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).
Technical analysis of the Bleriot Phi electrical cut-out, detailing its operation through resistance and ampere turns.
| Identifier | ExFiles\Box 48\3\ Scan162 | |
| Date | 6th December 1920 | |
| Contd. -4- EFC {E. Fowler Clarke - Electrical Engineer} 1/T6.12.20. the same condition would again be reached. In the Bleriot Phi cut-out there is, however, the insertion of resistance at one point only when the gap is approximately at 2/5 magnitude. This point can be illustrated graphically in the manner shown on diagram next page. The curves shown are drawn on a gap base, the single sloping line PQ representing the rise of force PWQ due to spring control in opposition to the attraction on the armature. A family of curves such as PR, SQ, TU may be drawn representing the traction-gap law for different values of the ampere turns. In order to operate a single stage cut-out (thinking of the Bleriot Phi as a two stage cut-out), the ampere turns on the shunt winding would have to rise to an amount corresponding to the curve PR. {Percy H. Rose} In order to allow the instrument to de-operate, the ampere turns would have to fall to an amount corresponding to SQ, i.e. by an amount corres- ponding to RQ. If one inserts a resistance during the motion, as in the case of the Bleriot Phi, the curve followed in the ideal case would be a curve such as PV WU, in which the fall VW just lowers the ampere turns to an amount corresponding to spring tension for the the gap at the instant of break of auxiliary contact. It could possibly fall a little more, relying upon inertia to carry the armature over the range where the ampere turns were slightly less than required. Our point is that although there is some gain by the insertion of resistance, a fall of ampere turns corres- ponding to UQ must still take place before the cut-out can Contd | ||