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).
The examination and modification of the field winding on a large shunt dynamo.
| Identifier | ExFiles\Box 168a\3\ img077 | |
| Date | 5th January 1939 | |
| 6142 To By.{R.W. Bailey - Chief Engineer} c. to La.{L. A. Archer} c. to By/RD. RM{William Robotham - Chief Engineer}/RC.{R. Childs}5/JH.5.1.39. FIELD WINDING ON LARGE SHUNT DYNAMO. Owing to the complaints made by production, concerning the tightness of the field winding on the large dynamo, the machine has been examined with a view to using an easier fitting winding. At present the winding consists of 263 turns per pole of 19 s.w.g. superfine D.C.C. wire having a resistance of approximately 5.90 ohms. This winding, on account of its size and the fact that it has to be forced in, is a common source of breakdown. As a first step 20 S.W.G. wire was decided upon, and the Drawing Office asked to draw out a set of coils, based on this gauge of wire that they considered would be mechanically suitable. Such a set of coils consisting of 250 turns per pole of 20 S.W.G. D.C.C. wire and having a resistance of 7.02 ohms, was eventually made and fitted into our Laboratory standard dynamo, 7" coil machine No.1.C.3. (Arr. 2). A series of tests were then carried out on this machine which showed as anticipated a reduction in heating when run on load, but on the other hand an appreciable increase in the cutting in speed. In order to regain the original early cutting in speed, the brush angle was reduced by about 10° from 14° to 4°. This was achieved by lifting and moving the end connections, two segments round the commutator (Arr.3). The variations in the characteristics of the machine with each stage of the modification as compared with the standard condition, are shown below. Cont'd.{John DeLooze - Company Secretary} | ||