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).
Letter to Lucas Electrical Co. Ltd. regarding the optimal positioning and combination of fuses in a dynamo circuit.
| Identifier | ExFiles\Box 61\2\ scan0320 | |
| Date | 17th February 1920 | |
| X.2575 c. Bu c. By c. Da.{Bernard Day - Chassis Design} c. EP.{G. Eric Platford - Chief Quality Engineer} Ck{Mr Clark}3/T. 17th February, 1920. The Lucas Electrical Co.,Ltd., Well Street, Birmingham. Dear Sirs, X.3014 Re Positions of Fuses in Dynamo Circuit. X.2575 On the Lucas switchboxes which you are at present supplying to us as standard, there is provision for one fuse only, and that in the field circuit. This was arranged by you because we had questioned the advisability of using fuses in the control and negative circuits. We have recently, however, given a lot of thought and time to this matter experimentally and we are now satisfied that the best combination of fuses for complete protection consists of (1) A fuse in the field circuit, as we have at present. (2) A heavy current fuse in the main connection between the four point switch and the series coil of the cut-out. It will be noticed by you that fuse (1) gives protection against the dynamo being roasted, should at any time the battery become disconnected, and the dynamo run with the switch on; and that fuse (2) gives protection to the battery and dynamo, should at any time the cut-out stick on with the dynamo stopped and the charging switch left on. We divide the protection desired into the above two classes which we call A and B type respectively. A field fuse gives complete protection of the A type but none of the B type; on the other hand, the main circuit fuse in the position suggested, if properly chosen in size, gives complete protection of the B type but none of the A type. Hence the two fuses together*give complete protection of the dynamo and battery. * together with a suitable fuse system in the consuming circuits. Contd. | ||