Patent Description:
Large rotating shafts, such as those seen in generators must be continuously grounded to prevent damage to shaft bearings from electrical charges that may build up in the shaft or rotor during operation. The shaft itself rides on a thin film of oil or other suitable lubricant in a pair of bearings, and accordingly is electrically insulated from ground potential. However, the buildup of an excessive electrical charge on the shaft can cause a discharge through the oil film, resulting in damage to the bearings. To prevent such a discharge, and to ground the rotating shaft, shaft grounding devices (SGD) are placed in continuous contact with the rotating shaft as it rotates to provide a discharge path to ground. The following prior art documents disclose rotor ground devices: <CIT>, <CIT>, <CIT>.

Various technologies that pertain to systems and methods will now be described with reference to the drawings, where like reference numerals represent like elements throughout. The drawings discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged apparatus. It is to be understood that functionality that is described as being carried out by certain system elements may be performed by multiple elements. Similarly, for instance, an element may be configured to perform functionality that is described as being carried out by multiple elements. The numerous innovative teachings of the present application will be described with reference to exemplary non-limiting embodiments.

Also, it should be understood that the words or phrases used herein should be construed broadly, unless expressly limited in some examples. For example, the terms "including," "having," and "comprising," as well as derivatives thereof, mean inclusion without limitation. The singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. Further, the term "and/or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. The term "or" is inclusive, meaning and/or, unless the context clearly indicates otherwise. The phrases "associated with" and "associated therewith," as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like.

Also, although the terms "first", "second", "third" and so forth may be used herein to refer to various elements, information, functions, or acts, these elements, information, functions, or acts should not be limited by these terms. Rather these numeral adjectives are used to distinguish different elements, information, functions or acts from each other. For example, a first element, information, function, or act could be termed a second element, information, function, or act, and, similarly, a second element, information, function, or act could be termed a first element, information, function, or act, without departing from the scope of the present disclosure.

In addition, the term "adjacent to" may mean: that an element is relatively near to but not in contact with a further element; or that the element is in contact with the further portion, unless the context clearly indicates otherwise. Further, the phrase "based on" is intended to mean "based, at least in part, on" unless explicitly stated otherwise. Terms "about" or "substantially" or like terms are intended to cover variations in a value that are within normal industry manufacturing tolerances for that dimension. If no industry standard as available, a variation of <NUM> percent would fall within the meaning of these terms unless otherwise stated.

<FIG> illustrates a generator rotor <NUM> of the type commonly used in large-scale power generation such as at fossil fuel fired plants, nuclear plants, and the like. The rotor <NUM> includes an elongated central portion <NUM> into which coils are placed to define one or more windings. Each end includes a retaining ring <NUM> positioned to support and restrain the ends of the windings. The rotor <NUM> extends beyond the central portion <NUM> in both directions to define bearing surfaces <NUM> where bearings engage and support the rotor <NUM> for rotation as well as other surfaces and features required for proper operation of the rotor <NUM>. One or more couplings <NUM> are provided at each end to connect the rotor <NUM> to other rotating equipment such as a gas turbine engine, a steam turbine, a hydro turbine, a wind turbine, and the like. A stator, and other stationary components <NUM>, surround the rotor <NUM> and remain substantially stationary during rotor operation.

Turning to <FIG>, a perspective end view better illustrates two support brackets <NUM> attached to a stationary component <NUM> positioned near the rotor <NUM> and including two generator grounding modules <NUM> (sometimes referred to as generator grounding strap modules) each attached to one of the two support brackets <NUM>. The stationary component <NUM> could be a bearing housing, a stator housing, a generator housing, a seal housing, and the like. As should be evident, a single generator grounding module <NUM>, or more than two grounding modules <NUM> could be employed at one end, or both ends of the rotor <NUM> as may be required.

