Patent Publication Number: US-2022228571-A1

Title: Large inductors for lightning protection of power systems

Description:
BACKGROUND 
     Field 
     Embodiments presented in this disclosure generally relate to protective systems for wind turbines. More particularly, the present disclosure relates to a lightning discharge filter system with improved operational and manufacturing characteristics. 
     Description of the Related Art 
     Wind turbine generators are an increasing popular source for generating electricity and may be deployed singly or in groups of several wind turbines, often referred to as a wind farm. To increase the efficiency, safety, and durability of wind turbines and wind farms, designers may incorporate various powered systems into the blades of the wind turbines, such as, for example, lights, de-icing systems, sensors, etc. These powered systems may receive operational power delivered via one or more electrical leads running along the length of the blade. These electrical leads carry power to the powered systems during normal operations, but also present a conductive path that lightning or other electrical discharges may take. Lightning strikes are a concern for wind turbine operators, as wind turbines are often the tallest objects in the vicinity and one or more of the electrical leads incorporated in the blades can offer a path of least impedance that passes through sensitive components. 
     SUMMARY 
     In one embodiment, a wind turbine blade is provided, which includes: a discharge filter, located in a root of the wind turbine blade, including a first cable wound into a first inductor using the root as a mandrel; a powered system, located in a body of the wind turbine blade; an electrical panel, located between the discharge filter and the powered system in the body of the wind turbine blade, wherein the first cable is configured to provide power to the powered system through the electrical panel. 
     In the present disclosure the expression “using the root as a mandrel” means that the cable is wound about the root of the wind turbine blade. The expression does not mean that the cable can only be wound onto the outside of the root. The cable can also be wound on the inside of the root. In other words, the inductor is supported by a diameter of the root. 
     In some embodiments, in combination with any wind turbine blade described above or below, wherein the mandrel is an exterior surface of the root or an interior surface of the root. 
     In some embodiments, in combination with any wind turbine blade described above or below, the first inductor is at least partially embedded in a material comprising the root. 
     In some embodiments, in combination with any wind turbine blade described above or below, the first cable is a bundled cable including a live line, a neutral line, and a protective earth line. 
     In some embodiments, in combination with any wind turbine blade described above or below, the discharge filter further includes: a second cable wound into a second inductor using the root as a mandrel and is intertwined with the first inductor; and a third cable wound into a third inductor using the root as a mandrel. 
     In some embodiments, in combination with any wind turbine blade described above or below, a pathway between the first cable and the powered system is linked via a surge protection device to a lightning protection system offering a lower impedance path to ground than the first cable. 
     In one embodiment, a wind turbine blade is provided, which includes: an electrical panel, receiving at an input: a first cable; a second cable; and a third cable; and a discharge filter located between a power source and the electrical panel in a root of the blade, the discharge filter comprising: a first inductor, comprising a portion of the first cable wound around the root as a mandrel; a second inductor, comprising a portion of the second cable wound around the root as a mandrel; and a third inductor, comprising a portion of the third cable wound around the root as a mandrel. 
     In some embodiments, in combination with any wind turbine blade described above or below, the root is a hollow cylinder and the mandrel is an interior surface of the root. 
     In some embodiments, in combination with any wind turbine blade described above or below, wherein the electrical pan&amp; further receives a fourth cable at the input, and the discharge filter further comprises: a fourth inductor, comprising a portion of the fourth cable wound around the root as a mandrel. In further embodiments, wherein the electrical panel further receives a fifth cable at the input, and the discharge filter further comprises: a fifth inductor, comprising a portion of the fifth cable wound around the root as a mandrel. 
     In some embodiments, in combination with any wind turbine blade described above or below, the first cable, the second cable, and the third cable are included in a single bundled cable wound into a bundled inductor. 
     In some embodiments, in combination with any wind turbine blade described above or below, the first inductor is intertwined with the second inductor. 
     In some embodiments, in combination with any wind turbine blade described above or below, the first inductor, the second inductor, and the third inductor are wound sequentially about the root. 
     In one embodiment a wind turbine is provided which comprises a plurality of blades, wherein each blade of the plurality of blades is electrically connected to a power source via rotatable contacts in a nacelle from which a root of the blade extends towards a tip of the blade, each blade comprising: a first cable, electrically connected to the power source via the nacelle, and wound into a first inductor supported by a diameter of the root and connected to an input of an electrical panel, and a powered system, connected to an output of the electrical panel via an electrical lead and located tipward of the electrical panel; 
     In one embodiment, a wind turbine is provided, which includes: a plurality of blades, wherein each blade of the plurality of blades is electrically connected to a power source via rotatable contacts in a nacelle from which a root of the blade extends towards a tip of the blade, each blade comprising: a first cable, electrically connected to the power source via the nacelle, and wound into a first inductor supported by a diameter of the root and connected to an input of an electrical panel; a second cable, electrically connected to the power source via the nacelle, and wound into a second inductor supported by the diameter of the root and connected to the input of the electrical panel; a third cable, electrically connected to protective earth via the nacelle, and wound into a third inductor supported by the diameter of the root and connected to the input of the electrical panel; a powered system, connected to an output of the electrical panel via an electrical lead and located tipward of the electrical panel; and a lighting protection system, that is electrically isolated from the first cable, the second cable, and the third cable in the blade, that is connected to ground via the nacelle, and that is selectively connected to the electrical panel, wherein when connected to the electrical panel, the lightning protection system provides a lower impedance path to ground than the first cable, the second cable, and the third cable. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments. 
         FIG. 1  illustrates a diagrammatic view of an exemplary wind turbine generator, according to embodiments of the present disclosure. 
         FIG. 2  illustrates a diagrammatic view of typical components internal to a wind turbine generator, according to embodiments of the present disclosure. 
         FIG. 3  illustrates the relative placement of several electrical components of a wind turbine blade, according to embodiments of the present disclosure. 
         FIG. 4  is a block diagram of the circuity for supplying power to the powered systems via an electrical panel fed by a Lightning Discharge Filter System according to embodiments of the present disclosure. 
         FIGS. 5A-5F  illustrate the inductors using the internal surface of the root as a mandrel, according to embodiments of the present disclosure. 
         FIGS. 6A-6F  illustrate the inductors using the external surface of the root as a mandrel, according to embodiments of the present disclosure. 
         FIGS. 7A-D  illustrate additional cable winding patterns for a Lightning Discharge Filter System using four cables to produce four corresponding inductors, according to embodiments of the present disclosure. 
         FIGS. 8A-8E  illustrate additional cable winding patterns for a Lightning Discharge Filter System using five cables to produce five corresponding inductors, according to embodiments of the present disclosure. 
     
