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).
Report from The Morgan Crucible Company regarding armature tooth ripple and coil commutation issues.
| Identifier | ExFiles\Box 168a\3\ img136 | |
| Date | 23th January 1935 | |
| RM{William Robotham - Chief Engineer} 2751 -2- To Messrs.Rolls Royce, Limited, DERBY. The Morgan Crucible Company, Limited. January 23rd, 1935. The armature tooth ripple shows up very prominently on Charts Nos. 2 and 4. Further, to each of these large ripples three smaller ones can be observed which coincide with segment or coil frequency. The very pronounced tooth ripple as compared with that corresponding to the segments suggests that the present brush position is the best one for two of the three coils, but is unsatisfactory for the third. It appears possible that a small adjustment in the amount of lead may give a more uniform commutation of the three coils housed in one armature slot. We are checking up this point with the machine in our possession. With the very weak main field corresponding to 4770 r.p.m it is unlikely that the short circuited coil will operate in a fringe sufficient to neutralise the reactance voltage of the coils for any brush position. It is necessary therefore in order to improve commutation to reduce the very high peak voltages under the brush by other means. The most promising procedure appears to us to be to reduce the number of coils per slot. An advantage might be expected from two considerations. Firstly the field cut by the group of coils in a slot would be more uniform and, secondly, the | ||