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).
Technical description of the action of a dynamo, focusing on brush systems and current characteristics.
| Identifier | ExFiles\Box 3\5\ 05-page097 | |
| Date | 13th August 1919 | |
| Contd. -4- EFC1/T13.8.19. to these two connected pairs of brushes must therefore be reduced, and this is effected by turning the whole system of brushes back against the rotation through an angle of about 20° until the current speed characteristic is rendered nearly flat after its maximum. This has the advantage of increasing that component of the cross magnetisation due to the auxiliary currents which tends to assist the main flux in the early stages, also of introducing a magnetising component of armature cross magnetisation due to main and field currents. The general result of this is, that for the same cutting in speed, a more rapid rise of current is secured in the early stages. The action of the present dynamo up to a certain point is similar to that already described, if we substitute "connecting links" for "resistances" but the increase of auxiliary brush current is carried considerably beyond a value of half the main field currents, namely up to (and beyond) a point where this current is equal to the whole main and field current. This may be seen on the accompanying table of currents (which may be compared with similar tables already given for the C.A.V. and Lucas dynamo) to occur at a speed of about 2900 R.P.M. under normal conditions. At this speed the auxiliary brushes have taken the place of the main brushes and the latter may be removed without affecting the operation. It is to be noted that the whole of the armature is now traversed by half the total current as in a simple machine. Above this speed the main brush current reverses slightly. Contd. | ||