System and method for controlling current distribution to electrical brushes used in dynamoelectric machine

Abstract

To disclose a system and method for controlling current distribution to electrical brushes used in a dynamoelectric machine.SOLUTION: A method includes using an arrangement 54 of a plurality of resistor devices electrically connected to a plurality of electrical brushes 40 to control a distribution of electrical current between an external source 48 and the plurality of electrical brushes. The arrangement of the plurality of resistor devices is configured to control an amount of the electrical current that is distributed to the individual brushes and / or one or more groups of brushes while a dynamoelectric machine is operating.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] Cross - Reference to Related Applications This patent application is related to the invention of U.S. Patent Application No. 18 / 493906, entitled "SYSTEM AND METHOD FOR SELECTIVE ACTIVATION AND DEACTIVATION OF ELECTRICAL BRUSHES USED IN DYNAMOELECTRIC MACHINE FOR CURRENT DENSITY OPTIMIZATION", which was filed simultaneously, is co - pending, and has been assigned to the assignee of the present invention. The disclosure of which is hereby incorporated by reference herein. Embodiments of the present disclosure generally relate to rotating electrical machines, and more specifically, to arranging an array of resistor devices electrically connected to electrical brushes maintained on the collecting surface disposed on the rotating shaft of a rotating electrical machine to control the current distribution of individual brushes or groups of brushes.

Background Art

[0002] A rotating electrical machine (e.g., a generator, etc.) includes a rotor body that can be made of a ferromagnetic metal material and is rotatably attached to a shaft via a bearing assembly. Circumferentially arranged around the middle part of the rotor body are a plurality of axially directed slots that extend radially outward from the center of the rotor body, and these slots hold a plurality of field windings of a coil that can be made of copper or aluminum. These field windings of the coil can include a longitudinally directed center winding fixed in the slot and an end winding of a plurality of turns extending from the slot at the axial end of the rotor body. The shaft of the generator can include a drive end having a coupling for a prime mover (e.g., a gas turbine or a steam turbine, etc.) that operates to rotate the shaft. When the shaft is rotated by the prime mover, a rotating magnetic field is generated within the machine. Thereby, a set of three-phase voltages is induced in the stator windings of the stator that surrounds the rotor body of the generator. The end on the opposite side of the shaft can be called the non-drive end and includes a collecting ring. The collecting ring is mounted on or attached to the shaft and rotates with the shaft when the shaft rotates. The stationary electrical brush is typically loaded with a spring and is continuously maintained on the surface of the collecting ring as the ring rotates with the shaft. Current from an external source can be supplied to the collecting ring through the electrical brush. The current flows from the collecting ring through the interior of the shaft to the field windings of the coil of the rotor body. Thus, the current flowing from the electrical brush through the collecting ring to the field windings of the coil can maintain the rotating magnetic field at a constant polarity.

[0003] In operation, the electric brush can be configured to function as a manifold that distributes current from an external source to collection. In such a manifold configuration, the typical number of electric brushes available for each collection is in the range of, for example, between 10 and 100. If the resistance in each individual brush path or leg from the external source to collection varies even slightly compared to other legs, it affects the current shunting among all the electric brushes. Generally, the resistance of each leg includes a plurality of resistance components that contribute to the overall resistance of the leg. FIG. 1 shows the resistance components existing between an external source 48 that supplies current to a collection 32 through a plurality of conventional electric brushes 40 and the collection 32. The main resistance in each leg is the sliding contact between the electric brush 40 and the collection 32. In FIG. 1, the contact resistance of the sliding contact is indicated by Rc. By its nature, the contact resistance Rc is a very variable resistance. The variation of the contact resistance Rc worsens when the electric brush operates at a low current density or a high current density. This is becoming more common as power plants increase their turndown capabilities to operate over a wide range of loads. Operating over a wide range of loads typically requires operating at a wide range of field currents that are outside the typical current density requirements of the brushes.

[0004] Other resistance components in the electrical path of each leg from the external source 48 to the collection 32, which are variable in nature and are considered to affect the current distribution, include the resistance of the electric brush 40 itself and other miscellaneous resistances resulting from electrical connections formed in the path from the external source 48 to the collection 32 and unintended electrical paths. In FIG. 1, the resistance of the electric brush 40 is shown as Rb, and the miscellaneous resistance is shown as Rm. The resistance Rb of the electric brush typically varies inversely with the temperature of the brush during operation and the length of the brush when it wears. The miscellaneous resistance Rm typically results from electrical connections and unintended electrical paths arising from the need to mechanically support the electric brush during the operation of the generator.

[0005] All resistance components present in the leg between the external source 48 and the collecting 32 may have a significant impact on the distribution or shunting of the current flowing through the leg. Some electrical brushes may have almost zero current, while other brushes may receive currents that are two to three times the average current value optimal for the brushes to handle. Such non-uniform current distribution among the electrical brushes is often referred to as selectivity, which may result in overheating of the brushes and insufficient film formation between the brushes and the collecting (film formation is essential for maintaining the life of the brushes and minimizing fluctuations in the contact resistance Rc). Such a state may ultimately lead to arc discharge, resulting in serious arc damage and melting of components, posing a safety risk to nearby operators. SUMMARY OF THE INVENTION

[0006] In the following, a simplified summary of the disclosed subject matter is presented to provide a basic understanding of some aspects of the various embodiments described herein. This summary is not an extensive overview of the various embodiments. Nor is this summary intended to exclusively identify key features or essential features of the claimed subject matter described in the claims, nor is it intended to be helpful in determining the scope of the claimed subject matter. The sole purpose of this summary is to present some concepts of the present disclosure in a simplified form as a prelude to the more detailed description that follows.

[0007] Solutions provided by various embodiments that avoid the aforementioned selectivity problems resulting from the inherent variations in resistance in the individual brush paths or legs from the external source to the collector include providing an array of resistor devices between the external source and the electrical brush so as to remove the variable resistance between the external source and the brush. In this way, the resistor device can control the amount of current distributed from the external source to the individual brushes and / or one or more groups of brushes by canceling out the variations in the resistance of each leg. Thereby, a specified current can be reliably passed through each electrical brush. In one embodiment, a resistor device can be used to control the amount of current from the external source and drive each current brush so that an equal current is distributed. In any application, whether passive or active, the resistor device that can be used in any of the various embodiments can be selected from the group including fixed resistors, variable resistors, power electronics-based resistors, and combinations thereof.

