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).
Design calculations for an electric motor armature, including torque, flux, conductor, and slot specifications.
| Identifier | WestWitteringFiles\K\June1923\ Scan74 | |
| Date | 19th June 1923 guessed | |
| -2- Contd. The static torque at this current must be 10% greater (say) than the running torque, i.e. it must be 82 lb inches. Take a useful polar flux density of 6700 lines per cm² reckoned on minimum pole face. Armature diameter = 3.100" Armature circumference corresponding to 69% polar embrace (about 7 teeth) 69 = --- x π x 3.100 400 = 1.68" = 4.27 cm. Useful length of armature = 2.75" = 6.99 cm. Useful flux per pole = 6700 x 6.99 x 4.27 = 200,000 lines. Number of conductors Tb x 10⁸ = --------- 1.41 P Ø C 82 x 2 x 10⁸ = ----------------------- 1.41 x 4 x 200,000 x 178 = 81.7 i.e. 82 nearly. Number of slots or sections = 41 (This conforming to the 4n+1 rule). Contd. | ||