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).
Car dynamo performance, brush control, and potential winding modifications to manage output at different speeds.
| Identifier | WestWitteringFiles\V\March1931-September1931\ Scan026 | |
| Date | 9th March 1931 | |
| EFC. HS.{Lord Ernest Hives - Chair} ) FROM R.{Sir Henry Royce} E.{Mr Elliott - Chief Engineer} BY.{R.W. Bailey - Chief Engineer} ) (At Le CanadelHenry Royce's French residence.) C. to SG.{Arthur F. Sidgreaves - MD} WOR.{Arthur Wormald - General Works Manager} PN.{Mr Northey} RR. CAR DYNAMOS. ORIGINAL R1/M9.3.31. X6099 I have noticed that with the usual 3rd. brush control it is natural for the output to fall with speed; if not you cannot get the control at the low speed. I had not noticed that if we put on a few turns (on say 2 of the 4 poles) of series winding the effect of these will be less at low speeds than at high, and so easily maintain the output at the higher speeds. Mr. Clark mentioned something about this but did not say how it could act with a constant current, but as the flux generated by this constant current would be more effective in generating volts when the speed was high it appears that it would not do much harm at low speeds as its effect would be much less than the de-magnetising effect of the armature reaction and the 3rd. brush control. It is also possible to imagine a second shunt winding right across the main brushes that with constant volts would be more effective at increased speed. Such a scheme might cut in earlier than the series winding. I am not sure if Mr. Clark has given us the dynamo temperature at its natural output at different speeds: for instance, is it equally hot with maximum current speeds or with the reduced current at high speed i.e. if run continuously at these speeds. I should have thought that at the high speed and smaller armature and field current the dynamo would be cooler, and hence if we could keep up the output with speed we should get a more constant temperature. Experience has for some time shewn us that we do not want a reduced output with speed as we imagined at one time. Fast drivers want powerful headlights, whereas we thought fast drivers did more charging so we anticipated their overcharging by reducing the rate at high speed. It now seems that this feature comes natural to the 3rd. brush control and is difficult to get away from. R.{Sir Henry Royce} | ||