How do I calculate the kW output on a generator when changing from 60Hz to 50Hz?
i.e. if I have a 70kVA generator at 60Hz producing 56kW, how do I calculate what the kVA and kW's would be if I converted it to 50Hz?
You could estimate that reducing the speed to reduce the frequency from 60 Hz to 50 Hz will reduce the voltage to 5/6 of the original voltage. At the reduced speed and voltage too, the generator could likely be loaded with the same current, so that would reduce the kVA in proportion to the voltage reduction. The torque required would likely not change much, so you could assume that whatever is driving the generator could continue to produce the same torque and the available power would also be reduced in proportion to the speed reduction.
If you know the details of the characteristics of the generator and whatever is driving it, you could make a better estimate.