directly adjacent to slot  711  may have only two conductors of the same winding group, and slot  715  which may be directly adjacent to slot  713  may have three conductors of the same winding group. The sequence  701  continues until the slot is filled with 9 conductors. A second sequence  703  follows the sequence  701  where the conductors may be removed from the slot, starting with a completely filled slot of conductors, one by one until the slot is left with a single conductor. Sequence  701  may begin again. Slot sizes may be formed in different sizes to accommodate conductor quantity. 
         [0061]    The first group of stator slots  651 , the third group of stator slots  655 , the fifth group of stator are slots  659  and the seventh group of stator slots  663  may follow the single winding first sequence  701  in stair step arrangement. 
         [0062]    The second group of stator slots  653 , the fourth group of stator slots  657 , the sixth group of stator are slots  661  and the eight group of stator slots  665  may follow the single winding second sequence  703  to in stair step arrangement. 
         [0063]      FIG. 9  additionally illustrates eight groups of stator slot groups which may be substantially truncated pie shaped and extend around the inner peripheral edge of the rotor  103  and may include an equal number of slots. 
         [0064]      FIG. 9  illustrates a first group of stator slots  651  which may be adjacent to an eighth group of stator slots  665  and adjacent to a second group of stator slots  653  and illustrates a third group of stator slots  655  which may be adjacent to the second group of stator slots  653  and which may be adjacent to a fourth group of stator slots  657 . A fifth group of stator slots  659  may be adjacent to the fourth group of stator slots  657  and may be adjacent to a sixth group of stator slots  661 . A seventh group of stator slots numerals  663  may be adjacent to the sixth group of stator slots  661  and may be adjacent to the eighth group of stator slots  665 . 
         [0065]    The first group of stator slots  651  may include the first sequence  801  in stair step arrangement of windings and the second group of stator slots  653  may the second sequence  803  in stair step arrangement of windings, and the third group of stator slots  655  may include the first sequence  801  in stair step arrangement of windings of windings. The fourth group of stator slots  657  may include the second sequence  803  in stair step arrangement of the windings and the fifth group of stator slots  659  may include the first sequence  801  in stair step arrangement of windings, the the sixth group of stator slots  661  may include second sequence  803  in stair step arrangement of the windings. The seventh group of stator slots  663  may include the first sequence  801  in stair step arrangement of windings, and the eighth group of stator slots  665  may include the second sequence  803  in stair step arrangement of windings. 
         [0066]      FIG. 9  illustrates eight groups of rotor slot groups which may be substantially truncated pie shaped and extend around the outer peripheral edge of the rotor  103  and may include an equal number of slots. The first group of rotor slots  621  may be adjacent to the second group of rotor slots  623  and may be adjacent to the eighth group of rotor slots  635 . The third group of rotor slots  625  may be adjacent to the second group of rotor slots  623  and may be adjacent to the fourth group of rotor slots  627 ; the fifth group of rotor slots  629  may be adjacent to the fourth group of rotor slots  627  and the sixth group of rotor slots  631 . The seventh group of rotor slots  633  may be adjacent to the sixth group of rotor slots  631  and may be adjacent to the eighth group of rotor slots  635 . 
         [0067]      FIG. 9  illustrates two sequences  701   703  of a single winding sequence which may be formed in stair step arrangement which may be that the slot may only include a single conductor. Similar to the sequences  801  and  803 , the change in the number of conductors either increases or decreases by a single conductor. For example, the slot  711  may have sufficient space for 10 conductors but actually may have only one conductor. Slot  713  which may be directly adjacent to slot  711  may have only two conductors of the same winding group, and slot  715  which may be directly adjacent to slot  713  may have three conductors of the same winding group. The sequence  701  continues until the slot is filled with 9 conductors. A second sequence  703  follows the sequence  701  where the conductors may be removed from the slot, starting with a completely filled slot of conductors, one by one until the slot is left with a single conductor. Sequence  701  may begin again. Slots may be formed in different sizes to accommodate conductor quantity with consideration given to rotor mechanical balance. 
         [0068]    The first group of stator slots  651 , the third group of stator slots  655 , the fifth group of stator are slots  659  and the seventh group of stator slots  663  may follow the single winding first sequence  801  in stair step arrangement. 
         [0069]    The second group of stator slots  653 , the fourth group of stator slots  657 , the sixth group of stator are slots  661  and the eight group of stator slots  665  may follow the single winding second sequence  803  to in stair step arrangement. 
         [0070]    As in  FIG. 7 , one winding group in round stator configuration about the stator may be illustrated and, the calibrated slip rotor can be utilized. Specifically for the stator, there is one winding group distributed around the stator face. This winding group is laid in the slots in stair step fashion. This winding group is connected to a direct current source. This stair stepped slot configuration distributes an approximate sinusoidal mmf wave around the stator when it is connected to a direct current source. For the rotor as illustrated in  FIG. 7 , there are at least two winding groups distributed around the rotor face. Each winding group is energized by its own set of slip rings. Each winding group is laid in the slots in stair step fashion. It is most advantageous for the number of slots on the rotor to be two times the number of poles times any odd integer that is greater than one. It is most advantageous for the number of turns in each slot is any integral multiple of this odd integer plus one (1). The two winding groups should be continuously stair stepped with respect to each other as you move from slot to slot around the rotor face. This configuration may distribute the approximate sinusoidal mmf wave around the rotor for any given desired mmf pole position angle, and this configuration may aid in mechanically balance the rotor. The sinusoidal distributed mmf wave transitions mostly the fundamental wave pattern of this sinusoidal magnetic field intensity of the rotor face into the air gap which forms the distributed magnetic flux density patterns through the air gap across to a sinusoidal distributed mmf stator face. The torque-speed characteristic of this stator configuration of the calibrated slip direct current machine should allow the machine to operate at moderate speeds while undergoing moderate to severe load or prime mover torque-position disturbances. 