<FIG> illustrates one of the support brackets <NUM> and generator grounding modules <NUM> of <FIG>. As illustrated in <FIG>, and better illustrated in <FIG>, the support bracket <NUM> includes a mounting plate <NUM> and a support bracket <NUM> attached to the mounting plate <NUM>. The mounting plate <NUM> includes an elongated rectangular section <NUM> and two smaller rectangular extensions <NUM> at a first end. The smaller rectangular extensions <NUM> are positioned to receive fasteners <NUM> that facilitate the attachment of the mounting plate <NUM> to the stationary component <NUM>. Other shapes or arrangements could be used for the mounting plate <NUM> depending upon the arrangement of the stationary component <NUM> to which the mounting plate <NUM> must attach.

The support member <NUM> is substantially L-shaped and includes an attachment portion <NUM> that attaches to the mounting plate <NUM> and a support portion <NUM> oriented at about ninety degrees to the attachment portion <NUM> that supports the generator grounding module <NUM> as will be described. With continued reference to <FIG>, the attachment portion <NUM> includes a slot <NUM> or other apertures sized to receive fasteners <NUM> that facilitate the attachment of the support member <NUM> to the mounting plate <NUM>. The fasteners <NUM> could alternatively pass through the mounting plate <NUM> and engage the stationary component <NUM> to complete the attachment of the mounting plate <NUM> and support member <NUM> to the stationary component <NUM> if desired. In other constructions, the fasteners <NUM> attaching the mounting plate <NUM> are the sole fasteners attached to the stationary component <NUM> and dowels or other alignment members are provided between the mounting plate <NUM> and the stationary component <NUM> to provide the desired positional stability of the mounting plate <NUM> and the support member <NUM>.

The support portion <NUM> of the support member <NUM> includes a circular aperture <NUM> that passes through the support portion <NUM> from a first surface <NUM> to a second surface <NUM> and a first slot <NUM> that also passes through the support portion <NUM>. A mounting axis <NUM> is defined as extending along the centerline of the circular aperture <NUM>. With reference to <FIG>, the second surface <NUM> of the support portion <NUM> includes a larger circular counterbore <NUM> that extends partially through the support portion <NUM> and that has a diameter equal to a length of the first slot <NUM>. A second slot <NUM> is arranged normal to the first slot <NUM>, has the same length as the first slot <NUM>, and extends partially through the support portion <NUM> from the surface of the counterbore <NUM>.

A pair of guide rods <NUM> are also visible in <FIG> and <FIG>. The guide rods <NUM> attach to the first surface <NUM> and extend parallel to the mounting axis <NUM> in a direction from the first surface <NUM> and away from the second surface <NUM>. In the illustrated construction, fasteners <NUM> attach each rod <NUM> to the support portion <NUM> of the support member <NUM> with other attachment mechanisms being possible.

Also visible in <FIG> and <FIG> is a sensor <NUM>, in the form of a switch <NUM> or microswitch. The switch <NUM> is fixedly attached to the attachment portion <NUM> and includes an actuating arm <NUM> that extends from the switch <NUM> to a position where it can be actuated as will be discussed in greater detail below.

With reference to <FIG>, the generator grounding module <NUM> includes a handle <NUM> (illustrated completely in <FIG>) that extends along the mounting axis <NUM>, a plate member <NUM>, a mounting block <NUM>, a biasing assembly <NUM>, a grounding strap assembly <NUM>, and a mounting arm <NUM>. The handle <NUM>, illustrated in <FIG> includes a shaft <NUM>, a gripping portion <NUM> fixedly attached to one end of the shaft <NUM>, a first pin <NUM>, a second pin <NUM>, a biasing element <NUM>, and a locking member <NUM>. The gripping portion <NUM> is sized and shaped to be easily grasped by a user to allow the user to manipulate the handle <NUM> and the generator grounding module <NUM> as required. The first pin <NUM> passes through the shaft <NUM> near a second end of the shaft <NUM> and is fixed with respect to the shaft <NUM>. A roll pin or solid pin could be employed as desired and is fixed using any suitable arrangement including welding, soldering, brazing, adhesives, friction, and the like. The second pin <NUM> passes through the shaft <NUM> at a point between the gripping portion <NUM> and the first pin <NUM> and is fixed with respect to the shaft <NUM> much like the first pin <NUM>. The second pin <NUM> is arranged normal to the first pin <NUM> but could be arranged at other angles if desired. In addition, the first pin <NUM> has a length that is less than or equal to the length of the first slot <NUM> and the second slot <NUM>.