[0008] In addition to using an array of resistors, embodiments can include placing switches for selectively operating and selectively stopping the operation of the electrical brushes to control the current density of the current supplied to the electrical brushes. For example, selected ones of a plurality of switches can be opened and closed for a predetermined time to adjust the average current density of the current flowing through the electrical brush within a predetermined current density range. In embodiments where switches are placed to adjust the average current density supplied to the electrical brush, a resistor device can be used to control the amount of current received by each electrical brush to a specified amount of current.

[0009] According to one embodiment, a system is provided. The system includes a collecting disposed on a rotating shaft of a rotating electrical machine, and a plurality of electrical brushes maintained on a surface of the collecting when the collecting rotates with the rotating shaft, the plurality of electrical brushes configured to conduct an electric current between an external source and the rotating electrical machine through the collecting, and an array of a plurality of resistor devices electrically connected to the plurality of electrical brushes and configured to control a distribution of the electric current between the external source and the plurality of electrical brushes, the array of the plurality of resistor devices configured to control an amount of the electric current distributed to an individual brush and / or one or more groups of brushes among the plurality of electrical brushes while the rotating electrical machine is operating.

[0010] According to another embodiment, a rotating electrical machine is provided. The rotating electrical machine includes a rotatable shaft, a rotor body attached to the rotatable shaft, the rotor body having a plurality of field windings of coils fixed around the rotor body, at least one collecting disposed at one end of the possible shaft, and a plurality of electrical brushes maintained on a surface of the at least one collecting when the at least one collecting rotates with the rotatable shaft, the plurality of electrical brushes configured to conduct an electric current between an external source and the field windings of the coils fixed to the rotor body through the at least one collecting, and an array of a plurality of resistor devices electrically connected to the plurality of electrical brushes and configured to control a distribution of the electric current flowing between the external source and the plurality of electrical brushes, the array of the plurality of resistor devices configured to control an amount of the electric current distributed to an individual brush and / or one or more groups of brushes among the plurality of electrical brushes while the rotating electrical machine is operating.

[0011] According to yet another embodiment, there is provided a method for controlling the current density of a plurality of electrical brushes maintained on the surface of a collecting arranged on a rotating shaft of a rotating electrical machine and flowing a current between an external source and the rotating electrical machine. The method includes the steps of arranging a plurality of resistor devices so as to be electrically connected to the plurality of electrical brushes and the external source, and controlling the distribution of current between the external source and the plurality of electrical brushes using the plurality of resistor devices, wherein the plurality of resistor devices are configured to control a specified amount of current distributed to individual brushes and / or one or more groups of brushes among the plurality of electrical brushes while the rotating electrical machine is operating.

Brief Description of the Drawings

[0012] The present invention can be further understood by reading the following description of non-limiting embodiments with reference to the drawings.

Figure 1

Figure 2

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Figure 4

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Figure 6

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Figure 8

Figure 9

Figure 10

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Figure 12

DETAILED DESCRIPTION OF THE INVENTION

[0013] Exemplary embodiments of the present invention will be described in more detail below with reference to the drawings, which show some embodiments but not all embodiments. In fact, the present invention can be embodied in many different forms and should not be construed as limited to the embodiments described herein. These embodiments are provided so that this disclosure will satisfy the applicable legal requirements. Like reference numerals represent like elements throughout.

[0014] The present disclosure generally relates to a rotating electrical machine, and more specifically to an arrangement of resistor devices that are electrically connected to an external source that passes current between an electrical brush maintained on a collecting surface disposed on a rotating shaft of the rotating electrical machine and the collecting. In operation, the resistor device is configured to remove variable resistance between the external source and the brush. In this regard, the resistor device can control the amount of current distributed to individual electrical brushes and / or one or more groups of brushes while the rotating electrical machine is operating. Thereby, a specified current can be surely passed through each electrical brush.

[0015] Although various embodiments are described with respect to generators, it is understood that these embodiments are also applicable to other types of rotating electrical machines that utilize collecting and electrical brushes that move supported by the collecting during operation of the machine. Examples of other rotating electrical machines to which various embodiments are applicable include, but are not limited to, electric motors and alternators.

[0016] Referring to the figures, Figure 2 shows an isometric view of a generator 10 according to the prior art. As shown in Figure 2, the generator 10 includes a rotor body 12 that can be made of a ferromagnetic metal material and is rotatably attached to a shaft 14 via a bearing assembly (not shown). Circumferentially arranged around the middle portion of the rotor body 12 are a plurality of axial slots 16 that extend radially outward from the center of the rotor body. These slots are used to hold a plurality of field windings 18 of a coil made of copper or aluminum. The plurality of field windings of the coil can include a longitudinally aligned center winding 20 fixed within the slot 16 and a winding portion of an end winding 22 that extends from the slot 16 at the axial end 24 of the rotor body 12.

[0017] The shaft 14 of the generator 10 can include a drive end 26 having a coupling 28 for a prime mover such as a gas turbine or a steam turbine that operates to rotate the shaft. When the shaft is rotated by the prime mover, a rotating magnetic field is generated within the machine. Thereby, in the generator 10, a three-phase voltage is induced in the stator windings of the stator surrounding the rotor body 12. For the purpose of clarity of the figure, neither the stator nor the stator windings are shown. The end of the shaft 14 on the opposite side can be called a non-drive end 30 and is a collecting ring 32 fixed to or attached to the shaft, such as a slip ring 32 that rotates with the shaft as the shaft rotates, and a coupling 34 that can be used to couple a generator excitation system in one embodiment or a gear reduction unit in another embodiment. A fixed electric brush (not shown in Figure 2) loaded with a spring is continuously maintained on the surface of the collecting ring 32 as the ring rotates with the shaft 14. Current from an external source (such as a generator excitation system) can be supplied to the collecting ring 32 through the electric brush. The current from the collecting ring 32 flows through the interior of the shaft 14 to the field windings 18 of the rotor body 12. In this way, the current flowing from the electric brush through the collecting ring 32 to the field windings 18 can maintain the rotating magnetic field with a fixed polarity.

