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 oscillatory current within a magneto's primary circuit, including the function of the condenser and safety gap.
| Identifier | ExFiles\Box 4\5\ 05-page083 | |
| Date | 13th June 1920 guessed | |
| -14- Contd. condenser connected across the primary points. Such an oscillatory current, damped by the effect of primary resistance, therefore takes place. The frequency of this oscillatory current can be estimated if the inductance of the primary winding corresponding to the armature position at break, the capacity of the condenser, and the resistance of the primary winding, be known. The time of one oscilla- tion is comparable with, though a good deal smaller than, the timeinterval between break and the next make, so that the regularity of the dying away oscillations would be disturbed by the E.M.F. produced in the primary winding by the continued rotation of the armature in the average field of flux due to the permanent magnets. We say average because there is an alternating flux due to the oscillation superposed upon the flux due to the permanent magnets. Actually, however, this state of affairs is not allowed to occur except at slow speeds, as every magneto is provided with a safety gap over which the secondary discharge can take place, so that there is always one path or another for this discharge. Immediately after break an initial portion, not more than one quarter period, of this oscillation, would occur. At break the primary current is not brought to a dead stop as in the case of ideal primary break without condenser, but is reduced to zero, more slowly at first, and more quickly afterwards, as the condenser becomes charged up due to the influx of this current. In the absence of the possibility of a secondary discharge the primary CODE H-W-N-H-R.{Sir Henry Royce} NOV. M-U. PROG. M-R-H Contd. | ||