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 discussing the principles of core flux, electromotive force, and primary current in an ignition system.
| Identifier | ExFiles\Box 4\5\ 05-page076 | |
| Date | 1st November 1930 | |
| -7- Contd. would be less, but the core flux has to be maintained with the rapidly decreasing assistance of the permanent magnet, and after a certain point against the E.M.F. of the permanent magnet, and for this reason thee current must be greater, also the rate of slipping back of the flux proportionately greater. On the whole, the primary current will in general increase right up to the point of break. Another way of viewing the matter is to consider that the open circuit E.M.F. wave still exists though the circuit be closed, and starting from a zero value at the instant of maximum flux, rises rapidly as it does on open circuit, to a peak value, after which it falls. This E.M.F. operating against the resistance and inductance of the primary winding, sets up a current in the primary winding which also would increase up to a peak value and then fall, unless cut short by the opening of the contact breaker. At any given speed, we will say for the sake of argument a moderate speed such as 500 r.p.m., the peak value of the current will become smaller as the point of make is made to be later, the fully advanced point of make, as referred to above, being coincident with the zero on the curve of open circuit voltage. This is, as would be expected, owing to the loss of the early portion of the open circuit E.M.F. curve. The peak value will also occur very slightly later for the later make. Generally, the point of Contd. | ||