Rotor field winding configuration and control method

Abstract

An electric motor rotor, comprising a plurality of wound field poles each having a single winding coil, a first group of wound field poles of a same field polarity, and a second group of wound field p

Description

TECHNICAL FIELD The present disclosure relates a rotor for use in a synchronous electric motor. BACKGROUND Electric motors have become ubiquitous and are vital in areas as wide-ranging as electric vehicles and kitchen appliances. The different types and ways of constructing electric motors are thus as diverse as their applications. Synchronous motors driven with multi-phase AC have found specific uses in traction applications as the rise of the electric vehicle has accelerated in recent years. They can offer high power density. Many of these types of motors usually use permanent magnets to function, which presents several issues. Firstly, the production of permanent magnets requires scarce resources, such as nickel, cobalt or rare-earth metals. Secondly, the strength of the magnetic field of a permanent magnet wanes over time, and hence synchronous motors that use them tend to become less efficient with prolonged use. Furthermore, use of permanent magnets means that there always exist magnetic fields within the motor which may interact with other elements of the motor in an adverse manner and cause negative issues during production, functional safety during operation and during recycling. There is therefore a need for an improved synchronous electric motor that does not require the use of permanent magnets. The field-wound type of synchronous motors exert excellent practical utility in speed-variable type rotary electric machines used, for example, for generating power for automotive performances, in that there is no need to place expensive permanent magnets in a rotor core, there is no need to consider resistance to centrifugal force of the magnets, and torque and generated (induced) voltage can be freely controlled by field flux control. However, a great disadvantage of prior art field-wound synchronous motors is the need to provide the transfer of electrical energy externally to the rotating rotor on which the field windings are situated. Prior art solutions to this disadvantage include the use of slip-rings, but these will wear over the life of the motor. Alternative prior art solutions use a rotating transformer or a rotating exciter. Both of these later solutions remove the issue of wear, however, all of these solutions require an external source of electrical energy which increases the cost and size of the overall system. Prior art solutions to the disadvantage of the requirement for an external source of energy have so far focused on the use of additional windings or coils situated on the rotor, but this has the disadvantage of requiring additional space and weight. These methods also often result in a motor mechanical torque that contains a great deal of ac ripples which has the disadvantage of increased noise and vibration. The present invention has been made in light of the above problems and has an object of 5 providing a field-winding type of synchronous machine of which torque ripple is small. SUMMARY A first aspect of an electric motor rotor, comprising: a plurality of wound field poles each having a single winding coil; a first group of wound field poles of a same field polarity; a second group of wound field poles of a same field polarity; wherein the first group of wound field poles is configured as a series connection, and the second group of wound field poles is configured as a parallel connection. A second aspect wherein the first group of wound field poles is coupled to the second group of wound field poles. A third aspect wherein the first group of wound field poles can change to being configured as a parallel connection during a section of the periodic voltage induced across the wound field poles. A fourth aspect wherein the second group of wound field poles can change to being configured as a series connection during a section of the periodic voltage induced across the wound field poles. A fifth aspect wherein the first or second or both groups of wound field poles are connected to a current flow control device. A sixth aspect wherein the current flow control device allows only induced AC current components of a single direction pass through it. A seventh aspect wherein the first or second or both groups of wound field poles are connected to a first current regulation control device. An eight aspect wherein the first or second or both groups of wound field poles are connected to a second current regulation control device wherein the second current regulation control device is connected in parallel with the first second current regulation control device. A ninth aspect wherein the first and second current regulation control devices can control maximum current level to a plurality of current level demands. A tenth aspect wherein the first and second current regulation control devices current level demands are set in response to the frequency of the induced voltage wave across the wound field poles. An eleventh aspect wherein the first or second or both groups of wound field poles are connected in series with an energy storage device. A twelfth aspect wherein the energy storage device is a capacitor. A thirteenth aspect wherein the energy storage device is connected to the current flow control device. A fourteenth aspect wherein the energy storage device is connected to the current flow control device and the first current regulation control device. A fifteenth aspect wherein the second current regulation control device is connected to a load. A sixteenth aspect wherein the load is a resistor. A seventh aspect of a rotor of any preceding claim forms part of an electric motor comprising; A stator