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).
Page explaining armature core flux, current induction, and related electromagnetic principles at varying speeds.
| Identifier | ExFiles\Box 4\5\ 05-page075 | |
| Date | 1st November 1930 guessed | |
| V.E. No. DWT-3-B H.124.G:C.W.H -6- Contd. varying speeds. Generally speaking, the point of make in the fully advanced position should occur when, under open circuit conditions, the armature core flux is a maximum. In the absence of eddy current effects this will be when the armature is horizontal (Fig.1), in their presence it will occur a little later. when the armature passes forward from this point, the core flux begins to be reduced and current is induced in the primary coil as a result of this reduction. The current rises progressively in magnitude right up to the instant of break, except for full retard and low speeds of revolution and at any time has a value sufficiently great to maintain by its M.M.F. with the assistance, or later, opposition, of that of the permanent magnet, that portion of the original core flux which yet remains. At every instant there must exist in the primary coil a nett E.M.F. proportional to this current. This E.M.F. is produced by and is proportional to the rate of loss of core flux. We must consider that the armature core with its short circuited winding is dragging the core flux round with it away from its original direction across from pole to pole of the magnet (Fig.1) but that in order to maintain sufficient E.M.F. to maintain the current in the winding, which in turn maintains the necessary M.M.F. there must be a continual slipping back of the core flux towards its original direction. Note that as the armature gets further round, the core flux to be maintained is less, and for this reason alone the current Contd. | ||