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).
Explanation of the electrical phenomena occurring in a circuit immediately after the point of break.
| Identifier | ExFiles\Box 4\5\ 05-page080 | |
| Date | 13th June 1920 guessed | |
| -11- Contd. Sixthly. We now have to consider the phenomena which occur immediately after the point of break and during the interval succeeding this point up to the next point of make. In what has gone before we have considered the secondary winding to be absent. We now, in the first instance, consider the secondary circuit although present, to be open circuited and to have negligible distributed capacity effect, which amounts to the same thing, for the time being, as considering this winding to be absent. We must secondly assume that no safety spark gap exists and further that the insulation of the secondary winding is capable of standing up to any voltage induced in it. Just previous to the instant of break, there is a distribution of armature flux quite different from that which the permanent magnets alone would maintain in the armature core in its position at this instant, which distribution is held for the time being by the M.M.F. due to the current which has been built up in the primary winding. At this moment the primary circuit is broken by the separation of the contact points. Let us for the moment assume that no condenser exists across the points and that the break is electrically ideal. In such a case, the primary current comes to a dead stop. A very quick redistribution of flux takes place because now the only M.M.F. in the magnetic circuit is that due to the permanent magnets. A very high transient voltage is induced in the secondary winding which, however, we have assumed to be sufficiently well insulated to stand up to this without any Contd. | ||