that provides a varying magnetic field; wherein this magnetic field induces a voltage across the wound field poles. An eighteenth aspect is a method for operating an electric motor comprising the rotor of any preceding claims comprising: configuring the first or second group of wound field poles in series when the induced voltage is in the desired polarity of the energy storage device; charging the energy storage device when the induced voltage across the group of wound field poles is greater than the voltage across the energy storage device. A nineteenth aspect is a method further comprising: permitting current to flow through the load when the induced voltage across the group of wound field poles is less than the voltage across the energy storage. A twentieth aspect wherein the maximum current into the energy storage device and the maximum current into the load is regulated to a demand level. A twenty first aspect is a method for operating an electric motor comprising the rotor of any preceding claim comprising: configuring the first or second group of wound field poles in parallel when the induced voltage is in the opposite polarity to the desired polarity of the energy storage device; discharging the energy storage device when the induced voltage across the group of wound field poles is less than the voltage across the energy storage device. A twenty first aspect is a method for operating an electric motor of claims 21 wherein the maximum current out of the energy storage device is regulated to a demand level. A twenty third aspect is a further method comprising; the first and second group of wound field poles being electrically coupled; the first and second group of wound field poles being of different desired magnetic polarity; wherein the first group of wound field poles is connected in a series connection while the second group of wound field poles is connected in parallel configuration or, first group of 5 wound field poles is connected in a parallel connection while the second group of wound field poles is connected in series configuration. A twenty fourth aspect where the methods are implemented on a microprocessor or logic device situated on the rotor of claim 1. A twenty fifth aspect where the microprocessor or logic device of claim 24 communicates with 10 a control device that is external to the rotor of claim 1. BRIEF DESCRIPTION OF DRAWINGS Examples of the present disclosure will now be described with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic axial cross section illustrating an arrangement of a field-winding type of synchronous machine from patent US20060290316A1; Figure 2 schematically illustrates a cross section through a radial flux wound pole rotor assembly; Figure 3 schematically illustrates a cross section through an axial flux wound pole rotor assembly; Figure 4 schematically illustrates a field magnetic circuit made up of one North and one South rotor field pole and associated windings from prior art papers; Figure 5 shows the currents induced in the field windings with the stator U phase current shown as a reference, from a prior art method. Figure 6 shows the total rotor current induced in the field windings, from a prior art paper. Figure 7 shows a prior art field winding rectification and stabilization method from patent US20060290316A1; Figure 8 is a simulated waveform diagram showing composite armature current waveforms of individual phases, which have been obtained by superimposing high-frequency current components for imparting the field winding with an excitation current, upon fundamental wave components (sine wave) of an armature current, and showing waveforms of an excitation current that has been produced on that occasion in the rotor winding, from patent US20060290316A1; Figure 9 schematically illustrates single windings and current controlled capacitance charging and current controlled loading circuits. Figure 10 schematically illustrates current and voltage plots during the operation of a single North windings with current controlled capacitance charging and current controlled loading circuits. Figure 11 schematically illustrates two North windings in series with capacitor charging and loading with current control and then in parallel while discharging the capacitance with current control. Figure 12 schematically illustrates current and voltage plots during the operation of the circuits of figure 11. Figure 13 schematically illustrates a single combined circuit that may be used to provide the functions of figure 11 giving results as in the plots of figure 12. Figure 14 schematically illustrates current and voltage plots during the operation of the circuit of figure 13 and how the fluxes generated by the North and South pole windings combine on the same magnetic flux circuit. Figure 15 schematically illustrates a single combined circuit that may be used to provide the functions of multiple North and South windings sharing the same magnetic circuits and energy storage. Figure 16 schematically illustrates North and South winding and combined currents with low or zero energy storage. Figure 17 schematically illustrates North and South winding and combined currents with greater energy storage. Figure 18 schematically illustrates a single combined circuit that may be used to provide the functions of multiple North and South windings sharing the same magnetic circuits and energy storage with the inclusion of current regulation and loading. Figure 19 schematically illustrates the individual winding currents and the combined winding current when simulating the circuit of figure 18 without current regulation coordination. Figure 20 schematically illustrates current plots for a North and a South winding and combined when the is no energy storage. DETAILED DESCRIPTION There is disclosed a synchronous electric motor comprising: a stator configured