    
    
     To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation, 
     DESCRIPTION OF EXAMPLE EMBODIMENTS 
     To protect a wind turbine that uses blades containing powered systems from lightning strikes or other electrical discharges, an operator may physically disconnect the electrical lead from the turbine when at risk of lightning (thus de-powering the powered systems) or may include a Lightning Discharge Filter System (LDFS) and surge protection devices on the cabling that supplies power to the powered systems in the blades to shunt the lightning current away from sensitive systems and to ground. An LDFS includes one or more inductors at the power input to the blade, which may include inductors on the live (single or multi-phase), neutral, and protective earth lines. Because the majority of the damage to wind turbine components associated with lightning strikes has been observed to be due to the higher frequency components of the lightning compared to the power supplied from the turbine to the blades, the inductors of the LDFS provide a low-pass filter that blocks the current from lightning strikes, but allows power of 50 Hz (Hertz) or 60 Hz to continue to flow to the powered systems. 
     Due to the mass of the inductors included in the LDFS, the inductors are preferably included in the base or root of each blade to reduce rotational stresses on the wind turbine. Although an LDFS may use off-the-shelf discrete inductors to provide low-pass filters to block lightning and permit power flow, such inductors are bulky, difficult to mount within a blade assembly intended to rotate, and have relatively poor heat transfer properties, and thus suffer from thermal issues when conducting continuous power. The present disclosure therefore provides LDFSs using large-scale fabricated inductors that are adapted to the dimensions of the root of the blade in which the LDFS is deployed. Each large-scale inductor forms a low-pass filter, and uses the physical structure of the blade for support, thus improving the ease and security of mounting and reducing the mass of the blade (and the associated rotational stresses). Additionally, as the structure of a blade root can be in excess of 1 m (meter) in diameter, the large-scale inductors exhibit a surface area to volume ratio greater than prior LDFS inductors, and thus exhibit superior heat transfer properties. 
     EXAMPLE EMBODIMENTS 
       FIG. 1  illustrates a diagrammatic view of an exemplary Wind Turbine Generator (WTG)  100 , Although the WTG  100  is illustrated as a horizontal-axis wind turbine, the principles and techniques described herein may be applied to other wind turbine implementations, such as vertical-axis wind turbines. The WTG  100  typically comprises a tower  102  and a nacelle  104  located at the top of the tower  102 . A rotor  106  may be connected with the nacelle  104  through a low-speed shaft extending out of the nacelle  104 . As shown, the rotor  106  comprises three rotor blades  108  mounted on a common hub  110 , which rotate in a rotor plane, but the rotor  106  may comprise any suitable number of blades  108 , such as one, two, four, five, or more blades  108 . The blades  108  (or airfoil(s)) typically each have an aerodynamic shape with a leading edge  112  for facing into the wind, a trailing edge  114  at the opposite end of a chord for the blades  108 , a tip  116 , and a root  118  for attaching to the hub  110  in any suitable manner. 
     For some embodiments, the blades  108  may be connected to the hub  110  using pitch bearings  120 , such that each blade  108  may be rotated around a respective longitudinal axis to adjust the blade&#39;s pitch. The pitch angle of a blade  108  relative to the rotor plane may be controlled by linear actuators, hydraulic actuators, or stepper motors, for example, connected between the hub  110  and the blades  108 . 
       FIG. 2  illustrates a diagrammatic view of typical components internal to the nacelle  104  and tower  102  of the WTG  100 . When the wind  200  is incident on the blades  108 , the rotor  106  rotates and rotates a low-speed shaft  202 . Gears in a gearbox  204  mechanically convert the low rotational speed of the low-speed shaft  202  into a relatively high rotational speed of a high-speed shaft  208  suitable for generating electricity using a generator  206 . 
