Hybrid wound rotor motor and generator with inductive feed and continuous current

Abstract

Hybrid wound rotor motor and generator with inductive feed and persistent current. In one or more examples, a system operating in a generator mode includes a cryogenic refrigerator to cool a superconducting coil. The system also includes a magnetic flux pump to provide magnetic flux to the superconducting coil. Additionally, the system includes a shaft of a prime mover to receive torque to rotate a rotor. Additionally, the system includes a superconducting coil to electrically interact with a main stator coil through a rotating magnetic field. Furthermore, the system includes a control stator coil to receive current from a controller and electrically interact with a non-superconducting coil. In one or more examples, a size, phase, and / or frequency of the rotating magnetic field of the superconducting coil and the non-superconducting coil is varied compared to a size, phase, and / or frequency of a magnetic field generated by the superconducting coil alone to control a size, phase, and / or frequency of an output voltage.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a rotor electric machine / generator. In particular, the present disclosure relates to a hybrid wound rotor electric machine / generator with inductive feeding and persistent current. BACKGROUND

[0002] To increase the use of electric propulsion in aircraft, it has been desirable to develop technology with higher specific power. Examples include high power density electric machines and generators (M / Gs) and power conversion devices.

[0003] To achieve high specific power, superconducting windings in the electric machine / generator (M / G) are often desirable. The current density in superconductors is much greater than in traditional conductors such as copper or aluminum, and the power is often a function of the current in the rotor and the current in the stator windings. Superconducting windings are typically implemented in the rotor, which experiences a substantially constant magnetic field, thus having low losses. Since superconductors require cryogenic temperatures to maintain their superconducting state, any losses require a cooling device such as a cryocooler to remove heat. However, if the losses are very high, the weight of the cryocooler offsets the weight advantage of the superconducting device.

[0004] Typically, the stator windings for these superconducting M / Gs are traditional conductors, where the stator experiences a significantly varying magnetic field. In most designs, the losses due to these variations are too high for today's superconductors to be included in the stator windings.

[0005] Currently, one method of establishing current in a wound rotor is through the use of brushes. In addition to the maintenance issues due to the wear of the brushes, the presence of normal conductors that carry current into the superconducting windings bring a large amount of heat to the system, which must be removed by a refrigeration system. This often means that the design must be made up of many turns, which generates high inductance and low current.

[0006] One method of avoiding the introduction of current into the rotor is to use a superconductor in the form of a bulk trapped flux magnet, similar to a power permanent magnet. The problem with this concept is that it is difficult to excite the superconductor in situ. In addition, it is difficult to turn the magnetization off in a short time. Thus, if a short circuit is present in the stator windings, the magnetic field from the rotor will continue to exert a voltage on these coils, and there is a danger that the stator windings will overheat and possibly catch fire.

[0007] An alternative method is to use induction to excite the rotor windings. However, the varying field experienced by the superconductor causes large losses, which make the cooling system too heavy.

[0008] In view of the above, there is a need for improved high power density electrical M / G designs. SUMMARY

[0009] The present disclosure relates to a method, system, and apparatus for a hybrid wound rotor motor / generator with inductive feeding and persistent current. In one or more examples, a method for operation of an apparatus in generator mode includes cooling, with a cryogenic refrigerator, superconducting coils of a rotor until a temperature of windings of the superconducting coils is at a superconducting operating temperature. The method further includes providing, by a flux pump, magnetic flux to the superconducting coils until a persistent current flowing through the windings of the superconducting coils is at a persistent operating current. Additionally, the method includes receiving, from a shaft of a prime mover, torque to rotate the rotor. Additionally, the method includes generating, by the persistent current of the superconducting coils and the rotation of the rotor, a rotating magnetic field. Additionally, the method includes electrically interacting, by the superconducting coils, with a main stator coil through the rotating magnetic field. Additionally, the method includes generating, by the rotating magnetic field of the superconducting coils, an electromotive force (EMF) within the main stator coil coupled to the superconducting coils. Additionally, the method includes receiving, by a control stator coil, a current from a controller. Additionally, the method includes electrically interacting, by the control stator coil, with a non-superconducting coil of the rotor. Additionally, the method includes inducing, by a magnetic field of the current of the control stator coil, a control current within the non-superconducting coil. Additionally, the method includes generating, by the control current within the non-superconducting coil, a magnetic field to couple with the main stator coil. Additionally, the method includes modulating, by the magnetic field generated by the control current within the non-superconducting coil, the magnetic field generated by the superconducting coils. Further, the method includes varying at least one of a size, a phase, and a frequency of a combination of the rotating magnetic field of the coils and the non-superconducting coil compared to at least one of a size, a phase, and a frequency of the magnetic field generated by the superconducting coils alone to control at least one of a size, a phase, and a frequency of an output voltage.

[0010] In one or more examples, the main stator coil is connected to and delivers electrical power to a power distribution bus. In at least one example, the control stator coil is connected to and receives at least one control signal from a controller. In some examples, the control stator coil is connected to and receives at least one control signal from a system controller. In one or more examples, the output voltage is output at the main stator coil terminals.

[0011] In at least one example, the superconducting coils act as a constant flux source when electrically interacting with the main stator coil. In one or more examples, the superconducting coils electrically interact with the main stator coil substantially synchronously. In some examples, the superconducting coils electrically interact with the main stator coil asynchronously.

[0012] In one or more examples, the main stator coil is one of superconducting or non-superconducting. In some examples, the control stator coil is one of superconducting and non-superconducting.

[0013] In at least one example, the flux pump is located one of axially from the rotor and radially from the rotor. In some examples, the cryogenic refrigerator is one of located on the rotor and stationary.