A groove <NUM> is formed around the shaft <NUM> at a first distance from the first pin <NUM>. The groove <NUM> is sized and shaped to receive the locking member <NUM>, which includes a C-clip <NUM> in the illustrated construction. The C-clip <NUM>, and/or another member such as a washer, define a first stop for the biasing element <NUM> which includes a coil spring <NUM> that is disposed on the shaft <NUM> between the C-clip <NUM> and the first pin <NUM>. In other constructions, other components could be used in place of the coil spring <NUM>. For example, other constructions may employ a Belleville spring formed from a stack of Belleville washers with still other constructions using other components.

The biasing assembly <NUM>, best illustrated in <FIG> includes two separate springs <NUM> formed from a coiled metal band. Each spring <NUM> includes a coiled portion <NUM>, an extended portion <NUM>, and a free end <NUM> with the spring <NUM> producing a biasing force that tends to pull the free end <NUM> toward the coiled portion <NUM>. The use of coiled metal bands as springs <NUM> results in the biasing force of each spring <NUM> being substantially constant (plus or minus ten percent) regardless of the distance of the free end <NUM> from the coiled portion <NUM> (i.e., the length of the extended portion <NUM>). Of course, the biasing force is most constant when a small percentage of the total length of the coiled metal band extends between the coiled portion <NUM> and the free end <NUM>. For example, in a preferred construction the extended portion <NUM> of each spring <NUM> extends between one and three inches (<NUM>-<NUM>) with at least eight to ten inches (<NUM>-<NUM>) of spring <NUM> disposed in the coiled portion <NUM>. Thus, the coiled portion <NUM> includes between about two times and ten times more of the metal band than the extended portion <NUM>. In another construction, the coiled portion <NUM> includes about twelve complete coils and no more than one coil is required to move the biasing assembly <NUM> between a fully retracted and a fully extended position. This arrangement assures a substantially constant biasing force at all expected operating points.

<FIG> illustrate the plate member <NUM> in greater detail than is visible in <FIG>. As illustrated, the plate member <NUM> includes a biasing assembly mount <NUM>, a pair of guide rod bores <NUM>, and a first handle bore <NUM>. The biasing assembly mount <NUM> includes two recesses <NUM> each arranged to receive one of the coiled metal springs <NUM> of the biasing assembly <NUM>. More specifically, the recesses <NUM> are arranged to hold the coiled portion <NUM> and maintain it in the coiled shape while also allowing for the free end <NUM> and the extended portion <NUM> to extend from the plate member <NUM>. In some constructions, the biasing assembly mount <NUM> may include a blocking element that covers the recesses <NUM> to inhibit the unwanted removal of the coiled portion <NUM> from the recesses <NUM>.

The guide rod bores <NUM> are generally straight bores sized to receive the guide rods <NUM> while allowing the plate member <NUM> to move freely along the guide rods <NUM>. The first handle bore <NUM>, best illustrated in <FIG> includes a large counterbore <NUM> sized to receive a portion of the coil spring <NUM> of the handle <NUM>. A third slot <NUM> is formed in the surface opposite the counterbore <NUM> and is sized to receive the first pin <NUM>.

A guide screw <NUM> illustrated in <FIG> and <FIG> threadably engages the plate member <NUM> and is fixed with respect to the plate member <NUM>. The guide screw <NUM> includes an elongated screw that includes a head <NUM>, and a shoulder <NUM> adjacent a threaded portion <NUM>. The shoulder <NUM> is arranged to engage or partially restrain a bushing <NUM> or the plate member <NUM> to attach the bushing <NUM> to the plate member <NUM> and at least partially fix its position with regard to the plate member <NUM>. In other constructions, the bushing <NUM> and/or the guide screw <NUM> are formed as one piece, formed as part of the plate member <NUM>, and/or are permanently affixed to the plate member <NUM>.

The mounting block <NUM> is best illustrated in <FIG> and <FIG> and includes two guide rod bores <NUM>, a second handle bore <NUM>, and a bearing bore <NUM>. The guide rod bores <NUM> are generally straight through bores that are sized to receive the guide rods <NUM> and allow free movement of the mounting block <NUM> with respect to the guide rods <NUM>.

