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).
Continued discussion on dynamo fuses, voltage rise, and protection of the electrical system.
| Identifier | WestWitteringFiles\G\September1921\ Scan70 | |
| Date | 19th September 1921 | |
| EPCS/T19.9.21. -2- Contd. dynamo, and moreover to be operated at a much higher voltage than normal, in the absence of the dynamo field fuse, especially if the speed of the car be fast, owing to the rise of voltage on the dynamo, which may go to 40? Thus, there would be a possib- ility of roasting the dynamo. This fuse, therefore, does not protect the dynamo, it only protects the battery from earths on certain wires in connection with the dynamo and battery ignition. The result is to render the dynamo more liable to damage, and from our experience we should recommend either (1) Omitting the fuse in the dynamo circuit and relying on the excellency of the job for preventing earths on those wires, as we have to do in the case of the main positive wire leading from the battery. or (2) Providing a dynamo field fuse to take care of excessive dynamo voltage rise. We prefer (1). viz. the omission of all fuses. (except distributing fuses) This fuse also could not save the battery from running down, should the cutout stick on contact with the switch left on, because if fine enough to fuse in this circumstance, it would not be heavy enough to carry the normal charging current, so that the only protection it affords to the system is in the case of earths occurring on some of the wires immediately in connection with the four point switch. Cannot these be depended upon to be immune from earths as much as the main positive wire leading from the battery ? There is, of course, no arrangement which is | ||