[0014] In one or more examples, the method further includes powering the cryogenic refrigerator through a slip ring while the cryogenic refrigerator is located on the rotor. In some examples, the method further includes powering the cryogenic refrigerator through inductive power transfer.

[0015] In at least one example, the method further includes flowing cooling gas from the cryogenic refrigerator to a cold portion of the rotor including the superconducting coil via a channel. In some examples, the channel connects from the cryogenic refrigerator to one of an outer radius of the rotor and an axis of rotation of the rotor.

[0016] In one or more examples, the control current controls the non-superconducting coil to one of augment, suppress, and change a phase of a voltage generated in the main stator coil by the superconducting coil.

[0017] In at least one example, the method further includes detecting a short circuit in the main stator coil. Additionally, the method includes inducing a control current by the control stator coil into the non-superconducting coil such that a magnetic flux from the non-superconducting coil into a shorted portion of the main stator coil opposes a magnetic flux from the superconducting coil into the shorted portion of the main stator coil. Furthermore, the method includes simultaneously reducing a persistent current in the superconducting coil to zero by a magnetic flux pump and adjusting the control current in the control stator coil to continue to cancel the magnetic flux from the superconducting coil into the shorted portion of the main stator coil.

[0018] In one or more examples, the superconducting coil is located in a cold portion of the rotor and the non-superconducting coil is located in a warm portion of the rotor. In some examples, the cold portion of the rotor and the warm portion of the rotor are separated by a thermal barrier.

[0019] In at least one example, the rotor includes an outer mechanical shell and an inner mechanical shell, and the cooling gas from the cryogenic refrigerator flows into a space formed between the outer mechanical shell and the inner mechanical shell.

[0020] In one or more examples, a system for operating in a generator mode includes a cryogenic refrigerator to cool a superconducting coil of a rotor until a temperature of a winding of the superconducting coil is at a superconducting operating temperature. The system also includes a flux pump to provide a magnetic flux to the superconducting coil until a persistent current flowing through the winding of the superconducting coil is at a persistent operating current. Additionally, the system includes a shaft of a prime mover to receive a torque to rotate the rotor. In one or more examples, the persistent current of the superconducting coil generates a rotating magnetic field. Additionally, the system includes the superconducting coil to electrically interact with a main stator coil by the rotating magnetic field, where the rotating magnetic field of the superconducting coil coupled with the main stator coil generates an electromotive force (EMF) within the main stator coil. Moreover, the system includes a control stator coil to electrically interact with a non-superconducting coil of the rotor from a controller, where a magnetic field of the current of the control stator coil induces a control current within the non-superconducting coil. In one or more examples, the control current within the non-superconducting coil generates a magnetic field to couple with the main stator coil, and the magnetic field generated by the control current within the non-superconducting coil modulates the magnetic field generated by the superconducting coil. In at least one example, at least one of a magnitude, a phase, and a frequency of a combination of the rotating magnetic field of the superconducting coil and the non-superconducting coil changes compared to at least one of a magnitude, a phase, and a frequency of the magnetic field generated by the superconducting coil alone to control at least one of a magnitude, a phase, and a frequency of an output voltage.

[0021] In at least one example, a method for operation of a device in a generator mode includes cooling a superconducting coil of a rotor with a cryogenic refrigerator until a temperature of a winding of the superconducting coil is at a superconducting operating temperature. The method also includes providing a magnetic flux to the superconducting coil from a flux pump until a persistent current flowing through the winding of the superconducting coil is at a persistent operating current. Additionally, the method includes receiving alternating current input from a power distribution bus by a main stator coil. Additionally, the method includes receiving a control current from a controller by a control stator coil. Additionally, the method includes generating a rotating magnetic field by the alternating current within the main stator coil. Additionally, the method includes electrically interacting with the persistent current of the superconducting coil by the rotating magnetic field. Additionally, the method includes generating an electromagnetic torque to rotate the rotor by the rotating magnetic field interacting with the persistent current. Additionally, the method includes generating a current at a non-superconducting coil of the rotor by the control stator coil. Additionally, the method includes modulating the magnetic field generated by the alternating current of the main stator coil by a magnetic field generated by the current of the non-superconducting coil. Moreover, the method includes changing at least one of a magnitude, a phase, and a frequency of a combination of the rotating magnetic field of the main stator coil and the magnetic field of the non-superconducting coil compared to at least one of a magnitude, a phase, and a frequency of the rotating magnetic field generated by the main stator coil alone to control a speed of the rotor.

[0022] In one or more examples, the main stator coil has main stator coil terminals connected to the power distribution bus. In some examples, the control stator coil has control stator coil terminals connected to the controller.

[0023] In at least one example, a system for operation in motor mode includes a cryogenic refrigerator to cool superconducting coils of a rotor until a temperature of windings of the superconducting coils is at a superconducting operating temperature. The system also includes a magnetic flux pump to provide magnetic flux to the superconducting coils until a persistent current flowing through the windings of the superconducting coils is at a persistent operating current. Additionally, the system includes a main stator coil to receive alternating current input from a power distribution bus. Further, the system includes a control stator coil to receive control current from a controller. In one or more examples, the alternating current within the main stator coil generates a rotating magnetic field that electrically interacts with the persistent current of the superconducting coils, and the rotating magnetic field that interacts with the persistent current generates an electromagnetic torque to rotate the rotor. Additionally, in the system, the control stator coil also generates a current at a non-superconducting coil of the rotor, where a magnetic field generated by the current of the non-superconducting coil modulates a magnetic field generated by the alternating current of the main stator coil. In one or more examples, at least one of a magnitude, a phase, and a frequency of a combination of the rotating magnetic field of the main stator coil and the magnetic field of the non-superconducting coil is altered compared to at least one of a magnitude, a phase, and a frequency of the rotating magnetic field generated by the main stator coil alone to control a speed of the rotor.

