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).
Instructions and results for a voltage breakdown test on various insulating materials.
| Identifier | ExFiles\Box 24\2\ Scan229 | |
| Date | 26th January 1923 | |
| RR 238 (300 Bks.) (SF 152. 6-11-18.) MP 197880 ROLLS-ROYCE LIMITED. INSTRUCTIONS. To: E.F.C. Order No: P.B.76 (2) Customer's No.: X 1109 X 3513 and the faces so adjusted as to get the pressure as near as possible equally distributed over them. The fuses were then inserted, the primary short circuiting bar removed, the switches closed, and the resistance cut out with a pause of five seconds on each stop, the voltmeter readings being observed in the meantime. N° of Sample | Material | Thickness | Voltage Reading | Trans. Ratio | Breakdown Voltage | Volts per Mil. 1. | Paper | .0025 | — | 12.5 | — | — 2. | Oiled Silk | .002 | 126.0 | 25.0 | 3,150 | 1,575 3. | Diamond Fibre | .013 | 151.5 | 25.0 | 3,790 | 291 4. | Bakelite | .020 | 118.5 | 100.0 | 11,850 | 593 Signed: Cont'd This Sheet must be filed on completion of the work. | ||