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 performance and overheating issues of Lucas and Smith electrical cut-outs when hot.
| Identifier | WestWitteringFiles\D\March1920\ Scan37 | |
| Date | 5th March 1920 | |
| Contd. -3- Cut-out. Volts required on shunt coil to just operate when hot. Amperes. Ohms. Lucas present standard A.{Mr Adams} 15.5 .345 45 Lucas present standard B½ 17.0 .42 40.5 Smith cut-out (1) 13.5 .100 135 " " (2) 14.0 .069 203 The inspection of these figures will show that there may be considerable variation in the voltage required to operate the Lucas cut-out. Further, that the current taken is more than one would think should be necessary. It has been mentioned to us by the Test Dept. that these cut-outs get overheated even to the extent of doing damage. Allowing, say, a current of .35 ampere when hot at 16 volts, this is a consumption of 5¾ watts, and since this, taken with the heating effect due to the series coil, may perhaps be increased 50% it seems an undue amount of energy to be dissipated over the external area of the cut-out. We are not surprised that the cur-out gets unduly hot. We should mention that this point has only been apparent during these recent tests, because a previous Lucas cut-out tested by us on 6.8.19 only showed a consumption of .13 ampere at 14 volts to cause it to operate. Contd. | ||