     A controller  210  may sense the rotational speed of one or both of the low-speed shaft  202  and the high-speed shaft  208 , If the controller  210  determines that the shaft(s) are rotating too fast, the controller  210  may pitch the blades  108  out of the wind  200  or by increasing the torque from the generator  206  which slows the rotation of the rotor  106  i.e., reduces the revolutions per minute (RPM). A braking system  212  may prevent damage to the components of the WIG  100  by keeping the hub  110  from rotating when the hub  110  is already at, or very close, to standstill. The controller  210  may also receive inputs from an anemometer  214  (providing wind speed) and/or a wind vane  216  (providing wind direction). Based on information received, the controller  210  may send a control signal to one or more of the blades  108  to adjust the pitch  218  of the blades  108 . By adjusting the pitch  218  of the blades  108 , the rotational speed of the rotor  106  (and therefore, the shafts  202 ,  208 ) may be increased or decreased. Based on the wind direction, for example, the controller  210  may send a control signal to an assembly comprising a yaw motor  220  and a yaw drive  222  to rotate the nacelle  104  with respect to the tower  102 , such that the rotor  106  may be positioned to face more (or, in certain circumstances, less) upwind. 
       FIG. 3  illustrates the relative placement of several electrical components of a wind turbine blade  108 , according to embodiments of the present disclosure. The body of a wind turbine blade  108  is generally hollow, which reduces the weight of the blade  108  and allows for various components to be fully or partially included inside of the blade  108 . For example, a sensor may be mounted to an exterior surface of the blade  108  and include wires running on an interior surface of the blade or in the material of the blade  108 . 
     The blade  108  includes an electrical panel  310 , which selectively provides power to one or more powered systems  320   a - n  (generally, powered system  320 ) via associated electrical leads  330   a - n  (generally, electrical lead  330 ). The electrical panel  310  is mounted internally to the blade  108 , near or in the root  118 . The powered systems  320  are located at various positions in the blade  108  tipward from the electrical panel  310 , and may include de-icing systems, wind sensors, rotational sensors, flexion sensors, lights, etc., that may be mounted externally, internally, embedded in the material, and through the surface of the blade  108 . The electrical leads  330  may include live and neutral lines for carrying power to/from associated powered systems  320 , and may include optical communications channels or electrical communications channels for carrying data from or command signals to the various powered systems. Each of the powered systems  320  may be connected in parallel to the electrical panel  310  via an associated electrical lead  330 , or several powered systems  320  may be connected in series with one another via a shared electrical lead  330 . 
     To protect the WTG that supplies power for the various powered systems  320  from lightning and other electrical discharges carried rootward along the electrical leads  330 , the root 118 includes an LDFS located rootward of the electrical panel  310  and one or more surge protection devices  470  to shunt the lightning current away to ground. For example, in a system supplying 1-phase power to the blade  108 , the LDFS includes inductors  340  formed from the cables supplying, respectively, a live line (e.g., a powered path or “hot” wire), a neutral line (e.g., a return path), and a protective earth line (e.g., a grounding path). In other embodiments, more or fewer cables and associated inductors  340  carrying different power options are provided to the blade  108 , such as, for example: two-phases and ground, two-phases, neutral, and ground; three phases and ground; three phases, neutral, and ground; etc. In some aspects, several examples for how the individual inductors  340  for each cable in a three-cable system are formed and placed relative to one another are discussed in greater detail in regard to  FIGS. 5A-6F , Several examples for how the individual cables for four-cable systems and five-cable systems are formed and placed relative to one another are discussed in greater detail in regard to  FIGS. 7A-7D  and  FIGS. 8A-8E , respectively. 
     Generally, the inductors  340  use the physical structure of the root  118  as a mandrel and as physical support. The inductors can be located on the exterior or the interior of the root, or embedded within the material of the root. The cables are wound into a desired number of coils about the root  118  to provide an inductance value capable of providing a low-pass filter between the electrical panel  310  and a power source connected via the cables through the nacelle  104 . The cables may be connected to the power source via various rotatable contacts in the nacelle  104 . 
     The inductance of a coil inductor, such as the inductors  340  described herein that are formed from the cabling to the electrical panel  310 , may be determined according to Formula 1, where L is the inductance, p is the permeability of the core material(s), N is the number of turns, r is the radius of the core, and   is the length of the inductor. 
     
