7FUG 2020: National Electric Coil

An Improved Self-Locking Amortissuer Finger and Spring Assembly for 7FH2 Generator Rotors


Bill Harris, Field Services Manager, Rotating Electrical Equipment

Mr. Harris has more than 30 years in the manufacturing and service of large rotating electrical equipment. He is experienced with all aspects of the manufacture and service of high voltage generators from their overhaul, and retrofit to their repair and testing. He is also experienced with the manufacture of all OEM designs of rotor and stator coils. He has hands-on experience with all major OEM machines including GE, Alstom, Westinghouse, Siemens, ABB, Toshiba, Hitachi.

Presentation Synopsis

The Iconel Spring, a small but important part of GE 7FH2 generator’s amortisseur/damper segment, is prone to traveling on an axial migration path toward the retaining ring. Migration can lead to blocked cooling passages and the further effects of uneven heating across the rotor. Additionally, if the Iconel Spring makes its way under the retaining ring, damage to the retaining ring insulation and even a ground fault may result. This webinar reviews the mechanisms of the spring migration on the rotor components during operation. It discusses the structure and important function of the rotor’s amortisseur/dampering system, utilizing comparisons approaches used by several different OEMs. It also utilizes photos, diagrams and animated modeling, to show how thoughtful applications of engineering and hands-on knowledge led to an elegant solution that is both technically sound and effective, and efficient to apply in the repair facility or in the field.

Key Takeaways for Users

1. Iconel Spring migration can create conditions for larger problems.

2. The Amortisseur/Dampering Segment of the generator rotor has an important function in preventing some types of damage to the unit during operation.

3. Engineering and hands-on experience are both needed for a good solution to many O&M problems.


Dan Bucklew, Sr Vp, +1 614-580-9304, dbucklew@national-electric-coil.com

Steve Jeney, VP Sales & Marketing, +1 614-488-1151×105, sjeney@national-electric-coil.com

Howard Moudy, Director of Operations, +1 724-787-4967, hmoudy@national-electric-coil.com

Russell Chetwynd, Service Manager, +1 949-939-3307, rchetwynd@national-electric-coil.com

Bill Harris, Field Services Manager, Rotating Electrical Equipment, +1 614-464-7065, bharris@national-electric-coil.com

About National Electric Coil

Few non-OEM companies have serviced the Power Producing Industry for as long as National Electric Coil. In continuous operation since 1917, NEC grew up with the industry — initially servicing the mines in Bluefield, West Virginia — evolving in its first 30 years to a full-scale manufacturer and installer of stator and rotor windings for generators and high-voltage motors.

Since the late 1940s, NEC has expanded its product lines into the engineering and manufacture of coils for the very largest power generating units. We manufacture replacement windings and repair any generating unit, from the smallest air-cooled machines to the biggest water-cooled fleet leaders. And we are proud to serve the power generation industry, providing generator owners with an alternative to the OEM for their repair, retrofit and upgrade needs.

NEC customers include public utilities, investor-owned utilities (IOUs); public power producers, including, municipalities, public utility districts (PUDs) and retail and wholesale cooperatives (COOPs); independent power producers (IPPs) and non-utility generators (NUGs); industrial co-generators and combined heat and power generators (CHPs).

National Electric Coil, headquartered in Columbus, Ohio, provides manufacturing and services from its Columbus, Ohio and Brownsville, Texas locations. The company has small business status under NAICS 335312, Motor and Generator Manufacturing. Both locations also have HUB Zone status.

Products and Services

NEC is a specialist in-plant and on-site repair and upgrade services for generators and rotating exciters, as well as an experienced winding manufacturer, NEC offers expertise and a “Total Generator Solution” for generators of all makes and sizes, with windings for both stators and rotors. NEC also has a full-service engineering staff available for failure analyses, testing, uprates and replacement component design, and fully-equipped facilities and field services ready to address the needs of any generator maintenance, repair or overhaul project. NEC utilizes ISO 9001-certified Quality Management Systems.

Spec Sheets

GE Rotor Turn Migration

Dovetail Cracks

GE H2 Rotors Terminal Studs

Diagnosing End Winding Vibration

Dry Tie Replacement Endwinding Upgrades

J Straps

HV Coils Handout




800 King Avenue
Columbus, Ohio 43212
United States