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).
Description of the operation of a dynamo charging system with an automatic switch.
| Identifier | WestWitteringFiles\P\October1926-November1926\ Scan044 | |
| Date | 8th October 1926 guessed | |
| -5- Contd. of this switch, one of which is a pure volt coil operating directly from the voltage of the system, and the other of which is a coil in series with the supply to the headlamps. Supposing for the moment that the system is unloaded, except for starter motor load at starting, every time the chassis engine is started up we find the electro-magnetic switch closed, so that the dynamo proceeds to cut in and charge at the full normal rate. Such charging will continue until by rise of back E.M.F. of the battery the voltage of the system has risen to a pre-determined amount, say about 17 volts. The automatic switch then opens and the field resistance is inserted. The output of the dynamo falls to the reduced output curve for varying speeds and the switch remains in the open position so long as running is continued, whatever the duration of the run; the battery therefore receiving a relatively short initial 'boost' and afterwards a reduced rate of charge continuously. On stopping or slowing down sufficiently for the cutout to come out, the relay switch is restored to the "on" position, and then upon again starting or reaccelerating, the same process is repeated. If, now, during any run the headlamps are switched on, the reverse magnetising effect resulting from the passage of the headlamp current through the series coil puts up the voltage which would be required on the shunt coil now to operate the switch, to a value which it could never reach. Hence the dynamo would automatically supply current | ||