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 comparing the electrical properties of four different powder samples in a table format with analysis.
| Identifier | ExFiles\Box 61\1\ scan0129 | |
| Date | 12th September 1930 guessed | |
| -5- TABLE I - POWDER VARIATION. 1. 2. 3. 4. Electrical breakdown strength at 15°C. volts/mm. ........ 4,500 6,500 12,000 7,500 Electrical breakdown strength at 100°C. volts/mm. ........ Low 2,000 8,000 4,000 Insulation resistance 15°C. megohms at gap .650 > 3,000 > 3,000 > 3,000 Insulation resistance 100°C. megohms at gap ............ 49 98 1,360 422 Phase angle power loss 5.6 3.9 0.75 1.35 Specific inductive capacity ............ 9.4 8.7 3.2 4.6 Note - The last two figures taken at a frequency of 100,000 cycles per second. Criticism of such results is almost unnecessary. Sample 3 was taken from a delivery received soon after a complaint had been lodged, it was an excellent sample. The power loss and s.i.c. should be noted particularly; the high value of these figures in all but sample 3 renders the material unsuitable as a first-class insulator for either high voltage work or radio frequencies. The author's opinion is that, for safety, all mouldings required for exacting electrical work should be stoved for four hours at 110°C. to "stabilise" the resin, prevent shrinkage in service and improve their electrical properties. | ||