[0024] Features, functions, and advantages can be implemented independently of each other or can be combined in various examples of the disclosure. BRIEF DESCRIPTION OF DRAWINGS

[0025] These and other features, aspects, and advantages of the present disclosure will become better understood with reference to the following description, appended claims, and accompanying drawings where:

[0026] Figure 1 is a diagram illustrating the disclosed system for a hybrid-wound rotor motor / generator (M / G) operating in motor mode according to at least one example of the present disclosure, where the associated cryogenic refrigerator is stationary.

[0027] Figure 2 is a diagram illustrating the disclosed system for a hybrid-wound rotor motor / generator (M / G) operating in generator mode according to at least one example of the present disclosure, where the associated cryogenic refrigerator is stationary.

[0028] Figure 3 is a diagram illustrating the disclosed system for a hybrid-wound rotor motor / generator (M / G) according to at least one example of the present disclosure, where the associated cryogenic refrigerator is located on the rotor.

[0029] Figure 4A andFigure 4B is a flowchart together showing the disclosed method of the disclosed hybrid wound rotor electric machine / generator (M / G) operating in generator mode, according to at least one example of the present disclosure.

[0030] Figure 5A and Figure 5B is a flowchart together showing the disclosed method of the disclosed hybrid wound rotor electric machine / generator (M / G) operating in motor mode, according to at least one example of the present disclosure.

[0031] Figure 6 is a flowchart showing the disclosed method of stator coil short circuit operation of the disclosed hybrid wound rotor electric machine / generator (M / G), according to at least one example of the present disclosure. DETAILED DESCRIPTION

[0032] The methods and apparatus described herein provide an operating system for a hybrid wound rotor electric machine / generator with induction feed and persistent current. In one or more examples, the system of the present disclosure provides a brushless electric machine / generator (M / G) that uses a wound rotor composed of a hybrid induction feed assembly and a persistent current superconducting assembly to achieve high specific power and speed control. The persistent current is achieved with a flux pump. Additional advantages of this concept are a low inductance high current rotor that is easily de-energized in the event of a stator short circuit and the ability to reduce the voltage on the stator during a rotor de-energization.

[0033] The system of the present disclosure employs a superconducting wound rotor. The brushes are avoided by energizing the windings with a flux pump, a non-contact method of inducing current into the windings. Since this will occur at the initial energization of the M / G and only on a limited portion of the windings, it will not suffer from long term heating as does the traditional induction process. It should be noted that the flux pump can be operated in reverse to de-energize the rotor windings relatively quickly. This allows the design of a low inductance high current rotor without the thermal burden that accompanies a brush system.

[0034] The rotor also uses traditional non-superconducting windings in an induction mode. The magnetic field from these induction feed coils is in conjunction with the magnetic field from the superconducting windings into the stator coils. In normal operation, these coils can act in series with the superconducting windings to increase the power of the M / G. If a short circuit occurs in the stator windings, these coils can act in opposition to the superconducting coils to cancel all or part of the magnetic field into the stator to avoid any safety issues.

[0035] In addition to the above advantages, the hybrid rotor approach also has the ability to control the output of the M / G to match the load requirements under varying input conditions. In generator mode, the inductive part of the system can be used to maintain a constant frequency output if the speed of the mechanical shaft that turns the rotor is variable. In motor mode, the inductive part of the system can be used to better regulate varying speed requirements. These advantages are similar to those of a doubly-fed induction machine.

[0036] In the following description, numerous specific details are set forth to provide a more thorough description of the system. It will be apparent, however, to one skilled in the art that the disclosed system can be practiced without the specific details. In other instances, well-known features have not been described in detail so as not to unnecessarily obscure the system.

[0037] Examples of the present disclosure can be described herein in terms of functional and / or logical components and various processing steps. It should be understood that these components can be implemented by any number of hardware, software, and / or firmware components configured to perform the specified functions. For example, an example of the present disclosure can employ various integrated circuit components, e.g., memory elements, digital signal processing elements, logic elements, look-up tables, or the like, which can be configured to perform the functions described herein. Additionally, the various embodiments of the disclosure can be practiced in conjunction with other components not expressly described herein, but well known in the art.

[0038] For the sake of brevity, conventional techniques and components related to rotor machines / generators (M / G) and other functional aspects of the system (as well as the various operational components of the system) can not be described in detail herein. Most machines / generators (M / G) have three (3) or more electrical phases. In the disclosed system, only one electrical phase is shown. However, the disclosed system can have more than one electrical phase. Moreover, the connections between various elements in the various figures contained herein are intended to represent example functional relationships and / or physical couplings between the various elements. It should be noted that there can be many variations of the state of the art or alternate examples that can be practiced with the disclosed system.

[0039] Figure 1 is a disclosed system (or apparatus) 100 showing a hybrid wound rotor machine / generator (M / G) for operation in motor mode, in accordance with at least one example of the present disclosure, wherein the associated cryocooler 170 is stationary. Specifically, Figure 1 The basic configuration of the system 100 is shown schematically in FIG. 1. Most machines / generators (M / G) have multiple modes of operation. In Figure 1 In FIG. 2, the disclosed system 100 is operating in motor mode to rotate the rotor 120.

[0040] InFigure 1 In this system 100, a stator 110 and a rotor 120 are included. The stator 110 includes a main stator coil 130 and a control stator coil 140. The rotor 120 includes a continuous current superconducting coil 150 and a non-superconducting coil 160. The superconducting coil 150 interacts only with the main stator coil 130. The control stator coil 140 interacts only with the non-superconducting coil 160. The non-superconducting coil 160 interacts with both stator coils (i.e., the main stator coil 130 and the control stator coil 140). Furthermore, the main stator coil 130 interacts with both rotor coils (i.e., the superconducting coil 150 and the non-superconducting coil 160).

