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).
Electrostatic and dielectric losses in the Goshawk ignition coil and the choice of casing materials.
| Identifier | ExFiles\Box 45\4\ Scan073 | |
| Date | 11th November 1922 | |
| To EFC. from R.{Sir Henry Royce} COPY RL/M11.11.22. X.4079 - GOSHAWK IGNITION COIL. X.3513. You seem right in assuming that it is not simple electric leakage due to the material of the case, and evidently your views that it is due to the electrostatic dielectric losses also. It is probably due to the natural properties of the gum, and the Elo may contain more gum than mouldensite. Evidently from experiments the stabalite material has quite different characteristics and our safest policy will be to use stabalite cases for the immediate supplies. Energy losses in the H.T. system must evidently be kept low by reducing the electrostatic capacity and dielectric losses of the whole system. One should realise that the L.T. circuit and terminals are earthed connections to the coil case and apparently these could with advantage be brought down the middle of the coil inside instead of close to the outside. The outer layers of the secondary must of necessity act as one plate of a condenser and be surrounded with a suitable material having extremely low di-electric losses right up to temperatures of 100°C. We shall leave it to you to find out what material is best, and the choice of possible materials. We have noticed that some of the cheap coils have a paper tube. Contd. | ||