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).
Technical explanation of the characteristics of a shunt wound machine for battery charging.
| Identifier | ExFiles\Box 61\2\ scan0215 | |
| Date | 12th December 1925 guessed | |
| -3- contd. With an ordinary shunt wound machine these characteristics are such, for instance, not crossing one another at all, that whatever the characteristic of the external circuit, increase of speed (except in very extreme cases) is always accompanied by increase of both amperes and volts. It will be seen that it would be possible for a shunt machine to charge a battery of normal voltage about one third of the normal voltage of the machine, the battery having a charging volt-ampere characteristic something like B. In any case, with a shunt wound machine, once we have reached the point in speed where its O.C. voltage is equal to that of the battery, we can by speeding up continue to increase the amperes until we get what we want, and it is not really generally necessary to think what the volts are at all. But if we are running the machine very slowly and charging the battery very slowly, we are working on the top portion of the characteristic. When we have raised the speed so as to make the characteristic like that one containing the points Q and R, it is clear that we are actually working at a point S on the characteristic, so that when any change in the volt-ampere characteristic of the external circuit occurs, the rise of volts and amperes will go together, and this applies in particular if the resistance and/or the E.M.F. of the battery rises for any reason. Contd. | ||