An electrical power generator system has: an input shaft for receiving a rotary input drive; plural output shafts connected by respective gear shifting arrangements to the input shaft thereby providing different gear ratios between the input shaft and each output shaft; and plural electrical generators powered by rotation of the respective output shafts, electrical power outputs of the generators being combined to supply a total power to a load. The input shaft operates over a range of rotation frequencies, and the gear shifting arrangements are configured to shift the gear ratios between the input shaft and the output shafts such that the output shafts operate over a narrower range of rotation frequencies.