[0041] The rotor 120 is divided into two parts: a cold part 123 and a warm part 124. These two parts are separated by a heat insulation element 126. The superconducting coil 150 is located in the cold part 123 of the rotor 120, and the non-superconducting coil 160 is located in the warm part 124 of the rotor 120.

[0042] The rotor 120 also includes an inner mechanical housing 127 that supports the rotor coils (i.e., superconducting coil 150 and non-superconducting coil 160). In addition, the rotor 120 includes an outer mechanical housing 128, which together with the inner mechanical housing 127 forms a space 122 through which cooling gas can flow into or out from a channel 175 connected to the cryogenic refrigerator 170.

[0043] exist Figure 1 In this configuration, the cryogenic refrigerator 170 is fixed. For convenience (e.g., for ease of illustration), channel 175 is... Figure 1 The channel 175 is shown connected to the rotor 120 on its outer radius, but it would preferably be connected along the axis of rotation of the rotor 120. Power can be supplied to the cryogenic refrigerator 170 via inductive power transfer. In other examples, when the cryogenic refrigerator 170 is located on the rotor 120 (see reference...) Figure 3 It can supply power to the cryogenic refrigerator 170 through slip ring 377.

[0044] It should be noted that Figure 1 Additional motor / generator components, such as support bearings, coil frames, and stator coil cooling, are not shown. Additionally, it should be noted that, besides the heat insulation 126 shown, the inner housing 127 and outer housing 128 can also be mechanically connected via other components.

[0045] The superconducting coil 150 includes a section 155 that interacts with a flux pump 180 to induce a continuous current in the superconducting coil 150. The primary electrical interaction occurs between the superconducting coil 150 and the main stator coil 130. When the superconducting coil 150 interacts electrically with the main stator coil 130, the superconducting coil 150 acts as a constant flux source. The superconducting coil 150 interacts with the main stator coil 130 substantially synchronously (or asynchronously).

[0046] The control stator coil 140 induces a current into the non-superconducting coil 160 such that the non-superconducting coil 160 acts to augment or can counteract the voltage generated by the superconducting coil 150 in the main stator coil 130 or can act to change the effective phase of the interaction. Thus, the control current controls the non-superconducting coil 160 to achieve one of the following: augment the voltage generated by the superconducting coil 150 in the main stator coil 130, suppress the voltage generated by the superconducting coil 150 in the main stator coil 130, or change the phase of the voltage generated by the superconducting coil 150 in the main stator coil 130.

[0047] In one or more examples, the stator coils (i.e., the main stator coil 130 and the control stator coil 140) can be superconducting or non-superconducting.

[0048] In Figure 1 , the flux pump 180 is shown to be located in the axial direction of the rotor 120. In separate examples of the present disclosure (refer to Figure 3 ), the flux pump 180 is located in the radial direction of the rotor 120.

[0049] Additionally, in Figure 1 , the motor load (e.g., propeller) 195 is shown to be connected to the rotor 120 via the shaft 190. During operation of the system 100 in motor mode, the rotor rotates to drive the motor load 195.

[0050] Figure 1 Also shown in , the main stator coil 130 is connected to an external power distribution bus 192 via main stator coil terminals 131. A power supply 193 delivers power to the power distribution bus 192. Additionally, the control stator coil 140 is connected to a controller 194 via control stator coil terminals 141. A system controller 196 is connected to the controller 194 and sends at least one control signal 198 to control the control stator coil 140.

[0051] Figure 2 is a diagram showing the disclosed system (or apparatus) 200 for a hybrid-wound rotor motor / generator (M / G) operating in generator mode according to at least one example of the present disclosure, where (similar to Figure 1 ) the associated cryogenic refrigerator 170 is stationary. Figure 2 Most of the components of the system 200 are the same as the components of the system 100 shown in Figure 1 , which shows a basic configuration. Figure 2 In , the disclosed system 200 operates in generator mode to generate an output voltage.

[0052] Figure 2In the diagram, prime mover 295 is shown connected to rotor 120 via shaft 190. During operation of system 200 in generator mode, shaft 190 of prime mover 295 delivers torque to rotate rotor 120. The generated output voltage is output at main stator coil terminal 131. Main stator coil 130 is connected to (via main stator coil terminal 131) power distribution bus 192 and delivers power to power distribution bus 192. Power distribution bus 192 is connected to electrical load 293 that receives power.

[0053] Figure 3 This is a diagram illustrating at least one example of the disclosed system (or apparatus) 300 for a hybrid wound-rotor motor / generator (M / G) according to this disclosure, wherein the associated cryogenic refrigerator 170 is located on the rotor 120. For convenience (e.g., for ease of illustration), Figure 3 Not all components of the disclosed system 300 are shown. (See reference...) Figure 1 and Figure 2 To view all components of system 300.

[0054] Specifically, Figure 3 Another example of the disclosed system 300 is shown, wherein, for system 300, a cryogenic refrigerator 170 is located on a rotor 120. Additionally, Figure 3 The example also shows a flux pump 180 located radially on rotor 120.

[0055] In this configuration, the cryogenic refrigerator 170 can conductively cool the superconducting coil 150. In this case, the cryogenic refrigerator 170 is powered via the slip ring 377. Alternatively, as previously mentioned above, the cryogenic refrigerator 170 can be powered via inductive power transfer, similar to charging an electric vehicle.

