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).
Description of the Bleriot Compensated Cut-out and its operational advantages.
| Identifier | ExFiles\Box 48\3\ Scan147 | |
| Date | 2nd November 1920 guessed | |
| THE BLERIOT COMPENSATED CUT-OUT. This design of cut-out differs from all others, in that a method has been adopted for compensating for the change in the air gap. Cut-outs of the usual types possess the inherent defect that whilst a pressure of, say, 13.5 volts is just sufficient to make it close the circuit, the pressure must fall very considerably below this value before the circuit is broken. This is, of course, due to the change in the air gap (between the armature and the pole piece). It is necessary therefore, to allow a certain reverse current to flow through the series winding, which reduces the attraction to such a value that the controlling spring can operate. This means that the cut-out always breaks the circuit when an appreciable current is passing, and the accumulator is being discharged. The first of these points is the more serious as sparking occurs which tends to destroy the contacts. The Bleriot Compensated cut-out overcomes these defects entirely, and possesses other valuable advantages. The arrangement of the windings is shown in the accompanying diagram. It will be seen that a resistance coil C is wound in series with the shunt winding, and is short circuited by the subsidiary contacts K.K. when the cut out is "out". When, however, the main contacts are closed, the short circuiting path is broken and the resistance is then inserted in series with the shunt. The result is that the shunt current is reduced and by adopting a suitable value for the resistance of the coil (which is wound in an opposite sense to that of the shunt) the attractive force acting on the armature may be kept | ||