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).
Letter to Mr. Symons of H.D. Symons & Co. Ltd. discussing the electrical principles and components of H.T. systems.
| Identifier | ExFiles\Box 61\1\ scan0180 | |
| Date | 11th March 1931 | |
| Mr. Symons, Messrs. H.D. Symons & Co.Ltd. Kingston Hill, Surrey. 11th March, 1931. -3- The combination of battery, trembler coil and spark gap is really only a means of stepping up the 6-volts of the battery to a high D.C. potential and collecting it on the H.T. D.C. main in much the same manner electrically as a hydraulic ram acts hydraulically. The positive pressure on the H.T. D.C. main in relation to the datum conductor is measured by the use of a calibrated sphere gap H.T. voltmeter reading directly, the sparking over between the balls being a known calibrated function of the distance between them as indicated by the axial and circumferential divisions cut on the head carrying the movable ball. The insulation on test, built up if necessary to the required thickness, is subjected to the action of the steady D.C. pressure by being placed between an H.T. plate and an earth conductor, and a microammeter with shunted condenser registers the flow of return current after this has passed through the insulation on its way back to the negative of the battery, the function of the condenser in parallel with the micro-ammeter being a smoothing action to suppress the existance of H.F. surge voltages across the terminals of the instrument which might cause damage by internal sparking. This condenser can conveniently be of approximately .2 mf. The main H.T. condenser may conveniently be of .3 mf. but should be of a type capable of a working pressure of 12,000 volts continuously and rated accordingly. | ||