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).
Revised calculations for an E.A.C. Dynamo.
| Identifier | WestWitteringFiles\J\March1923\ Scan29 | |
| Date | 19th March 1923 | |
| S/h 19.3.23. X.9700 - E.A.C. DYNAMO (REVISED CALCULATIONS AFTER EI/428.I.23). Dynamo must, in hot condition, put up 13.6 Volts on open circuit at a speed of 500 r.p.m. As a shunt machine it should do it at 450 R.P.M.(say). Hot armature resistance = .4 ohms (say) Max. field current say 4 amperes. Loss of volts = 1.6 Hence E.M.F. to be produced at 440 R.P.M. = 15.2 Assumed useful polar flux density = 5500 lines per cm2 on minimum pole face. Armature circumference corresponding to five slot pitches = 29/32 x π x 6.5 = 1.895" = 48 mm. Length of pole face = 3.25 = 82.5 mm. This gives a useful flux per pole of 5500 x 4.8 x 8.25 = 218,000. Since E = (Ø Z N p) / (60 x 10^8 x b) Z = (60 x 10^8 x b x E) / (Ø N p) = (60 x 10^8 x 2 x 15.2) / (218,000 x 450 x 4) = 465 No. of conductors decided upon - 464 No. of slots and coils 29. 8 turns per coil of 18 S.W.G. (.048"). Contd. | ||