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).
The issues and experimental modifications of a new shunt dynamo.
| Identifier | ExFiles\Box 179b\2\ img211 | |
| Date | 17th December 1932 | |
| ORIGINAL K.{Mr Kilner} From He/Wst. c. to HY.{Tom Haldenby - Plant Engineer} c. to Ry/Ro.{C. C. Rose - Export Manager} He/Wst.2/MA.17.12.32. Y6637 NEW SHUNT DYNAMO FOR PARCHIMENE, JAPAN AND RONSPORT TO D.SCHON 348. This dynamo as received in its design form was found to give a poor cutting in speed and low output. The sparking at high speeds was also abnormal. We attribute the poor performance to :- (a) The armature and field core lengths being too long thus putting up, out of proportion, the resistances of the windings. (b) The use of too low a number of ampere turns on the field core due to the use of bolts securing the end plates instead of screws into the carcase. (c) The effect of an unstable main field causing armature reaction effects at high speed. We accordingly experimentally modified this machine to make it reasonably OK. for putting on experimental cars. We did this by :- (1) Reducing the diameter of the armature to 3.078" and winding 3 turns per coil of 17 S.W.G. wire instead of 4 turns. This gave us 12 conductors per slot instead of 16. The effect of doing this was to reduce armature reaction effects, due to a decrease in the armature reluctance, and increase the max. output. (2) Increasing the pole core proportionately with the reduced armature diameter and winding on 187 turns per pole of 21 S.W.G. wire instead of 21 S.W.G. These modifications produced a big difference in the performance of the machine, the cutting in point being considerably better and owing to the main field being much stronger, and more stable, we were enabled to run up to very high speeds without undue sparking at the brushes. The machine in its present state, however, is still unsatisfactory with regard to its max. peak output for a given temp. rise. This, at the moment, is only about 10.5 amperes and we propose to carry on | ||