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- Sep 7, 2024
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Hello Star Tech,That RPM range drops the Hz down to 57.5-58.34 Hz and not 59-60 Hz which would be 3540-3600 rpm for a two pole alternator.
Formula is RPM / 60 for Hz. The formula changes to RPM / 30 for 4 pole alternators but of these are on diesel generators.
If they are servo-controlled throttle they maintain a close target speed goal of 60Hz (3600 RPM).
When it comes to the conventional linkage type with a surge spring I try to set them at 61.5Hz under no load conditions and then test for governor droop under full load. I seldom see a properly loaded conventional small generator drop below 58Hz unless there is a governor issue or the motor is just plain worn out and compression is low.
I would prefer to have a larger industrial diesel 4-pole generator when times get tough, but I just don't have that in the budget, and I do not have enough power outages (yet) to justify going any larger than what I have. Aside from that, I would likely have to rewire direct for larger input automatic transfer switch. Even worse is the price of diesel fuel, so I do not see any savings happening in the long run.
Even though my generator is rated for 15KW continuous running Watts, the most it can produce through a 50A outlet is 12KW. This is what confuses people who buy larger portable generators. The total rated Wattage is calculated by adding the output of all the outlets on the generator and not just the 1 outlet.