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).
Test report on a production sample of Bakelaque sheet insulation, comparing its performance to an original sample.
| Identifier | ExFiles\Box 39\3\ Scan322 | |
| Date | 28th February 1930 | |
| X3513. COPY. AD.53. 28.2.30. X.3513. BAKELAQUE SHEET INSULATION FROM PRODUCTION. The sample mentioned in Ry/RD5/DM{D. Munro}24.2.30 has been examined and tested similarly to the sample of this material first submitted by the makers in October 1928, report ref. AD.15. of October 20th 1928. It is of inferior appearance to the original piece and the thickness varies from .039" to .042". There are various streaks, dark spots and dull patches on the surface. On receipt it was first tested for leakage on trembler coil and valve apparatus with the following results :- Rising. | Falling. Temperature °C. | 20 | 40 | 60 | 80 | 100 | 80 | 60 | 40 | 20 Leakage micro-mho mils. | .513 | 2.28 | 3.89 | 8.34 | 12.00 | 6.18 | 3.37 | 1.06 | .075 From thisit will be seen that the leakage was considerably worse than was the case with the similar original sample of cloth-base bakelaque at first, though the improvement on cooling down again after heating makes the final difference only slight. Whilst taking the last reading the piece broke down at a voltage estimated by the sphere gap of 18,200, or takingthe thickness at .040" of 455 volts per mil. The piece was now clamped at a spot away from the broken down part, between electrodes connected to the H.T. transformer, and withstood 19,100 volts R.M.S. or a peak gradient on 675 volts per mil without failure. The figure obtained with the original sample was 477 volts per mil. | ||