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).
Continuation of a report analyzing different electrical cutout and charging switch configurations to minimize sparking.
| Identifier | ExFiles\Box 65\2\ scan0113 | |
| Date | 16th May 1928 guessed | |
| -2- Contd. connection, there is a slightly stronger flash than normal because the potential of the field brush is more negative than in normal running. After that the cutout points separate with no flash. N.B. All these results are taken with the dynamo running at such a speed as to be on peak output. Case 3. Cutout shunt coil positive now connected to distribution board terminal C. Dynamo Charging switch breaks field circuit first. On the first break, i.e. of the field circuit, there is the normal field breaking flash. The voltage across the cutout shunt coil goes down and the cutout opens with a relatively small spark, due to the fact that it probably comes out while the main current is passing through zero. Subsequently on breaking the armature contact there is no flash. Case 4. Cutout shunt coil positive, as in case 3, connected to dist. box terminal C. Dynamo Charging switch breaks armature circuit first. On the armature contact being broken there is a main current flash of the same calibre as in Case 2. The field coil is momentarily left on the battery via the cutout contacts and series coil, but the reverse current from the battery through the field coil and dynamo armature cutout contacts and series coil causes the cutout to come out with some amount of flashing. Subsequently on the field contact being broken by the switch there is no flash. Of the four arrangements we have established that Case 3 is really the best taken allround. In this the field connection is broken first by the switch and there is the ordinary field breaking flash. The cutout points open with a very small spark, and the armature contact comes off with no spark. The field flash is less destructive to the switch contacts than when the armature circuit is broken first (Case 4.). The spark on opening the cutout is smaller than if the shunt coil is connected to distribution box terminal B (Case 1). The field is still broken first by the switch. | ||