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 effects of varying condenser capacity and position on the secondary spark and voltage.
| Identifier | ExFiles\Box 52\3\ Scan299 | |
| Date | 11th December 1917 | |
| Contd. -10a- EFC {E. Fowler Clarke - Electrical Engineer} /T11.12.17. (4) Effect of variation of condenser capacity and position. Assuming the condenser to be connected in its correct position, right across the contact points, and the break to be perfect, then the effect of increase of its capacity is to increase the period of the primary oscillatory current both before and after the instant of secondary spark. Considering the period before this instant, the rate of fall of magnetic flux is decreased, and therefore the secondary voltage is lowered. The effects vary as the square root of the capacity. Thus, if the capacity be quadrupled the period is doubled and the secondary voltage halved. Thus mathematically a comparatively small capacity is desirable, if a good break can be obtained with such. This, however, not being the case on ordinary contact points, a condenser must be provided to act as an alternative path or reservoir for the current which otherwise would form an arc across these points. The best capacity is therefore purely a matter of experiment. At first, addition of capacity increases the secondary voltage, later on it reduces it. Practically the secondary voltage is usually a maximum before sufficient capacity has been added to minimise sparking at the points, and more capacity than that for maximum secondary voltage may be used with advantage. Contd. | ||