[0018] Figure 3 shows a partial perspective view of a brush mounting portion installed on a collector ring 32 of a generator according to the prior art as shown in Figure 2 or a single brush holder - rigging assembly 36 installed on a collector shoe 38. Although not shown in Figure 3, the collector ring 32 rotates together with the shaft and rotor body of the generator. For clarity, only one brush holder - rigging assembly 36 is shown in Figure 3, but it is understood that more rigging assemblies can be attached to the collector shoe 38 and at least partially distributed around the collector ring 32. Each brush holder - rigging assembly 36 can include one or more electrical brushes 40, one or more corresponding brush holders 42 for the brushes, and a fixed support member 44. For example, Figure 3 shows that the brush holder - rigging assembly 36 can include a pair of electrical brushes 40 within the brush holder 42. The electrical brushes 40 are typically blocks of carbon compounds such as graphite, and these blocks of carbon compounds can freely conduct electricity and generally have a very low friction so as not to wear the collector ring 32. The brush holder 42 holds the brushes received in the brush holder 42 at least in the axial and circumferential directions. In one embodiment, the brush holder 42 can use a brush spring to bias one or more electrical brushes downward in the radial direction to maintain contact with the surface of the collector ring 32. The fixed support member 44 is configured to be electrically connected to the collector shoe 38. In this regard, the fixed support member 44 is made of or includes a conductive material and further can have electrical wiring for conducting current to or from one or more brushes. The brush holder - rigging assembly 36 can be fixed to the collector shoe 38 with bolts or screws, but it is understood that other fixing methods, mounting methods, etc. can also be utilized. The details of the brush holder - rigging assembly 36 are well - known and are disclosed, for example, in U.S. Patent No. 10,158,206, the disclosure of which is incorporated herein by reference.

[0019] The foregoing description of the brush holder - rigging assembly 36 represents only one configuration that can be used to continuously maintain an electrical brush on the surface of the collector ring 32 as the ring rotates with the shaft 14 while operating to pass current between the field winding 18 of the rotor body 12 of the generator 10 and the generator excitation system, and is not meant to limit the scope of the various embodiments. One of ordinary skill in the art will understand that the embodiments described herein can be implemented using other types of brush holder - rigging assemblies.

[0020] FIG. 4 shows a schematic diagram of an electrical circuit 46 through which current flows between an external source 48 (such as a generator excitation system) and a plurality of field windings 18 of the coils of the rotor body 12 of the generator 10 shown in FIG. 2 via an electrical brush 40 continuously maintained on the surface of the collector ring 32 of a prior - art generator as shown in FIG. 3. As shown in FIG. 4, the generator excitation system 48 can be a power source (e.g., a direct - current (DC) source, etc.) and supplies DC power to the brush in the form of current through electrical wiring 50. The electrical brush 40 supplies current to the collector ring 32, and the collector ring 32 supplies current to the field windings 18 of the coils. As shown in this figure, one ring 32 to which the electrical brush 40 is operatively coupled is connected to the positive terminal of the external source 48, and the other ring 32 to which the brush 40 is coupled is connected to the negative terminal of the external source 48. With this configuration, not only can current flow from the electrical brush 40 and the collector ring 32 to the field windings 18 of the coils, but current can also flow from the field windings 18 of the coils through the collector ring 32 and the electrical brush 40 to the external source 48.

[0021] The schematic diagram of FIG. 4, like the schematic diagrams of the other figures disclosed herein, shows only four electric brushes 40 for each collecting 32, and the four electric brushes 40 are configured to supply current to the ring through corresponding parallel paths. However, it is understood that a greater number of brushes operably coupled to the collecting may be used. For example, it is possible to have from 10 to 100 parallel path electric brushes for each collecting 32.

[0022] As described above with respect to FIG. 1, in the electrical circuit 46, for each individual brush path or leg from the external source 48 through the electric brush 40 to the contact surface between the brush and the collecting 32, each has an inherent resistance that can affect the distribution of current from the external source to the brush. For example, each leg has a contact resistance Rc between the electric brush 40 and the collecting 32, a resistance Rb of the electric brush itself, and a miscellaneous resistance Rm resulting from electrical connections and unintended electrical paths, and the sum of all these resistances contributes to the overall resistance of each leg. When the resistance of a leg is high, the electric brush 40 of that leg receives a smaller amount of current from the external power source 48 compared to the brushes of legs with lower resistance. Similarly, when the resistance of a leg is low, the electric brush 40 of that leg receives a larger amount of current from the external power source 48 compared to the brushes of legs with higher resistance. Due to the imbalance in the current received by the electric brushes 40 caused by the resistance inherent in each leg, the current flowing through some electric brushes becomes almost zero, while through other brushes, a current 2 to 3 times the average current value optimal for the brush to handle flows. Such a non-uniform current distribution, i.e., selectivity, among the electric brushes can lead to overheating of the brushes because the brushes receive excessive current. Furthermore, such a non-uniform distribution of current among the electric brushes can result in insufficient film formation between the brushes and the collecting, which is essential for maintaining the life of the brushes and reducing the impact of large variations in the contact resistance Rc. Such an impact of the selectivity of the electric brushes 40 that can occur in the configuration shown in FIG. 4 causes flashover, which can lead to safety and operational risks (e.g., serious arc damage, melting of components, endangering nearby operators).

[0023] The various embodiments described herein address variations in the intrinsic resistance that occur in the brush path or leg from an external source 48 through an electric brush 40 to the contact surface between the brush and the collector ring 32, for example, by arranging an array of resistor devices (such as a balance resistor device) that can control the resistance of each leg so that the balance of current distribution can be achieved. In this way, the array of resistors can further evenly distribute the current among the electric brushes 40 in various embodiments. As a result, the array of resistor devices can control the amount of current distributed to individual brushes and / or one or more groups of brushes so that each brush can receive a specified amount of current in various embodiments.

[0024] The array of resistor devices can be implemented in several different locations. These locations include, but are not limited to, the brush holder and the brush holder - rigging assembly (such as a fixed support member or other components within the brush holder - rigging assembly that include electrical wiring, such as electrical wiring within the rigging assembly that includes a wiring pigtail).

