A sudden increase in the load on a generator can cause the generator to slow down. The engine for the generator takes time in order to respond with more power for the increase in load. When the generator speed is decreased the output frequency will drop. If the output frequency drops below the operating threshold or the knee frequency, the AVR will reduce the output voltage in order to reduce the active load on the generator. Reducing the active load on the generator will enable the generator to return to the nominal voltage and frequency at a faster rate.
The R250 AVR has two different modes of recovering from a block load. The desired mode of recovery that is selected for the AVR is selected with the same switch that is used in order to set the nominal operating frequency for the AVR. The two operating modes are referred to as Constant Volts per Hertz with Knee Frequency and Load Acceptance Module (LAM). The desired operating mode will need to be determined by the loading conditions for the generator.
Refer to Service Manual, KENR9008, "Constant Volts Per Hertz with Knee Frequency Operation" or Service Manual, KENR9008, "Load Acceptance Module Operation" in order to gain a better understanding of the two different operating modes.
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