[0056] Figure 4A and Figure 4B Together they illustrate at least one example of the disclosed hybrid wound-rotor motor / generator (M / G) according to this disclosure (e.g., Figure 2 A flowchart of the disclosed method 400, in which the system (or apparatus) 200) operates in generator mode. When operating in generator mode, the disclosed hybrid wound-rotor motor / generator (M / G) operates as a generator to generate an output voltage. Figure 4A and Figure 4B The method, refer to Figure 2 The components shown.

[0057] At the beginning of the method 405, at step 410, the cryogenic refrigerator 170 cools the superconducting coil 150 of the rotor 120 until a temperature of a winding of the superconducting coil 150 is at a superconducting operating temperature (e.g., a predetermined operating temperature of the superconducting coil 150). At step 415, the flux pump 180 provides magnetic flux to the superconducting coil 150 until a persistent current flowing through the winding of the superconducting coil 150 is at a persistent operating current (e.g., a predetermined persistent operating current). At step 420, the shaft 190 of the prime mover 295 receives torque to rotate the rotor 120.

[0058] At step 425, the persistent current of the superconducting coil 150 generates a rotating magnetic field. At step 430, the superconducting coil 150 electrically interacts with the main stator coil 130 through the rotating magnetic field. At step 435, the rotating magnetic field of the superconducting coil 150 coupled with the main stator coil 130 generates an electromotive force (EMF) within the main stator coil 130.

[0059] At step 440, the control stator coil 140 receives a current from the controller 194. At step 445, the control stator coil 140 electrically interacts with the non-superconducting coil 160 of the rotor 120. At step 450, a magnetic field of the current of the control stator coil 140 induces a control current within the non-superconducting coil 160. At step 455, the control current within the non-superconducting coil 160 generates a magnetic field to couple with the main stator coil 130. At step 460, the magnetic field generated by the control current within the non-superconducting coil 160 adjusts the magnetic field generated by the superconducting coil 150.

[0060] At step 465, at least one of a size, a phase, and a frequency of a combination of the rotating magnetic fields of the superconducting coil 150 and the non-superconducting coil 160 is changed compared to at least one of a size, a phase, and a frequency of the magnetic field generated by the superconducting coil 150 alone to control at least one of a size, a phase, and a frequency of an output voltage. Then, the method ends at 470.

[0061] Figure 5A and Figure 5B is a system (or apparatus) 100 that collectively illustrates a disclosed hybrid-wound rotor electric machine / generator (M / G) (e.g., a hybrid-wound rotor electric machine / generator (M / G) 100) according to at least one example of the present disclosure operating in a motor mode. Figure 1 is a flowchart of a disclosed method 500 of the system (or apparatus) 100 operating in a motor mode. When operating in the motor mode, the disclosed hybrid-wound rotor electric machine / generator (M / G) operates as an electric machine to rotate the rotor 120. For the method of Figure 5A and Figure 5B is a flowchart of a disclosed method 500 of the system (or apparatus) 100 operating in a motor mode. When operating in the motor mode, the disclosed hybrid-wound rotor electric machine / generator (M / G) operates as an electric machine to rotate the rotor 120. For the method of Figure 1 is a flowchart of a disclosed method 500 of the system (or apparatus) 100 operating in a motor mode. When operating in the motor mode, the disclosed hybrid-wound rotor electric machine / generator (M / G) operates as an electric machine to rotate the rotor 120. For the method of

[0062] At the beginning of the method 505, at step 510, the cryogenic refrigerator 170 cools the superconducting coil 150 of the rotor 120 until the temperature of the windings of the superconducting coil 150 is at a superconducting operating temperature (e.g., a predetermined operating temperature). At step 515, the flux pump 180 provides magnetic flux to the superconducting coil 150 until the persistent current flowing through the windings of the superconducting coil 150 is at a persistent operating current.

[0063] At step 520, the main stator coil 130 receives alternating current (AC) input from the power distribution bus 192. At step 525, the control stator coil 140 receives control current from the controller 194. At step 530, the alternating current (AC) within the main stator coil 130 generates a rotating magnetic field. At step 535, the rotating magnetic field electrically interacts with the persistent current of the superconducting coil 150. At step 540, the rotating magnetic field interacting with the persistent current generates an electromagnetic torque to rotate the rotor 120.

[0064] At step 545, the control stator coil 140 generates a current at the non-superconducting coil 160 of the rotor 120. At step 550, the magnetic field generated by the current of the non-superconducting coil 160 modulates the magnetic field generated by the alternating current (AC) of the main stator coil 130. At step 555, at least one of the size, phase, and frequency of the combination of the rotating magnetic field of the main stator coil 130 and the magnetic field of the non-superconducting coil 160 is changed compared to at least one of the size, phase, and frequency of the rotating magnetic field generated by the main stator coil 130 alone to control the speed of the rotor 120. Then, the method ends at 560.

[0065] Figure 6 is a flowchart illustrating a disclosed method 600 of stator coil short circuit operation of a disclosed hybrid-wound rotor electric machine / generator (M / G) (e.g., a hybrid-wound rotor electric machine / generator (M / G) according to at least one example of the present disclosure, Figure 1 and Figure 2 is a flowchart illustrating a disclosed method 600 of stator coil short circuit operation of a disclosed hybrid-wound rotor electric machine / generator (M / G) (e.g., a hybrid-wound rotor electric machine / generator (M / G) according to at least one example of the present disclosure, Figure 6 is a flowchart illustrating a disclosed method 600 of stator coil short circuit operation of a disclosed hybrid-wound rotor electric machine / generator (M / G) (e.g., a hybrid-wound rotor electric machine / generator (M / G) according to at least one example of the present disclosure, Figure 6 is a flowchart illustrating a disclosed method 600 of stator coil short circuit operation of a disclosed hybrid-wound rotor electric machine / generator (M / G) (e.g., a hybrid-wound rotor electric machine / generator (M / G) according to at least one example of the present disclosure, Figure 1 and Figure 2 is a flowchart illustrating a disclosed method 600 of stator coil short circuit operation of a disclosed hybrid-wound rotor electric machine / generator (M / G) (e.g., a hybrid-wound rotor electric machine / generator (M / G) according to at least one example of the present disclosure,

