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 cut-in speed and the instability of the dynamo-battery-load system.
| Identifier | WestWitteringFiles\T\2July1929-December1929\ Scan181 | |
| Date | 14th December 1929 | |
| LFC2/AD14.12.29 contd. -4- We consequently recommend that we should be cautious in too far increasing the road speed at which dynamo cut-in occurs. It will be gathered from the above that in our opinion it is impossible with any of the above outlined variations of the present arrangement satisfactorily to cater for all cases in one machine or that almost inevitably either overcharging or undercharging troubles will occur. An aspect of the whole matter that has recently occurred to us from actual first hand experience is that there is an instability in the dynamo - battery - load system for any steady value of the average load. Starting initially from a condition in which the average load is balanced by the output of the dynamo, the effect of a slightly lower average load is greater in the direction of overcharging than is at first sight apparent. Not only is the voltage and therefore output of the dynamo thereby increased, but the consumptions of (a) Lamps (b) Starter Motor, etc. are not increased proportionally, and in the case of the starter motor the actual ampere-minute consumption is very probably reduced. On the other hand, if the average load is consistently only a little greater than the output in the initial condition the at first gradual loss of ground of the battery lowers the voltage of the system and so reduces the dynamo output. | ||