       
         
           
             
               
                 
                   L 
                   = 
                   
                     μ 
                     * 
                     
                       
                         
                           N 
                           2 
                         
                         ⁡ 
                         
                           ( 
                           
                             π 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             
                               r 
                               2 
                             
                           
                           ) 
                         
                       
                       / 
                       ℓ 
                     
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
     Accordingly, using the structure of the root  118 , which may be greater than 1 m in diameter, as a mandrel about which the cables are wound provides a similarly large value for r. By using a larger radius, the inductors  340  may be wound fewer times and thus extend for a shorter distance compared to a discrete inductor of a similar inductance but smaller radius, allowing a fabricator to place the mass of the inductor closer to the mounting point of the blade  108  and the hub  110 , thus reducing the moment of the blade  108 . The large radius of the inductors  340  wound about the root  118  also provides the inductors  340  with a greater ratio of surface area to volume compared to a discrete inductor of a smaller radius but equivalent inductance. The greater surface area to volume ratio provides the inductors  340  with superior heat dissipation characteristics compared to discrete inductors with a smaller radius. 
     In various embodiments, the value for p is the value of free space permeability (e.g., when using an air core of the hollow space of the interior of root  118 ), but may also include the permeability effects of the material of the root  118  (e.g., when the inductors  340  are wound around the exterior or embedded in the material of the root  118 ) or the permeability effects of any other devices or cabling co-located in the root  118 . The coils may be arranged so that they form a common mode choke that presents a low impedance for the power from the hub  110  to the powered systems  320 , but a high impedance for the lightning transients from the blade  108  towards the hub  110 . 
     Depending on the radius of the root  118 , permeability of the core, and desired cutoff frequency for the low-pass filter, the fabricator can determine the associated length and number of coils to employ when designing and manufacturing the inductors  340  for the desired inductance. Additionally, depending on the placement of the individual inductors  340  relative to one another, the inductors  340  may exhibit mutual inductance, which the fabricator also accounts for when designing and manufacturing the inductors  340  for the desired cutoff frequency. 
       FIG. 4  is a block diagram of the circuitry  400  for supplying power to the powered systems  320  via an electrical panel  310  fed by an LDFS according to embodiments of the present disclosure. In the illustrated electrical panel  310 , the circuitry is configured for operation with three cables  410   a - c  (generally, cable  410 ) supplying power and reference values, although in other examples, the electrical panel  310  may receive more cables that carry additional phases of power or reference values. 
     In one embodiment, the electrical panel  310  receives, at an input side, a live line via a first cable  410   a  wound into the first inductor  340   a , a neutral line via a second cable  410   b  wound into the second inductor  340   b , and a protective earth line via a third cable  410   c  wound into the third inductor  340   c . The protective earth line supplies a ground reference to the electrical panel, while the live line and neutral line provide power and a return path to selectively activate one or more powered systems  320 . In other three-cable configurations, the electrical panel  310  and associated circuitry  400  receive a first phase of power via the first cable  410   a , a second (different) phase of power via the second cable  410   b , and protective earth via the third cable  410   c . In a further embodiment, the electrical panel  310  and associated circuitry  400  receive four cables  410  wound into associated inductors  340  that provide two different phases of power, neutral, and ground references or three different phases of power and a ground reference. In another embodiment, the electrical panel  310  and associated circuitry  400  receive five cables  410  wound into associated inductors  340  that provide three different phases of power, neutral, and ground references, Although  FIG. 4  is primarily discussed in relation to a live/neutral/ground configuration of a three-cable embodiment, the present disclosure envisions the deployment of large-scale inductors  340  formed from the cables  410  supplied to an electrical panel  310  in a blade  108  of a WTG  100  using various configurations of various numbers of cables. 
