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).
Note explaining the standardized definition of an 'ideal battery' for comparing dynamo performance.
| Identifier | WestWitteringFiles\E\July1920\ Scan26 | |
| Date | 22th July 1920 | |
| Contd. -2- EFC1/T22.7.20. NOTE:- To explain what we mean by an ideal battery, it will be appreciated that unless matters are arranged such that the terminal voltage and the ampere output of a dynamo, or combined dynamo and regulator, bear a definite scheduled relation, the relative performances of different machines are not strictly comparable and particularly not so in the case of vibrator regulator control. We therefore have standardised, as the ideal volt ampere relation for a battery circuit fed by a cold dynamo, an open circuit E.M.F. of 12.4 together with a combined resistance of leads and battery of .1 ohm and a battery E.M.F. rise of .1 volt for every ampere delivered to the battery. The nett result of this is that for every ampere delivered, an addition of .2 volt to the 12.4 initial back E.M.F. is allowed. Similarly the standard volt ampere relation for a battery being charged by a hot dynamo is 13.6 volts at no amperes, rising by .1 volt for every ampere delivered. A table of these two standard volt-ampere characteristics is attached. Open Circuit Volt-Speed Curves 10 to 17 Volts. X.2014 a X.796 X.295 So far as our investigations have proceeded, with the exception of the large Lucas A.400 machine, the Bosch dynamo gives the lowest speed for a given voltage under similar temperature conditions. Confining our attention as we are now doing to dynamos which are either Contd. R.R. 199 (250T) (SD676 19-7-17) MPI80865 | ||