Field Services

NEC's Generator Service Group also supports our generator Inspection and Testing Services.

National Electric Coil's Generator Services Group 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 GSG is responsible for the installation of our stator windings, stator cores and hydro field poles by NEC's Generator Services Group or an authorized Generator Service Partner (GSP) insures they will perform as designed. Care is taken to assure that the windings and laminations arrive complete and ready-to-install at your site. NEC's Generator Services Group 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 project teams. Many have worked for with various OEMs.

Typical field service scope for a stator rewind installation will include:

  • Stator core preparation, including cleaning, repairs to interlaminar insulation, testing and re-painting. (Some scopes may include a core restack. In other cases, age of the unit or testing results may indicate problems requiring a core replacement.)
  • Installation of upgraded end winding support system (Certain fossil units).
  • Installation of new surge and bus rings ( may include provisions for a future Main-Neutral Interchange).
  • Installation of stator bars, RTDs and wedging and blocking system and testing of individual coils or groups of coils at specified points in the installation.
  • Brazing and circuit connections
  • Testing of the completed winding
  • Painting and miscellaneous finishing details

NEC's Generator Services Group has the proven experience and extensive expertise to rig and perform stator core restacks for any type or size of hydro or fossil unit. National Electric Coil has extensive experience with stator core restacks for both hydro and fossil units. This experience ranges from repairs to individual laminations and partial restacks to complete stator core restacks. Although restacking a unit with its old iron is not unusual, there are some advantages to owners restacking with new laminations. A core restack with new iron may be found necessary if there are hot spots or other forms of degradation of the core iron. With earlier vintage units with core laminations of low-grade, high loss iron, new laminations made of the newer high-efficiency iron may be helpful in increasing a unit's power output.p>

Vertical Core Restacks

NEC's Generator Services Group has the proven experience and extensive expertise to rig and perform core restacks for some of the largest generator units. Sometimes, a vertical restack of a turbogenerator is a more budget-friendly option than some of the OEM approaches. NEC has vertically restacked units ranging in size from 7.5 MVA to 810 MVA.

Hydrogenerator Rotors Need Special Attention

When hydrogenerator field poles are refurbished at our Rotating Equipment Service Center, they still need to be uninstalled and then reinstalled when returned to the owner's site. Our skilled field service technicians make sure that the rotor is properly disassembled so field poles can be shipped to the service center in Columbus, Ohio for refurbishment and repairs. If the rotor has been redesigned for for an uprate or frequency change, they make any necessary modifications to the spider and rim. When the refurbished poles are returned to the job site, they reinstall the poles, along with any modified keys or connectors. Read more about field pole refurbishments. Download our Technical Maintenance Memo (TMM) 601 for a description and solutions to rotor rim problems.

Inspection & Testing Services
NEC's Inspection & Testing Services are available to owner's needing specialists to supplement their own workforce during outages or to assist them in troubleshooting a machine failure. Depending on the specific project's needs, these services may be provided by technicians of our Generator Services Group in conjunction with engineers from our Technical Services Group. Read more about Failure Modes and our services for Inspections & Testing.
Capabilities for Major Overhauls
Major generator overhaul projects may require rewinds of generator stators and rotors to run on parallel schedules. Because of the unique manufacturing and capabilities found at each of its factory sites, NEC can easily support projects of this complexity.
Project Management
NEC's Project Management Group provides comprehensive coordination necessary for the most complex projects. As the owner's primary contact throughout the project, our project managers keep their eyes on project schedules and budgets, interfacing with NEC's manufacturing and service units, as well as key interfaces with other contractors and sub-contractors at the owner's site.