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 current speed characteristic and operation of a dynamo, including magnetisation and brush currents.
| Identifier | WestWitteringFiles\C\August1919\ Scan43 | |
| Date | 8th August 1919 | |
| R.R. 235 A (100 T) (S.F. 575, 16-4-19) G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 2354. Contd. -4- EFC1/T18.8.19. 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 and field currents, namely up to (and beyond) a point where this current is equal to the whole main and field current. This (which may be compared with similar tables already given may be seen on the accompanying table of currents) 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. The Smith type A dynamo has aluminium end brackets carrying ball bearings for the armature, one of which carries a system of four brushes as already described and illustrated diagrammatically on sheet F.{Mr Friese} The actual positions of the poles in the casing end of the brushes on the commutator are not, Contd. (for the C.A.V. and Lucas dynamos) | ||