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).
Analysis of two electrical circuit protection arrangements as alternatives to a battery fuse.
| Identifier | Morton\M1.7\ img006 | |
| Date | 3rd December 1921 | |
| Contd. -2- EFC1/T3.12.21. The full buzzing condition is sustained with a current of 7 amperes, this being the case with the Head short on the battery lead. In the case of the second instrument, the moment the current reaches 32 amperes, the contacts fall apart and are held apart by the shunt coil which is connected across the contacts. The minimum current required on the shunt coil to maintain the full separation of the contacts is .025 amp. but the current through the coil at 6 volts is about twice this (.05 amp). Either of these arrangements seems to be an attractive proposition in place of a battery fuse, or for that matter, in place of any fuses. In any case, so long as the earth remains on the wire, there is no change of the dynamo roasting, because it cannot excite, the snag about the ordinary fuse being that the earth may have disappeared without the fuse being put back. In the first instance, of the circuit breaker, the buzzer will operate taking 7 amperes from the battery until the earth is removed. The second instance seems rather attractive inasmuch as if an earth occurs, the current is virtually switched off automatically except for a slight amount, and cannot be switched on again until the circuit is entirely unloaded. Therefore, if lamps were switched on when the earth occurred [Upside down text at bottom] R.R. 285A 100 (T) (S.H. 708. 10-12-20) G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 2547 | ||