[0025] FIG. 5 is a schematic diagram of an electrical circuit 52 in which a current flows between an external source 48 and a plurality of field windings 18 of a coil, and an array 54 of resistor devices 56 is connected between the external source and an electrical brush. As shown in FIG. 5, the resistor device 56 can include fixed resistors. In one embodiment, the fixed resistor is selected to have a resistance greater than the contact resistance Rc between the electrical brush 40 and the collecting ring 32. By making the resistance value of the fixed resistor of each leg greater than the contact resistance Rc, the leg resistance of the leg can be controlled to a resistance value that overcomes the variation in the inherent resistance of each leg. In this regard, the resistor device 56 can more evenly shunt the current from the external source 48. In particular, by making the resistance value of the fixed resistor of each leg greater than the contact resistance Rc, the current can be more evenly distributed between the electrical brushes 40. As used herein, more evenly distributing the current means that the electrical brushes distribute substantially the same current (e.g., all current values are within 10% of each other), as contrasted with unevenly distributing (e.g., some brushes have no current flowing through them while other brushes have twice the average current or more flowing through them). Although there is still some variation in the leg resistance of the legs, by making the resistance of the fixed resistor greater than the contact resistance Rc, the current is sufficiently evenly distributed between the electrical brushes 40.

[0026] Selecting the resistance value of the fixed resistor is understood to be within the common general knowledge of those skilled in the art and is determined by various factors (such as, but not limited to, the contact resistance Rc of the leg, the electrical brush resistance Rb, and the miscellaneous resistance Rm, as well as the current supplied by the external source 48). In one embodiment, the resistance of the fixed resistor of each leg can be set to the same resistance value. As long as the same resistance value of the fixed resistor is large enough so that the ratio of the variation in the resistance of other resistance sources (e.g., Rc, Rb, and Rm) of the leg is small, the variation in the resistance can be overcome and the current is evenly distributed.

[0027] To use fixed resistors with the same resistance value, since it is necessary to use a value large enough to overcome the resistance variations of other resistance sources in the legs, there may be losses in the collector 32 of the electrical circuit 52 in FIG. 5. To avoid losses in the collector, the configuration of other types of balancing resistor devices can be utilized. For example, instead of using fixed resistors, variable resistors can be arranged.

[0028] FIG. 6 shows a schematic diagram of an electrical circuit 58 in which a current flows between an external power source 48 and a plurality of field windings 18 of a coil, and an array 60 of resistor devices 62 in the form of variable resistors is connected between the external source and the electrical brush 40. When using variable resistors, the resistance value of the resistor devices 62 in FIG. 6 can be adjusted so that the current is reliably and evenly distributed between the electrical brushes 40 as needed. In one embodiment, the variable resistors can be adjusted so that substantially equal resistance values are obtained in each leg. As used herein, "substantially equal resistance values" means resistance values within 10% of each other. By having the ability to adjust the variable resistors to obtain substantially equal resistance values, the electrical circuit 58 in FIG. 6 can supply a more stable current to each individual electrical brush 40.

[0029] In one embodiment, the variable resistors of the electrical circuit 58 in FIG. 6 can be adjusted to have different resistance values in order to supply a specified amount of current from the external source 48 to each electrical brush 40. Note that the position of the arrow used to depict the variable resistor is related to the resistance value of the resistor. Generally, in the variable resistor shown in FIG. 6, when the width of the resistor indicated by the pointer is wide, it represents a small resistance value, and when the width of the resistor is narrow, it represents a large resistance value. For example, a variable resistor in which the pointer indicates substantially the full width of the resistor indicates that the resistance is zero.

[0030] It will be appreciated that other types of devices can be utilized to adjust the resistance of each leg, in addition to the variable resistor shown in FIG. 6, so that current is more evenly distributed among the electric brushes 40. For example, a power electronics-based resistor device can be connected between the external source 48 and the electric brushes 40, and the power electronics-based resistor device can be used to adjust the resistance of each leg so that the current in the leg flowing to each brush reaches a specified current amount. In one embodiment, the power electronics-based resistor device can distribute current so that the current flowing to each brush is substantially equal. In another embodiment, the power electronics-based resistor device can pass a specified amount of current through each electric brush 40. As used herein, "power electronics-based resistor device" means a power electronics device that can function as a solid-state switch to specify the resistance value of the leg of the brush path. Examples of power electronics-based resistor devices include power diodes, metal-oxide-semiconductor-field-effect transistors (MOSFETs), bipolar junction transistors (BJTs), insulated gate bipolar transistors (IGBTs), and thyristors (e.g., silicon controlled rectifiers (SCRs), gate turn-off (GTO) thyristors, and MOS controlled thyristors), but these are illustrative and not intended to include all possible ones.

[0031] FIG. 7 shows a schematic diagram of an electrical circuit 64 in which current flows between the external source 48 and a plurality of field windings 18 of the coil, and an array 66 of resistor devices in the form of power electronics-based resistors 68 is connected between the external source and the electric brushes 40. Similar to the variable resistor shown in FIG. 6, the power electronics-based resistor 68 has the ability to finely adjust the resistance of each leg so that the current between the brushes is evenly shunted and / or a specified amount of current flows through each electric brush 40. The array 66 of power electronics-based resistors 68 has the advantage of reducing losses, similar to the variable resistor, but is considered to occupy less space when implemented because of its small size.

[0032] The embodiments described with respect to FIGS. 5-7 illustrate an arrangement of resistor devices, where the resistor devices of each leg are connected in series with the external source 48 and the electrical brush 40. However, it should be understood that other arrangements of resistor devices with respect to the external source, the legs, and the brush are also conceivable. For example, FIG. 8 shows a schematic diagram of an electrical circuit 70 in which current flows between the external source 48 and a plurality of field windings 18 of a coil, and an arrangement 72 of resistors 56, where each resistor is electrically connected to a group of electrical brushes 40. As shown in FIG. 8, the resistors 56 can be fixed resistors. In this embodiment, each fixed resistor 56 of the arrangement 72 is coupled to a group of electrical brushes 40. In particular, each fixed resistor 56 with respect to a particular group of electrical brushes 40 is connected in series with the external source 48 and a parallel path of the leg leading to the corresponding electrical brush within the group. With this configuration, if the resistance value of the fixed resistor 56 is greater than the value of the contact resistance Rc of each electrical brush 40 of each group of electrical brushes, the fixed resistor 56 can control the flow of current from the external source 48 towards the brushes of each group. Thus, the fixed resistor 56 can conduct current from the external source 48 such that the current is evenly shunted between each group of electrical brushes 40.

