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).
Observation of the field break spark on charging switch contacts when the dynamo charge is switched off.
| Identifier | WestWitteringFiles\S\September1928-October1928\ Scan088 | |
| Date | 25th September 1928 | |
| To R.{Sir Henry Royce} from EFC. EFC3/T25.9.28. CHARGING SWITCH. X8730 Answering your RL/M22.9.28, we have made a visual observation of the character of the field break spark when the dynamo charge is switched off on full output, and we have examined the contacts of switches whose operation has been to break the field repeatedly to take the dynamo off charge. We have not yet, however, made a systematic test of a large number of breaks in order to see whether the burning is cumulatively bad in such circumstances. We are now arranging to make such a test on a R.R. switchbox arranged for automatic mechanical switching which will be repeated a large number of times. Our impression from experience so far is that the burning effect of the field break spark at the contacts is not as bad as might at first sight be thought, and particularly so where a quick break takes place. Undoubtedly the effect is less bad the quicker the break, and we have no evidence whatever that the quickest break that can be made is anywhere near putting up sufficient voltage stress to cause any damage to the winding of the field itself. EFC. | ||