     The electrical panel  310  selectively provides, on an output side, an associated live line and neutral line for each powered system  320  as a respective primary lead  440  and secondary lead  450  of the electrical leads  330  that provide live/neutral electrical inputs or different phases of power as electrical inputs. For example, a first powered system  320   a  includes a first primary lead  440   a  and a first secondary lead  450   a  connecting the first powered system  320   a  to the electrical panel  310 , which selectively provides power to the first powered system  320   a . Similarly, an nth powered system  320   n  includes an nth primary lead  440   n  and an nth secondary lead  450   n  connecting the nth powered system  320   n  to the electrical panel  310 , which selectively provides power to the nth powered system  320   n.    
     Additionally, the electrical panel  310  may receive control signals or output status signals to a control unit  460 , either located internally to the electrical panel  310  or as a separate device. The control unit  460  can relay data to the powered systems  320 , receive data from the powered systems  320 , and monitor and control various components of the electrical panel  310 . In various embodiments, the control unit  460  is a computing device including a processor, a memory storage device (e.g., a hard drive) that is included in each blade  108  for controlling systems thereof, that is included in the WTG  100  for controlling the systems thereof and in several blades  108 , or that is included in a wind farm for controlling the systems thereof and in several WTGs  100 . 
     Internally, the electrical panel  310  includes a primary path  313   a  connecting the first cable  410   a  to the primary leads  440   a - n  of the powered systems  320   a - n  and a secondary path  313   b  connecting the second cable  410   b  to the secondary leads  450   a - n  of the powered systems  320   a - n . Generally, the primary path  313   a  and the secondary path  313   b  may be referred to as internal paths  313  (along with a tertiary path, quaternary path, etc., connected to the third, fourth, etc., cables respectively (not illustrated)). The primary path  313   a  includes a first selective switch  311   a  (generally, selective switch  311 ) and a first circuit breaker  312   a  (generally, circuit breaker  312 ). Similarly, the secondary path  313   b  includes a second selective switch  311   b  and a second circuit breaker  312   b . The selective switches  311  are selectively controlled (e.g., via signals from the control unit  460 ) to open or close to establish or disconnect an associated internal path to the powered systems  320   a - n . The circuit breakers  312  are controlled by the thermal and/or electrical properties experienced on the internal paths to automatically open and disconnect an associated internal path  313  to the powered systems  320   a - n . In various embodiments, the relative positions of the selective switches  311  and the circuit breakers  312  may be swapped from the order illustrated in  FIG. 4  or the selective switches  311  and circuit breakers  312  on a given internal path  313  may be combined into one component (e.g., a selectively switched circuit breaker). 
     Each powered system  320   a - n  is connected to two or more internal paths  313  by respective system switches  314   a - n  that may be controlled to selectively provide power to individual powered systems  320   a - n.    
     Each internal path  313  is connected by one or more surge protection devices  470  to a lightning protection system  480  for the blade  108 . A lightning protection system  480  provides an alternative, lower-impedance, path for lightning striking the blade  108  to run than the higher-impedance path offered by the cables  410  and the associated inductors  340 . The lightning protection system  480  is a conductive pathway that runs from the tip  116  of the blade  108  (e.g., via a solid metal contact or a conductive cap at the tip  116 ) to the root  118  of the blade  108  (e.g., to a ferrule or conductive band that is electrically isolated from the cables  410 ) and is connected via a lightning current transfer unit  490  to ground via a conductive path through the tower  102 . 
