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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).
Alterations to volt-ampere characteristics for hot and cold conditions.

Identifier  ExFiles\Box 31\1\  Scan083
Date  1st October 1920
  
Contd. -2- EFC6/T1.10.20.

characteristics was given with our EFCl/T22.7.20. We have,
however, now altered the characteristic for the hot condition
in such a manner that the hot and cold characteristics now
called A and B converge to the same voltage, namely, 15.6
at 16 amperes. Our new standard A and B characteristics are
shown on the attached sheet. We also attach a further sheet
of two special volt-ampere characteristics for hot and cold
conditions which will be seen to converge to the same voltage
16.0 at 12 amperes out-put.

In working to these characteristics a carbon
plate resistance is used in the main battery circuit for the
purpose of increasing the operating voltage above that of the
battery, and when it is necessary to reduce the voltage of
the battery, a discharge circuit is switched on which takes
current from the battery. With these, it is possible in
making the test to adjust the operating voltage to suit the
particular ampere output at the time, and therefore to realise
the equivalent of working upon a battery circuit of volt-
ampere characteristic defined by our tables.

Of the six ampere output curves shown, two
are for the plain shunt condition cold, and at the highest
temperature to which the machine could be warmed up on the
bench (carcase about 35°C), these two curves being determined
on the A and B characteristics. Corresponding to these, there
are two curves for the controlled condition, one cold on
characteristic A, the other hot on characteristic B.

Contd.
  
  


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