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Hydrogenerator Field PolesFor many years, NEC has provided hydrogenerator refurbishment services to several U.S. Government agencies and large investor owned utilities. These projects have involved the complete rehabilitation and refurbishment of large hydrogenerators. Work scopes typically have included the refurbishment and reinsulation of rotor field windings along with the replacement of stator cores and new stator windings. Because of our experience with these projects, we have identified several critical issues related to the rehabilitation and refurbishment of field poles in older hydrogenerators. These include:
These conditions have been seen repeatedly and can ultimately affect your unit's performance if not addressed properly. For an owner, prior knowledge of these types of problems may save time and money when planning a refurbishment project. Including provisions to address these conditions in your project scope work, should they be an issue with your machine, can mean improved reliability over the operational life of the unit once the project is complete. Download our technical paper discussing these conditions in depth. Field Pole RefurbishmentsA general scope for field pole refurbishment is given below.
With our engineering capabilities and dedicated manufacturing production line, we can easily address your field pole refurbishment needs, or should your project scope require it, the manufacture of completely new pole pieces. DOWNLOAD our Synchronous Rotor Field Pole Refurbishment brochure.
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Rotor Repairs & Requalifications
Hydrogenerator rotors consist of a rotating spider mounted on a shaft with field poles mounted on the spider rim. Because of improvements in insulating materials, older hydrogenerator units can often be significantly uprated through the redesign of the stator winding. If a frequency change also is involved, the number of field poles may need to be increased. In either case, the rotor may require repairs or modifications to requalify it to meet the new rating.
We are experienced with cast and fabricated rotors, including those with segmented rims. We have manufactured new field poles for more than a dozen units whose frequency was increased from 25 cycles to 60 cycles, as well as cases where pole laminations were damaged in some way. We have also repaired casting cracks in older rotors, and we have made modifications to rotor rims and pole key assemblies to allow more pole weight and resolve distortion and re-fit issues. Because of the long lead time required to fabricated replacement rotors, our ability to fully rehabilitate these rotors can benefit your project budget and schedule. READ about hydrogenerator rotor inspection and testing.
