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).
Performance comparison and analysis of a dynamo against a C.A.V. model, detailing construction and test results.
| Identifier | WestWitteringFiles\C\May1919\ Scan47 | |
| Date | 7th May 1919 | |
| R.R. 235A (500 T) (S.D. 408. 26-4-17.) Bm. 2/156/13. -4- EFC1/T7.5.19. Contd. than in the C.A.V. case, therefore, other things being the same, the armature heating should.be less. The general construction and insulation of the whole of the dynamo is very good. The commutator and brushes are of particularly ample surface for the currents to be carried, and the fact that there are two/brushes to each brush holder is a very good point in favour of this machine. We have found the running of the commutator and brushes, under all conditions, remarkably good and we do not get the blackening effects on this commutator that we obtained on the C.A.V. dynamo which appeared to be due (Lucas) to the use of two high a current density. The worst condition occurs at very high speeds when there is some sparking on the con-trol brushes. When in a cold condition, the voltage attains the value of 12.4 at a speed of 620 R.P.M. and a value of 13.6 at a speed of 665 R.P.M. The Lucas machine gets quite hot, but not quite as hot, we think, as the C.A.V. machine, under similar conditions. [Handwritten notes near R.P.M. values: Output 5amps. at 860. at 1000, & at 1250.] In all the tests described below, the dynamo was previously warmed up by running on load, so that all tests were made at approximately the same average temperature, as owing to the considerable veriation of field resistance, a slight alter-ation of temperature makes quite a difference in the performance. The curves marked A show voltages generated across the main brushes and from the main brush to the control brush at two speeds of 1500 and 2500 R.P.M. The voltages from control brush to negative brush can be deduced from these curves by the differences in the ordinates. Curves on sheet B show the voltages generated on open circuit when the machine is self-excited, first as a plain shunt wound machine, connected according to diagram (a) on sheet F.{Mr Friese} Contd. | ||