[0033] To further enable control of the current supplied to each electric brush 40 in a group of electric brushes, another arrangement of fixed resistors 56 can be placed in each leg connecting the electric brushes 40 in the group of electric brushes. For example, FIG. 9 shows a schematic diagram of an electric circuit 74 in which current flows between an external source 48 and a plurality of field windings 18 of a generator coil, and an additional arrangement 76 of fixed resistors 56 is placed in each leg of the electric brushes 40 in a particular group of brushes. Basically, the embodiment shown in FIG. 9 is a step - by - step approach. With the step - by - step approach, the arrangement 72 of resistors distributes the current from the external source 48 among various groups of electric brushes 40, while the additional arrangement 76 of fixed resistors 56 controls the current distribution distributed by the group of electric brushes 40 to manage how much of the shunted current flows through each brush within the group. Thus, the arrangement 72 of resistors performs primary control to evenly distribute the current flowing to each group, and the additional arrangement 76 of fixed resistors 56 performs fine - grained secondary control to evenly distribute the current received by the group among each electric brush 40 within the group.

[0034] Both FIGS. 8 and 9 show an arrangement 72 of fixed resistors 56 connected to a group of electric brushes 40 that includes four electric brushes, but this configuration merely represents one approach and is not intended to be limiting. For example, the arrangement 72 of fixed resistors 56 can be connected to a group of electric brushes 40 that includes more than four or fewer than four brushes. Also, instead of connecting the arrangement 72 of fixed resistors 56 to a group of electric brushes 40, it is also possible to connect these resistors to multiple pairs of electric brushes.

[0035] Furthermore, both FIGS. 8 and 9 show that the arrangement of resistor devices used in these embodiments is a fixed resistor, but those skilled in the art should note that other types of resistor devices can be arranged. For example, the fixed resistors 56 in FIGS. 8 and 9 can be replaced with other types of resistors described above (excluding, for example, variable resistors and power - electronics - based resistors).

[0036] The embodiments described with respect to FIGS. 5 to 9 are arrays of resistor devices, and all the resistor devices in each embodiment are targeted at an array of resistor devices including the same type of resistor device. However, it should be understood that other arrays of resistor devices can include combinations of any of the aforementioned resistor devices. That is, the embodiments have arrays of different resistor devices, and the resistor devices can be selected from the group including fixed resistors, variable resistors, power electronics-based resistors, and combinations thereof.

[0037] Furthermore, as described above, there can be 10 to 100 parallel paths of the electric brush for each collecting. Therefore, it should be understood that the figures with fewer path numbers shown in FIGS. 5 to 9 do not represent all the various resistor devices that can be arranged in a typical configuration. Furthermore, the representation of the resistor devices and the level of pairing of the resistor devices for connection to individual brushes or groups of brushes represent only some of the possible options and do not mean to limit the various embodiments.

[0038] In another embodiment, when using various resistor device arrays to control the distribution of current between electric brushes, it can be used as part of a collector brush monitoring system. For example, a collector brush monitoring system having the ability to monitor brush wear and temperature, as well as the amount of current supplied to the brushes, can be configured to monitor the current regarding various resistor devices and adjust the resistance of the resistor devices so that current is distributed between the brushes and / or a specified amount of current is supplied to individual brushes.

[0039] FIG. 10 shows a schematic diagram of an electrical circuit 78 having a monitoring system 80 that monitors the current for each resistor device of various resistor devices in the circuit based on the current measurement values obtained from the current sensing device 82. In this embodiment, the current sensing device 82 measures the current for each resistor device that can include, in one embodiment, a power electronics-based resistor 68. The current sensing device (which can include, but is not limited to, a current transformer and a current sensor) is preferably disposed between the external source 48 and the power electronics-based resistor 68. In an alternative embodiment, the current sensing device 82 can be disposed between the power electronics-based resistor 68 and the electrical brush 40. In another embodiment, the current sensing device 82 can be disposed between the external source 48 and the resistor device and between the resistor and the electrical brush.

[0040] In any of these embodiments, the current sensing device 82 can provide the monitoring system 80 with electrical measurement values regarding the power electronics-based resistor 68. The monitoring system 80 can include a control unit that monitors the current measurement values, automatically adjusts the resistance of the power electronics sub-based resistor 68 based on the measurement values, distributes the current among the electrical brushes 40, and / or ensures that a specified amount of current is supplied to each brush. Accordingly, the control unit of the monitoring system 80 can finely adjust the resistance for each power electronics-based resistor 68 in the various legs so that a specified brush current is obtained at the brushes.

[0041] The embodiment shown in FIG. 10 is described with respect to the use of a power electronics-based resistor, but it should be understood that other types of adjustable resistor devices can be arranged with the monitoring system to adjust the resistance of the resistor device. For example, in a similar monitoring system, an adjustable variable resistor can be used instead of the power electronics-based resistor.

[0042] Furthermore, it should be understood that the monitoring system 80 can perform additional functions in addition to monitoring the current measurements from the current sensing device 82, adjusting the resistance of the adjustable resistor device to supply current to the electric brush 40, and adjusting the current flowing through the electric brush 40. For example, the control unit of the monitoring system 80 can perform a plurality of functions (including, but not limited to, controlling the supply of current from the external source 48, setting and monitoring protection limits for excessive current measurements so that trips and warnings can be issued, and monitoring the wear of the electric brush 40).

[0043] The various embodiments shown in FIGS. 5-10 are all described with respect to using at least one array of resistor devices to evenly distribute current among the electric brushes 40 and / or to pass a specified amount of current to individual brushes or groups of brushes, but other electrical components can be used to control the current supplied from the external source 48 to the brushes. For example, an array of switches can be electrically connected between the external source 48 and the resistor device. In one embodiment, an array of switches can be used to ensure that an optimal average current density is supplied to the electric brush 48. In one scenario, the switches can be turned on and off to operate or stop the operation of one or more of a single electric brush, a pair of brushes, and a group of brushes for a predetermined time to adjust the average current density of the current flowing through the active brushes so that the average current density is within a predetermined current density range. In this way, by turning the switches on / off to selectively operate or stop the operation of the brushes, all the active brushes can be ensured to operate at an optimal average current density. This can prevent the electric brush 40 from getting too hot, and thus prevent the brush from wearing out acceleratively due to more current flowing through the brush and heating it up, and the current increasing and heating it further.

