Abstract:
A remote-controlled dynamoelectric machine maintenance vehicle that can fit and travel within the air gap between a stator and rotor of a dynamoelectric machine. The maintenance vehicle has an effectuator that can remotely attach to an adjustable wedge within a coil slot of the stator and tighten the wedge in position and then move on to repeat the process until all the wedges on the stator are secured.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to remote-controlled unmanned robotic vehicles. More specifically, the present invention relates to remote-controlled vehicles capable of movement within the air gap between a rotor and stator of a dynamoelectric machine to tighten wedges in the machine&#39;s stator slots. 
     2. Description of Related Art 
     In dynamoelectric machines and, particularly in the stators of large dynamoelectric machines, it is conventional to build up an annular magnetic mass by stacking thin laminations of magnetic material on key bars. The laminations conventionally include slot-shaped openings therein which are aligned in the stacking process with corresponding openings in all other laminations to form a set of parallel slots in the inner surface of the annular magnetic mass. One or more conductors are placed in each slot to receive the generated electricity if the dynamoelectric machine is a generator or, to receive the driving electric power if the dynamoelectric machine is a motor. The conductors in the slots of a large dynamoelectric machine carry large currents and are subjected to large magnetic fields. They therefore experience very high forces tending to displace them within the slots. If steps are not taken to prevent such an occurrence, the forces acting on the conductors are sufficient to displace them in the slots and to damage or destroy the stator. 
     In the power generation industry, hundreds of stator wedges are often used to assist in retaining the coils in the stator of a power generator or a motor. The wedges are positioned to overlie the coils. The stator wedges are positioned into wedge grooves or wedge slots formed in the peripheries of the core laminations within the coil slots. The laminations are conventionally formed of coated steel material. The stator wedges are conventionally formed of an epoxy-laminated glass material. Because the stator coil laminations are formed of a coated steel material, it is important that such wedges be formed of a non-conducting material so that a short is not created which can damage various portions of the generator. During use, the large magnetic forces generated by the rotor of a large dynamoelectric machine are sufficient to distort the cross section of the stator from circular to slightly elliptical. The major axis of the elliptical distortion rotates with the magnetic pulse of the rotor at a speed of, for example, 3,600 rpm. The stator slots are thereby cyclically widened and narrowed a very small amount at a frequency of 120 Hz as the maxima and minima of the elliptical distortion travels there past twice per revolution of the rotor. With years of normal operation of such dynamoelectric machines, the stator wedges holding the stator coils can become loose. An undetected loose wedge condition can result in excessive vibration of the coils and eventually lead to a catastrophic failure of the machine. The typical assembly for a stator slot includes the stator coils, stator wedges, and wedge filer material. Normally, when wedges become loose, the generator rotor has to be removed, the loose wedges are removed and new wedges and filler material are installed. This is a time-consuming and expensive process. 
     Stator wedges have been developed that can be tightened after they have been installed. This style wedge has a main body that is tapered on the underside to which a wedge insert (tapered to match the wedge) is slid beneath it. As the wedge insert is forced against the wedge in the taper of the wedge, it increases the thickness of the wedge assembly, thus compressing the slot contents and tightening the wedge in the wedge grooves or wedge slots referred to above, which are also referred to as the dovetail. 
     It is an object of this invention to provide an apparatus that can tighten such wedges without removing the rotor. 
     It is a farther object of this invention to provide an apparatus that can tighten the stator wedges remotely. 
     It is a further object of this invention to provide such apparatus that can tighten the stator wedges from within the air gap of a dynamoelectric machine remotely under the supervision of an operator. 
     SUMMARY OF THE INVENTION 
     The present invention is a remote-controlled maintenance vehicle for tightening wedges in a generator coil slot that can travel and is operable within the air gap of a generator between the rotor and stator. Thus, employing the remote-controlled maintenance vehicle of this invention, generator wedges may be tightened without removing the rotor. While this invention is described in an application to generators, it should be appreciated that it can be applied equally as well to large motors. 
     The maintenance vehicle of the present invention includes a frame and at least one drive module attached to the frame and having a drive train that utilizes magnetic adhesion to traverse an interior ferromagnetic surface of the dynamoelectric machine. A motor is operatively connected to the drive module and responsive to a signal from a remote controller to provide a motive force to the drive train. An effectuator is attached to the frame and is operable upon command from the remote controller to engage a wedge on the dynamoelectric machine and remotely tighten the wedge in a coil slot on the dynamoelectric machine. The dynamoelectric machine maintenance vehicle is sized and configured to fit between the stator and the rotor of the dynamoelectric machine. Preferably, the wedge comprises a main body and an insert configured so that movement of the insert relative to the main body in one direction increases the width of the wedge in the dynamoelectric machine slot and tightens the coil within the slot. The effectuator comprises a first and a second, spaced, telescoping member. The first telescoping member is operable, upon command, to extend from one side of the frame and engage the wedge insert. The second telescoping member is operable to extend from the one side of the frame and engage the main body of the wedge and at least one of the first and second telescoping members is operable to move in the one direction relative to the other of the first and second telescoping members and tighten the wedge in the slot. 