     The higher impedance presented by the inductors  340  offers a less attractive path to ground for the lightning than the lower impedance presented by the lightning protection system  480 . The surge protection devices  470  are selectively activated or nonlinear devices that shunt current flow from the electrical leads  330  to the lightning protection system  480  in the event of a lightning strike or other electrical discharge to the blade  108 . The surge protection devices  470  include one or more of: spark gaps, metal oxide varistors, gas discharge tubes, Transient Voltage Suppression (TVS) diodes, or other non-linear devices to shunt the current of a lightning strike or other electrical discharge away from the cables to the lightning protection system  480  when the voltage across the inductors  340  is sufficiently high. 
     The inductors  340  provide a common mode choke connection between the electrical panel  310  and the power source. As common mode chokes that are wound around a shared core, the inductors provide potential electrical paths with opposing impedances that cancel out to appear as a zero impedance link from the perspective of the power source, but appear as a high impedance link to the perspective of a powered system  320  or a lightning strike tipward of the electrical panel  310 . 
       FIGS. 5A-6F  illustrate various cross-sectional views of an LDFS that highlight various relative positions and arrangements of the inductors 340 in relation to the section of the root  118  used as a mandrel and the portions of the cables used to define the inductors  340 .  FIGS. 5A-5F  illustrate the inductors  340  using the internal surface of the root  118  as a mandrel.  FIGS. 6A-6F  illustrate the inductors  340  using the external surface of the root as a mandrel. The portion of the root  118  illustrated in cross section in 
       FIGS. 5A-6F  is hollow and generally cylindrical in shape, although other shapes are contemplated and various supports and other components may be included in other portions of the root  118 .  FIGS. 5A-6F  illustrate winding patterns using three cables  410   a - c  to produce three corresponding inductors  340   a - c . In various embodiments, each of the individual three cables  410   a - c  may provide electrical inputs of a phase of power, a neutral line, or a ground line to an electrical panel  310 , and a fabricator may select a winding pattern and designate any cable  410  to handle a particular electrical input according to the power requirements of the powered systems  320  in the blade  108 . 
       FIGS. 5A and 5B  illustrate arrangements of the inductors  340  that are intertwined in which the inductors  340  are free from the material of the root  118  and at least partially secured by the material of the root  118 , respectively. The first cable  410   a , the second cable  410   b , and the third cable  410   c  are wound into coils on the inner surface of the root  118  as a mandrel to form the respective inductors  340 , and are wound sequentially to each other to produce intertwined inductors  340 . 
       FIGS. 5C and 5D  illustrate arrangements of the inductors  340  that wind the third cable  430  separately from the first and second cables  410   a ,  420   b  in which the inductors  340  are free from the material of the root  118  and at least partially secured by the material of the root  118 , respectively. The first and second cables  410   a, b  are intertwined with one another, and the third cable  430   c  is wound separately. Winding the inductors  340  on an internal surface of the root  118 , as in  FIGS. 5A-5D , results in a diameter D (and associated radii) for the inductors  340  based on the internal diameter of the root  118  and the diameters of the first, second, and third cables  410   a - c.    
       FIGS. 5E and 5F  illustrate arrangements of the inductors 340 that employ a bundled cable  510  that includes the first, second, and third cables  410   a - c  as sub-cables defined therein. The bundled cable  510  is wound internally to the root  118  as a mandrel and imparts coils to each of the included first, second, and third cables  410   a - c  to form the inductors  340   a - c . The interior distances between the individual cables  410  within the bundled cable  510  define individual diameters and associated radii that determine the inductance for the inductors  340  (i.e., D1 for the first cable  410   a , D2 for the second cable  420   b , and D3 for the third cable  430   c ). In various embodiments, D1=D2=D3, but in other embodiments, different diameters can be defined for the various cables  410  by altering the placement of the cables within the bundled cable  510  or altering the individual sizes of the cables  410 . 
     In various embodiments, such as in  FIGS. 5A, 5C, and 5E , one or more cable clamps (not illustrated) mounted to or built into the inner surface of the root  118  hold the wound cables in place to define the inductors. In other embodiments, such as in  FIGS. 5B, 5D, and 5F , the body of the root  118  may secure a portion or all of the inductors  340 . For example,  FIGS. 5A  (or  5 C or  5 E) may be an alternative point of view of the cross section presented in  FIG. 5B  (or  5 D or  5 F, respectively) rotated by a predefined angle of view. 
