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).
Motor flux density and its effect on performance, with calculations for a Goshawk motor.
| Identifier | ExFiles\Box 35\4\ scan 141 | |
| Date | 5th May 1923 guessed | |
| -3- Contd. By reducing the flux density to 6,000 we bring this down to 2.33 x 10^10, but to bring it down to the major limit would necessitate a flux density as low as 5780. This would require so few exciting turns per pole that in order to have an ohmic resistance consistent with the speed at which the motor is to be run, the size of the field wire would seem too small. If this size were then e increased, leaving the number of turns the same, this would increase the speed of the motor. Thus the number of conductors ought to be less and the flux proportionally more, if the speed is to remain 1760. But even then, as demonstrated to you, the machine would be unsuitable, the quantities appearing ridiculous because this size of motor, owing to its high speed, is asked to develop such a relatively small torque. In the case of the Goshawk motor on the other hand Ø = 161,000 Z = 58 (proposed) N = 1760 (as above) Ø Z N = 1.64 x 10^10 which in this instance is too small. If we put the flux density up to 7,000 the figure becomes 1.765 x 10^10, which is better but still not high enough. It would be undesirable to put up the flux much Contd. | ||