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).
Theoretical analysis of open and closed circuit ignition coil systems, comparing efficiency and speed of operation.
| Identifier | ExFiles\Box 52\3\ Scan297 | |
| Date | 11th December 1917 | |
| H.R. 235 a (100 T) (S.F. 816 6.8.19) G. {Mr Griffiths - Chief Accountant / Mr Gnapp} 2460 Contd. -9- EFC {E. Fowler Clarke - Electrical Engineer} 2/T11.12.17. and increase this voltage and the total primary resistance at the same time, and proportionally, by the addition of ballast resistance, in which case we get a still further increase in the speed of operation without any loss of efficiency. (b). The energy supplied by the battery per spark is least of all, (or the efficiency of magnetic field production is greatest of all), when Co is as large as practically possible, in relation to C (once more supposed fixed). Since Co = E {Mr Elliott - Chief Engineer} /R we may make E as large as possible, R as small as possible, or both. In any case, the rise of primary current to its specified value C takes place as quickly as possible, only being limited in the extreme cases by the inductance (which we are supposing fixed). This is the principle of the open circuit system, and gives a high efficiency, as very little energy is wasted on resistance. In the more usual closed circuit systems, we cannot increase E or reduce R unduly because we want to limit the current at low speeds, and in case the contact breaker is left on. In such systems, the claims of rapidity of action and efficiency are to some extent contradictory. This is, at any rate, the case when we have a fixed voltage and are drawing a comparison between two coils with different rates of working. The above points are exemplified in the numerical tabular comparison of the Remy 12 and Remy 6 cylinder coils. | ||