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).
Investigation of a dynamo problem and potential solutions for improving performance.
| Identifier | ExFiles\Box 60\4\ Scan077 | |
| Date | 24th June 1931 | |
| Hs.{Lord Ernest Hives - Chair} from R.{Sir Henry Royce} c. Sg.{Arthur F. Sidgreaves - MD} Wor.{Arthur Wormald - General Works Manager} c. PN.{Mr Northey} By.{R.W. Bailey - Chief Engineer} c. E.{Mr Elliott - Chief Engineer} Da.{Bernard Day - Chassis Design} V6099 R3/M24.6.31. X.6099 X.6126 DYNAMOS. During the discussion at Brooklands on 19.6.31 I asked Hs.{Lord Ernest Hives - Chair} to investigate the dynamo problem (which I understood from him however is at present giving good satisfaction to owners) in the following way :- The series winding was tried and when connected to the battery did not promise to give any improvement in performance without increasing the dynamo temperature, in fact, under these conditions it seemed rather worse than the standard single winding. The experiment suggests however, that we may get a different characteristic as I have before suggested by increasing the span of the control brush, namely, bringing it nearer to the main brush of the same polarity, and therefore nearer like a plain shunt machine, which would increase in charging current with an increase in speed. There may, however, be difficulties which prevent us doing so. The second hope is in increasing the saturation limit of some part of the dynamo magnetic circuit, and the most practicable would appear to be in the armature teeth. This could easily be tested by making 3 armatures of the same number of turns, but increasing the width and depth of the slot by stages until the peak voltage became definitely less, which would be shown by the armature teeth being saturated during periods of maximum magnetisation, namely, the slower end of the curve. I think the increased copper and decreased internal resistance would actually lower the temperature of the machine more than the increase of temperature due to the higher magnetisation of the teeth. The Foucault currents in the iron core should be the same. If this turns out as one would expect, the peak amperes would be less and the current at high speeds rather more. The length of the air space should not be shortened and the magnetising circuit would not need any modification, but the 3rd. brush might bear a greater span so as to cut in at least as early, and if the temperature would allow I should increase the span slightly more. | ||