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).
Analysis of a fault in a cutout component concerning operating voltage and reverse current.
| Identifier | WestWitteringFiles\G\June1921\ Scan115 | |
| Date | 24th June 1921 | |
| Contd. -2- EFC2/T24.6.21. A fault of this cutout upon which perhaps too little stress was laid in our previous report is that, quite apart from the wide range of operating voltage due to temperature variation, there is a relatively large change of magnetic reluctance from the "off" to the "on" position, which means that a comparatively large reverse current is necessary to effect the cut out, if, as is the case, the operating voltage point at the cut-in is reasonably early. This was pointed out in our previous report EFC2/T9.4.21, and results, whether the cutout be cold or hot, in a reverse series current of 2½ amperes, whereas the limit given in our specification of cutout is 2 amperes for an ordinary cutout, and 1 ampere in the case of a special cutout such as the Bleriot which is specially designed to minimise reverse current. A large reverse current is, of course, undesirable because the car speed, after being reduced may be hanging round about this point, so that the battery may be discharging at 1 or 2 amperes for a period. The argument against a large difference between cold and hot operating voltage is not so muc one affecting the cutout itself, but that it makes the dynamo appear later than it really is when the system is hot and also entails some loss of valuable charging current in the early stages after the dynamo has risen to a speed at which its voltage is sufficient to begin charging a battery. It should be borne in mind that in two respects this cutout does not fulfil xxx our specification:- (upside down text) R.R. 235A (100 T) (S.H. 738. 10-12-20 ©) 2347 Contd. | ||