to generate a varying magnetic field; a rotor configured to rotate about a rotation axis in response to the varying magnetic field, the rotor comprising a set of rotor pole windings and coupling electronics that harvest AC energy from the stator to provide rotor pole magnetic fields. Figure 1 is a diagrammatic axial cross section illustrating an arrangement of a field-winding type of synchronous machine from patent US20060290316A1; In figure 1, (from patent US20060290316A1) indicated by 1 is a stator, by 2 is a stator core, and by 3 is a stator winding (armature winding) wound about the stator core 2. Further, indicated by 4 is a rotor, by 5 is a rotor core, by 6 is a rotor winding (field winding) wound about the rotor core 5, and by 7 is a rotor shaft. Indicated by 9 is a frame (so-called housing) which is fixed to the stator 1 and rotatably supports the rotor 4. Indicated by 10 is a position sensor for detecting a rotational position of the rotor. The position sensor 10 is fixed to the rotor shafts 7 . Indicated by 20 is an inverter for controlling armature current of the stator winding 3 based on signals output from the position sensor 10 and a controller 40, and by 30 is a DC power source for supplying power required by the inverter 20. Figure 2 schematically illustrates a cross section through a radial flux wound pole rotor assembly where 201 denotes the rotor that rotates about the axial, 203. Around the circumference edge of the rotor are equidistantly arranged rotor field poles, 202, which are energised by each having a field winding. In prior art methods, the field windings are connected and energised by a DC field current. The current is either provided externally or through self-excitation within the rotor assembly. In the case that the field current is provided externally, a method such as slip ring contacts, or a rotational transformer are used to transmit power from a stationary source to the rotating rotor. There are wear issues when using a slip ring. In all examples where the field current is provided external to the rotor, there is the need for power electronics externally to converter and control the field current. In the case that the field current is provided internal to the rotor, through self-excitation, the field current power electronics and circuits are situated on the rotor, shown by 204. Figure 3 schematically illustrates a cross section through an axial flux wound pole rotor assembly where 301 denotes the rotor that rotates about the axial, 303. Around the axial of the rotor are equidistantly arranged rotor field poles which are energised by each having a field winding. 302 shows a pole where the flux lines are in the direction out of the page and is denoted North. 306 shows a pole where the flux lines are in the direction into the page and is denoted South. In prior art methods, the field windings are connected and energised by a DC field current. The North poles, 302, with current in one direction (by convention positive) and the South poles, 306, with current in the other direction (by convention negative). In the case that the field current is provided internal to the rotor, through self-excitation, the field current power electronics and circuits are situated on the rotor, shown by 304. In the paper "Permanent-Magnet-Free-Synchronous Motor with Self-Excited Wound-Field Technique Utilising Space Harmonics", by Aoyama and Kumai, self-excitation of the rotor field current is provided using auxiliary coils on additional rotor poles that are placed between the field poles. In the paper "Adjustable Speed Drive Capability of Self-Excited Wound-Field Synchronous Motor Utilising Space Harmonics", by Aoyama and Kumai, self-excitation of the rotor field current is provided using auxiliary coils on the field poles. Figure 4 schematically illustrates a field magnetic circuit made up of one North and one South rotor field pole and associated windings from prior art papers. Fl denotes the North filed winding and II denotes the auxiliary induction winding that is wound on the same field pole as Fl. F2 denotes the North filed winding and 12 denotes the auxiliary induction winding that is wound on the same field pole as F2. All windings have the same winding direction as denoted with the dot at the top of each winding. The motor rotating stator current produces a stator magnetic field that passes through the airgap and through the rotor including the rotor poles. The stator magnetic field rotates, with respect to a stationary reference, and interacts with the rotor magnetic poles to produce torque. The rotor field coils experience stator magnetic field components including spatial harmonics and field excitation injection currents as described in the previously noted papers and prior art patent US2969491A. The stator magnetic field components experienced by the rotor poles give rise to induced ac voltages. Due to the similar winding direction, these induced voltages will have the same polarity on each of the windings shown in figure 4. When the induced voltage has positive polarity, the combined voltage of the series connected windings Fl and II is greater than the voltage induced on F2 and so current flows through DI. This action provides a negative current through F2, which is a South pole, and positive current through Fl, which is a North pole. The magnetic rotor field produced is shown by the dashed loop with a direction shown by the arrow heads. When the induced voltage has negative polarity, the combined voltage of the series connected windings F2 and 12 is greater than the voltage induced on Fl and so current flows through D2. Again, this action provides a negative current through F2, which is a South pole, and positive current through Fl, which is a North pole. The magnetic rotor field produced is shown by the dashed loop with a direction shown by the arrow heads. Figure 5 shows the currents induced in the field windings with the stator U phase current shown as a reference, from a prior art method. The light trace shows the current induced in the forward voltage polarity direction when DI is conducting. The mid shade trace shows the current induced in the negative voltage polarity direction when D2 is conducting. It should be noted that the field currents, and thus the field magnetic field, is not held constant which gives rise to ripple on the torque produced by the motor. Figure 6 shows the total rotor current induced in the field windings, from a prior art method. Again this is not a constant current of constant magnetic field strength. Figure 7 shows a prior art field winding rectification and stabilization method from patent US20060290316A1. With reference to figure. 