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).
Continued explanation of primary current behaviour in relation to speed, magnetic flux, and eddy currents in an armature core.
| Identifier | ExFiles\Box 4\5\ 05-page079 | |
| Date | 13th June 1920 guessed | |
| -10- Contd. revolves. In general, the primary current at the instant of break for moderate speeds will be greater the greater the speed. It will be readily seen, however, that the maximum possible peak value of the primary current will approach a limit equal to that value which produces sufficient M.M.F. to still maintain the original instantaneous armature core flux at make, when the armature has moved round into such a position that the M.M.F. of the permanent magnet directly opposes this. Hence the peak value and therefore also the current at break for a given timing does not increase indefinitely with increase of speed but reaches a value for some speed which it cannot be made to exceed by further increase of speed. (compare p.5 middle paragraph). It will further be shown when dealing with the phenomena which occur between break and make, that the effect of eddy currents in the armature core is to cause the peak value to fall again at very high speeds, the reason being that the instantaneous core flux at make starts off at a lower value, so that there is less flux to maintain. | ||