Columbus,  OH 
United States
  • Booth: 4083

NEC's generator expertise, quality, versatility, reliability

NEC specializes in winding design solutions that address performance & reliability issues, including machine uprates, redesigns, conversions and alterations, field services for all sizes of generator units of any OEM, including “Legacy” units, discontinued brands. NEC QA systems are ISO 9001-certified.

Brands: generator hydro motor stator rotor exciter field poles frame core laminations windings coils bars manufacturer retrofit repair engineer refurbish rewind balance inspect test upgrade uprate


  • Roebel bars for Hydrogenerators
    NEC manufactures half-turn bars for hydros. Our engineering design and manufacturing can produce windings for a wide range of OEM machines, including various options for insulation and gradient systems and unit uprates....

  • NEC manufactures both multi-turn (diamond) coils and half-turn bars. Our engineering design and manufacturing can produce windings for a wide range of OEM machines, including units with wave windings or skewed slots, as well as offer various options for insulation and gradient systems. NEC is also experienced with all manner of unit uprates and frequency conversions.
  • Multi-Turn Coils for Hydrogenerators
    NEC is the leading manufacturer of high-voltage stator windings for hydrogenerators, including both VPI and Resin Rich diamond coils and related engineering design for machine uprates, refurbishments. ISO9001-certified quality management systems....

  • At every step of our manufacturing process, quality checks are made to assure the best workmanship. NEC's Brownsville factory utilizes ISO9001-certified quality management systems.A coil or bar must be uniformly shaped in order to wind the machine properly and to avoid problems that may initiate corona during operation. Dummy cores are used to check critical clearances in the end turns and overall fit in the stator core. Multiple checks are made at different stages of manufacture. Every coil and bar undergoes both in-process testing and final testing before it leaves the factory. These "tests" include both specified electrical tests as well as various dimensional checks.

    National Electric Coil’s premier stator coil and bar design utilizes a proven, Class F, epoxy mica insulation system called NECCOBond-E. 

    NEC has developed an unparalleled record for reliability in the new stator windings it has manufactured and installed, and this record surpasses that of many major OEM’s.Our conservative design approach, high-quality manufactured materials, methods and processes, combined with ourextensive R&D development program and routine and type testing, all contribute to making long-term reliability for your generator possible. 

    A key difference, the NEC system features individually Vacuum Pressure Impregnated stator bars and coils. Each VPI’d coil consists of a number of key components shown in the first tabbed section below. NEC’s individually VPI’d coils and bars with the NECCOBond-E proven insulation system meets every National and International Standard, and is the right solution for your next rewind.

    NECCOFlex-E™ multi-turn stator coils provide owners with the dielectric advantages of a traditional VPI coil but with a specially-engineered flexibility at the coil knuckles that eases its installation in a small bore machine or one with a tightly lapped winding. Small bore machines typically have slots that cannot always accommodate conventional multi-turn Roebel bars. The NECCOFlex coil exceeds the flexibility needed to properly install the coil cells in the slots. Compared to the alternative of using spliced half coils, a NECCOFlex winding requires only half the number of connections.

  • Rewinds & Overhauls for Hydrogenerators
    Besides stator rewinds, NEC’s Generator Field Services provides related on-site services ranging from testing and inspections to stator rewedging to a wide range of repairs and modifications to both generator stators and the rotors....

  • NEC has a staff of design engineers who are experts in addressing a wide range of generic design issues, as well as designing machine modifications to improve the unit’s efficiency, reliability and maintainability. National Electric Coil's Field Service can be instrumental in the successful completion of a planned or unplanned outage. Whether an on-site installation or other generator field work, returning your unit/s to service as soon as possible is our ultimate goal. NEC's Field Service utilizes proprietary installation methods and techniques developed out of our long-term experience with all makes and sizes of machines and working under various site conditions. Our Field Service supervisors and senior staff bring years of experience to our crews. Many also have worked for the various OEMs at some point in their careers.

    Our trained and certified installation crews set up at your site with the assistance mobile workshops and storage units for tools, tooling, test equipment, materials management, portable machining and carpentry. With these resources, work platforms and protection against contamination deemed by site conditions can easily be erected. Additionally, NEC's Health, Environmental & Safety (HES), Logistics, and Quality Assurance teams work with the owners representatives to assure that our on-site workforce meets all the owner's requirements training and certifications, and is fully-stocked and -supported.

    When a stator is rewound, core repairs are an expected and routine part of the preparation of the core for reuse in a stator rewind. Some problems are obvious upon visual inspection, once the core is stripped and cleaned. Depending on the damage, some repairs may require high-speed mechanical milling and/or electrochemical machining. A Core Loop test or an EL Cid may also be required to confirm the overall viability of core. In hydros, issues with the frame, core splits, finger plates may become more obvious and require modifications. With the right experience, equipment and personnel these repairs are a standard part of our pre-rewind preparation of the unit.

    Generally, the need for a full core restack will be known well-ahead of the outage and already have been included in the project specification and schedule. For these projects, NEC's ability to arrive at the site with the right tools, tooling and proven engineering design, technical support and procedures for removal and restack of laminations, can offer customers savings in both time, schedule and budget.

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