The bearing bore <NUM> is a straight bore that passes through the mounting block <NUM> and is sized to receive a bearing member <NUM> illustrated in <FIG>. The bearing member <NUM> bolts to the mounting block <NUM> or is otherwise attached to fix its position with respect to the mounting block <NUM>. The bearing member <NUM> preferably includes an insert or inner piece <NUM> that closely engages the guide screw <NUM> for movement of the mounting block <NUM> with respect to the plate member <NUM>. The insert <NUM> could be a bushing, a linear bearing, or soft packing that allows for the desired linear movement while maintaining the desired alignment.

The second handle bore <NUM> includes a through bore sized to allow for the passage of the shaft <NUM> and a fourth slot <NUM> sized to allow for the passage of the second pin <NUM>. The fourth slot <NUM> passes through the mounting block <NUM>. As illustrated in <FIG>, a counterbore <NUM> can be provided to reduce the thickness of the mounting block <NUM> in the area of the fourth slot <NUM>.

Two mounting apertures <NUM> are provided in opposite sides of the mounting block <NUM> and are arranged to receive fasteners <NUM> that attach the free end <NUM> of the coiled metal springs <NUM> to the mounting block <NUM>. In the illustrated construction, threaded apertures <NUM> are employed. However, other constructions may employ other attachment mechanisms as desired.

As illustrated in <FIG>, the mounting arm <NUM> attaches to the mounting block <NUM> between the mounting block <NUM> and the bearing member <NUM> and extends from the mounting block <NUM> to define a first end <NUM> and a second end <NUM>. The mounting arm <NUM> is substantially bow-shaped and is formed from a metallic material such as copper, brass, bronze, steel, or aluminum, and the like. While the illustrated construction includes a one-piece mounting arm <NUM>, other constructions may employ two or more pieces that define the mounting arm if desired. The mounting arm <NUM> and the grounding strap assembly <NUM> have a length and size that assures that when the grounding strap assembly <NUM> is engaged with the rotor <NUM>, only the grounding strap assembly <NUM> touches the rotor <NUM>. The mounting arm <NUM> remains spaced apart from the rotor <NUM> regardless of the position or configuration of the generator grounding module <NUM>.

The grounding strap assembly <NUM> is preferably formed from a braided metal material such as copper, brass, bronze, steel, or aluminum, and the like. In one construction, a length of grounding strap material is folded onto itself such that the two free ends <NUM> are disposed adjacent the first end <NUM> of the mounting arm <NUM> and a loop end <NUM> is positioned adjacent the second end <NUM> of the mounting arm <NUM>. The first end <NUM> of the mounting arm <NUM> includes a first clamp <NUM> that engages both free ends <NUM> of the folded grounding strap material. The second end <NUM> includes a second clamp <NUM> that engages a top strap <NUM> of the grounding strap assembly <NUM> before the loop <NUM>. Attaching the grounding strap material in this way results in two separate grounding straps <NUM>, <NUM> adjacent one another. In addition, if the first grounding strap <NUM> wore through or otherwise failed, the second grounding strap <NUM> would still be firmly mounted in the mounting arm <NUM> and could engage the rotor <NUM> with the desired contact pressure. The mounting arm <NUM>, the first clamp <NUM>, and the second clamp <NUM> cooperate to define an attachment assembly that supports the grounding strap assembly <NUM>.

To assemble the support bracket <NUM> the user first attaches the mounting plate <NUM> to the stationary component <NUM>. As is best illustrated in <FIG>, two fasteners <NUM> attach one end of the mounting plate <NUM> to the stationary component <NUM>. Circular protrusions <NUM> extending from the stationary component <NUM> engage the opposite end of the mounting plate <NUM> and act as dowels to maintain the position of the mounting plate <NUM>. The support member <NUM>, including the guide rods <NUM> and the sensor <NUM> are attached to the mounting plate <NUM> either before or after it is attached to the stationary component <NUM>. This assembly provides a mounting point onto which the entire generator grounding module <NUM> can be placed or removed as desired and without the need for any special tools, processes, or procedures.

