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).
Analysis of the dynamo's cut-out regulator windings and their effect on voltage and current at different speeds.
| Identifier | ExFiles\Box 31\1\ Scan103 | |
| Date | 2nd February 1921 guessed | |
| -2- EFC1/T2.2.21 the regulator side of the cut-out consist of (1) The usual compound winding carrying the main current delivered by the dynamo in an additive direction magnetically. (2) A winding carrying the main field current of the dynamo, also in an additive direction magnetically. One can readily appreciate the function of the first winding as being the function of any compound winding on vibrator regulator control, e.g. to limit the rush of current when the battery is low in voltage. The function of the other winding we have not been able to appreciate. Such a winding introduces a speed effect. As the dynamo is driven faster, the field current for a given voltage is necessarily smaller, this being regulated by the contacts. Hence the main voltage must rise in order to produce additional ampere turns on the shunt coil, to compensate for this. There will follow as a consequence of this, the fact that the current delivered to the battery in a given condition will be greater at higher speeds than at lower speeds within the regulating range. The ordinary compounding coil on the other hand cannot have such a speed effect. We have taken an open circuit volt speed curve of the dynamo and regulator, together with associated field current speed curve for two conditions, one inwhich this main field current regulator coil was included in the circuit as on the diagram, the other in which the connection was altered so that the field current did not have to traverse this coil in passing to the main field. These curves are given on the accompanying photostat sheet and correspond to the same setting, a setting in the correct neighbourhood for operating a 12 volt battery, but it will be readily understood that the correct setting in the two different cases for a 12 volt battery would differ slightly. It will be seen from these curves that when the coil is omitted the regulated open circuit voltage is nearly constant. There is still a slight rise which may be partly due to the fact that in the open circuit case of this Westing-house regulator, the field current has still to pass through the main series compounding coil before reaching the field winding, which coil however is of many fewer turns than, and less than one tenth of, the resistance of the regulator field current coil. It may, however, in part be due to other causes as, as it may be remembered, a rise of voltage with speed occurred in the case of the system with the regulator entirely volt coil operated. On the other hand, with the coil left in circuit, the voltage rises considerably with speed within the regulating range (its average being lower due to the magnetising effect of this coil). As would be expected, with the dynamo and | ||