7, a field-winding type of synchronous machine using armaturewinding power supply technique. A capacitor 14 is connected parallel to the diode 12. This arrangement may stabilize the excitation current flowing through the rotor winding 6 and voltage generated therein. However, effective size of the field flux becomes small because, among the AC currents induced to the rotor winding 6, half-wave components of opposite phase that should be shut out are passed through the capacitor 14. It should be noted that this prior art method which includes the capacitance for voltage stabilisation, produces a low level of rotor magnetic field flux and so does may not result in an efficient motor. Figure 8 shows a prior art timing diagram showing composite waveforms of armature currents of individual phases, which have been obtained by superimposing high-frequency current components for imparting the field winding with excitation current upon fundamental wave components (sine waves) of the armature current, and a waveform of the excitation current produced in the rotor winding at the time of superimposition, from patent US20060290316A1. In the figure, lu indicates a composite armature current of the U-phase, Iv indicates a composite armature current of the V-phase, Iw indicates a composite armature current of the W-phase, and Ir indicates the excitation current that is a rectified induced current. The excitation current Ir is rectified by the diode and passed through the rotor winding. As can be seen from FIG. 8, the excitation current Ir is passed through the rotor winding by superimposing the pulsed high-frequency components during a short period of one cycle of the fundamental wave components of the armature current of each of the phases. It should be noted that the field current, Ir, is not held constant and suffers from notches during the excitation periods. The stator currents also suffer from notches which may result in torque ripple. The inverter producing the stator currents must be sized to provide not only the fundamental stator currents but also the superimposed injected currents which are of a high magnitude. Detailed description of illustrative embodiments The present disclosure relates to a synchronous electric motor, and certain components of a synchronous electric motor. In examples, there is provided a synchronous electric motor comprising a stator configured to generate a varying magnetic field. The synchronous electric motor comprises a rotor configured to rotate about a rotation axis in response to the varying magnetic field. Figure 9 schematically illustrates single windings and current controlled capacitance charging and current controlled loading circuits. The current flow control elements (Current flow control 1 and Current flow control 2) could be passive elements such as diodes or active elements such as switch devices. The loading elements (Load 1 and Load 2) could be passive elements such as resistors or temperature dependent resistors, where the impedance of the load could be fixed or varying and have values including zero ohms. The current regulator elements (Current regulator 1, Current regulator 2, Current regulator 3, Current regulator 4) may include passives such as temperature dependent resistors, discrete electronics such as comparators and semiconducting switches, or intelligent such as logic / microprocessor-controlled semiconductor devices. Those skilled in the art will imagine that the current regulators can be self-powering or drawn on a supply derived from Cl or C2 or from a supply derived from a separately rectified feed from the windings. Figure 10 schematically illustrates current and voltage plots during the operation of a single North windings with current controlled capacitance charging and current controlled loading circuits. 1001 denotes the voltage or current axis. 1002 denotes the time axis. 1003 denotes the voltage induced on the winding NW1 and 1006 denotes the voltage across the capacitance, Cl. 1004 denotes the current through the capacitance, Cl, during charging when current regulator 1 has no limit and when current regulator 2 has a limit of zero amps. In this case the circuit is equivalent to a simple diode and capacitor in series with the NW1 winding. This current is unidirectional and will thus produce a unidirectional magnetic field in the NW1 winding pole. However, this current is not held constant and is not at a controlled level. The flux will thus not be constant and not at the required level. Those skilled in the art will see that a low-cost version of the present invention can be produced with simple diodes as the current flow control and no current regulators or loads. 