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 vibration of the auto switch and cutout under various speed and load conditions.
| Identifier | WestWitteringFiles\R\2October1927-November-1927\ 134 | |
| Date | 11th November 1927 guessed | |
| -5- Contd. vibration of the auto switch and of the cutout. This vibration continues until a speed of 2700 r.p.m. (in the 20 HP. case, equivalent to 37 m.p.h.) is reached, after which the cutout remains on contact and the auto switch remains off contact. The steady voltage of the system in these new circumstances is somewhat above that required to hold the cutout on contact. It is more than sufficient to hold the auto switch off contact, though the voltage required to operate that switch in the first instance is greater than the may be/present voltage of the system. In the vibrating case, when, as so far supposed, there is no load on the system, this low frequency vibration acts usefully as an audible warning of the open circuit condition. It is only at the high speeds, i.e. above 37 m.p.h. that the audible warning ceases and then with the resistance which we have at present, the voltage of the system does not become excessive until extremely high speeds are reached. Even then, only the shunt coils of the auto switch and cutout would be receiving the over-voltage and the dynamo itself would take no harm. That refers to the entirely open circuit condition of the load on the dynamo. We have shown on the bench that it requires a comparatively small load on the system in the shape of a lamp taking about 2 amperes at 12 volts (battery still disconnected) to prevent the auto switch being held over, and the voltage rising abnormally, even at the very high speeds. Thus, with a side lamp load Contd. | ||