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 of calculations for motor armature specifications and performance, including flux density, dimensions, and back E.M.F.
| Identifier | WestWitteringFiles\T\November1928\ Scan057 | |
| Date | 27th November 1928 guessed | |
| -2- Contd. Assume for the condition of the motor taken as the basis of these calculations useful polar flux density of 6450lines per cm^2 reckoned on the minimum pole face. Armature diameter 3.100/3.000 will be taken as 3.050" for the purposes of these calculations. Armature circumference corresponding to 69% polar embrace = (69/400) x π x 3.050 = 1.65 inches or 4.20 cm. Armature length = 3.500" or 8.89 cm. Useful flux per pole = 4.20 x 8.89 x 6450. = 240. x 10^3 No. of conductors = (Tb x 10^8) / (1.41 x P Ø C) = (90 x 2 x 10^8) / (1.41 x 4 x 240,000 x 180) = 74 nearly. i.e. 37 coils one turn per coil and 37 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) = (240000 x 74 x 640 x 4) / (60 x 10^8 x 2) = 3.78 volts. Contd. | ||