1007 denotes the current through the NW1 winding when current regulator 1 has a limit of zero and current regulator 2 has a current limit equal to the plateau in plot 1005. In this case the field current is constant for part of the induced voltage wave. However, the energy is lost in the load. The desired winding current level is the plateau in plot 1005. The present invention uses two current regulators (current regulator 1 and current regulator 2) to provide the winding current wave 1005, and also to charge the capacitance as per plot 1006. During section 1007 (bounded by plot 1005 and plot 1004) the current flows through current regulator 2. Both current regulators have a limit set at the desired winding current level. The winding current, 1005, cannot immediately reach the desired winding current level as the induced winding voltage is too small. As the induced winding voltage rises, so does the winding current until it reaches the desired winding current level where it is held by current controller 2. During this stage in the induced winding voltage there is not enough voltage to charge the capacitance at the required winding current level. At the boundary of section 1007 and 1008 (which is part of the plot 1004) current regulator 2 reduces its limit so that current can flow through current regulator 1 to charge the capacitance, Cl. Those skilled in the art will image how the control of the regulator's limits can be based on the induced winding voltage level, or by logic / microprocessor sequencing. During section 1008 the current flow has changed from fully through the load to fully charging the capacitance, Cl, where it is limited by current regulator 1. At the boundary of sections 1008 and 1009 the balance of current flow is reversed by increasing the current limit of current regulator 2 so that current flows through the load once more. This method is repeated during the next positive half cycles of the induced winding voltage until the voltage across the capacitance, 1006, results in no current flowing through current regulator 1. The next set of figures will explain how the invention utilises the stored energy in capacitor, Cl, which results in the capacitor always charging during the positive half cycle of the induced winding voltage wave. The previous description has related to the NW1 winding which is a North pole winding. Those skilled in the art will be able to see the mirrored symmetry of currents which will be provided by the circuit in figure 9 drawing 901 which contains SW1 winding which is a South pole. In this case, it is the negative half cycle of the induced winding voltage that is used to charge the capacitor, C2 through current regulator 3 and is loaded by Load 2 through current regulator 4. Figure 11 schematically illustrates two North windings in series with capacitor charging and loading (1101) with current control and then in parallel while discharging the capacitance (1102) with current control. Turning to figure 11 drawing 1101, the two North windings (each on its own field pole), NW1 and NW2 are connected in series to give the maximum induced voltage peak which is then current flow controlled by Current flow control 1. This could be a simple diode or alternatively a switch etc. Current Regulator 1 controls the current charging the capacitor, Cl. Current regulator 2 controls the current through the load. Load 1. Turning to figure 11 drawing 1102, the two North windings, NW1 and NW2 are connected in parallel resulting in the minimum induced voltage peak which maximises the time for which the voltage on the Cl is greater so current can flow through Current flow control 11 under the control of Current Regulator 5. Figure 12 schematically illustrates current and voltage plots during the operation of the circuits of figure 11. The numbers denote features as before on figure 10. The half period of the positive induced voltage, 1003, when the two windings are in series is denoted by 1203 during which the current, 1005, is controlled by Current Regulator 1 while charging the capacitor, Cl and Current regulator 2 while current passes through the load. Load 7. The half period of the negative induced voltage when the two windings are in parallel is denoted by 1204. During this time the capacitor, Cl, is discharged, when its voltage is greater than the induced voltage on the windings. This occurs in two places where the current is denoted 1201 and 1202. During these times the current is controlled by Current flow control 77 and Current Regulator 5. Figure 13 schematically illustrates a single combined circuit that may be used to provide the functions of figure 11 giving results as in the plots of figure 12. Turning to figure 13, Current flow control 3 provides both the combined functions of Current flow control 1 (when current flows out of the series connected windings to charge the capacitance) and Current flow control 11 (when current flows out of the capacitance and into the parallel connected windings) in figure 11. Current regulator 6 in figure 13 provides both the charging control of Current Regulator 1 of figure 11 and the discharge current control of Current Regulator 5 of figure 11. Current regulator 7 in figure 13 provides the same function as Current Regulator 2 of figure 11. The parallel to series connector is made by Parallel and series controller 1 and the combined winding current polarity is controlled by the H bridge made up of SI, S2, S3 and S4. Alternatively, some or all the switches can be exchanged for diodes depending on the desired overall functionality required. Those skilled in the art will know if electrical connection methods that can provide similar functionality. During the positive half cycle of the induced winding voltage, the current flow is shown by the fine dotted lines. The windings are connected in series and only switches S2 and S3 are conducting. The current path is either / or charging Cl through Current Regulator 6, or / and through Load 1 and Current Regulator 7. During the negative half cycle of the induced winding voltage, the current flow is shown by the "fine line plus dot" lines. The windings are connected in parallel and only switches SI and S4 are conducting. The current path is discharging