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).
Volt excitation curve tests for various armatures using modified commutator brushes.
| Identifier | ExFiles\Box 34\3\ Scan122 | |
| Date | 15th February 1916 | |
| R.Y. 288 a (400 T) (S.C. 520. 15-2-16) G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 1546. -8- Volt Excitation Curves. These were taken with brushes narrowed down to the width of one commutator segment of the 51 part commutator. Opposite pairs of brushes were cross connected during these readings. We found that removing the cross connections, made a slight, but measure~~ment~~able increase in the voltage reading. Of course the brushes were not quite in the neutral position, and we should say that the same amount had been filed off the brush on each side thus:- [Diagram of a brush on a commutator segment] The results for the three armatures are given in the accompanying curves. We had previously tried to obtain these curves with standard sized brushes, but found that owing to the heavy brush-short-circuited currents, the curves lay very much lower in this case and of course, have no useful meaning. For instance, we could only get about 5 volts at the most, in place of 8 1/4, under these circumstances. The flux results for these curves are as follows- At 75 amps. excitation, corresponding to 1012 A.T. per pole, flux comes out at (handwritten: 13 1/2 h/m) (handwritten: 1500 R.P.M.) 183,800 for 45 slot armature. 156,000 for 17 -------- 178,000 for 24 -------- The true flux may be about 1 to 2% higher than these | ||