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).
Explaining experiments with series turns on shunt dynamos to suppress sparking at high speeds.
| Identifier | ExFiles\Box 60\3\ Scan217 | |
| Date | 18th March 1933 | |
| 86092 From Hs{Lord Ernest Hives - Chair}/Wst. D.{John DeLooze - Company Secretary} to Sge C. to Eor. C. to W.Hy.{Tom Haldenby - Plant Engineer} B. to PMR Hs{Lord Ernest Hives - Chair}/Wst.2/MA.18.3.33. VIBRATOR CONTROLLED DYNAMOS. Re. R.5/M.10.3.33. We ought to explain more fully our reason for trying a few series turns on the main poles of our shunt dynamos in order to suppress sparking at high speeds. We wound the main poles with 20 SWG. wire of as many turns as possible, and we found this winding gave the least field distortion at high speeds consistent with a minimum field current. This winding however gave a bigger temperature rise on the whole machine than the 21 SWG. winding as might be expected owing to the increased ampere turns. The temperature rise limited our maximum safe output from the dynamo and the idea of trying series turns was to be able to revert to the 21 SWG. winding which gave us the maximum output for a given temperature and produce the same field rigidity at high speeds by the series turn effect. A preliminary experiment confirmed our theory as we got a higher output from the machine and the sparking at high speeds was reasonable. We found on this preliminary experiment that only a very few/turns were necessary as any increase in this direction /series produces an unstable condition of the main field magnetic circuit at high speeds where the regulator is inserting resistance into the shunt field, i.e. we must not allow the series effect to appreciably strengthen the main field at high speeds where we are trying to weaken it in order to control output. The whole idea at the moment is purely experimental and we tried it as it seemed an easy way to maintain the high output from the machine for a given temperature rise with sufficient suppression of sparking at higher speeds We have thought of the possibility of small inter poles on the large 40/50 HP. machine and we would welcome your views regarding these. Hs{Lord Ernest Hives - Chair}/Wst. | ||