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).
Preliminary experiments and issues encountered with brush-short-circuited currents during motor testing.
| Identifier | ExFiles\Box 34\3\ Scan119 | |
| Date | 18th March 1916 | |
| W.P. 1024 a (400 T) S.C. 580. 18-3-16. C. 1545. -5- (Contd). Some preliminary experiments in which the results were not very consistent showed us that it would be advisable to leave over the measurements of item (5), until other items had been satisfactorily determined. The reason for this was that we found the brush-short-circuited currents to be so great as to constitute too big a load on the driving motor and belt, and therby to alter the conditions of working. In fact, at an excitation of about 70 amperes, on the starter fields, there was a tendency for the belt to slip, sparking at the brushes, and some noise, especially in the case of the 17 slot armature. We are aware that the brushes are not in the neutral position, but set back about 90 against the direction of rotation to suit motor conditions, but even so the magnitude of the losses due to brush-short-circuited-currents seem large. We took particular care that the brushes were bedded down properly before each test, as we found that this made an enormous difference. We afterwards put in some very narrow brushes, specially filed down to only cover one commutator segment, and tried again, when the results were, as anticipated, quite normal. We cut these down more particularly for finding the volt-excitation curves, for which wee separate sheets. Accordingly, we first made measurements of (1) (2) and (3), in order to obtain (a) and (c). (Contd). | ||