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).
Dynamo output curves, performance, and temperature control methods, including third brush control.
| Identifier | WestWitteringFiles\V\2January1931-April1931\ Scan072 | |
| Date | 27th March 1931 | |
| -2- In adopting this method we should not so much be calling upon the dynamo to give a better shape of curve as to give the larger output at all speeds when such larger output is required. A better shape of curve, irrespective of head lamp load, is known to be given by providing a shunt winding connected across the main brushes and proportionally reducing the third brush winding whilst at the same time reducing its span on the commutator. This brings us back to the Lucas four-terminal machine exemplified by the Lucas E.575 which we used to use. It will be remembered that in that case the switching and fusing was more complicated and though the output curve with speed was very good, the cutting in (in these particular machines) was not good. We are anxious to do any desired experiment, but on the score of economy and best utilisation of staffs' time, it is well if we can first be agreed as to a specific proposal for experiment on these lines. In regard to the dynamo temperature at its natural output at different speeds, other things being the same, the speed at which the greatest heating occurs on the dynamo is very slightly less than the speed at which peak output is given, in fact so slightly less that we can practically say that the dynamo heats most when on its peak of output speed performance. It is very much cooler when running continuously at the high speeds. In all the curves we give we artificially maintain the dynamo at one temperature for all points on the curve i.e. it is as if we imagine the curve to be run through very quickly without allowing the dynamo time to change. It would be quite true to say that from the temperature point of view it would very definitely be an advantage to get the machine to give greater output at the higher speeds. This problem is still being worked at but all the time from the point of view of retaining the elegant simplicity of the simple third brush control. | ||