     In one preferred embodiment, the telescoping members are pins that substantially fully retract within the frame when not fully extended. Desirably, the pins are operated by miniature pneumatic pistons to retract and extend from the frame. Preferably, the miniature pneumatic pistons are biased in the retracted position so that the first and second telescoping members are in a retracted position if pneumatic supply is disconnected from the pistons. In another embodiment, a camera assembly is provided for remotely viewing the engagement of the first telescoping member and/or the second telescoping member with the main body of the wedge and/or the insert of the wedge. 
     In still another embodiment, the first telescoping member engages a hole in the insert to the wedge, and the second telescoping member engages a first end of the main body of the wedge that is opposite to a second end of the main body of the wedge into which the insert enters. Preferably, the wedge has an inclined, tapered surface where the insert contacts the main body of the wedge and desirably the main body of the wedge has a mating inclined, tapered surface where the insert contacts the main body of the wedge. A hydraulic or pneumatic cylinder and piston connected to either the first or second telescoping member moves either the first or second telescoping member in the one direction to increase the width of the wedge. Preferably, the other of the telescoping members is held in a stationary position while the insert is moved into the main body of the wedge. Desirably, the wedge insert has a hole that is engaged by either the first or second telescoping member and the main body of the wedge has a slot through which the hole in the insert can be engaged. When fully extended, the extended length of the telescoping member and width of the frame exceeds the clearance distance between the stator and rotor of the dynamoelectric machine. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a better understanding of the invention, reference may be made to the preferred embodiments exemplary of the invention, shown in the accompanying drawings in which: 
         FIG. 1  is a sectional view of a portion of a generator rotor and stator showing the coils in the stator slots anchored by a wedge and the remote controlled maintenance vehicle of this invention seated in the air gap on the stator over a wedge; 
         FIG. 2  is a perspective view of the main body of a wedge with a wedge insert in place; 
         FIG. 3  is a top plan view of  FIG. 2 ; 
         FIG. 4  is a side plan view of  FIG. 2 ; 
         FIG. 5  is a perspective view of the remote controlled maintenance vehicle of this invention with the top cover shown removed; 
         FIG. 6  is a sectional view of a portion of the remote controlled maintenance vehicle of  FIG. 5  illustrating the telescoping members fully extended engaging a wedge; 
         FIG. 7  is a sectional side view of a portion of the remote controlled maintenance vehicle of  FIG. 5  illustrating the telescoping members and miniature piston drive mechanisms in their fully extended position; 
         FIG. 8  is a sectional side view of the remote controlled maintenance vehicle of  FIG. 5  illustrating the telescoping members in a 50% retracted position; and 
         FIG. 9  is a side sectional view of a portion of the remote controlled maintenance vehicle of  FIG. 5  showing the telescoping members and miniature piston drive mechanisms in a fully retracted position. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a partial cross-section of a generator rotor  52  and stator  48  with coil slots  51 . A top coil  50  and bottom coil  49  is firmly situated in each of the coil slots  51  and, as will be described more fully hereafter, is held firmly in place by the wedge  38 . The wedge  38  includes a main body  40  and insert  42  which cooperate together to firmly hold the wedge  38  within the dovetail  39  of the coil slot  51 . The remote controlled dynamoelectric machine maintenance vehicle  10  of this invention is shown resting on the surface of the generator stator  48 , flanked by its motorized track drive assemblies  30  and  32  within the air gap  54  between the generator stator  52  and the generator rotor  48 . The maintenance vehicle of this invention  10  is shown centered over the main body  40  of a wedge  38  in position to tighten the wedge, as will explained more fully hereafter. 
     The wedge  38  is more fully illustrated in  FIGS. 2 ,  3  and  4 . The peripheral cross-section of the main body  40  of the wedge  38  has a contour that matches the peripheral dovetail grooves  39  in the stator slot  51 . The lower surface of the cavity  43  of the main body  40  is preferably tapered along its length so that when a corresponding taper on the upper surface of the insert at  42  is driven within the cavity, the height of the wedge  48  is increased, bringing pressure on the coils  49  and  50  to firmly seat the coils in the slot  51 . As can best be seen from  FIG. 4 , preferably the upper surface of the insert  42  and the lower surface of the cavity  43  have matching tapers to maintain the upper surface of the main body  40  of the wedge  38  parallel with the lower surface of the insert  42  to firmly seat the wedge  38  within the dovetail groove  39  of the coil slot  51 . As will be explained more fully hereafter, the maintenance vehicle  10  of this invention has two latch pins for respectively securing the insert  42  and the main body  40  and driving the insert  42  inwardly within the cavity  43  of the main body  40  of the wedge  38 . One of the latch pins engages a hole  46  within the insert  42  though a slot  41  in the main wedge body  40 ; while the other of the latch pins of the maintenance vehicle  10  is positioned against a backing pin contact area  44  on the other side of the main body  40  of the wedge  38 . One or other of the latch pins are then driven towards the other to tighten the wedge within the coil slot  51 . 
