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).
Results of an investigation into dynamo control and negative circuits, focusing on fuse performance under different conditions.
| Identifier | ExFiles\Box 61\2\ scan0298 | |
| Date | 1st January 1921 | |
| Contd. -3- does not affect the results of the investigation, which was actually carried out using the 12 ampere wire for the control and negative circuits. The results of this investigation were as follows :- A.{Mr Adams} Battery removed or disconnected from any cause and dynamo run with charging switch on. (1). The maximum control current under these conditions is only very slightly larger than the maximum control current under normal working conditions, whether the dynamo be hot or cold, hence no protection can be obtained by the use of a control fuse in the A case. (2). Fuses of 4½ amperes capacity in the field circuit and 12 amperes capacity in the main negative circuit were therefore investigated. (3). Under normal running conditions with the dynamo cold, it was just possible to blow the main negative fuse at 12 amps., but with the dynamo hot, this fuse was O.K. under all conditions. A fuse of slightly greater capacity (say 15 amps) would not be blown under normal conditions. (4). Running with battery disconnected, with field fuse only, this fuse goes at a dynamo speed of about 1000 R.P.M. when the dynamo is cold and about 1250 R.P.M. when hot, subsequently to which the machine is still somewhat excited on the control winding, but the circulating current in the control winding and from control to negative brush is contd. | ||