Rotor

Large generator rotors have cooling holes drilled through the winding slots to allow hydrogen or air to circulate and remove heat. The holes are typically 8-15mm diameter, drilled lengthwise through the rotor forging. In my experience, a blocked cooling hole is one of the most common causes of generator rotor failure, so the quality of these holes matters more than most people realize. Rotor Forging Materials and Cooling Hole Layout The rotor material is usually a high-strength steel forging like 25CrMo4 or similar. The rotor can be 6-10 meters long with cooling holes running the full length. The position tolerance for the holes is typically within 0.5mm of the design coordinate. ...

Generator shafts connect the turbine to the generator rotor. They need a through-hole for the rotor assembly tie bolts and for cooling air circulation. The shaft is typically 4-8 meters long with a 100-300mm bore depending on the generator size. In my experience, the bore quality directly impacts rotor balance and cooling efficiency, both of which affect generator reliability over decades of service. Material Selection and Forging Considerations The material is usually a high-strength steel forging like 25CrMo4 or 34CrNiMo6. The shaft weight can be 10-30 tons. The bore concentricity requirement is typically within 0.5mm of the shaft centerline. ...

Steam turbine rotors are large forgings that rotate at high speed inside the turbine casing. They need a through-bore running the full length for borescope inspection access and for balancing. In my experience, the bore is one of the most critical features of the rotor because it enables the periodic inservice inspections that prevent catastrophic failure. Rotor Specifications and Material Properties A typical steam turbine rotor might be 4-8 meters long with a 100-200mm bore. The material is a high-strength alloy steel like 3.5NiCrMoV. The rotor can weigh 20-50 tons, which makes handling a major consideration. ...