Generator design, frame size 710-1250

 

Quality throughout
All generators are tailor made within a standard, modular concept offering great flexibility to ensure that correct generator characteristics are selected for each installation.

  • Compact and flexible design ensures a good match with the plant's requirements.
  • Rigid construction transfers dynamic and static stresses directly to the foundation.

Rotor with salient poles and solid pole plates

  • Ensures high thermal capacity and stability without the need for special damping winding.
  • Fast control and electric stability through adaptation of the air gap, design of the pole shoes and dimensioning of the pole core.
  • Solid pole shoes provide high damping without damper winding. Good overload capability and low harmonics.
  • Reliable operation and long service life ensured by large cooling surfaces and effective flow of cooling air, which also results in low, uniform rotor temperature. Class H insulation of the coils gives extra thermal margins.
  • Stiff rotor and minimized distance between bearings ensure low vibrations since the operating speed is well below the first critical speed.
  • Over-speed tests are performed as standard. The complete rotor is balanced at operating speed.

Stator design greatly influences stability and performance

  • High-grade, low-loss electrical steel increases efficiency and reduces operating costs.
  • Stiff frame transmits all forces directly to the foundation.
  • Well developed and proven methods for locking the coils into the slots and bracing the coil ends ensure long term reliability.
  • Insulation system that ensures reliability and long service life. The windings are insulated with Mica based tape. When the windings are in place, the complete stator is impregnated in a vacuum pressure impregnation (VPI) process. The windings are of insulation class F, resulting in good thermal margins.
  • Voltage drop and short circuit current limitation are achieved by designing the stator for optimized reactance values.

Bearings and bearing seats provide a reliable stator, rotor and shaft assembly

  • Bearing housing design permits easy access for inspection and maintenance. The bearing housings are insulated from the frame to eliminate circulating currents in the shaft. The shaft can be earthed. Labyrinth seals are used to prevent oil leakage.
  • Sleeve bearings are designed to be insensitive to misalignment and to permit large axial play.
  • Independent lubrication system gives high reliability. Oil rings or oil reservoir ensure lubrication during emergency rundown. Hydrostatic jacking oil systems are available for applications operating at low speed.

Exciter mounted external to the non-drive end bearing

  • Simple but highly developed design having few components and well adapted protection functions offers high reliability and easy access for maintenance.
  • Compact, brushless exciter unit is mounted on the rotor shaft outboard the bearing together with a PMG (permanently magnetized auxiliary generator). No independent support or alignment is required.
  • Improved system performance due to high field forcing possibilities. This is important when faults in the supply network arise and when increasing production of reactive power.

Efficient cooling

  • Very good cooling is obtained thanks to the the symmetrical cooling achieved with the shaft mounted fans, in combination with the design of the rotor and stator.
  • The wide line of cooling forms allows an optimum for the operating and environmental conditions of each application.
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