[0066] At the beginning of the method 605, at step 610, a short circuit is detected in the main stator coil 130. At step 620, the control stator coil 140 induces a control current into the non-superconducting coil 160 such that the magnetic flux from the non-superconducting coil 160 into the shorted portion of the main stator coil 130 is opposite to the magnetic flux from the superconducting coil 150 into the shorted portion of the main stator coil 130. At step 630, the flux pump 180 simultaneously reduces the persistent current in the superconducting coil 150 until the persistent current in the superconducting coil 150 is reduced to zero, and during this time, the control current in the control stator coil 140 is adjusted to continue to cancel the magnetic flux from the superconducting coil 150 into the shorted portion of the main stator coil 130. Then, the method ends at 640.

[0067] Further, the present disclosure includes examples in accordance with the following clauses:

[0068] Clause 1. A method for operation of an apparatus in a generator mode, the method comprising: cooling a superconducting coil of a rotor with a cryogenic refrigerator until a temperature of a winding of the superconducting coil is at a superconducting operating temperature; providing, by a flux pump, a magnetic flux to the superconducting coil until a persistent current flowing through the winding of the superconducting coil is at a persistent operating current; receiving, from a shaft of a prime mover, a torque to rotate the rotor; generating, by the persistent current of the superconducting coil, a rotating magnetic field; electrically interacting, by the superconducting coil, with a main stator coil through the rotating magnetic field; generating, by the rotating magnetic field of the superconducting coil coupled with the main stator coil, an electromotive force (EMF) within the main stator coil; receiving, by a control stator coil, a current from a controller; electrically interacting, by the control stator coil, with a non-superconducting coil of the rotor; inducing, by a magnetic field of the current of the control stator coil, a control current within the non-superconducting coil; generating, by the control current within the non-superconducting coil, a magnetic field to couple with the main stator coil; modulating, by the magnetic field generated by the control current within the non-superconducting coil, the magnetic field generated by the superconducting coil; and varying at least one of a magnitude, a phase, and a frequency of a combination of the rotating magnetic fields of the superconducting coil and the non-superconducting coil compared to at least one of the magnitude, the phase, and the frequency of the magnetic field generated by the superconducting coil alone to control at least one of a magnitude, a phase, and a frequency of an output voltage.

[0069] Clause 2. The method of clause 1, wherein the main stator coil is connected to and delivers electrical power to a power distribution bus.

[0070] Clause 3. The method of any one of clauses 1-2, wherein the control stator coil is connected to a controller.

[0071] Clause 4. The method of any one of clauses 1-3, wherein the control stator coil is connected to a controller and receives at least one control signal from the system controller.

[0072] Clause 5. The method of any of clauses 1-4, wherein the output voltage is output at the main stator coil terminals.

[0073] Clause 6. The method of any of clauses 1-5, wherein the superconducting coil acts as a constant flux source when the superconducting coil is in electrical interaction with the main stator coil.

[0074] Clause 7. The method of any of clauses 1-6, wherein the superconducting coil is in electrical interaction with the main stator coil substantially synchronously.

[0075] Clause 8. The method of any of clauses 1-7, wherein the superconducting coil is in electrical interaction with the main stator coil asynchronously.

[0076] Clause 9. The method of any of clauses 1-8, wherein the main stator coil is one of superconducting and non-superconducting.

[0077] Clause 10. The method of any of clauses 1-9, wherein the control stator coil is one of superconducting and non-superconducting.

[0078] Clause 11. The method of any of clauses 1-10, wherein the flux pump is located one of axially of the rotor and radially of the rotor.

[0079] Clause 12. The method of any of clauses 1-11, wherein the cryogenic refrigerator is one of located on the rotor and fixed.

[0080] Clause 13. The method of any of clauses 1-12, further comprising supplying power to the cryogenic refrigerator through a slip ring when the cryogenic refrigerator is located on the rotor.

[0081] Clause 14. The method of any of clauses 1-13, further comprising supplying power to the cryogenic refrigerator through inductive power transfer.

[0082] Clause 15. The method of any of clauses 1-14, further comprising flowing a cooling gas from the cryogenic refrigerator to a cold portion of the rotor including the superconducting coil via a passage.

[0083] Clause 16. The method of clause 15, wherein the passage is connected to one of an outer radius of the rotor and an axis of rotation of the rotor from the cryogenic refrigerator.

[0084] Clause 17. The method of any one of clauses 1-16, wherein the control current controls the non-superconducting coil to one of: augment a voltage generated by the superconducting coil in the main stator coil, suppress a voltage generated by the superconducting coil in the main stator coil, and change a phase of a voltage generated by the superconducting coil in the main stator coil.

[0085] Clause 18. The method of any one of clauses 1-17, further comprising: detecting a short in the main stator coil; inducing, by the control stator coil, a control current in the non-superconducting coil such that magnetic flux from the non-superconducting coil into the shorted portion of the main stator coil opposes magnetic flux from the superconducting coil into the shorted portion of the main stator coil; and simultaneously reducing, by the flux pump, a persistent current in the superconducting coil until the persistent current in the superconducting coil is reduced to zero and adjusting the control current in the control stator coil to continue to cancel the magnetic flux from the superconducting coil into the shorted portion of the main stator coil.

