NEC's Columbus Rotor Service Facility ProvidesComprehensive Products & Services for Rotor Winding Replacement, Repairs, Balancing & More

Turbogenerator Rotor Rewinds a Specialty

Wind Rotor Serving the entire power generation sector — utilities, cogenerators, refineries, paper mills and other industries — NEC can handle any rotor problem, large or small. We've seen a full range of failure modes or nearfailure conditions for machines of almost every make and model. Our engineers and technicians can diagnose a full range of problems, electrical or mechanical. They are skilled in dealing with rotors with shorts, grounds, or coil damage. Repairing damage to rotor forgings or retaining rings is a particular specialty. Our full machine shop capabilities make it possible for us to design and manufacture a replacement for almost any rotor component. Our ISO 9001:2008 certified quality mangement system and our premier balancing facility make NEC one of the top specialists for turbogenerator rotors in the USA.

With no loyalty to a particular machine design, our engineers can look instead to a wide range of makes and models to analyze which design solutions have worked effectively and which have not. This broader
perspective can provide you with a more innovative and cost-effective approach to your rotor repair. When we do a complete evaluation of your rotor, we also recommend repairs to correct problems and prevent them from occurring in the future.

National Electric Coil has developed proven solutions for a number of generic design discussed in various OEM TILs and OMMs. These problems can be unique to machines of a certain age or to those made by specific OEMs. To name a few on a long list, these include:

rotor dovetail cracking
rotor turn insulation migration
retaining ring stress corrosion
J-strap fatigue
top turn cracking
brazed joint cracking
ground failures
lead failures

With our experienced engineering team, we have been able to provide our customers with timely solutions to these and other problems, with no sacrifice of quality workmanship or machine
reliability. Download our complete Turbogenerator Rotor Products & Services brochure. For more on NEC's proven engineering solutions, see the information on our Specialized Engineering Solutions™.

Ability to Supply Rotor Windings of Any Type

• New or Refurbished Winding

• Copper or Aluminum

• Direct or Indirect Cooling

• Square or Edge-Bent End Winding Corners

At our Columbus turbogenerator rotor facility, we have made a significant investment in design, equipment and process development for our rotor winding manufacturing line. This includes the achievement of ISO 9001:2008 certification for our quality management systems. NEC manufactures windings with either style of end winding corners — square or edge-bent as shown above. Typically, old windings are replaced with new ones of similar design. Throughout manufacturing, our focus is quality. All brazed joints, whether in the corners or in the arch, are UT tested to prove their durability.

NEC's Balance Facility One of the Top in Country for Turbogenerator Rotor Fields, High-Speed Exciters & Salient Pole Rotors

Rotor Flux Probe Test With peak values of no more than 1 mil, NEC leads the industry in balancing your rotor down to the lowest possible vibration levels. NEC's engineers and skilled technicians also are experienced with all aspects of troubleshooting rotor balance problems, including running shorts. The photo at the left shows a large turbogenerator rotor undergoing a flux probe test. The rotor is spinning. The flux probe is located in the red cylinder hanging above the rotor.

Below is a summary of various features and pit capabilities:

Balance Pit Features

Ability to accommodate rotors up to 45 feet long
30-, 50- and 85-ton cranes for pit service
Rail-guided transport dollies for the larger rotors above crane capacity, up to 100 tons
Large inventory of bearings and stub shafts to fit nearly every rotor
SCR Digital Drive System and 4000 HP drive train motor
System redundancies and 24/7 availability
Proven track record balancing large three-bearing rotors, as well as, exciter assemblies, salient pole rotors and other rotating electrical apparatus

Testing Capabilities

Overspeed testing at rotations up to 3960 rpm
Running electrical tests for Insulation Resistance, Impedance and Flux Probe
Rotor Thermal Sensitivity Testing, including performing Heat Runs and locating Running Shorts
Absolute Vibration Monitoring System for detection of shaft vibration, as well as seismic probes for bearing and pedestals

NEC's balance facility is one of the few in North America capable of performing thermal sensitivity testing. Rotors can be heated up to 80°C above ambient temperature allowing tracking and plotting of changes in vibration, from cold condition to hot. Download additional information on our balance facility and its capabilities.