With reference to <FIG>, to assemble the generator grounding module <NUM> the user first positions the locking member <NUM> on the shaft <NUM> and positions the biasing element <NUM> adjacent the locking member <NUM>. The plate member <NUM> is then placed on the shaft <NUM> with the biasing element <NUM> at least partially resting within the counterbore <NUM> of the first handle bore <NUM> of the plate member <NUM>. The first pin <NUM> is then positioned in the shaft <NUM> such that the plate member <NUM> is trapped between the first pin <NUM> on one side and the biasing element <NUM> and the locking member <NUM> on the opposite side. The mounting block <NUM> is then positioned with the shaft <NUM> passing through the second handle bore <NUM> as illustrated in <FIG>. The second pin <NUM> is then placed in the shaft <NUM> or was already positioned in the shaft <NUM> and passed freely through the second handle bore <NUM>. The gripping portion <NUM> is then affixed to the end of the shaft <NUM> to complete the assembly of the handle <NUM> into the generator grounding module <NUM>. Once the gripping portion <NUM> and the first pin <NUM> are in place, the handle <NUM>, the plate member <NUM>, and the mounting block <NUM> are connected to one another and cannot be separated without removing at least the gripping portion <NUM> and/or the first pin <NUM>.

Next, the metal coil springs <NUM> are positioned in the respective recesses <NUM> with the free ends <NUM> extending toward and coupled to the mounting block <NUM> at the mounting apertures <NUM>. Once attached, the metal coil springs <NUM> define the biasing assembly <NUM> and generate a biasing force that tends to pull the mounting block <NUM> toward the plate member <NUM>. In preferred constructions, threaded fasteners attach the free ends <NUM> to the mounting block <NUM> with other attachment mechanisms being possible (e.g., pins, rivets, adhesives, welding, soldering, brazing, etc.).

To complete the assembly of the generator grounding module <NUM>, a conductor <NUM> including a wire <NUM>, two end connectors <NUM>, and two fasteners <NUM> attaches to the mounting block <NUM> at one end and the plate member <NUM> at the other end. The conductor <NUM>, best illustrated in <FIG> assures an electrical connection between the mounting block <NUM> and the plate member <NUM> during operation.

The grounding strap assembly <NUM> is attached to the mounting arm <NUM> as was described with regard to <FIG>. The mounting arm <NUM> is then positioned adjacent the mounting block <NUM> and the bearing member <NUM> is inserted into the bearing bore <NUM> with the mounting arm <NUM> sandwiched therebetween. The bearing member <NUM> is fixedly attached to the mounting block <NUM> with fasteners that also attach the mounting arm <NUM> and grounding strap assembly <NUM> to the mounting block <NUM>. In a preferred construction, the mounting arm <NUM> includes apertures that allow for the passage of the bearing member <NUM> and any fasteners used to attach the bearing member <NUM>. The guide screw <NUM> is then inserted through the bearing member <NUM> and the bushing <NUM> and threaded into the plate member <NUM>. The guide screw <NUM> provides a guide for movement of the mounting block <NUM> with respect to the plate member <NUM>.

To complete the assembly, the generator grounding module <NUM> is attached to the support bracket <NUM> by passing the guide rods <NUM> through the guide rod bores <NUM>, <NUM> in the plate member <NUM> and the mounting block <NUM> as illustrated in <FIG>.

To aid or simplify the assembly, the user first manipulates the handle <NUM> to configure the generator grounding module <NUM> into a first configuration (shown in <FIG> and <FIG>) before placing the generator grounding module <NUM> on the guide rods <NUM>. In the first configuration, the second pin <NUM> of the handle <NUM> is aligned with the fourth slot <NUM>, passed through the fourth slot <NUM>, and then the handle <NUM> is rotated to lock the position of the handle <NUM>. As illustrated in <FIG>, in this position, the second pin <NUM> is disposed in the counterbore <NUM> but is rotated <NUM> degrees with respect to the fourth slot <NUM> and is biased against the mounting block <NUM>. The first pin <NUM> is disposed in the second slot <NUM> such that the first pin <NUM> and the shaft <NUM> do not extend below the surface of the plate member <NUM>. In this configuration, the entire mounting block <NUM> is locked between the second pin <NUM> and the gripping portion <NUM> such that the mounting block <NUM> and the plate member <NUM> are at their maximum separation distance. In this position, the grounding straps <NUM>, <NUM> are retracted as far from the rotor <NUM> as possible, and the biasing assembly <NUM> is fully extended.

