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).
The performance variations of ignition coils and the role of condenser capacity.
| Identifier | ExFiles\Box 54\5\ Scan173 | |
| Date | 29th December 1921 | |
| contd:- -3- EFC {E. Fowler Clarke - Electrical Engineer} 2/LG29.12.21. ---------------- definite conclusions. For instance, it has appeared from our experimental work that coils that happen to be identical in construction and treatment are slightly different in results and we can only attribute this to complicated differences of leakage conductivity and inductivity and of insulations. As an instance of this, it is possible to stop a coil which is regularly firing to set gaps, completely, by placing a few square inches of tin foil on the outer side of the case and earthing it. One cannot describe this effect as a capacity effect as it does not produce the same result on the sparks as would a similar amount of pure capacity. There must be loss of energy due to the dielectric hysteresis and perhaps a certain amount due to leakage conductivity. This phenomenon is a little more pronounced with bakelite cases than with stabalite cases. / X4430. X4423. X2572 As regards the Condenser capacity, it would appear that other things being the same (supposing that it is already arranged to effectively quench the primary sparking at break) this, for the best results, should vary with the magnitude of the current at the instant of break. The current at break is small with the ignition running at high speed, or with the ignition running at very slow speed when the ballast resistance is hot or if the battery volts are low due to the Starter Motor current, and it is in these circumstances that the condenser capacity may be too big to allow the secondary to produce the necessary voltage and a good deal bigger than necessary to quench the primary spark. In increasing the capacity of the condenser, therefore, we must contd:- | ||