         [0071]    The DC machine illustrated in  FIG. 6  may provide virtual pole displacement on both stator and rotor, and the DC machine may run the rotor at a fast speed with high torque. In addition, the machine can function as a motor. 
         [0072]    The DC machine illustrated in  FIG. 7  may include fixed poles on the stator and may provide virtual pole displacement on the rotor. Consequently, the rotor may be larger in diameter. The DC machine of  FIG. 7  may be used in applications requiring a higher torque and a lower speed. The DC machine of  FIG. 7  may function as a motor or a generator. 
         [0073]    The DC machine illustrated in  FIG. 9  may include fixed poles on the rotor, and consequently the rotor may be smaller in diameter. The DC machine  FIG. 9  may include virtual pole placement on the stator and may be useful in applications with high speed and low torque is desired. The DC machine of  FIG. 9  may operate as a motor or generator. 
         [0074]      FIG. 6 ,  FIG. 7  and  FIG. 9  depict both rotor and stator winding distributions that project nearly-pure sinusoidal distributed magnetic field intensity across each pole face. This not only should reduce the transfer of class 2 energy (a non-electromechanical energy conversion like heat) across the air gap; more importantly, it allows nearly 100% of this precious air gap real estate to be utilized for the transfer of class 1 energy (electromechanical energy conversion). 
         [0075]    Both  FIGS. 6 and 7  illustrates a rotor that has two winding groups which allow the controller to virtually direct the vectors and magnitudes of the rotor poles with respect to a reference on the rotor axle. 
         [0076]      FIG. 6  illustrates a stator that also has two winding groups which allows the controller to virtually direct the vectors and magnitudes of the stator poles with respect to a fixed reference on the stator steel. The advantage of this machine is that it should be able to operate at angular velocities, both clockwise and anti-clockwise, over a wide range of speed magnitudes accurately controlled by the controller within the limits of the machine and the controller. This machine can be operated in motor mode. 
         [0077]      FIG. 7  illustrates a stator that may only have one winding group which allows the controller to virtually direct only the magnitudes of the stator poles while maintaining fixed vectors with respect to a fixed reference on the stator steel. The advantage of this machine is that this DC machine should be able to operate at angular velocities, both clockwise and anti-clockwise, over a more limited range of speed magnitudes accurately controlled by the controller within the limits of the machine and the controller. This machine can be operated in motor or generator mode. 
         [0078]      FIG. 9  illustrates a rotor that may only have one winding group which allows the controller to virtually direct only the magnitudes of the rotor poles while maintaining fixed vectors with respect to a fixed reference on the rotor axle. The advantage of this DC machine may be having torque-speed characteristics of higher speeds and lower torque. This machine can be operated in motor or generator mode. 
         [0079]      FIG. 10  illustrates another control system which may control the circuit of  FIG. 6  and which may include a control circuit  1102  for the calibrated slip DC machine and of the present invention and illustrates a stator  1101  which may extend around a rotor  1103  which may cooperate with a shaft  1105  which may rotate. The calibrated slip DC machine may operate as a motor in accordance with the teachings of the present invention. The shaft  1105  may be connected to a position sensor  1121  which may be an optical wheel to provide an indication of the position such as the rotational position of the shaft and to provide an indication of the slip of the calibrated slip DC machine and.  FIG. 10  additionally illustrates a first multiplier circuit  1117  and a second multiplier circuit  1119  which may be connected to slip rings  1107  which may be positioned on the shaft  1105  to connect to the first winding group and the second wiring group respectively which may be positioned within the rotor  1103 . The desired position and slip of the rotor  1103  and the output from the position and slip circuit  1123  which provides the actual position and slip of the rotor  1103  may be input to the summing circuit  1113  which may calculate the difference between the two inputs. Alternatively, only one of these two inputs is referenced against desired while the other input may establish an operational bandwidth (set of boundaries). The slip quantity is the time derivative of position quantities and is calculated. When actual position with respect to time is referenced against desired, the error quantity of slip can be “tuned” to optimize controllability to the most narrow bandwidth possible before stability becomes compromised. When slip is referenced against desired, the error quantity of position can be “tuned” to optimize controllability before stability becomes compromised. This makes it possible to apply a soft yet directional starting torque to the rotor when operated as a motor. The output of the summing circuit  1113  is input to the angle generator  1109  to generate an angle based upon the desired position and desired slip. The magnitude of the desired excitation is input to the magnitude summing circuit  1115  and the voltage V is additionally input to the magnitude summing circuit  1115 . The output of the magnitude summing circuit  1115  is input to the magnitude generating circuit  1111  to generate a magnitude for the first multiplier circuit  1117  and the second multiplier circuit  1119 , and the output of the angle generator  1109  is input to the first multiplier circuit  1117  and the second multiplier circuit  1119 . The first multiplier circuit  1117  multiplies the magnitude by the cosine of the angle and the second multiplier circuit  1119  multiplies the magnitude by the sine of the angle. The output of the first multiplier circuit  1119  and the second multiplier circuit  1119  is input to first winding group and the second winding group of the rotor  1103 . The control circuit as shown in  FIG. 10  may include a third multiplier circuit  1153  to multiply by −R where R is a constant and fourth multiplier circuit  1151  to multiplied by −T where T is a constant. Both the output from the third multiplier circuit  1153  and the fourth multiplier circuit  1511  are connected to the stator  1101 , and the input to the third multiplier circuit  1153  and the fourth multiplier circuit  1151  are connected to the cosine multiplier circuit  1117  and the sine multiplier circuit  1119 . 
         [0080]    While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed.