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 determining the specifications and resistance of an armature winding.
| Identifier | ExFiles\Box 51\1\ Scan017 | |
| Date | 6th July 1921 guessed | |
| -2- Contd. We allow say 2 volts for the loss of volts in the armature winding (hot)-due to the field current, giving an armature E.M.F. of 15.6 volts. Suppose we take a useful polar flux density of 5700 lines per square centimetre on minimum pole face. Armature circumference corresponding to five slot pitches = 5/29 x π x 3.10 = 1.68" = 42.6 mm. Length = 2.75 = 70 mm. This gives a useful flux per pole of 5700 x 4.26 x 7.0 = 170000 Since E = (Φ Z Np) / (60 x 10⁸ x b) Therefore Z = (60 x 10⁸ x b x E) / (Φ N p) = (60 x 10⁸ x 2 x 15.6) / (170,000 x 600 x 4) = 459. No. of conductors decided upon - 464, No. of slots and coils 29, 8 turns per coil, of 19 S.W.G. (.040") Total No. of armature turns = 232 Armature resistance is that of 58 turns in series. Contd. | ||