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).
Investigation into minimum fusing currents and the testing of a new distribution board with a Lucas switchbox.
| Identifier | WestWitteringFiles\D\February1920\ Scan3 | |
| Date | 1st February 1920 guessed | |
| Contd. -2- Ckl/T3.2.20. It will be seen from the above that the minimum fusing currents of any fuses which can be used must be approximately as follows :- Field 4.5 amps. Control. 20.0 amps. Main negative. 15.0 amps. There is less margin allowed on the control and negative fuses owing to the fact that, as reference to the table will show, the maximum currents in the latter two cases only exist at certain speeds. The control current is a maximum at the highest speeds, the main negative current is a maximum shortly after cutting in. The investigation was carried out in connection with the testing of the new R.R. distribution board on the bench, the two fuse holders of this board being used, as designed, for the control and main negative fuses. A four point switch and the field fuse holder of a Lucas switchbox were used properly connected to supply those other two items required in the investigation. The cut-out on the R.R. distribution board was used but an auxiliary switch was shunted across the contacts to imitate the sticking on of the cutout. The fusing currents of the fuse wires in their respective fuse holders were 4½ amperes for the field and 12 amperes for the field and control. We had not any fuse wire suitable for 15 or 20 amperes, but the lack of this Contd. | ||