| 1. Classic Frame 5 generators typically arrive at the shop in poor condition.
Mechanical, electrical, thermal, and environmental aging influences
have taken their toll. Stator and rotor winding insulation systems
usually are obsolete. Plus, retaining rings, collector rings, core iron,
and the end-basket support system are dated and should be upgraded. |
| 2. A classic commonly contains asphalt-mica stator windings.
The straight-section outer binder, strand insulation, and/or end
connection putty may contain asbestos; test prior to demolition. If
positive, use only trained abatement specialists. As the stator
windings are extracted, critical dimensions are taken for the
engineering and redesign process. |
| 3. Once stripped of the original windings,
the stator housing and core iron are grit-blasted clean. Great care is
required during this operation, because the stator laminations are
susceptible to “smear” damage. Perform a near-flux core loop test to
requalify the iron for reuse. |
| 4. A full core replacement can be performed
with either stamped punchings or laser-cut laminations. The lamination
steel used should be either grade M6, Cold-Rolled Grain-Oriented (CRGO),
or M15, Cold-Rolled Non-Grain-Oriented (CRNGO), with C5 core plating as
the interlaminar insulation. |
| 5. The original two-turn full diamond coils
are upgraded to two-turn, 360-deg Roebel half-coils, which are far
superior to the original windings in many ways, including these: They
have more copper (lower I2R losses), more conductors in-hand
(lower eddy-current losses), and a Roebel transposition (lower
circulating-current losses), as well as a modern resin-rich mica
thermosetting insulation system. |
| 6. The new and improved windings are installed
into the stator core iron together with the following upgrades:
End-basket support system, vertical slot fillers, side packing, stator
slot wedge system, encapsulated end connections, circuit ring bus, new
RTDs, new heaters, a flux probe, and partial-discharge monitoring
system. |
| 7. A comprehensive acceptance program is conducted
following a stator-winding upgrade and includes successful completion
of an El CID core test, wedge-tightness mapping, insulation resistance,
Polarization Index; controlled over-voltage; ac and dc high potential,
power factor and tip-up, and phase resistance. |
| 8. The rotor is dismantled down to a bare forging,
taking steps to avoid the release of asbestos-bearing materials, if
present. Copper samples are removed from the main field winding and
lab-tested for composition, tensile strength, hardness, and yield
strength. Main field windings generally are suitable for reuse. |
| 9. Rotor components—such as the rotor body forging,
retaining rings, blower hubs, and rotor body wedges—are cleaned down to
grey metal. Each individual part is subjected to requalifying
nondestructive testing, which may include dye-penetrant, ultrasonic,
eddy-current, and magnetic- particle examinations. Non-conforming parts
are either repaired or replaced. |
| 10. The reconditioned and requalified main field coils
are wound back into the rotor-body forging. The latest turn-to-turn and
ground-wall insulation systems are incorporated into the process.
Slip-planes, critical to unimpeded axial thermal expansion and
contraction of the windings, are designed into the upgraded main field
winding system. |
| 11. Specially designed and fabricated slot and end-winding
compression fixtures are installed on the newly installed coils,
forming a symmetrically round and dimensionally concentric main field
winding. The rotor is then induction-cured, to set and stabilize the
associated adhesives while seasoning the windings. |
| 12. All new top creepage blocking is installed
along with the rotor body wedges and a new permanent end blocking
system. Should resin-load materials be used, the end windings are
compressed once again, and the rotor windings are subjected to a second
and final induction curing process. |
| 13. The rewound, reassembled, and fully upgraded rotor
is placed in the high-speed balance facility. There it is balanced to
operational speed, subjected to a minimum 10% over-speed run, and
at-speed electrical testing—including insulation resistance, ac
impedance, RSO and/or flux probe. |
| 14. The generator rotor now is completely upgraded, uprated, and “zero houred.” With
all new turn-to-turn, ground wall, and retaining-ring insulation
systems, modern 18Cr18Mn retaining rings, and new collector rings, the
classic Frame 5 rotor is better than when it was new and ready to begin
its second life cycle. |
| 15. The Frame 5 generator is a true classic in every sense of the word:
simple in design, rugged in construction, and easily acceptant of
modern upgrades and uprates. Rebuilding of vintage machines typically
makes better economic and business sense than buying new. Owners can
expect years of relatively maintenance-free service.
source:http://www.ccj-online.com/how-to-make-a-frame-5-generator-new-in-15-easy-steps/ |
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