Critical Maintenance Issues for Generators & Exciters

• Stator winding end turn vibration — solutions range from retrofit bracing sysems for an existing winding to new windings with specially-designed decoupling bracing systems.
• Rotor turn insulation migration — a number of cases involve the breakdown of the adhesive bonding the insulation to the rotor winding's copper turns.
• Partial discharge — newer air-cooled machines designed with high-volts-per-mil windings have been experiencing an unprecedented number of problems.
• Contamination — this is a ever-present problem as maintenance intervals are extended.
• Excitation system — exciters need regular, thorough maintenance to prevent forced outages.
• Stator winding life extension — switching the main to neutral connection can help spread the wear and tear across the entire winding.
• Foreign object damage — problem "objects" are diverse and damage to the unit can range from minor to catastrophic.
• Fatigue cracking — high-cycle- and low-cycle-stresses are an issue for both stators and rotors, but affected rotor components dominate in these categories.
• Retaining ring stress corrosion cracking — a set of stressors, different from those causing fatigue cracking (above), drive SCC.
• Rotor winding distortion and turn displacement — the roots of this problem are in the design of the winding end turns and the retaining ring.
• Rotor overheating — the worst-case result is a ground fault and potential causes are many.
• Rotor vibration — a symptom of other problems but a problem that can cause a forced outage.
• Stator wedge looseness and failure — a clear-cut issue of preventive maintenance.
• Stator core damage — core looseness can lead to other problems, as well as damage to the laminations.