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).
Protection of a dynamo-battery system using fuses.
Identifier | ExFiles\Box 61\2\ scan0365 | |
Date | 25th August 1920 | |
R.R. 199 (250T) (SD676 19-7-17) MP 18.865 X. 2515 EFC3/T25.8.20. To R.{Sir Henry Royce} from EFC. c. to CJ. c. to E.{Mr Elliott - Chief Engineer} c. to Bn.{W.O. Bentley / Mr Barrington} c. to Dn. c. to PN.{Mr Northey} X. 25151 PROTECTION OF DYNAMO-BATTERY SYSTEM. X. 294. X. 295. BY FUSES. (1) The sole object of a main fuse in the dynamo battery circuit would appear to be to prevent discharge of the battery, should the cutout stick on. Therefore, it should be quite unnecessary with a perfectly reliable cutout. (2) In the case of a dynamo such as the Smith with no control winding complication, there are two alternative positions for the main fuse, shown in diagrams Fig. 1 and Fig. 2 on sheet attached. Each appears to have advantages and disadvantages not possessed by the other. (3) In Fig. 1 the main fuse has to carry the field current from the battery with dynamo stopped and cutout stuck, but not in Fig. 2. Conversely with dynamo in normal operation, the main fuse has to carry the field current from the dynamo in Fig. 2. but not in Fig. 1. Therefore the range between normal and abnormal main fuse currents in Fig. 1 is greater than in Fig. 2. by twice the amount of field current, thus allowing a safer fuse. This is the advantage of the Fig. 1 position. (4) If one can rely in every case upon the field fuse being replaced with the correct wire, Fig. 1 should be the better arrangement. Should we, however, have to consider the possibility of the field fuse being replaced with incorrect wire taking a much larger fusing current, then Fig 1 is dan- Contd. | ||