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).
Test results and temperature analysis for a dynamo under various conditions.
| Identifier | WestWitteringFiles\K\September1923\ Scan81 | |
| Date | 28th September 1923 | |
| Contd. -2- EFC5/T28.9.23. Speed. R.P.M. Main volts. Field volts. Field amps. Field Ohms. 725 15.2 10.0 2.8 3.57 960 23.0 15.3 4.1 3.73 1035 26.5 17.5 4.65 3.76 1325 37.0 24.3 6.3 3.86 1540 45.5 30.0 7.7 3.9 1810 55.5 36.5 9.2 3.97 2000 63.0 41.0 10.3 3.98 NOTE:- (1) Cold field resistance at 18°C is 2.6 ohms. (2) It may be mentioned in passing that lifting the negative brush had no effect on the field volts and amperes. A further test consisted in finding out at what rotational speed the dynamo, when mounted normally on its cast iron rig (bolted to cast iron table) would maintain, in this unloaded condition, its carcase temperature of 75°C, measured by thermometer in the usual way, the ambient temperature being 20°C. This speed was found to be only 1050 R.P.M. and the corresponding quantities are:- Main volts 28 Field volts 18 Field amps. 5.3 Field ohms 3.4 This is considered to be the carcase temperature on the rig which corresponds to a reasonably safe temperature in normal working 85° to 90°C on the chassis, so that a chassis road speed greater than 14 m.p.h. with the dynamo in this condition would be bad for the dynamo. EFC. | ||