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).
Performance characteristics of a dynamo unit showing voltage drops at various speeds and loads with a corresponding graph.
| Identifier | WestWitteringFiles\J\January1923\ Scan9 | |
| Date | 19th January 1923 guessed | |
| Contd. -3- consisting of resistance (variable) only (i.e. without the use of a battery) have been taken at various speeds 660, 825, 1050, 1500, 1750, 2000 and 2500 r.p.m. with the unit in an intermediate condition as regards temperature, and these show open circuit voltages at no amperes between the limits 14.3 and 15.3, the top and bottom limits approximately corresponding respectively, to the highest and lowest speeds. For 4 amps. the limits are 13.7 to 14.8 " 7 " " " " 13.3 to 14.1 " 10 " " " " 12.7 to 14.7 " 13 " " " " 12.3 to 13.0 " 15½ " " " " 11.9 to 12.7 The general tendency of these characteristics for the regulated portions, is a drop of about 1 volt of operating voltage per 10 amperes of load, the characteristic conforming to this rule more exactly in the second part of the regulating range. In the change from one portion of the range to another introduces a curvature of the characteristic at that point, in the manner shown in diagram:- VOLTS AMPERES It was found that with the dynamo unit in a fully hot condition and working on a fully charged battery. | ||