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 wire and coil specifications, including resistance, turns, and current for a shunt machine.
| Identifier | WestWitteringFiles\J\November1922\ Scan121 | |
| Date | 11th November 1922 guessed | |
| -4- Contd. Square C.S. area of this wire covered (D.C.C.) = (.056)² = .00313 inch² Available C.S. area of winding space estimated to be .875 x .475 = .415 inch². Hence number of turns = .415 / .00313 = 133 Length of wire in coil = 133 x 12.25 ÷ 12 = 136 feet. Resistance at 80°C of whole field winding = 4 x (136/1000) x 5.58 = 3.04 ohms. Field amperes at hot cutting-in point as shunt machine = 13.6 / 3.04 = 4.47 Amperes turns = 4.47 x 133 = 595 which gives a fair margin over those estimated to be necessary. Volts lost in armature due to field current = .4 x 4.47 = 1.79 (1.6 assumed) These are low and ampere turns are high because we have adopted 18 S.W.G. wire where 18½ S.W.G. would have been more exactly right. -------------------- Contd. | ||