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).
Analysis of the auto switch and dynamo, considering additional protection via a fourth wire and the effects of temperature on the system.
| Identifier | ExFiles\Box 59\1\ Scan270 | |
| Date | 15th February 1928 guessed | |
| -2- Contd. coils of the auto switch and the control brush of the dynamo. The practical difficulty at once apparent about this is that it means a fourth wire from the dynamo (to the auto switch) and another terminal on that machine connected to the control brush. Such an idea has been carefully tried out on the bench, and, suitably proportioned, it does give the expected additional protection, though with some slight variable effect on the operating voltage of the auto switch under normal running, due to the fact that the voltage operative on this coil varies considerably with the speed. It was concluded that the variation experienced was not such as would interfere to too great an extent with the normal operation of the auto switch and that were it not for the extra complication involved and the extra wire to the dynamo terminal mentioned above, an advantage would be gained by its use, viz. the advantage of a practically complete protection of the system against happenings against which the system would not be protected with the normal arrangement of the auto switch. Note. Resistance wire was used for the above experimental coil as being the more convenient way of getting a small number of ampere turns with a given voltage. (2) Temperature effect. It has been mentioned that there is some slight difficulty due to - (a) Rise of resistance of the main auto switch shunt coil with temperature. (b) The fall of battery E.M.F. with temperature. | ||