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 performance of an electrical machine under different brush contact positions and temperatures.
| Identifier | ExFiles\Box 50\5\ Scan225 | |
| Date | 1st October 1923 | |
| Contd. -2- EFCI/T1.10.23. The minimum output corresponding to the most retarded positions of the main brush contact surfaces and the most advanced position of the control brush contact surface, was only 7 amperes at 1350 r.p.m. at the average carcase temperature of about 40°C, at which temperature all the various outputs were noted. The position giving the maximum output was that with the three brushes exactly reversed, so that the two main brush contact surfaces would be in their most advanced positions and the control brush contact surface in its most retarded position (it being understood that the word "position" in these cases refers to the position of the bedding surface with fixed location of brush holder). With this worst arrangement, the corresponding output was 20 amperes at 1600 r.p.m., i.e. at 40°C carcase temperature, and in this case it was readily possible by further running the machine, allowing the temperature to rise and the output to fall somewhat, to melt out the solder from the commutator connections, in spite of every care having been taken that no suggestion of sticking of the brushes in the holders was possible. At this point the carcase temperature had risen to 90°C, indicated in the usual way, and the output had fallen to 14 amperes. In the next worst position, differing only from the worst position in the reversal of the positive brush contact surface from advance to retard, the corresponding output was 16 amperes at 1950 r.p.m. At the moment it Contd. | ||