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).
Fusing current for main and distributing fuses and the specifications for ammeters.
| Identifier | ExFiles\Box 61\2\ scan0492 | |
| Date | 19th September 1928 | |
| To R.{Sir Henry Royce} from EFC. c. c. E.{Mr Elliott - Chief Engineer} BJ. BY.{R.W. Bailey - Chief Engineer} X2515 X9780 EFC3/T19.9.28. Referring to your R1/M18.9.28 and in particular the fusing current of main and distributing fuses, the fusing current of 15 amperes for 30 S.W.G. copper wire is for an indefinitely long length. For the length we use in our fuse holders the fusing current is more like 28 amperes, so that the fusing current of the main fuse is something less than 3 x 28 amperes, viz, about 80 amperes. Because the ammeter may have to carry this current if a dead earth occurs on the wiring we specify that the ammeters must stand without damage a current of 90 amperes for 3 seconds each way. EFC. | ||