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).
Calculations for motor electrical resistance, including armature and field values at 20°C.
| Identifier | WestWitteringFiles\Q\2April1927-June1927\ 144 | |
| Date | 1st June 1927 guessed | |
| -3- Contd. Forward terminal P.D. = 8.68 volts. Hence E.M.F. to overcome ohmic resistance = 5.14 volts. Amperes = 166 Total motor ohms = .031 = R (say) Let field resistance = RF and armature " = RA Then R = 1.3RA + RF (say) to allow for brush and commutator resistance. Suppose RF = .6 RA Then R = 1.9 RA or RA = .0163 w RF = .0098 w These resistances are considered to be their values at 20°C in accordance with assuming engine cold for the value of its turning torque. Resistance of one armature turn at 20°C = (.0163 x 4) / 58 = .00112 w Length of armature turn = 11" approx. Resistance per 1000' = (12000 / 11) x .00112 = 1.22 w. Contd. | ||