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).
Electrical test results and resistance adjustments for a dynamo and battery system following a two-hour run.
| Identifier | ExFiles\Box 48\3\ Scan165 | |
| Date | 6th December 1920 | |
| Contd. -6- EFC {E. Fowler Clarke - Electrical Engineer} 1/T6.12.20. Figures exactly similar to the above for the instrument hot, after running two hours in connection with a 12 volt dynamo and battery, with 10 amperes through its series coil, were as follows :- Volts and amps. on shunt coil to operate = 14.2 volts, .190 amp. (74.8 ohms) after operation the current dropped to .120 amps. (118.3 ohms) Resistance inserted by auxiliary contact = 43.5 ohms. Volts and amps. on shunt coil to de-operate (battery disconnected) = 10.5 volts, .090 amp. (116.7 ohms). Amperes after de-operation = .145 on same voltage (72.5 ohms). Now connecting the battery it was found that at the point of de-operation the voltage was 12.8, shunt amperes .110 series coil amperes 2.4 reverse. It was now judged that the resistance and opposition effect inserted was not as large as it might be, i.e. not as large as to drop from the point V to a point W on the spring line PQ, but only to a point w somewhat above W. We therefore inserted additional resistance in the wire marked X on the diagram and adjusted this resistance to an amount which did not permit of any vibration of the armature (at cutting in voltage) in the neighbourhood of the point where the auxiliary contact opened. In other words, we first altered the position of w to some such point as w' and then adjusted it back again to coincide as nearly as possible with W. We found this additional resistance to be in the neighbourhood of 15 ohms. | ||