[0044] When an optimal average current density is supplied to the electric brushes, the resistor array described herein further controls the amount of current flowing through each electric brush 40 and complements the supply of the optimal average current density to the electric brushes. In particular, after using a switch to ensure that the optimal average current density is reliably supplied to the brushes, the resistor array can ensure that a specified amount of current is reliably supplied to the electric brushes. That is, the array of resistor devices can evenly shunt the current between the electric brushes and / or supply a specified amount of current to individual brushes or groups of brushes.

[0045] FIG. 11 shows a schematic diagram of an electrical circuit 84 in which an array 54 of fixed resistors 56 is operably coupled to an array 86 of switches 88 and electric brushes 40, according to one embodiment of the present invention. In one embodiment, the switches 88 are configured to be turned on / off to selectively operate or stop the operation of the brushes, and to ensure that all active brushes operate at an optimal average current density. As described above, the array 54 of resistors 56 is configured to remove the variable resistance between the external source 48 and the electric brushes 40. In this way, the array 54 of resistors 56 can ensure that a specified amount of current is reliably supplied to the electric brushes 40. That is, the array 54 of resistor devices 56 can evenly distribute the current between the electric brushes and / or ensure that a specified amount of current flows through individual brushes or groups of brushes.

[0046] Instead of using the fixed resistors shown in FIG. 11, an array of variable resistors can be used. For example, FIG. 12 shows a schematic diagram of an electrical circuit 90 in which an array 60 of variable resistor devices 62 is operably coupled to an array 86 of switches and electric brushes 40. The array of switches and resistors shown in FIG. 12 can operate in a manner similar to the embodiment described with respect to FIG. 11.

[0047] For details regarding the use of an array of switches to control the supply of current from an external source 48 to the electric brush 40, reference is made to U.S. Patent Application No. 18 / 493906, entitled "SYSTEM AND METHOD FOR SELECTIVE ACTIVATION AND DEACTIVATION OF ELECTRICAL BRUSHES USED IN DYNAMOELECTRIC MACHINE FOR CURRENT DENSITY OPTIMIZATION" (Attorney Docket No.: 608596-US-1), the disclosure of which is incorporated herein by reference.

[0048] From the description of the illustrated embodiments presented herein, it is apparent that the disclosure of the subject matter describes an effective solution for supplying a uniform current distribution to the electrical brushes operably coupled to the collecting disposed in a rotating electrical machine (such as a generator), thereby improving the performance of the machine. By supplying a uniform current distribution to the electrical brushes, in various embodiments, concerns of selectivity can be eliminated or minimized (selectivity leads to overheating of the brushes and makes it difficult to form a sufficient film between the brushes and the collecting (film formation is essential for maintaining the life of the brushes and minimizing fluctuations in the contact resistance Rc)). The elimination of concerns of selectivity can avoid flashovers that cause safety and operational risks (e.g., serious arc damage, melting of components, endangering nearby operators).

[0049] The foregoing description of the illustrated embodiments of the present disclosure is not intended to cover all possible embodiments, including those described in the abstract, nor is it intended to limit the disclosed embodiments to the exact form in which they are disclosed. Specific embodiments and examples are described herein for illustrative purposes, but as will be recognized by those of ordinary skill in the art, various modifications within the scope of such embodiments and examples are possible. For example, components, elements, steps, and aspects from different embodiments can be combined, or may be suitable for use in other embodiments, even if not described or illustrated in the present disclosure. Accordingly, specific changes may be made to the above-described invention without departing from the spirit and scope of the invention as included herein, and all of the subject matter of the above description shown in the drawings is intended to be construed herein as merely illustrative examples of the inventive concept and not as limiting the invention.

[0050] In this regard, while the disclosed subject matter has been described with reference to various embodiments and corresponding figures, it should be understood that, where applicable, other similar embodiments may be used or modifications and additions may be made to the described embodiments without departing from the disclosed subject matter, to perform the same, similar, alternative, or replaceable functions of the disclosed subject matter. Accordingly, the disclosed subject matter should not be limited to any single embodiment described herein, but rather its breadth and scope should be construed in accordance with the claims. For example, reference to "one embodiment" of the present invention is not intended to be construed as precluding the existence of additional embodiments that incorporate the recited features.

[0051] In the claims, the terms "including" and "in which" are used as plain English equivalents of the respective terms "comprising" and "wherein". Further, in the following claims, terms such as "first", "second", "third", "upper", "lower", "bottom", "top", etc. are used merely as labels and are not intended to impose numerical or positional requirements on the subject of those terms. The terms "substantially", "generally", and "about" indicate conditions within reasonable manufacturing tolerances and assembly tolerances with respect to the ideal desired conditions suitable for achieving the functional purpose of a component or assembly. Further, unless a phrase in which "means" is recited is expressly used before a description of a function that has no further structural recitation, and until a phrase in which "means" is recited is expressly used before a description of a function that has no other structural recitation, a claim limitation is not recited in means-plus-function format and is not intended to be construed as being recited in means-plus-function format.

[0052] The foregoing describes examples of systems and methods showing the disclosed subject matter. Of course, it is not possible to describe every combination of components or methodologies herein. One of ordinary skill in the art will recognize that many other combinations and permutations of the claimed subject matter are possible. Further, terms such as "includes," "has," "possesses," etc., when used in the embodiments, claims, appendices, and drawings of the invention, are intended to be as inclusive as the term "comprising" is construed when used as a transitional phrase in the claims. That is, unless expressly stated to the contrary, embodiments "comprising," "including," or "having" a single element or elements with a particular characteristic can include additional elements that do not have that characteristic. Further, the articles "a" and "an" as used herein and in the drawings are generally to be construed to mean "one or more" unless otherwise specified or clear from the context to be singular. Further, the phrase "one or more of" used after several possible choices or listings is intended to mean any of the natural inclusive permutations. For example, "one or more of A and B" satisfies only A, only B, and both A and B.