       FIGS. 6A and 6B  illustrate arrangements of the inductors  340  that are intertwined in which the inductors  340  are free from the material of the root  118  and at least partially secured by the material of the root  118 , respectively. The first cable  410   a , the second cable  410   b , and the third cable  410   c  are wound into coils on the outer surface of the root  118  as a mandrel to form the respective inductors  340 , and are wound sequentially to each other to produce intertwined inductors  340 . 
       FIGS. 6C and 6D  illustrate arrangements of the inductors  340  that wind the third cable  430  separately from the first and second cables  410   a,b  in which the inductors  340  are free from the material of the root  118  and at least partially secured by the material of the root  118 , respectively. The first and second cables  410   a,b  are intertwined with one another, and the third cable  410   c  is wound separately. Winding the inductors  340  on an outer surface of the root  118 , as in  FIGS. 6A-6D , results in a diameter D (and associated radii) for the inductors  340  based on the external diameter of the root  118  and the diameters of the first, second, and third cables  410   a - c.    
       FIGS. 6E and 6F  illustrate arrangements of the inductors  340  that employ a bundled cable  510  that includes the first, second, and third cables  410   a - c  as sub-cables defined therein. The bundled cable  510  is wound externally to the root  118  as a mandrel and imparts coils to each of the included first, second, and third cables  410   a - c  to form the inductors  340 . The interior distances between the individual cables  410   a - c  within the bundled cable  510  define individual diameters and associated radii that determine the inductance for the inductors  340  (i.e., D1 for the first cable  410   a , D2 for the second cable  410   b , and D3 for the third cable  410   c ), In various embodiments, D1=D2=D3, but in other embodiments, different diameters can be defined for the various cables  410   a - c  by altering the placement of the cables within the bundled cable  510  or altering the individual sizes of the cables  410 . 
     In various embodiments, such as in  FIGS. 6A, 6C, and 6E , one or more cable clamps (not illustrated) mounted to or built into the outer surface of the root  118  hold the wound cables in place to define the inductors  340 . In other embodiments, such as in  FIGS. 6B, 6D, and 6F , the body of the root  118  may secure a portion or all of the inductors  340 . For example,  FIG. 6A  (or  6 C or  6 E) may be an alternative point of view of the cross section presented in  FIG. 6B  (or  6 D or  6 F, respectively) rotated by a predefined angle of view. Although not illustrated, the externally wound inductors  340  may be covered by a protective cap and/or covered by a cowl or other portion of the hub  110  when the root  118  is installed to the hub  110 , and are electrically isolated from the lightning protection system  480 . The cables  410   a - c  of the externally defined inductors  340  may enter and exit the blade  108  via various through-holes (not illustrated) defined in the body of the root  118 . 
     A fabricator may determine whether to install the cables  410  internally (e.g., as in  FIGS. 5A-5F ) or externally (e.g., as in  FIGS. 6A-6F ) based on the different potential internal/external diameters for the inductors  340 , the structural strength of the root  118  (e.g., including the effect of through-holes on structural soundness), mounting hardware used between the blade root  118  and the hub  110 , the permeability of the material used for the root  118 , etc., to result in inductors  340  of a desired inductance and with desired physical properties. Accordingly, a fabricator can deploy large-scale inductors  340  made from the cables  410  supplying an electrical panel  310  as an LDFS with greater heat dissipation potential, a lower rotational moment, and less material than an LDFS using internal discrete inductors. 
       FIGS. 7A-7D  illustrate additional cable winding patterns for an LDFS using four cables  410   a - d  to produce four corresponding inductors  340   a - d . As will be appreciated, the cable winding patterns shown in  FIGS. 7A-7D  do not show the relative positions of the cables  410  of the root  118  used as a mandrel for the inductors  340 ; the cable winding patterns may be used with internal windings (e.g., as in  FIGS. 5A-5F ) or external windings (e.g. as in  FIGS. 6A-6F ), and may be fully, partially, or not captured in the material of the root  118  in various embodiments. In various embodiments, each of the individual four cables  410   a - d  may provide electrical inputs of a phase of power, a neutral line, or a ground line to an electrical panel  310 , and a fabricator may select a winding pattern and designate any cable  410  to handle a particular electrical input according to the power requirements of the powered systems  320  in the blade  108 . 
