GENERATOR ROTOR MODIFICATIONS, UPGRADES, AND UPRATES
A generator uprate (increase in rating) can be achieved during a rotor rewind. This can be done by installing new class F insulation. This allows the rotor to have higher field current. Thus, the real and reactive power of the generator can be increased.
Generators used with gas turbines, steam turbines, and combined-cycle power plants have been operating at higher power factor than originally designed, to increase the real power output from the machine. For example, these generators would operate at a power factor of 0.95 lag rather than 0.9 lag. This reduces the reactive power (MVAR) output from the machine. This mode of operation does not require any modifications to the generator, as long as it operates within its capability limits. This uprating practice is being used more commonly due to energy shortages.