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).
Page outlining tests on fibrous insulating materials, specifically focusing on electric strength.
| Identifier | ExFiles\Box 24\2\ Scan223 | |
| Date | 21th February 1922 guessed | |
| FIBROUS INSULATING MATERIALS. 799 straight line, in two opposite edges of the material. Insert pieces of 1/16 in. brass rod with square ends, as shown in Fig. 8, thereby making the path through the material less than the path across the surface of the material. It is essential that the two holes should be opposite each other and that the brass rod should not be a tight fit in the holes. The material should be drilled slowly so that the drill does not exert any wedging action which would tend to open up the layers. 13. TESTS AT HIGH FREQUENCIES. Investigations are being carried out with a view to drafting a suitable test to determine the electric strength at high frequencies. Fig. 7.—Arrangement of specimen for longitudinal breakdown test. Diagram 7 Labels: Insulating material, BRASS, Sample, 1/8” Dia, 1”&2”. Part II.—ABRIDGED TESTS ON ELECTRIC STRENGTH. The following methods for the determination of the electric strength of fibrous insulating materials are recommended when it is not required to ascertain the characteristics of the material in such detail as provided for in Part I. (a) Conditioning. (i) Prior to test the materials shall be exposed to the “Normal” atmosphere as detailed in Clause 3 (a). (ii) If the material claims to have special non-absorptive properties, it shall also be tested after exposure to either “Damp” or “Tropical” conditions, as detailed in Clause 3 (c) and (d). (b) Method of Expressing Electric Strength. The recognized method of expressing the electric strength of materials subjected to these abridged tests shall be the voltage required to produce breakdown in one minute when the material is at a temperature of 90° C. For ease of comparison the volts per mil, followed by a statement of the thickness to which it refers, shall also be given. In the past it has usually been the practice to take the electric strength of the material at air temperature, and by a rapid application of the voltage. Until the recognized standard, of one minute at 90° C., has come into general use, it may occasionally be desirable, for comparative purposes, to determine also the electric strength when the voltage is rapidly applied at air temperature. (c) Time-voltage Curves. In order that the voltage required to produce breakdown in one minute may be accurately determined, the following procedure is recommended:— Note: Hole has tapered bottom but brass rods are to have square ends Fig. 8.—Alternative arrangement for longitudinal breakdown. Diagram 8 Labels: 1/16” Dia. Brass Rods, These spaces to be filled with tinfoil, Sample. | ||