[0086] Clause 19. The method of any one of clauses 1-18, wherein the superconducting coil is in a cold portion of the rotor and the non-superconducting coil is in a warm portion of the rotor.

[0087] Clause 20. The method of clause 19, wherein the cold portion of the rotor and the warm portion of the rotor are separated by a thermal barrier.

[0088] Clause 21. The method of any one of clauses 1-20, wherein the rotor comprises an outer mechanical shell and an inner mechanical shell, and wherein cooling gas from the cryogenic refrigerator flows into a space formed between the outer mechanical shell and the inner mechanical shell.

[0089] Clause 22. A system for operating in a generator mode, the system comprising: a cryogenic refrigerator cooling a superconducting coil of a rotor until a temperature of a winding of the superconducting coil is at a superconducting operating temperature; a flux pump providing magnetic flux to the superconducting coil until a persistent current flowing through the winding of the superconducting coil is at a persistent operating current; a shaft of a prime mover receiving torque to rotate the rotor, wherein the persistent current of the superconducting coil generates a rotating magnetic field; the superconducting coil electrically interacting with a main stator coil through the rotating magnetic field, wherein the rotating magnetic field of the superconducting coil coupled with the main stator coil generates an electromotive force (EMF) within the main stator coil; and a control stator coil receiving a current from a controller and electrically interacting with a non-superconducting coil of the rotor, wherein a magnetic field of the current of the control stator coil induces a control current within the non-superconducting coil, wherein the control current within the non-superconducting coil generates a magnetic field to couple with the main stator coil, and wherein at least one of a magnitude, a phase, and a frequency of a combination of the rotating magnetic fields of the superconducting coil and the non-superconducting coil changes compared to at least one of a magnitude, a phase, and a frequency of the magnetic field generated by the superconducting coil alone to control at least one of a magnitude, a phase, and a frequency of an output voltage.

[0090] While particular examples have been shown and described, it will be understood that the above discussion is not intended to limit the scope of these examples. While examples and variations of many aspects of the present disclosure have been disclosed and described, such disclosure is made only to illustrate and exemplify. Thus, various changes and modifications can be made to the examples without departing from the scope of the claims.

[0091] Where the above methods indicate that particular events occur in a particular order, one of ordinary skill in the art benefiting from the present disclosure will recognize that the order can be modified and that these modifications are within the scope of the present disclosure. Additionally, parts of the methods can be performed at the same time in parallel processing where possible. Furthermore, more steps or fewer steps can be performed.

[0092] Accordingly, examples are intended to be illustrative, but not limiting, of alternatives, modifications, and equivalents of aspects of the present disclosure.

[0093] While specific illustrative examples and methods have been disclosed, it will be apparent to those skilled in the art with the benefit of this disclosure that various changes and modifications can be made therein without departing from the true spirit and scope of the present disclosure. There are many alternative examples that will be readily apparent to those skilled in the art with the benefit of this disclosure. Each of the examples is merely illustrative of the alternatives, modifications, and equivalents of the present disclosure. Accordingly, the present disclosure is intended to be limited only by the scope of the appended claims as applicable and the rules and principles of applicable law.

Claims

1. A method (400) for operation of an apparatus (200) in a generator mode, the method (400) comprising the steps of: cooling (410) a superconducting coil (150) of a rotor (120) with a cryogenic refrigerator (170) until a temperature of a winding of the superconducting coil (150) is at a superconducting operating temperature; providing (415) magnetic flux to the superconducting coil (150) from a flux pump (180) until a persistent current flowing through the winding of the superconducting coil (150) is at a persistent operating current; receiving (420) torque from a shaft (190) of a prime mover (295) to rotate the rotor (120); generating (425) a rotating magnetic field by the persistent current of the superconducting coil (150); electrically interacting (430) by the superconducting coil (150) with a main stator coil (130) by the rotating magnetic field; generating (435) an electromotive force, EMF, in the main stator coil (130) by the rotating magnetic field of the superconducting coil (150) coupled with the main stator coil (130); receiving (440) current from a controller (194) by a control stator coil (140); electrically interacting (445) by the control stator coil (140) with a non-superconducting coil (160) of the rotor (120); inducing (450) a control current in the non-superconducting coil (160) by a magnetic field of the current of the control stator coil (140); generating (445) a magnetic field by the control current in the non-superconducting coil (160) to couple with the main stator coil (130); modulating (460) a magnetic field generated by the superconducting coil (150) by the magnetic field generated by the control current in the non-superconducting coil (160); and changing (465) at least one of a magnitude, a phase, and a frequency of a combination of rotating magnetic fields of the superconducting coil (150) and the non-superconducting coil (160) compared to at least one of the magnitude, the phase, and the frequency of the magnetic field generated by the superconducting coil (150) alone to control at least one of a magnitude, a phase, and a frequency of an output voltage.

2. The method of claim 1, wherein, the main stator coil (130) is connected to and delivers electrical power to a power distribution bus (192).

3. The method of any one of claims 1-2, wherein, the control stator coil (140) is connected to the controller (194) and receives at least one control signal (198) from a system controller (196).

4. The method of any one of claims 1-2, wherein, the output voltage is output at a main stator coil terminal (131).

5. The method of any one of claims 1-2, wherein, at least one of the following is true: the superconducting coil (150) acts as a constant magnetic flux source when electrically interacting with the main stator coil (130); electrically interacts substantially in synchronism with the main stator coil (130); and electrically interacts asynchronously with the main stator coil (130).

6. The method of any one of claims 1 to 2, wherein, each of the main stator coil (130) and the control stator coil (140) is one of superconducting and non-superconducting.