       FIG. 7A  illustrates that the four cables  410   a - d  may be co-wound about the mandrel to produce the four inductors  340   a - d .  FIG. 7B  illustrates that a first cable  410   a  (e.g., carrying a ground electrical input) may be wound separately into a first inductor  340   a  about a shared mandrel from the second through fourth cables  410   b - d  (e.g., carrying two phases of power and neutral, or three phases of power), which are co-wound about the mandrel with one another to produce the second through fourth inductors  340   b - d .  FIG. 7C  illustrates that a first and a second cable  410   a,b  may be co-wound about a shared mandrel to form a first common mode choke with the first and second inductors  340   a,b  separately from a third and a fourth cable  410   c,d  that are co-wound with one another about the mandrel to form a second common mode choke with the third and fourth inductors  340   c,d .  FIG. 7D  illustrates that a bundled cable  510  may include the first through fourth cables  410   a - d  as sub-cables thereof, which are wound about the mandrel to produce the inductors  340 . 
       FIGS. 8A-8E  illustrate additional cable winding patterns for an LDFS using five cables  410   a - e  to produce five corresponding inductors  340   a - e . As will be appreciated, the cable winding patterns shown in  FIGS. 8A-8E  do not show the relative positions of the cables  410  of the root  118  used as a mandrel for the inductors  340 ; the cable winding patterns may be used with internal windings (e.g., as in  FIGS. 5A-5F ) or external windings (e.g. as in  FIGS. 6A-6F ), and may be fully, partially, or not captured in the material of the root  118  in various embodiments. In various embodiments, each of the individual five cables  410   a - e  may provide electrical inputs of a phase of power, a neutral line, or a ground line to an electrical panel  310 , and a fabricator may select a winding pattern and designate any cable  410  to handle a particular electrical input according to the power requirements of the powered systems  320  in the blade  108 . 
       FIG. 8A  illustrates that the five cables  410   a - e  may be co-wound about the mandrel to produce the five inductors  340   a - e .  FIG. 83  illustrates that a first cable  410   a  (e.g., carrying a ground electrical input) may be wound separately into a first inductor  340   a  about a shared mandrel from the second through fifth cables  410   b - e  (e.g., carrying three phases of power and neutral), which are co-wound about the mandrel with one another to produce the second through fifth inductors  340   b - e .  FIG. 8C  illustrates that a first and a second cable  410   a, b  may be co-wound about a shared mandrel to form a first common mode choke with the first and second inductors  340   a,b  separately from the third through fifth cables  410   c - e  that are co-wound with one another about the mandrel to form a second common mode choke with the third through fifth inductors  340   c - e .  FIG. 8D  illustrates that the five cables  410  may be wound into the associated inductors  340  in three separate groups, in which the first cable  410   a  is wound into a first inductor  340   a  by itself, the second and third cables  410   b,c  are co-wound to form a first common mode choke with the second and third inductors  340   b,c,  and the fourth and fifth cables  410   d,e  are co-wound to form a second common mode choke with the fourth and fifth inductors  340   d,e .  FIG. 8E  illustrates that a bundled cable  510  may include the first through fifth cables  410   a - e  as sub-cables thereof, which are wound about the mandrel to produce the inductors  340 . Throughout the present disclosure, reference is made to embodiments presented. However, the scope of the present disclosure is not limited to specific described embodiments. Instead, any combination of the features and elements provided above, whether related to different embodiments or not, is contemplated to implement and practice contemplated embodiments. Furthermore, although embodiments disclosed herein may achieve advantages over other possible solutions or over the prior art, whether or not a particular advantage is achieved by a given embodiment is not limiting of the scope of the present disclosure. Thus, the aspects, features, embodiments, and advantages described herein are merely illustrative and are not considered elements or limitations of the appended claims except where explicitly recited in a claim(s). 
     In view of the foregoing, the scope of the present disclosure is determined by the claims that follow,