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).
The operation of main and auxiliary switches to minimize sparking at the copper contacts.
| Identifier | WestWitteringFiles\T\2January1929-June1929\ Scan178 | |
| Date | 26th March 1929 guessed | |
| -2- Contd. Referring to the main and auxiliary switch, it has been found advantageous to arrange that the main switch arm picks up the relay switch arm earlier in its travel than called for by LeC.2620, in such a way that the auxiliary carbon [struck through text] break occurs before the main copper make. There appear to be two reasons for this, both contributing to the same end, viz. the minimisation of sparking at the main copper contacts at make :- (1) The inertia load of the auxiliary switch arm slows down the main switch arm and therefore reduces the inertia lag of the main switch carbon arm. (2) The sooner the teazer circuit is broken in relation to the main circuit being made, the less the virtual non-inductive effect of the main circuit. The teazer current establishes a considerable portion of the magnetic energy of the motor field, so that when the main switch comes on, there may be in some circumstances a very big possible current at first contact. It is exactly at first contact that a main switch copper spark occurs, if the teazer circuit is fully made when the main copper contacts come on, especially if the main carbon contacts have not suff- icient advance. EPC | ||