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).
Summary of the advantages of American Central H.T. coils, detailing construction, performance, and issues with corrosion.
| Identifier | ExFiles\Box 69\1\ scan0072 | |
| Date | 7th January 1928 | |
| EFC. WC.60. X8710 xXX 7.1.28. AMERICAN CENTRAL H.T. COILS+ We give below a summary of what we consider to be the chief advantages of these coils. (1) Easier and cheaper to manufacture as the case need not be an expensive moulding but could be made of sheet metal. (2) Low resistance secondary winding with maximum insulation from the case. (3) The primary being wound on the outside has maximum heat radiation, also the resistance is automatically increased and an additional ballast could be omitted even if the switch was left on contact. (4) There should be less coronal effect as owing to the secondary being inside it can be more effectively insulated from the air. Coronal discharges occurring at voltages of 6 KV and upwards ionise any air present in the vicinity of the windings and charged metal parts, and the resulting ozone produces deterioration of the insulation forming, after a long period of time, white conducting powder deposit which ultimately results in a breakdown. Oxides of nitrogen which corrode exposed metal parts are also produced. On our standard production coils, the H.T. spring terminal corrodes after a short period and we had a case from a customer of a faulty coil with this terminal almost corroded away by the destructive effect of nitric acid deposited due to ozone. EFC/H.E.West. | ||