While in this first configuration, the generator grounding module <NUM> is placed onto the guide rods <NUM> with the plate member <NUM> being free to slide into contact with the support portion <NUM> of the support member <NUM>. This configuration also advantageously pre-aligns the first pin <NUM> with the first slot <NUM> which allows the user to simply push the shaft <NUM> toward the support member <NUM> in order to move the first pin <NUM> through the first slot <NUM>.

In a second, or operational configuration shown in <FIG>, the second pin <NUM> of the handle <NUM> is disposed between the gripping portion <NUM> and the mounting block <NUM>. In this position, the biasing assembly <NUM> pulls the plate member <NUM> and the mounting block <NUM> to their closest possible position, thereby pulling the biasing assembly <NUM> to its most retracted position. One of the bushing <NUM> and the coil spring <NUM>, both positioned between the mounting block <NUM> and the plate member <NUM>, engages both the plate member <NUM> and the mounting block <NUM> to stop any additional movement and define the closest position between the mounting block <NUM> and the plate member <NUM>.

To move the generator grounding module <NUM> from the first configuration to the second or operational configuration, the user first positions the generator grounding module <NUM> in the first configuration and places it on the guide rods <NUM> until the plate member <NUM> contacts the support member <NUM>.

To move the generator grounding module <NUM> into operational engagement with the rotor <NUM> (i.e., engaged with the desired contact pressure between the straps <NUM>, <NUM> and the rotor <NUM>), the user starts with the generator grounding module <NUM> in the first configuration illustrated in <FIG> and <FIG>. In this configuration, the shaft <NUM> is positioned such that the first pin <NUM> is aligned with the first slot <NUM>. The second pin <NUM> is preferably oriented at a ninety-degree angle with respect to the first pin <NUM> and can be used as a guide to properly orient the shaft <NUM>. The user next pushes the shaft <NUM> toward the plate member <NUM>. The locking member <NUM> and spring <NUM> push the plate member <NUM> into engagement with the support portion <NUM> of the support member <NUM>. Further pressure compresses the coil spring <NUM> against the plate member <NUM> and allows the user to push the shaft <NUM> until the first pin <NUM> passes through the first slot <NUM> and is disposed in the counterbore <NUM> of the support portion <NUM>. The user then rotates the shaft <NUM> ninety degrees such that the first pin <NUM> engages the second slot <NUM> and the coil spring <NUM> holds the plate member <NUM> against the support member <NUM>. The rotation of the handle <NUM> also aligns the second pin <NUM> with the fourth slot <NUM> which allows the biasing assembly <NUM> to pull the mounting block <NUM> toward the plate member <NUM> with a desired constant biasing force as the second pin <NUM> passes through the fourth slot <NUM>. However, before the mounting block <NUM> reaches the fully retracted position (i.e., the second configuration shown in <FIG>), the grounding strap assembly <NUM> contacts the rotor <NUM> and generates a force in the mounting arm <NUM> that opposes the biasing force. Once these forces are balanced, the generator grounding module <NUM> has reached an operating position in which the grounding strap assembly <NUM> is in contact with the rotor <NUM> with a desired contact pressure as illustrated in <FIG>. In the operating position, the mounting block <NUM> is still spaced a non-zero distance from the actuating arm <NUM> of the switch <NUM>.

Once the grounding strap <NUM> contacts the rotor <NUM>, a grounding path is fully established. The grounding path begins at the grounding strap <NUM> and flows into the mounting arm <NUM>. From the mounting arm <NUM>, any current flows into the mounting block <NUM>, through the conductor <NUM> into the plate member <NUM>, and finally into the support member <NUM>. The support member <NUM> can be grounded to the stationary component <NUM> by the fasteners or an additional wire, or the grounding path can continue via wire to a current measuring device for monitoring.

