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).
The performance characteristics of generators and their interaction with batteries and external circuits.
| Identifier | ExFiles\Box 61\2\ scan0218 | |
| Date | 12th December 1925 guessed | |
| -6- contd. the performance of generators it is very important to compare them on the same external circuit characteristic. It may be considerably different on two similar size batteries if they have different internal resistances, and will obviously be a higher output for the higher resistance at all speeds except low ones. Now, because we are going to work the machine normally at lower voltage than corresponds to its speed and full excitation, we provide the field with a coarser winding. If, therefore, the battery is disconnected, i.e. the resis- tance of the external circuit is made infinite, the working point reaches the top of the characteristic curve for the speed at the moment, where the volts are very high and the amperes zero, and of course, the field winding gets excess- ively overloaded. This condition is initially guarded against by the use of a field which melts when the battery is disconnected and the charging switch put on. It will be understood that (1) We do not really want the condition in which rise of volts and amperes can occur together. (2) We cannot avoid this because it is an essential result of working in a region of the volt-ampere characteristics at different speeds, where rise of speed gives a fall of current after the initial rise. Contd - | ||