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Surge rope is a fiberglass rope used in electric motors to anchor each coil to the next coil. This rope provides strength and stability to coils, preventing them from bending once a motor is powered. There are two types of surge rope: Dry Surge and B-Stage.


Dry surge rope is an untreated rope comprised of a texturized fiberglass core with a fiberglass over-braid. These ropes also have the option of a heat-resistant core known as an aramid fiber core. A Vacuum Pressure Impregnation (VPI) system, which seals gaps in generators' materials and high voltage motors, uses dry surge ropes. The standard varnishing technique known as dip and bake can also use dry surge ropes. The untreated fiberglass version has a Class C (over 240°C) rating; however, the end-user rating will depend on the resin used for vacuum impregnation. Typically, the class rating will take on the temperature class rating of the resin.


Treated ropes are considered B-Stage surge ropes. A core of glass yarns coated or impregnated with thermosetting modified polyester resins or epoxy resin systems forms the B-Stage product. They are rated from Class N 180˚C up to Class H 220 ˚C depending on the resin used. The B-Stage core is over braided with a spun polyester fiber that encapsulates the core. 

EIS recommends surge ropes for use as replacements for both steel and laminated fiberglass surge rings, spacers on DC armatures, winding head supports on random wound (mush coils) machines, and support systems for the nose sections of AC form wound coils.