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 from The National Physical Laboratory discussing methods for measuring peak voltage on a condenser.
| Identifier | ExFiles\Box 163\7\ img319 | |
| Date | 13th October 1937 | |
| TELEGRAMS:- "PHYSICS TEDDINGTON" TELEPHONE:- MOLESEY 1380 (11 LINES) 6013 The National Physical Laboratory. Teddington. Middlesex. YOUR REF: RM{William Robotham - Chief Engineer}/RC.{R. Childs}8/JH OUR REF: RD/DHM 13th October, 1937. ALL COMMUNICATIONS TO BE ADDRESSED TO THE DIRECTOR. Messrs.Rolls-Royce Ltd., DERBY. R.C. Dear Sirs, We acknowledge the receipt of your letter dated October 8th. When a condenser is charged from a voltage source through a rectifying valve certain conditions are necessary to ensure that the voltage acquired by the condenser corresponds to the maximum value of the supply. These are dealt with in the two following papers:- (1) Note on the Measurement of the Peak Potential of an Alternating Source. Paterson and Campbell. Philosophical Magazine, 1919, Vol.37, page 301. (2) The Measurement of High Voltages, with Special Reference to the Measurement of Peak Voltages. Davis, Bowdler and Standring. Journal of the Institution of Electrical Engineers, 1930, Vol.68, page 1222. The measurement of the voltage on the condenser requires the use of apparatus which takes no current from the condenser, or as in the case of the sphere gap voltmeter, until the value of the voltage is recorded, at the instant of flashover of the gap. We have found that the response of a sphere gap to direct voltages is very erratic. Performance in this respect can be greatly improved by the use of a radium salt placed near the gap, or alternatively by the use of the metal magnesium as the electrode material. For suitable electrostatic instruments for measuring the voltage (assumed to be of the order 10 to 20 kV) we would suggest that you consult a firm of instrument makers. If it were possible to connect a condenser voltage divider across the supply voltage without appreciably modifying its wave shape and output, a fraction of the supply voltage could be rectified and the peak value measured by means of a | ||