[0053] This specification discloses some embodiments of the present invention (including the best mode) using examples, and enables those skilled in the art to implement the embodiments of the present invention (including manufacturing and using any device or system and performing the incorporated methods). The patentable scope of the present invention is defined by the claims, and other embodiments conceived by those skilled in the art can be included. Such other embodiments are intended to be within the scope of the claims if the other embodiments have structural elements that are not different from the literal language of the claims, or if the other embodiments include equivalent structural elements that have no substantial difference from the literal language of the claims.

[0054] Further aspects of the present invention are provided by the following embodiments. [Embodiment 1] A collecting arranged on a rotating shaft of a rotating electrical machine, a plurality of electrical brushes maintained on the surface of the collecting when the collecting rotates with the rotating shaft, the plurality of electrical brushes being configured to pass an electric current between an external source and the rotating electrical machine through the collecting, and an array of a plurality of resistor devices electrically connected to the plurality of electrical brushes and controlling the distribution of the electric current between the external source and the plurality of electrical brushes, the array of the plurality of resistor devices being configured to control the flow rate of the electric current distributed to individual brushes and / or one or more groups of brushes among the plurality of electrical brushes while the rotating electrical machine is operating, a system including the array of the plurality of resistor devices. [Embodiment 2] The system according to Embodiment 1, wherein the array of the plurality of resistor devices is configured to equally distribute the electric current among the plurality of electrical brushes. [Embodiment 3] The system according to Embodiment 1 or 2, wherein each resistor device of the plurality of resistor devices is electrically connected to different electrical brushes among the plurality of electrical brushes. [Embodiment 4] The system according to any one of Embodiments 1 to 3, wherein some of the plurality of resistor devices are electrically connected to one group of a plurality of different electric brushes. [Embodiment 5] The system according to any one of Embodiments 1 to 4, wherein the other resistor devices of the plurality of resistor devices are arranged on different electric brushes of each group in a brush path leg leading to one electric brush of the plurality of electric brushes in the group. [Embodiment 6] The system according to any one of Embodiments 1 to 5, wherein the plurality of resistor devices are selected from the group consisting of a fixed resistor, a variable resistor, a power electronics-based resistor, and combinations thereof. [Embodiment 7] The system according to any one of Embodiments 1 to 6, further comprising a monitoring system, the monitoring system having a control unit operably coupled to the plurality of resistor devices to control the resistance of the resistor devices. [Embodiment 8] The system according to any one of Embodiments 1 to 7, further comprising a plurality of current sensing devices for measuring the amount of current distributed to the plurality of electric brushes, each current sensing device of the plurality of current sensing devices being arranged on one of the plurality of resistor devices to measure the amount of current of the one resistor device. [Embodiment 9] The system according to any one of Embodiments 1 to 8, wherein the control unit of the monitoring system is configured to receive a current measurement value from each current sensing device of the plurality of current sensing devices and adjust the resistance of each resistor device of the plurality of resistor devices as a function of the amount of current measured by the corresponding current sensing device. [Embodiment 10] The system further includes an array of a plurality of switches electrically connected to the external source and the array of the plurality of resistor devices, and the plurality of switches are configured to selectively operate the plurality of electric brushes and selectively stop the operation of the plurality of electric brushes while the rotating electrical machine is operating, in order to control an average current density of a current supplied to the electric brushes, according to any one of Embodiments 1 to 9 of the system described. [Embodiment 11] In order to adjust an average current density of a current flowing through the electric brush within a predetermined current density range, a selective switch among the plurality of switches can be opened and closed for a predetermined time, and the plurality of resistor devices are configured to control an amount of current flowing through each electric brush to a specified amount of current, according to any one of Embodiments 1 to 10 of the system described. [Embodiment 12] A rotating electrical machine, comprising: a rotatable shaft; a rotor body attached to the rotatable shaft, the rotor body having a plurality of field windings of coils fixed around the rotor body; at least one collector disposed at one end of the possible shaft; a plurality of electric brushes maintained on a surface of the at least one collector when the at least one collector rotates with the rotatable shaft, the plurality of electric brushes being configured to flow a current between an external source and a field winding of a coil fixed to the rotor body through the at least one collector; and an array of a plurality of resistor devices electrically connected to the plurality of electric brushes and configured to control a distribution of a current flowing between the external source and the plurality of electric brushes, the array of the plurality of resistor devices being configured to control an amount of current distributed to an individual brush and / or one or more groups of brushes among the plurality of electric brushes while the rotating electrical machine is operating. [Embodiment 13] The array of the plurality of resistor devices is configured to equally distribute current among individual brushes and / or one or more groups of brushes among the plurality of electric brushes, the rotating electrical machine according to any one of Embodiments 1 to 12. [Embodiment 14] Each resistor device of the plurality of resistor devices is electrically connected to different electric brushes among the plurality of electric brushes, the rotating electrical machine according to any one of Embodiments 1 to 13. [Embodiment 15] Some of the resistor devices among the plurality of resistor devices are electrically connected to different groups of a plurality of electric brushes, the rotating electrical machine according to any one of Embodiments 1 to 14. [Embodiment 16] The plurality of resistor devices are selected from the group including fixed resistors, variable resistors, resistors of power electronics, and combinations thereof, the rotating electrical machine according to any one of Embodiments 1 to 15. [Embodiment 17] The rotating electrical machine includes a plurality of current sensing devices for measuring the amount of current distributed to the plurality of electric brushes, and a monitoring system having a control unit that controls the resistance of the resistor device as a function of the amount of current measured by the plurality of current sensing devices, the rotating electrical machine according to any one of Embodiments 1 to 16. [Embodiment 18] The rotating electrical machine further includes an array of a plurality of switches electrically connected to the external source and the array of the plurality of resistor devices, and the plurality of switches are configured to selectively operate and selectively stop the operation of the plurality of electric brushes while the rotor body is rotating in order to control the current supplied to the electric brushes, the rotating electrical machine according to any one of Embodiments 1 to 17. [Embodiment 19] While the rotor body is rotating, in order to adjust the average current density of the current flowing through the electric brush within a predetermined current density range, a selective switch among the plurality of switches can be opened and closed for a predetermined time, and the plurality of resistor devices are configured to control the amount of current received by each electric brush to a specified amount of current. The rotating electrical machine according to any one of Embodiments 1 to 18. [Embodiment 20] A method for controlling the current density of a plurality of electric brushes that are maintained on the collecting surface arranged on the rotating shaft of a rotating electrical machine and conduct current between an external source and the rotating electrical machine, the method comprising: arranging a plurality of resistor devices so as to be electrically connected to the plurality of electric brushes and the external source; and controlling the current distribution between the external source and the plurality of electric brushes using the plurality of resistor devices, wherein the plurality of resistor devices are configured to control a specified amount of current distributed to an individual brush and / or one or more groups of brushes among the plurality of electric brushes while the rotating electrical machine is operating.

