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 the output characteristics of a battery-controlled third brush generator.
| Identifier | ExFiles\Box 61\2\ scan0213 | |
| Date | 12th December 1925 | |
| COPY. X3374. 0. EFC1/T2.12.25. X.294. EXPLANATION OF OUTPUT CHARACTERISTICS OF BATTERY X.3374 CONTROLLED THIRD BRUSH GENERATOR BY WHICH A RISE OF VOLTS AND A RISE OF AMPERES TAKE PLACE SIMULTANEOUSLY WHEN THE BACK E.M.F. AND/OR RESISTANCE OF THE EXTERNAL CIRCUIT ARE/IS INCREASED. The intrinsic volt-ampere characteristic of an ordinary shunt wound generator run at one given speed is shaped like the heavy Q R T S curve/in diagram 1. Similar characteristics for higher and low rotational speeds are shown as light curves, increase of speed causing the characteristic to grow, as it were, outwards and upwards, and vice versa. (These characteristics in the ideal case are on the assumption that the temperature remains the same throughout the machine and that the electrical characteristics of brush and commutator contact are quite consistent. So actually the characteristics will be a little indefinite, though the explanation based upon them is not thereby invalidated). In obtaining one such characteristic we can imagine that we start with an open circuit, and gradually reduce the resistance of the external circuit from infinity to zero. Any straight line through O, such as L, represents a fixed resistance, in fact the line L is the intrinsic characteristic of the resistance which is the ratio of the scale reading in volts at any point P on the line to the scale reading in amperes, thus the steeper the line, the higher the resistance represented. Contd - | ||