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).
Miscellaneous points on the auto charge control switch, focusing on an extra coil for protection.
| Identifier | WestWitteringFiles\R\2December1927-February1928\ Scan168 | |
| Date | 15th February 1928 | |
| To R.{Sir Henry Royce} from EFC c. BJ. E.{Mr Elliott - Chief Engineer} c. Da.{Bernard Day - Chassis Design} PN.{Mr Northey} c. CWB. By.{R.W. Bailey - Chief Engineer} c. Oy. WOr.{Arthur Wormald - General Works Manager} ORIGINAL AUTO CHARGE CONTROL SWITCH. Miscellaneous further points. X4008 (1) Extra coil for extra protection. As explained the auto switch does not give protection against discontinuities in the circuit between the battery side of the cutout at which the negative end of the auto switch shunt coil is connected, and the surface of the commutator under the negative dynamo brush, i.e. (a) If the cutout fails to make contact. (b) If there is a break in the negative wire from the dynamo to the cutout. (c) If the dynamo negative brush sticks up in its holder. Although no harm can come to any portion of the system except the dynamo itself and in certain circumstances to the cutout shunt coil, e.g. (a) above, it might still be possible for the dynamo to be overexcited and have its field coil charred in the circumstances indicated. This possibility led us to the idea of an additional coil on the auto swtch which would receive the high voltage available from the dynamo in these special abnormal circumstances. If the negative end of such a coil is connected to the main negative brush it is still ineffective if the main negative brush sticks up. The only other negative brush is the field negative or control brush, therefore one arrives at the idea of placing a weak coil (small number of ampere turns) connected between the positive terminal of the shunt Contd. | ||