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).
Notes on the action of a revolving armature type magneto.
| Identifier | ExFiles\Box 4\5\ 05-page068 | |
| Date | 6th October 1920 | |
| X.430 R R DRG. INST:CS H.{Arthur M. Hanbury - Head Complaints} 11A. 21-8-20 G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 200 6.10.20. NOTES ON THE ACTION OF A REVOLVING ARMATURE TYPE MAGNETO. First, consider an unwound armature of magnetically ideal material, that is to say, suffering from no hysteresis and having laminations of molecular thickness. As this is rotated slowly between the pole pieces of the permanent magnet (which pole pieces must also be considered as constructed of this ideal material), the armature core flux will vary roughly sinusoidelly (the actual wave shape depending upon the shapes of the various portions of the magnetic system). The core flux will be exactly a maximum when the armature is horizontal (Fig.1) and exactly zero when the armature is vertical (Fig.2) If now the armature be rotated very fast, the above still holds practically to a degree beyond the mechanical limits of possible speed. It is true that there is a very slight time lag of magnetisation behind magnetising force (actually existing resultant value) more especially for comparatively weak magnetising forces; this effect in a hypothetical material with laminations of molecular thickness, so that no ordinary eddy currents can exist, may perhaps be considered as due to intra-molecular eddy currents. Contd. | ||