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 an auto switch phenomenon, resistance, and shunt coil connections in a dynamo-battery circuit.
| Identifier | WestWitteringFiles\R\2October1927-November-1927\ 50 | |
| Date | 5th October 1927 guessed | |
| -9- (3) If the resistance thrown into series with the field was more than the amount to reduce the charging current approximately 60%, though still considerably less than the amount referred to in the Note above, the auto switch may act as a vibrator regulator, within a certain range of slowly varying dynamo speed, i.e. with the non-flexible contacts at present on trial). With the 50% reduction we have arranged on the units on cars there is a slight tendency for this to happen when the car is standing and the auto switch is about to operate, but when running on the road the road bumps give the necessary stimulus to enable the switch to go right over. This phenomenon, being one of normal running, is independent of the method of connection, but very dependent upon the resistance R, and would take place on the road if R.{Sir Henry Royce} is too large. (1) and (2) have been entirely overcome in the two auto switches arranged on chassis by making the negative end connection of the shunt coil as shown on the blueprint diagram (sent with the first portion of this report). Clearly, in this case the shunt coil receives the battery voltage and not the dynamo voltage when the dynamo is disconnected from the battery by the cutout, so that the shunt coil voltage cannot be prematurely excessive. The connection of the shunt coil then becomes very similar to that of the voltmeter and some of the same remarks apply. From the point of view of the unit as a protective device to the system generally, the change in the negative end connection of the shunt coil puts us less well off as regards protection against breaks in the dynamo-battery circuit because it does not (as shown on the diagram) include breaks on that portion of that circuit comprising the cutout contacts and the series coil, but only in that portion from the main switch to earth, viz. the ammeter, main fuse, and battery. (No (3), as explained, does not practically exist on the two auto switches we have on the cars, the reduction of the charging current being Contd. | ||