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).
Modifying auto switches by adding an extra terminal for the shunt coil to enhance protection.
| Identifier | ExFiles\Box 59\1\ Scan168 | |
| Date | 27th October 1927 guessed | |
| -10- Contd. explained, does not practically exist on the two auto switches we have on the cars, the reduction of the charging current being only 50%. These two switches work regularly and consistently on normal running, connected as shown by the full lines on the present diagram. So far as we know, they have not been called upon to operate as the result of a break in the dynamo-battery circuit. These present switches have five terminals, as shown, but if we provide an additional terminal (dotted in diagram) for the shunt coil and connect the shunt coil (dotted line) to distribution box terminal B, instead of C, this would (though slightly complicating the auto switch by the addition of an extra terminal) provide the additional element of protection which was referred to when speaking of the danger lamp unit as the reason for supplying this from terminal B, and it will be remembered, the reason for not supplying the cutout shunt coil from that terminal, but preferably from C). (In the case of the danger lamp unit we assume that the coil is not on the high voltage for a long enough time to be damaged, and in the case of the auto switch unit the voltage of the dynamo is automatically reduced immediately a high voltage becomes applied to its shunt coil. Either coil can be made to stand the necessary temporary small overload, but in the case of the cutout shunt coil the burning out condition we have referred to is that of this coil being on the high voltage for a considerable time). On the whole, although as shown dotted, it would Contd. | ||