Cl through Current Regulator 6. Figure 14 schematically illustrates current and voltage plots during the operation of the circuit of figure 13 and how the fields generated by the North and South pole windings combine on the same magnetic field circuit. Turning to figure 14, the time denotes by 1002 has been broken down into three sections, 1401, 1402 and 1403. The two North windings are employed as per the circuit and function of Figure 13. There is also a set of two South pole windings which are in a similar circuit configuration as the North windings but with different elements. Each unique North winding shares the same magnetic circuit as a unique South winding. Alternatively, all windings can be on the same magnetic circuit, or in groups as long as there is the same number of Norths and Souths per group. During section 1401 the induced winding voltages of all windings are positive and the North windings will charge their capacitance or be loaded. During section 1402 the induced winding voltages of all windings are negative and the North winding circuit is discharging through the North windings. Simultaneously, the South winding circuit is charging its capacitance. During section 1403 the induced winding voltages of all windings are positive once more, the North winding circuit is charging through the North windings and the South winding circuit is discharging its capacitance through its windings. Sections 1402 and 1403 repeat. The lower plot of figure 14 shows the combined currents through one North and One South winding. The control of the capacitance charging, loading, and discharging may be designed to create a constant magnetic field strength, 1404, through their shared magnetic circuit. Note that each North and South windings passes current only half the time so the design requires double the turns to get same field level as would be provided if both the North and South carried current at the same time, however, the wire used may be half the cross-sectional area so will fit in approximately the same volume. Those skilled in the art will image how the control of the regulator's limits can be based on the induced winding voltage level in either the windings that are currently in series (this voltage will be affected by the loading) or more usefully the windings currently in parallel (this voltage is not affected by loading), or by logic / microprocessor sequencing. Figure 15 schematically illustrates a single combined circuit that may be used to provide the functions of multiple North and South windings sharing the same magnetic circuits and energy storage. Turning to figure 15, this shows how a shared energy storage, capacitance Cl can be used by combining instances of the circuits described earlier. Current flow control 4 controls the current from the South windings and switches S5, S6, S7 and S8 can control the flow polarity. Note that there is no current regulation or loading in this simplified circuit. The value of the energy storage, in the illustration Cl, can be optimised to provide a unidirectional current offset versus the time required to initial charge the capacitance. Figure 16 schematically illustrates North and South winding and combined currents with low or zero energy storage. Turning to figure 16, the energy storage is low or zero so the combined current (in black) from one North (dotted line) and one South winding (in grey) follows a fully rectified shape of AC with a low average. Note that in this example the current passes through two windings in series into two windings in parallel. This results in the parallel winding having half as much current flowing through it that the series connected winding. Winding utilisation is good as current flows through all windings at the same time. Figure 17 schematically illustrates North and South winding and combined currents with higher energy storage. Turning to figure 17, the energy storage is greater so the combined current (in black) from one North (dotted line) and one South winding (in grey) has a greater average and does not drop to zero. The shape of the individual winding currents is similar to those in figure 12. Figure 18 schematically illustrates a single combined circuit that may be used to provide the functions of multiple North and South windings sharing the same magnetic circuits and energy storage with the inclusion of current regulation and loading. Turning to figure 18, requires only one load (Load 1) and one load current regulator (Current Regulator 7) and all current regulators may be controlled in a coordinated manner. Item labels are consistent with earlier figures. Figure 19 schematically illustrates the individual winding currents and the combined winding current when simulating the circuit of figure 18. The combined winding currents (in black) can further be made constant by tuning the coordinated current regulators. Turning to figure 20, 2001 denotes the combined current of one North and one South winding. 2001 denotes the current in the North winding and 2003 denotes the current in the South winding. The plot is separated into sections 2004 through 2009. During sections 2004 and 2006 the current is provided by the controlled loading of the North winding. During section 2005, the current is shared between the North and South winding. The North windings are in series at this stage so pass the full current and the South windings are in parallel so pass half that current. Hence the plot shows that the combined current is a third through the South winding and two thirds through the North winding. Note that this ratio will change depending on the number of windings that are combined in a single circuit. The roles of the South and North windings are reversed in sections 2007, 2003 and 2009. Generally, the case with low or zero energy storage will provide less winding current and hence less magnetic field for the same induced voltage conditions. Those skilled in the art will realise that one or more combined groups of windings, each with a circuit, can be used on the same rotor. Those skilled in the art will realise that the preceding methods and circuits can be combined and also implemented in different forms. ASPECTS OF THE DISCLOSURE Non-limiting aspects of the disclosure are set out in the following numbered clauses. 