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Retaining Rings for Generators

Nowadays, electrical energy is produced almost exclusively in rotating electric generators. By far the largest proportion of current produced in such units comes from turbine-driven generators. These operate at 3000 revolutions per minute. The rotating magnetic field is generated by windings of alternating polarity that are excited by direct current. The windings protrude from longitudinal grooves in the rotor at the rotor body ends and form the winding overhang, which has to be secured in place against the centrifugal force. These functions are fufilled by retaining rings, which are the most highly stressed components of a turbine-driven generator. The retaining rings are mostly shrunk onto the rotor body ends and secured against rotational and axial movements by a type of bayonet fastening, for instance. In many cases a supporting ring is shrunk into the retaining ring on the side facing away from the rotor body to take up the winding overhang forces acting in longitudinal direction.
The development of ever-larger power-generating units is leading to greater stresses being exerted on the retaining rings, meaning that these rings and, therefore, also their production technology have to meet the most stringent demands. The material used to manufacture the retaining rings must therefore have the following characteristics:

• high yield strength
• adequate hot and cold forming properties
• sufficient thermal expansion
• non-magnetisability in most cases
• corrosion resistance.

The P900 nitrogen-alloyed steel developed by Energietechnik Essen represents the current material standard for this application.

P900
Material number/DIN Code: 1.3816, ASTM A 289, Class C

Retaining rings can be manufactured to your drawings or specifications as well as to national or international standards.

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