An electrical power generator system having: an input shaft for receiving a rotary input drive; plural output shafts (32a, 32b) connected to the input shaft by respective gear shifting arrangements thereby providing different gear ratios (33a-c) between the input shaft and each output shaft; and plural electrical generators (41a, 41b) powered by rotation of the respective output shafts, electrical power outputs of the generators being combined to supply a total power to a load; wherein 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; the system further having a controller configured to control the gear shifting arrangements, the controller changing the gear ratios of the output shafts when the rotation frequencies of the output shafts reach a limit of the narrower range of rotation frequencies by sequentially performing the steps of: (i) disconnecting a selected one of the generators from the load such that the remaining connected generator(s) increase their electrical power output(s) to continue to supply the total power to the load, (ii) changing the gear ratio between the input shaft and the output shaft of the disconnected selected generator so that the rotation frequency of the output shaft of the selected generator moves away from the frequency limit to remain within the narrower range of rotation frequencies, (iii) reconnecting the selected generator to the load, and (iv) repeating steps (i) to (iii) for each of the other generators in turn until the gear ratios of the plural generators are changed. an input shaft for receiving a rotary input drive; plural output shafts (32a, 32b) connected to the input shaft by respective gear shifting arrangements thereby providing different gear ratios (33a-c) between the input shaft and each output shaft; and plural electrical generators (41a, 41b) powered by rotation of the respective output shafts, electrical power outputs of the generators being combined to supply a total power to a load; wherein 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; the system further having a controller configured to control the gear shifting arrangements, the controller changing the gear ratios of the output shafts when the rotation frequencies of the output shafts reach a limit of the narrower range of rotation frequencies by sequentially performing the steps of: (i) disconnecting a selected one of the generators from the load such that the remaining connected generator(s) increase their electrical power output(s) to continue to supply the total power to the load, (ii) changing the gear ratio between the input shaft and the output shaft of the disconnected selected generator so that the rotation frequency of the output shaft of the selected generator moves away from the frequency limit to remain within the narrower range of rotation frequencies, (iii) reconnecting the selected generator to the load, and (iv) repeating steps (i) to (iii) for each of the other generators in turn until the gear ratios of the plural generators are changed. (i) disconnecting a selected one of the generators from the load such that the remaining connected generator(s) increase their electrical power output(s) to continue to supply the total power to the load, (ii) changing the gear ratio between the input shaft and the output shaft of the disconnected selected generator so that the rotation frequency of the output shaft of the selected generator moves away from the frequency limit to remain within the narrower range of rotation frequencies, (iii) reconnecting the selected generator to the load, and (iv) repeating steps (i) to (iii) for each of the other generators in turn until the gear ratios of the plural generators are changed.