Chuck Yung
Technical Support Specialist
Electrical Apparatus Service Association, Inc.
St. Louis, MO
The paper "Wind Generators: Unique Repair Tips" by Chuck Yung, presented at the EASA Convention 2006, provides valuable insights into the repair and maintenance of wind generators, highlighting opportunities for improvement in insulation strength and mechanical construction. Wind power is rapidly growing in North America, with significant installations in 2005 and projections for continued growth. Most commercial wind generators in North America are rated between 660 kW and 1.5 MW, although larger units exist. The paper emphasizes the importance of cost-effective repairs due to the high expense of crane services required to remove generators from tall towers.
Yung discusses several application issues and opportunities for improvement identified by end users, manufacturers, and repairers. These include reactive versus real power, economic impacts, weak connections, rotor lead connections, inadequate rotor banding, special construction issues, high volts per coil, shaft currents, and ventilation. Wind generators can be either squirrel-cage or wound-rotor design, with wound-rotor generators offering advantages such as varying torque and speed by adjusting external resistance.
Economic factors have historically been a barrier to wind generation growth, but improvements in technology, legislative mandates, and consumer concerns for the environment have paved the way for increased construction of wind farms. Renewable Energy Credits (RECs) and Renewable Portfolio Standards (RPS) provide financial incentives for clean energy production, further supporting the growth of wind power.
The paper highlights special testing issues for wind generators, including the use of megohmmeters to test for resistance between phases and the importance of maintaining phase isolation. On-site testing cautions are provided to avoid misinterpretation of results. Rotor connections, including lead and wye rings, are prone to fatigue failure and require careful inspection and reinforcement.
Yung discusses the benefits of converting from concentric to lap windings for better heat dissipation and the importance of adequate rotor banding to prevent failures. High turn-turn voltage stresses in rotors require special insulating techniques, and partial discharge concerns necessitate multiple varnish treatments to achieve void-free windings.
Bearing failures are a significant issue in wind generators, often caused by shaft currents. The paper recommends hybrid bearings with ceramic balls to prevent damage and the use of grounding brushes to discharge static electricity. Ventilation within the nacelle is crucial to prevent overheating, and modifications may be necessary in hot climates.
The paper concludes by emphasizing the substantial potential for wind generator repair, particularly in high-wind areas and regions with strong tax incentives. Understanding the unique challenges and implementing the recommended repair tips can help service centers effectively support the growing wind power industry.
Key Points Covered:
- Growth and potential of wind power in North America
- Importance of cost-effective repairs due to high crane expenses
- Application issues and opportunities for improvement
- Economic factors supporting wind generation growth
- Special testing issues and on-site testing cautions
- Rotor connections and reinforcement
- Benefits of converting to lap windings
- Importance of adequate rotor banding
- High turn-turn voltage stresses and partial discharge concerns
- Bearing failures caused by shaft currents
- Ventilation within the nacelle
Key Takeaways:
- Wind power is rapidly growing, with significant repair opportunities.
- Cost-effective repairs are crucial due to high crane expenses.
- Understanding application issues and implementing improvements can enhance wind generator performance.
- Economic incentives support the growth of wind power.
- Proper testing and reinforcement of rotor connections are essential.
- Converting to lap windings improves heat dissipation.
- Adequate rotor banding prevents failures.
- Addressing high voltage stresses and partial discharge concerns is important for winding longevity.
- Hybrid bearings and grounding brushes prevent bearing failures caused by shaft currents.
- Ensuring proper ventilation within the nacelle is crucial to prevent overheating.
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