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 ampere turns, resistance, wire gauge, and number of turns for a coil.
| Identifier | ExFiles\Box 51\1\ Scan020 | |
| Date | 6th July 1921 guessed | |
| Contd. -5- Ampere turns required - 498 per pole Resistance of mean turn = volts per coil / ampere turns per coil = 3.4 / 498 = .00683 Length of mean turn of field coil = 5.9 + 1.2π = 9.6" Ohms per 1000' at 100°C = (12000 / 9.6) x .00683 = 8.54 At 0°C, this will become = (1 / (1 + 100 x .0042)) x 8.54 = 8.54 / 1.42 = 6.01 W The most suitable wire is considered to be No.19 S.W.G. at 5.97 w per 1000' at 0°C. Square cross sectional area of this wire = (.050)2 (covered) = .00250 inch2 Available C.S. area of winding space estimated to be = .750 x .400 = .300 inch2 Hence number of turns = .300 / .0025 = 120 Contd. | ||