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).
Test report on the dissipation of field resistance suitable for reducing dynamo output.
| Identifier | ExFiles\Box 163\6\ img015 | |
| Date | 15th February 1930 | |
| X6016. To E.{Mr Elliott - Chief Engineer} from EFC. EFC1/AD15.2.30. X.6016. X.8780. X.6005. MAGNITUDE OF DISSIPATION OF FIELD RESISTANCE SUITABLE FOR THE REDUCTION OF DYNAMO OUTPUT BY THE REDUCED CHARGE SWITCH. As mentioned with you in conversation, we have now carried out a rough test on a 20 HP. dynamo with 48 coil armature and unsymmetrical pole pieces (this dynamo having been referred to as the one going on experimental chassis 14-GIV for 10,000 mile test) to ascertain the maximum dissipation of that value of the resistance inserted in the field circuit suitable for reducing the high output curve to an output curve (namely about half) considered suitable as a reduced charge curve. The dynamo having been brought to an intermediate temperature condition, for each value of the resistance inserted, dynamo speed was varied until first the maximum field current and secondly the maximum peak output were obtained, the results are as shewn below :- Field resistance Main Volts Amperes Ohms Watts Amperes. 3.3 2.72 1.21 8.98 11.5 4.05 2.5 1.62 10.12 10.5 4.9 2.25 2.18 11.03 9.4 6.05 1.9 3.18 11.5 7.9 6.05 1.8 3.36 10.9 7.4 The watts quoted on each line being the speed maximum for the corresponding inserted resistance also quoted. It will be observed that the maximum watts are an absolute maximum when the inserted resistance is about 2.9 ohms, the watts dissipated being then 11.5. The peak output of the machine for that field resistance inserted is about 8.5 amperes as compared with a 16.0 ampere peak when the resistance is omitted. One other point, and that is the peak output | ||