7. The method of any one of claims 1 to 2, wherein, The magnetic flux pump (180) is one of located on the rotor (120) and stationary on the rotor (120).

8. The method of any one of claims 1 to 2, wherein, The cryogenic refrigerator (170) is one of located on the rotor (120) and stationary.

9. The method of any one of claims 1 to 2, wherein, The method further comprises at least one of the following steps: supplying power to the cryogenic refrigerator (170) through a slip ring (377) when the cryogenic refrigerator (170) is located on the rotor (120); and supplying power to the cryogenic refrigerator (170) through inductive power transfer. The method further comprises flowing cooling gas from the cryogenic refrigerator (170) to a cold part (123) of the rotor (120) comprising the superconducting coil (150) via a channel (175), and wherein the channel (175) is connected from the cryogenic refrigerator (170) to one of an outer radius of the rotor (120) and an axis of rotation of the rotor (120).

10. The method of any one of claims 1 to 2, wherein, The control current controls the non-superconducting coil (160) to one of enhance a voltage generated by the superconducting coil (150) in the main stator coil (130), suppress the voltage generated by the superconducting coil (150) in the main stator coil (130), and change a phase of the voltage generated by the superconducting coil (150) in the main stator coil (130).

11. The method of any one of claims 1 to 2, wherein, The method further comprises the following steps:

12. The method of any one of claims 1 to 2, wherein, detecting (610) a short circuit in the main stator coil (130); inducing (620) the control current into the non-superconducting coil (160) from the control stator coil (140) such that magnetic flux from the non-superconducting coil (160) into a shorted part of the main stator coil (130) is opposite to magnetic flux from the superconducting coil (150) into the shorted part of the main stator coil (130); and simultaneously reducing (630) the persistent current in the superconducting coil (150) by the magnetic flux pump (180) until the persistent current in the superconducting coil (150) is reduced to zero and adjusting the control current in the control stator coil (140) to continue to cancel the magnetic flux from the superconducting coil (150) into the shorted part of the main stator coil (130). The superconducting coil (150) is located in a cold part (123) of the rotor (120) and the non-superconducting coil (160) is located in a warm part (124) of the rotor (120), and wherein the cold part (123) of the rotor (120) and the warm part (124) of the rotor (120) are separated by a thermal barrier (126).

13. The method of any one of claims 1 to 2, wherein, The rotor (120) comprises an outer mechanical shell (128) and an inner mechanical shell (127), and wherein cooling gas from the cryogenic refrigerator (170) flows into a space (122) formed between the outer mechanical shell (128) and the inner mechanical shell (127).

14. The method of any one of claims 1 to 2, wherein, 15. A system (200) for operating in a generator mode, the system (200) comprising: ​ a cryogenic refrigerator (170) that cools a superconducting coil (150) of a rotor (120) until a temperature of a winding of the superconducting coil (150) is at a superconducting operating temperature; a flux pump (180) that provides magnetic flux to the superconducting coil (150) until a persistent current flowing through the winding of the superconducting coil (150) is at a persistent operating current; a shaft (190) of a prime mover (295) that receives torque to rotate the rotor (120), wherein the persistent current of the superconducting coil (150) generates a rotating magnetic field; the superconducting coil (150) that electrically interacts with a main stator coil (130) through the rotating magnetic field, wherein the rotating magnetic field of the superconducting coil (150) coupled with the main stator coil (130) generates an electromotive force EMF within the main stator coil (130); and a control stator coil (140) that receives a current from a controller (194) and electrically interacts with a non-superconducting coil (160) of the rotor (120), wherein a magnetic field of the current of the control stator coil (140) induces a control current within the non-superconducting coil (160), wherein the control current within the non-superconducting coil (160) generates a magnetic field to couple with the main stator coil (130), and wherein the magnetic field generated by the control current within the non-superconducting coil (160) modulates a magnetic field generated by the superconducting coil (150), and wherein at least one of a size, a phase, and a frequency of a combination of the rotating magnetic fields of the superconducting coil (150) and the non-superconducting coil (160) changes compared to at least one of the size, the phase, and the frequency of the magnetic field generated by the superconducting coil (150) alone to control at least one of a size, a phase, and a frequency of an output voltage. a cryogenic refrigerator (170) that cools a superconducting coil (150) of a rotor (120) until a temperature of a winding of the superconducting coil (150) is at a superconducting operating temperature; a flux pump (180) that provides magnetic flux to the superconducting coil (150) until a persistent current flowing through the winding of the superconducting coil (150) is at a persistent operating current; a shaft (190) of a prime mover (295) that receives torque to rotate the rotor (120), wherein the persistent current of the superconducting coil (150) generates a rotating magnetic field; the superconducting coil (150) that electrically interacts with a main stator coil (130) through the rotating magnetic field, wherein the rotating magnetic field of the superconducting coil (150) coupled with the main stator coil (130) generates an electromotive force EMF within the main stator coil (130); and a control stator coil (140) that receives a current from a controller (194) and electrically interacts with a non-superconducting coil (160) of the rotor (120), wherein a magnetic field of the current of the control stator coil (140) induces a control current within the non-superconducting coil (160), wherein the control current within the non-superconducting coil (160) generates a magnetic field to couple with the main stator coil (130), and wherein the magnetic field generated by the control current within the non-superconducting coil (160) modulates a magnetic field generated by the superconducting coil (150), and wherein at least one of a size, a phase, and a frequency of a combination of the rotating magnetic fields of the superconducting coil (150) and the non-superconducting coil (160) changes compared to at least one of the size, the phase, and the frequency of the magnetic field generated by the superconducting coil (150) alone to control at least one of a size, a phase, and a frequency of an output voltage.

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