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).
Page 2 of calculations for motor characteristics, including armature circumference, flux per pole, number of conductors, and back E.M.F.
| Identifier | WestWitteringFiles\Q\2April1927-June1927\ 198 | |
| Date | 22th June 1927 guessed | |
| -2- Contd. Armature circumference corresponding to 69% polar embrace = 69/400 x π x 3.100 = 1.68 inches or 4.27 cm. Armature length = 2.750" = 6.99 cm. Useful flux per pole = 4.27 x 6.99 x 6500 = 194,000 No. of conductors = (Tb x 10^8) / (1.41 P.Ø C) = (89 x 2 x 10^8) / (1.41 x 4 x 194000 x 180) = 90 (nearly) i.e. 45 coils one turn per coil and 45 armature slots. Motor speed = 640 r.p.m. Back E.M.F. when rolling engine = (Ø Z N P) / (60 x 10^8 x b) = (194000 x 90 x 640 x 4) / (60 x 10^8 x 2) = 3.73 volts. Forward terminal P.D. = 8.40 volts. Hence E.M.F. to overcome ohmic resistance = 4.67 volts. Amperes = 180. Contd. | ||