     The basic drive carriage of the remote-controlled dynamoelectric machine maintenance vehicle  10  of this invention is generally described in U.S. Pat. No. 6,889,783,issued May 10, 2005 to the assignee of this invention. The main carriage and drive train of the remote-controlled dynamoelectric machine  10  of this invention is basically shown in  FIG. 5 . The vehicle  10  is a low clearance motorized vehicle that is comprised of a main body  28 , two motorized track drive assemblies  30  and  32 , and a “tail” section  20  which manages the electrical/hydraulic/pneumatic cables and is used as a handle for insertion and removal of the vehicle  10  in and out of the generator air gap  54 . Though the vehicle  10  is shown and described as applied to a generator, it should be appreciated that it can be applied in any large dynamoelectric machine that employs wedges that can be tightened in place. The main body  28  houses two wedge compression pistons  12  and  14  which can be either hydraulic or pneumatic. In this example, the wedge compression pistons  12  and  14  have a 0.875″ (2.22 cm) diameter bore. These pistons will extend and retract a forward drive pin assembly positioning the telescoping drive pin  36  over the hole  46  in the wedge  38  with the ability to exert up to 200 pounds of force to tighten the wedge  38 . The drive pin assemblies can best be viewed from the side cross-sectional view shown in  FIG. 6 . The main body of the remote controlled dynamoelectric machine maintenance vehicle  10  of this invention also incorporates two miniature pneumatic, spring return pistons  16  and  18 . Each of the miniature pistons  16  and  18  is independently activated and mechanically linked to telescoping pin mechanisms  34  and  36 , one of which is inserted into the tapered wedge insert hole  46  and the other is inserted at the backing pin contact area  44  at the other end of the main body of the wedge  38 . Since the vehicle  10  will be used around the inside diameter of the stator  48 , the main body  28  also has provisions for embedding eight rare-earth magnets  22  at various locations to assure adhesion at all points in the generator. The spring return action of the miniature pneumatic pistons  16  and  18  will act as a “fail safe” to remove the drive pins  34  and  36  from the wedge  38  if a pneumatic system failure should occur. Two remote video cameras  62  and  64 , respectively located near the telescoping pins  36  and  34 , are used to observe the positioning and insertion of the telescoping pins  34  and  36 . Two “side car” track drives  30  and  32 , located on either side of the main body  28 , are mounted on pivoting mounts  66  and  68  to accommodate various diameter stators. These drives are motorized with variable speed motors  70  and  72 . Rare-earth magnets  22  are embedded in the drive units to maintain contact in all areas of the generator. A forward-looking video camera  24  with lights  26  is mounted in the front of the main body  28 , as shown in  FIG. 5 . 
     The tail section  20  of the vehicle  10  is used to house the umbilical cable containing the wiring and hoses to operate the unit. It is also used as an insertion/removal handle for placing the vehicle carriage  10  inside the generator. 
     As can be best appreciated from  FIGS. 6 ,  7 ,  8  and  9 , the telescoping drive pins  34  and  36  are mechanically linked to the miniature pneumatic pistons  16  and  18  by the mechanical linkage  58  that has a diagonal slot  60  that captures a pin  56  in the upper end of the telescoping pins  34  and  36 . The pins  34  and  36  are retracted when the miniature pneumatic pistons  16  and  18  are de-energized and the linkage  58  is fully extended. This telescoping action is necessary, since the combined length of the pins  34  and  36  and the width of the main frame  28  at full pin insertion in the wedge  38 , exceeds the clearance distance for the air gap  54  between the stator  48  and the generator rotor  52 . 
     The wedge tightening process proceeds as follows. The vehicle  10  of this invention will be driven into position using the video cameras  24 ,  62  and  64  to view the forward progress and pin  34  and  36  alignment with the wedge  38 . With the hydraulic wedge compression pistons  12  and  14  in the fully-extended position (the drive pin  36  positioned above the tapered wedge insert hole  46 ), viewing the fixed pin  34  via the video camera  64 , the fixed pin  34  will latch to the back  44  of the tapered wedge  38 . Then, while viewing the insertion pin camera  62 , the hydraulic pistons  12  and  14  will be actuated, drawing the insertion pin  36  into position over the tapered wedge insert drive hole  46 . Pneumatic piston  18  is then energized to insert the pin  36  into the hole  46 . Regulated hydraulic pressure is then applied to the hydraulic wedge compression pistons until the proper force is achieved, tightening the wedge  38 . The miniature pneumatic pistons  16  and  18  are then de-energized, retracting the pins  34  and  36 , and the carriage  10  is driven to the next position. 
       FIG. 7  more fully shows the position of the linkage  58  extending from the miniature pneumatic pistons  16  and  18  when the telescoping pins  34  and  36  are fully extended.  FIG. 8  shows the position of the linkage  58  with the telescoping pins 50% retracted, and  FIG. 9  shows the arrangement of the linkage  58  between the miniature pneumatic pistons and the telescoping pins with the telescoping pins  34  and  36  fully retracted. 
     Thus, by using this remotely-controlled “low clearance” style carriage  10 , the need to remove the rotor  52  for wedge tightening is eliminated. Thus, down time for the generator can be greatly reduced. 
     While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular embodiments disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the appended claims and any and all equivalents thereof.