1. An electric motor rotor, comprising: a plurality of wound field poles each having a single winding coil; a first group of wound field poles of a same field polarity; a second group of wound field poles of a same field polarity; wherein the first group of wound field poles is initially configured as a series connection, and the second group of wound field poles is initially configured as a parallel connection. 2. The rotor of any preceding claim wherein the first group of wound field poles is coupled to the second group of wound field poles. 3. The rotor of any preceding claim wherein the first group of wound field poles can change to being configured as a parallel connection during a section of the periodic voltage induced across the first group of wound field poles. 4. The rotor of any preceding claim wherein the second group of wound field poles can change to being configured as a series connection during a section of the periodic voltage induced across the second group of wound field poles. 5. The rotor of any preceding claim wherein the first or second or both groups of wound field poles are connected to a current flow control device. 6. The rotor of any preceding claim wherein the current flow control device allows only induced AC current components of a single direction to pass through it. 7. The rotor of any preceding claim wherein the first or second or both groups of wound field poles are connected to a first current regulation control device. 8. The rotor of any preceding claim wherein the first or second or both groups of wound field poles are connected to a second current regulation control device wherein the second current regulation control device is connected in parallel with the first second current regulation control device. 9. The rotor of any preceding claim wherein the first and second current regulation control devices can control maximum current level to a plurality of current level demands. 10. The rotor of any preceding claim wherein the first and second current regulation control devices current level demands are set in response to the frequency of the induced voltage wave across the wound field poles. 11. The rotor of any preceding claim wherein the first or second or both groups of wound field poles are connected in series with an energy storage device. 12. The rotor of any preceding claim wherein the energy storage device is a capacitor. 13. The rotor of any preceding claim wherein the energy storage device is connected to the current flow control device. 14. The rotor of any preceding claim wherein the energy storage device is connected to the current flow control device and the first current regulation control device. 15. The rotor of any preceding claim wherein the second current regulation control device is connected to a load. 16. The rotor of any preceding claim wherein the load is a resistor. 17. The rotor of any preceding claim forms part of an electric motor comprising; A stator that provides a varying magnetic field; wherein this magnetic field induces a voltage across the wound field poles. 18. A method for operating an electric motor comprising the rotor of any preceding claims comprising: configuring the first or second group of wound field poles in series when the induced voltage is in the desired polarity of the energy storage device; charging the energy storage device from the group of wound field poles when the induced voltage across the group of wound field poles is greater than the voltage across the energy storage device. 19. The method for operating an electric motor of claim 18 further comprising: permitting current to flow through the load when the induced voltage across the group of wound field poles is less than the voltage across the energy storage. 20. The method for operating an electric motor of claims 18 and 19 wherein the maximum current into the energy storage device and the maximum current into the load is regulated to a demand level. 21. A method for operating an electric motor comprising the rotor of any preceding claim comprising: configuring the first or second group of wound field poles in parallel when the induced voltage is in the opposite polarity to the desired polarity of the energy storage device; discharging the energy storage device through the group of wound field poles when the induced voltage across the group of wound field poles is less than the voltage across the energy storage device. 22. The method for operating an electric motor of claims 21 wherein the maximum current out of the energy storage device is regulated to a demand level. 23. The methods of claims 18 to 22 further comprising; the first and second group of wound field poles being electrically coupled together; 5 the first and second group of wound field poles being of different desired magnetic polarity; wherein the first group of wound field poles is connected in a series connection while the second group of wound field poles is connected in parallel configuration and, the first group of wound field poles is connected in a parallel connection while the second group of wound 10 field poles is connected in series configuration. 24. The methods of claims 18 to 23 are implemented on a microprocessor or logic device situated on the rotor of claim 1. 25. The microprocessor or logic device of claim 24 communicates with a control device that is external to the rotor of claim 1. Amendments to the claims have been filed as follows:

