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).
The importance of minimizing inductance and ohmic resistance in ignition system circuits.
| Identifier | WestWitteringFiles\M\2April1925-June1925\ Scan61 | |
| Date | 7th May 1925 | |
| Contd. -3- EFCH/T7.5.25. (1) The absolute minimum inductance in this circuit - hence the necessity of placing the condenser mechanically as close to the points as possible. (2) The absolute minimum of ohmic resistance in the circuit, in which connection it has to be remembered that an ohmic resistance at a high frequency of this order may be many times more than the ohmic resistance as measured for ordinary D.C. or low frequency currents. In addition to which at a point of poor contact a higher frequency current of the same R.M.S. value has, we believe, a greater tendency to make the contact still worse than in the case of an ordinary current, hence the necessity in this local circuit of taking every possible care that the ohmic resistances, which are mainly at the pressure contacts, are as low as possible. momentarily It has been and is urged that there should be as far as possible continuous solid metallic connection between contact points and condenser foils. We have, however, in our present standard battery ignition system no less than seven breaks in the metallic continuity of this local circuit. It is difficult to imagine that harm would come to contact points if, in imagination, the contact points were themselves the centre points and metallically part of the plates of a condenser of sufficient capacity. It may be agreed, therefore, that it is somewhat difficult to account for the fact that some ignition points behave satisfactorily whilst others give trouble, without ascribing the difference to differences in the goodness of the seven connections. Contd. | ||