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).
Continued analysis of dynamo charging outputs and resistance stages for vehicle electrical systems.
| Identifier | WestWitteringFiles\V\2January1931-April1931\ Scan077 | |
| Date | 1st March 1931 | |
| AEC/ADSO.3.31 contd: -4- A somewhat smaller output than this, made effective by the inclusion of one stage of field resistance, is considered to be the full output or charge rate for winter charging conditions. N.B. Although this output is, in similar circumstances, less than the large output, it may not actually be less when the battery voltage rises due to the completion of charge, for in the other case the voltage can never rise in the same way owing to the load of the head lamps. The introduction of a third stage of resistance reduces the charging output rate still further for summer charging purposes. The driver has only to think of two rates of charge, winter rate and summer rate, although in each case there is a field resistance operative. There is this about this three-rate charge arrangement, that the driver, being provided with what is called the full charge rate, is not so likely to remove his head lamp fuses for the purpose of increasing what he might consider to be a reduced charge rate to a full charge rate and thus risk the burning out of the dynamo. With this two stage resistance it is therefore possible for the head lamp lighting output to be set higher than with only a single stage of resistance and, in fact, to such an amount on the dynamo that, were the load of the head lamps taken off, the dynamo would be running at a dangerous setting. We have shown that in the Lucas case, this risk, corresponding to the output shown by curve A, (see below), is definitely existent. Attached will be found blue print sheet of curves labelled 2, upon which are exhibited (all at constant operating voltage of 14.0 and a carcase temperature of 80°C.) the following curves :- I. That of our 56 coil present standard 20/25 machine with a 58°C temperature rise setting. II. That of our 48 coil high output machine with a 65°C temperature rise setting. A.{Mr Adams} That of the Lucas model C5-O type N-O machine with what would be a dangerous temperature rise setting were the machine run with battery load only. B. That of the same machine with a lowered temperature rise setting of 58°C arrived at by advancing the control brush 2° round the commutator from the makers position. | ||