Description of Signs

[0055] 10 Generator 12 Rotor body 14 Shaft 18 Field winding 20 Central winding 22 End winding 24 Axial end 26 Drive end 28 Coupling 30 Drive end 34 Coupling 36 Brush holder - rigging assembly 38 Collector shoe 42 Brush holder 44 Fixed support member 46 Electric circuit 50 Electrical wiring 52 Electric circuit 54 Array 58 Electric circuit 60 array 64 electric circuit 66 array 70 electric circuit 72 array 74 electric circuit 76 array 78 electric circuit 80 monitoring system 82 current sensing device 84 electric circuit 86 array 88 switch 90 electric circuit

Claims

1. a collector ring disposed on a rotating shaft of the rotating electrical machine; a plurality of electric brushes maintained on a surface of the collector ring as the collector ring rotates with the rotatable shaft, the plurality of electric brushes being configured to pass electric current through the collector ring between an external source and the rotating electric machine; and an array (54, 60, 66, 72, 76) of resistor devices electrically connected to the plurality of electric brushes and configured to control a distribution of current between the external source and the plurality of electric brushes, the array (54, 60, 66, 72, 76) being configured to control an amount of current distributed to individual brushes and / or one or more groups of brushes of the plurality of electric brushes while the rotating electric machine is operating; Including, the system.

2. The system of claim 1 , wherein the array of resistor devices (54, 60, 66, 72, 76) is configured to distribute current equally among the electrical brushes (40).

3. The system of claim 1 , wherein each resistor device of the plurality of resistor devices is electrically connected to a different one of the plurality of electrical brushes (40).

4. The system of claim 1 , wherein some of the resistor devices of the plurality of resistor devices are electrically connected to different electrical brushes (40) of a group.

5. 5. The system of claim 4, wherein other resistive devices of the plurality of resistive devices are disposed at different electrical brushes (40) of each group in a brush path leg leading to one electrical brush of the plurality of electrical brushes in the group.

6. The system of claim 1 , wherein the plurality of resistor devices are selected from the group including fixed resistors (56), variable resistors (62), power electronics based resistors (68), and combinations thereof.

7. 2. The system of claim 1, further comprising a monitoring system (80), the monitoring system having a control unit operatively coupled to the plurality of resistor devices to control resistances of the resistor devices.

8. 8. The system of claim 7, further comprising a plurality of current sensing devices (82) for measuring an amount of current delivered to the plurality of electric brushes (40), each current sensing device of the plurality of current sensing devices being disposed in one resistor device of the plurality of resistor devices and measuring an amount of current in the one resistor device.

9. 9. The system of claim 8, wherein a control unit of the monitoring system (80) is configured to receive a current measurement from each current sensing device of the plurality of current sensing devices (82) and adjust a resistance of each resistor device of the plurality of resistor devices as a function of an amount of current measured by a corresponding current sensing device.

10. 2. The system of claim 1, further comprising an array (86) of switches (88) electrically connected to the external source (48) and the array of resistor devices (54, 60, 66, 72, 76), the plurality of switches being configured to selectively operate and selectively deactivate the plurality of electric brushes (40) while the rotating electric machine (10) is operating to control an average current density of current supplied to the electric brushes.

11. 11. The system of claim 10, wherein selective ones of the plurality of switches (88) can be opened and closed for predetermined times to regulate an average current density of current through the electric brushes (40) within a predetermined current density range, and the plurality of resistor devices are configured to control an amount of current through each electric brush to a designated current amount.

12. A rotating electrical machine (10), comprising: A rotatable shaft (14), a rotor body (12) attached to the rotatable shaft, the rotor body having a plurality of field windings (18) of coils fixed about a periphery of the rotor body; At least one collector ring (32) disposed at one end of the movable shaft; a plurality of electric brushes (40) maintained on a surface of the at least one collector ring when the at least one collector ring rotates with the rotatable shaft, the plurality of electric brushes being configured to pass an electric current through the at least one collector ring between an external source (48) and a field winding of a coil fixed to the rotor body; and an arrangement (54, 60, 66, 72, 76) of resistor devices electrically connected to the plurality of electric brushes for controlling a distribution of electric current flowing between the external source and the plurality of electric brushes, the arrangement (54, 60, 66, 72, 76) being configured to control an amount of electric current distributed to individual brushes and / or one or more groups of brushes of the plurality of electric brushes while the rotating electric machine is operating; A rotating electric machine (10).

13. 13. The rotating electric machine (10) of claim 12, wherein the array (54, 60, 66, 72, 76) of resistor devices is configured to distribute current equally among individual brushes (40) and / or one or more groups of brushes of the plurality of electric brushes.

14. The rotating electric machine (10) of claim 12, wherein each resistor device of the plurality of resistor devices is electrically connected to a different one of the plurality of electric brushes (40).

15. 1. A method for controlling current density in a plurality of electric brushes (40) carried on a surface of a collector ring (32) disposed on a rotating shaft (14) of a rotating electric machine (10) and carrying electric current between an external source (48) and the rotating electric machine, comprising the steps of: disposing a plurality of resistor devices in electrical communication with the plurality of electric brushes and the external source; and Controlling a distribution of current between the external source and the plurality of electric brushes with a plurality of resistor devices configured to control a specified amount of current delivered to individual brushes and / or one or more groups of brushes of the plurality of electric brushes while the rotating electric machine is operating. A method comprising:

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