From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Technical explanation of generator characteristics, shunt wound machines, voltage, and amperage.
| Identifier | ExFiles\Box 61\2\ scan0216 | |
| Date | 12th December 1925 guessed | |
| -4- contd. This will give us a characteristic such as C, cutting the generator characteristic at T, both the volts and amperes being increased. All the above is with reference to the plain shunt wound machine, and in working such a machine low down on its characteristic, we are naturally working the machine inefficiently, because, though we are getting perhaps the maximum amperes of which its armature is capable, we could get the same amperes at roughly speaking three times the voltage, if we made the external circuit suit the machine. This would not load the armature any more, but would only increase the commutation duty due to the higher re-active voltage; In passing, we can always get more output (in volts, not in amperes) in any shunt machine by increasing the speed, provided we make the field winding finer to suit the higher voltage, the only limits in this direction being a mechanical one of speed and an electrical one of commutation. Returning, however, to operation at the point S on the shunt machine, it will be seen that we are working on a weaker excitation than normally, because the excitation of a shunt machine is made to suit the voltage on the top portion of the characteristic at normal speed. If, however, we re-wind the field winding to suit the lower voltage we can, if we choose, run the generator/on this lower voltage, Contd - | ||