Claims

1. An electric motor comprising: a stator and a rotor, the rotor comprising:a plurality of wound field poles each having a winding coil;a first group of wound field poles of a same field polarity;5 a second group of wound field poles of a same field polarity;wherein the first group of wound field poles is initially configured as a series connection, and the second group of wound field poles is initially configured as a parallel connection;wherein the first of group of wound field poles are electrically connected to a first current 10 regulation control device;wherein a current level demand is set in response to the frequency of the induced voltage wave across the wound field poles.

2. The rotor of claim 1 wherein the first group of wound field poles is coupled to the second 15 group of wound field poles.

3. The rotor of claim 1 wherein the first group of wound field poles can change to being configured as a parallel connection during a section of the periodic voltage induced across the first group of wound field poles.LOCM20 4. The second group of wound field poles of claim 1 wherein the second group of wound field poles can change to being configured as a series connection during a section of the periodic voltage induced across the second group of wound field poles.

5. The rotor of claim 1 wherein the first or second or both groups of wound field poles are 1 electrically connected to a second current regulation control device wherein the second1 25 current regulation control device is electrically connected in parallel with the first currentregulation control device.

6. The rotor of claim 5 wherein the first and second current regulation control devices can control maximum current level to a plurality of current level demands.

7. The rotor of claims 1 wherein the first or second or both groups of wound field poles are 30 electrically connected with an energy storage device.

8. The rotor of claim 7 wherein the energy storage device is electrically connected to the current flow control device.

9. The rotor of claim 7 wherein the energy storage device is electrically connected to the current flow control device and the first current regulation control device.35 10. The rotor of claim 5 wherein the second current regulation control device is connectedto a load.

11. A method for operating an electric motor comprising the rotor of claims 1 and 7 comprising:configuring the first or second group of wound field poles in series when the resulting induced voltage is greater than that of the energy storage device;charging the energy storage device from the group of wound field poles when the induced voltage across the group of wound field poles is greater than the voltage across the energy storage device.

12. The method for operating an electric motor of claim 11 further comprising:permitting current to flow through the load when the induced voltage across the group of wound field poles is less than the voltage across the energy storage.

13. The method for operating an electric motor of claims 11 and 12 wherein the maximum current into the energy storage device and the maximum current into the load is regulated to a demand level.

14. A method for operating an electric motor comprising the rotor of claims 1 and 7 comprising:configuring the first or second group of wound field poles in parallel when the induced voltage is in the opposite polarity to that of the energy storage device;discharging the energy storage device through the group of wound field poles when the induced voltage across the group of wound field poles is less than the voltage across the energy storage device.

15. The method for operating an electric motor of claims 14 wherein the maximum current out of the energy storage device is regulated to a demand level.

16. The methods of claims 11 to 15 further comprising;the first and second group of wound field poles being electrically coupled together;the first and second group of wound field poles being of different magnetic polarity;wherein the first group of wound field poles is electrically connected in a series connection while the second group of wound field poles is electrically connected in parallel configuration and, the first group of wound field poles is electrically connected in a parallel connection while the second group of wound field poles is electrically connected in series configuration17. The methods of claims 11 to 16 are implemented on a microprocessor or logic device situated on the rotor of claim 1.

18. The microprocessor or logic device of claim 17 communicates with a control device that is external to the rotor of claim 1.LDCM

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