During operation, the rotor <NUM> tends to wear the grounding strap <NUM> in contact with the rotor <NUM> to the point that the strap <NUM> will fail. The arrangement of the grounding strap assembly <NUM> does provide a second grounding strap <NUM> that engages the rotor <NUM> upon failure of the first strap <NUM>. The first grounding strap <NUM> engages the rotor <NUM> in a position that is maintained by the balance of the forces between the mounting arm <NUM> and the biasing assembly <NUM>. When the first grounding strap <NUM> fails, the force produced by the mounting arm <NUM> will drop as the desired contact pressure is no longer being maintained. The biasing force produced by the biasing assembly <NUM> remains constant and thus causes the mounting block <NUM> to move toward the plate member <NUM> until the second grounding strap <NUM> contacts the rotor <NUM> and the forces produced by the biasing assembly <NUM> and the mounting arms <NUM> are again balanced.

With reference to <FIG>, movement of the mounting block <NUM> toward the plate member <NUM> could be measured or an indication of that movement could be provided. For example, the length of the guide screw <NUM> above the mounting block <NUM> could be periodically measured, with any increase in the measurement indicating that the first grounding strap <NUM> has failed. In other constructions, the guide screw <NUM> could include a colored strip that is hidden below the mounting block <NUM> when both grounding straps <NUM>, <NUM> are intact. The colored strip would become visible upon failure of the first grounding strap <NUM>. A second color could be provided to indicate when both straps <NUM>, <NUM> have failed.

As discussed above, the sensor <NUM> is provided in the form of the switch <NUM> and can be used to indicate when both grounding straps <NUM>, <NUM> have failed. Upon failure of the second grounding strap <NUM>, the biasing assembly <NUM> will pull the mounting block <NUM> toward the plate member <NUM> to the fully retracted position. In this position, the mounting block <NUM> contacts and actuates the actuating arm <NUM> of the switch <NUM>. The switch <NUM> can be connected to an indicator (e.g., a visual device such as a light, an audible device such as an alarm, etc.) or to a control system to provide an immediate indication, upon actuation of the actuating arm <NUM>, that both grounding straps <NUM>, <NUM> have failed.

Claim 1:
A generator grounding module (<NUM>) mountable to a support bracket (<NUM>) attached to a stationary component (<NUM>) positioned near a rotor (<NUM>) of a generator, the generator grounding module (<NUM>) comprising:
a plate member (<NUM>) movable along a mounting axis (<NUM>) to attach the generator grounding module (<NUM>) to the support bracket (<NUM>), the plate member (<NUM>) movable between a first position and a second position in which the plate member (<NUM>) is fixed with respect to the support bracket (<NUM>), wherein the mounting axis (<NUM>) extending radially inward to the rotating axis of the generator;
a mounting block (<NUM>) movable along the mounting axis (<NUM>) with respect to the plate member (<NUM>);
a grounding strap (<NUM>) coupled to the mounting block (<NUM>) and movable between a disengaged position and an engaged position in which the grounding strap (<NUM>) contacts the rotor (<NUM>);
a biasing assembly (<NUM>) connected to the plate member (<NUM>) and the mounting block (<NUM>) and operable to bias the mounting block (<NUM>) along the mounting axis (<NUM>) toward the plate member (<NUM>), wherein the plate member (<NUM>) is fixedly attached to the support bracket (<NUM>) when in the second position and the biasing assembly (<NUM>) biases the grounding strap into the engaged position,
wherein the biasing assembly (<NUM>) is in the most retracted position when the plate member (<NUM>) and the mounting block (<NUM>) are in their closest possible position; and
a mounting arm (<NUM>) fixedly attached to the mounting block (<NUM>) and defining a first end (<NUM>) and a second end (<NUM>) spaced apart from the first end (<NUM>), the grounding strap (<NUM>) attached to the first end (<NUM>) and the second end (<NUM>), wherein the ground strap (<NUM>) is substantially perpendicular to the rotating axis so that when contacting the rotor the grounding strap (<NUM>) generates a force in the mounting arm (<NUM>) that opposes the biasing force, wherein a desired contact pressure between the grounding strap (<NUM>) and the rotor (<NUM>) is reached once these forces are balanced.