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).
Continued analysis of a dynamo's performance under different control schemes and connections.
| Identifier | WestWitteringFiles\C\August1919\ Scan45 | |
| Date | 13th August 1919 | |
| R.R. 285 A (100 T) (S.E. 575. 16-4-19) G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 2354. Contd. -6- EFC1/T13.8.19. in this scheme of control so much of the armature is short-circuited that the voltage is considerably reduced. There results from this, the fact that the cutting in point is later than as a shunt machine, and that the current delivered to a battery at speeds only just above the cutting in point is less. But the rise of current with speed is so rapid that the characteristic curve crosses that for the simple shunt case and recrosses it again later, as seen on curves E.{Mr Elliott - Chief Engineer} (Not yet taken) Curves C shew the current speed characteristics of the machine when connected as a simple shunt wound dynamo. These are similar to those for Lucas E.575, but occur much earlier. Curves D shew out-put speed curves with the machine correctly connected to 4,5,6 and 7 fully charged large capacity cells in series. It will be seen from these to what extent the ampere out-put of the dynamo increases with the voltage against which it is working. There are also plotted on this sheet, the field currents and control currents. Curves E (which will be taken when time permits and sent later) will show the out-put speed curves with the machine arranged in various ways (a) (b) (c) (d) as below and set to charge a six cell battery. (a) As a plain shunt machine (Both control brushes removed). (b) One control brush removed. (c) Correctly connected. (d) Control brushes connected to main brushes through equal resistances of such value as to cause half of the armature only to carry current at 3000 R.P.M., i.e. to cause equality of all brush currents. | ||