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Sound Engineering Design at the Heart of Our Work

While selling and servicing new generator designs remains high in importance to the OEMs, it is important to remember that NEC focuses solely on generator retrofit designs. With every rewind or repair, it remains our goal is to find every way we can to increase the lifetime return on investment (ROI) for your generator. At National Electric Coil, no generator stator or rotor rewind design proceeds without a thorough examination of the possible opportunities to improve machine performance and efficiency. Additionally, a rewind or retrofit project often provides the opportunities for improving aspects of the original machine design, which can compromise machine efficiency or maintainability and may only come to light during several years of operation. Our retrofit designs routinely address these generic design issues as part of any rewind or repair we do.

End Turn Vibration Tops Our List of Specialized Engineering Solutions™

As generators age, windings and end turn bracing systems loosen, and stator winding end turn vibration may become a problem. This can be especially true of machine classes in which the original design was upsized. A number of Westinghouse inner-hydrogen-cooled machines have experienced winding end turn vibration problems. And sometimes the existing end winding support system is the culprit. GE's conventionally-cooled medium-sized generators have stator end winding axial support systems. A large number of the bolts of have been found with loose, missing or non-locking locknuts, and vibration results.

Natural frequencies in the end basket can approach 120 hertz (hz), the same as the double operating force frequency. So as windings approach resonance, vibration can cause movement approaching 20 to 30 mils. Visual inspection of the winding can confirm the existence of this condition. Dusting, greasing and broken strands are common idicators. READ MORE

Engineering Studies Help Identify & Define Solutions for Project-Critical Issues

NEC design engineers are ready to respond to any generator design issue that may arise during a generator repair or retrofit project. While the individual backgrounds of our engineers may vary, many began their careers at OEMs or worked for major utilities before coming to NEC, or both. This diversity of knowledge and experience gives our design team a wide-ranging base of experience with generating units of all ages, makes, sizes and types. READ MORE

Past Project Experience Spans More than 85 Years

Past projects have Involved generator rewinds, uprates or repairs to rotating electrical equipment manufactured by nearly every supplier in the world. A partial list includes General Electric, Westinghouse, Siemens, Allis Chalmers, Electric Machinery, NS Peebles, Brush, Elliott, Alstom, English Electric, Reliance, Toshiba, Hitachi, GEC, Mitsubishi and ABB. These projects have services turbogenerators, hydrogenerators, AC and DC motors, exciters, frequency changes and synchronous condensers. Sizes have ranged from motors of a couple thousand horsepower, to 1000 MVA generators. READ MORE

 
   
   
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