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 armature and field winding specifications of an electric motor.
| Identifier | WestWitteringFiles\Q\2April1927-June1927\ 146 | |
| Date | 1st June 1927 guessed | |
| -5- Width of tooth one quarter of the way up = .095 + 1/4 of .093 = .115" say. (Here see table p.6). In the ampere-turn estimation table, the figures for the armature teeth can vary enormously owing to the fact that at the assumed load, the armature teeth are approaching saturation. The figure arrived at may be considered to be the minimum, having been taken on a basis of 75% polar embrace and on the section of the tooth one quarter of the way up from the bottom. The total ampere- turns arrived at, viz. 614 are therefore only a rough minimum estimate and the actual ampere-turns for the armature flux of 201,000 might be as high as 1000 or even more. Since the motor current is 166 amperes, the number of turns suggested by the calculations is 4½, 5½ or 6½ per pole, according to which gives the best result on test. The figure for the field resistance already arrived at is .0098 ohms at 20°C. Referring to previous calculations, we see that 4½ turns per pole with an approximate length of mean turn of 9¾" leads to a cross sectional area of .0117 inch². This would be correspondingly more than for 6½ turns with the same resistance, viz. .025 inch², though it is not possible, in providing a teazer winding also, to obtain 6½ turns of greater section than about .0140 inch². Thus the field resistance cannot be as low as we would like it. Contd. | ||