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).
The testing of different types of fuses, detailing fusing currents and material performance.
| Identifier | ExFiles\Box 166\7\ img042 | |
| Date | 18th January 1935 | |
| -3- Ha/Tst.1/WA.{Mr Wallis}18.1.35. Cont'd.{John DeLooze - Company Secretary} (b) The fusing current was taken to be that current, which would melt the fuse within 30 secs., after being raised quickly to that value. In the case of the links, this current was found to be about 90 amperes. With the catridge type, however, the current was only 50 amperes. These, latter, were found to be loaded with 24 S.W.G. plain copper wire. After a number of trials it was found that, when loaded with 22 S.W.G. wire, tinned by hand the fusing current was about 90 amperes. Tests were continued with this loading. (c) This test consisted of finding the current, which, when maintained through the fuse for 30 minutes, just discoloured it. On this test the links showed no signs of discolouration right up to the fusing point; being quite clean when blown. With the catridge fuse this current was from 50 to 55 amperes. The fuse links appear to be made of zinc, or zinc alloy. (d) The volt drop between the terminals of the fuse was measured with currents of 30 and 50 amperes flowing. For the links this was, on the average .035 volt, and .06 volt respectively, while for the cartridge fuse it was respectively .042 volt, and .074 volt. These values increased fairly quickly, with the copper fuse, as it heated up. (e) It was found with the cartridge fuse that if a current near the solder at the ends of the fuse would melt and run out. This is not serious apart from the fact that loose, molten, solder may cause damage elsewhere. H.M.P. solder should obviate this trouble. (f) With the cartridge fuse it was found that, on blowing, the copper wire came into contact with the glass; badly marking it. (g) There was a tendency for the links to twist and kink when being tightened under the terminal screws. This could probably be overcome by the use of locked washers. | ||