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 and analysis of Circuits 3 and 4, detailing resistance and current calculations.
| Identifier | ExFiles\Box 64\4\ scan0214 | |
| Date | 14th March 1929 guessed | |
| -4- Contd. Circuit 3. (MAIN) Black. The resistances of this circuit are as follows : Motor main field ......... .0088 ohm. Motor armature and brushes. ............. .014 " TOTAL ................ .023 " Upon this main circuit being switched on, it is considered, as already stated, that the available voltage has dropped to 9. The initial ampere rush will therefore be 9/.023 = 390 and the condition for correct operation will be :- (f) The main contacts of the main switch must, when made as described in (e), be capable of carrying a current of 350 amperes for half a minute without shewing signs of distress. Circuit 4. (HOLD-OFF) (Green). When the main switch circuit 2 is made by the motor switch and the main switch lever operates, it also operates mechanically through the main switch lever arm, the auxiliary switch lever causing circuit 1 to be broken and circuit 4 made. Circuit 4 is supplied with current through the push button switch to the bottom contacts of the auxiliary switch and the current passes through the fine wire coil of the auxiliary switch to earth. The resistance of this fine coil is 2.27 ohms. The current through it at 9.0 volts is 9.0/2.27 = 4.0 amperes. The condition of correct operation as regards | ||