A 2,000-Frequency Alternator
William Duddell · Proceedings of the Physical Society of London · 1911
The author described and exhibited a small 2,000-frequency alternator which he had designed and had constructed for testing purposes, mainly in connection with telephonic measurements. The alternator is of the salient pole revolving field type running at 8,000 revs. per min. The stator is smooth and wound like a gramme ring, the object being to obtain as near as possible a sine wave. The author gave curves showing the open circuit characteristic, the short-circuit current and the regulation of the alternator at four different frequencies. The output of the alternator amounted to as much as ½ kw. at the higher frequencies. Oscillograph curves of the alternator on open circuit and when loaded with non-inductive resistance, inductances and condensers were shown. These appeared to be practically sine waves. This is not, however, strictly the case, as there is a slight third harmonic present. To demonstrate this a further set of oscillograph curves of the P.D. of the alternator were exhibited. In taking these curves the non-inductive resistance in series with the oscillograph strips was replaced by a small condenser so as to accentuate the upper harmonics. The author described an attempt at 2000 frequency, which had failed, to repeat Dr. Thompson's experiment on the effect of an alternating magnetic field on the brain.