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GENERATOR COMPONENTS, AUXILIARIES, AND EXCITATION

            13.6                     CHAPTER THIRTEEN

            SEAL FACE
            LANDING   STOP KEY                  VANE    BACK PLATE  KEY





                                                           INBOARD
                                                             END





                                                                   GAS
                                                                   RESTRICTOR




                                                                    BALANCE
                                                                    WEIGHT

                OUTBOARD
                   END







                      ROTOR SHAFT
                                                               VENTILATION
                                                               SLOT
            FIGURE 13.6 Rotor fan.

              Flexible leads made of thin copper strips are connected to the ends of the winding. These
            leads are placed in two shallow slots in the shaft. Wedges retain them. The leads are con-
            nected to radial copper studs, which are connected to D-shaped copper bars placed in the
            shaft bore. Hydrogen seals are provided on the radial studs. The D leads are connected to
            the slip rings by radial connection bolts (Fig. 13.7).


            Rotor End Rings
            The end rings (Fig. 13.8) are used to restrain the rotor end windings from flying out under cen-
            trifugal forces. These rings have traditionally been made from nonmagnetic austenitic steel,
            typically 18% Mn, 4% Cr. A ring is machined from a single forging. It is shrunk-fit at the end
            of the rotor body. The material of the end rings was proved to be liable to stress corrosion
            cracking. A protective finish is given to all the surfaces except the shrink fit to ensure that
            hydrogen, water vapor, etc., do not contact the metal. The rings should be removed during long
            maintenance outage (every 8 to 10 years) and inspected for detailed surface cracking using a
            fluorescent dye. Ultrasonic scanning is not sufficient due to the coarse grain structure. A recent

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