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).
Continued discussion on testing methods for magnets, armatures, and treated magnet steel.
| Identifier | ExFiles\Box 4\5\ 05-page255 | |
| Date | 1st February 1924 guessed | |
| contd:- -2- in which to work an armature, are, the remanence on the one hand, and the coercive force on the other, and that roughly the product of the two constitutes a figure of merit for the treated magnet steel. On the open circuit volt test, there is pract-ically no back magneto-motive-force of the armature and therefore the figure obtained is largely (though not exactly) representative of the remanence of the magnets. Likewise, since there is a very large back magneto-motive-force during a short circuit test, the figure of amperes obtained (provided the speed is high enough that the ohmic resistance of the winding is relatively negligible, the condition which is indicated by the ampere speed curve having become nearly horizontal at the speed in question) is largely representative of the coercive force of the magnets. It is therefore suggested that, sufficiently accurately for a practical test such as is desired, the product of open circuit volts and short circuit amperes so observed, would be quite a representative figure of merit of the magnets on test. We trust this suggestion will be of some utility to you and shall be very interested to hear as to the sort of results which you obtain and the general practical usefulness of the test, should you arrange to adopt it. Yours faithfully, | ||