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).
Defining the standard conditions for comparing dynamo output curves, setting specific voltage and temperature parameters.
| Identifier | ExFiles\Box 163\6\ img087 | |
| Date | 9th December 1930 | |
| EFC2/AD9.12.30 contd. -3- For other circumstances of running two other resistances of suitably graded value will probably meet the case. In any case it is a very easy matter to charge these resistances and that in itself is an argument for having more than one standard, though it is not considered that any one client should be provided with more than one resistance. We wish particularly to emphasise the fact that it is very difficult to give an output curve which represents with any degree of accuracy what may actually be observed in running circumstances. The temperature and other conditions being the same, the peak output ordinate and other ordinates of an output curve are increased or diminished very greatly according to the operating voltage of the system as controlled by the state of battery charge and/or the load upon the system. A machine which may give a peak output of 16 amperes to a fully charged battery (if allowed to do so), the operating P.D. of the system being above 18.5 volts, may only give just over 12 amperes in the same temperature conditions when the head lamps are on and the system voltage standing at 14.0. In fact it has been reasoned on principle, and confirmed experimentally, that the peak ampere output of a machine is proportional to the voltage at which the system is operation (as determined by the battery and load conditions). This is so very nearly the case that it is not impossible for one who understands this principle, to interpret the peak output indications of the ammeter in terms of voltage and thereby to know, for subsequent use, when the battery is fully charged, merely by observing the ammeter. We have decided that when the head lamps are on a suitable average operating voltage of the system for the purpose of comparative curves, is a constant voltage of 14.0. In line with this, our future basis for the comparison of output curves will be (a) The machine carcase to be at 80°C. as indicated by our usual thermometer method and (b) The voltage against which the dynamo is working will be strictly 14.0 for all outputs. Until the advent of the half charge scheme, it has been our practice to compare dynamo output curves with the dynamo carcase always at a temperature of 80°C. as above referred to, but by allowing the rise of | ||