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 detailing temperature compensation for a green lamp and auto charge control switch units.
| Identifier | WestWitteringFiles\S\March1928-May1928\ Scan063 | |
| Date | 30th March 1928 guessed | |
| -5- Contd. connecting the negative end of the shunt coil to earth, so green lamp will not light if cutout sticks off contact. Further it has been arranged that the green lamp will duly go out when the charging switch is put off. In regard to temperature compensation, our remarks refer equally to the green lamp scheme and the experimental auto charge control switch units. After some amount of calculation and experiment, we have arrived at a suitable relative apportionment of an entirely non-temperature coefficient wire on the pivot bobbin, and we have obtained a ratio of resistance of rather over four to one of copper, and a ratio of ampere turns of about two-thirds of the total in the copper winding. The watts dissipated in the resistance coil are slightly more than the original watts dissipated in the copper wire bobbin when this constituted the whole shunt winding, but these watts are still easily within a reasonable margin. It is anticipated that the temperature effect must necessarily by this means be reduced to not more than one-fifth of its previous value, and this will mean that the instruments can be set to allow the battery to go up much higher in voltage on its final kick-up than has been previously the case, which is all to the good and may make just the difference between the battery losing ground over a protracted period as previously explained, and not doing so perceptibly. Contd. | ||