File:The principles underlying radio communication (1922) (14571631427).jpg

Identifier: principlesunderl00unit (find matches)
Title: The principles underlying radio communication
Year: 1922 (1920s)
Authors: United States. National Bureau of Standards Ould, Richard Sheldon, 1889- United States. Army. Signal Corps
Subjects: Telegraph, Wireless Radio
Publisher: Washington, Govt. Print. Off.
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lot and tooth together, and even with this designthe peripheral velocity of the rim is approximately 12 milesper minute. The rotor consists of a steel disk with a thin rim and a muchthicker hub shaped for maximum strength. Instead of havingteeth on the edge, slots are cut on each side of the rotor verynear the edge and may not extend entirely through the rotordisk. The spokes of steel which remain form the inductors,and a solid rim of steel is left. To cut down the friction of the HIGH-FREQUENCY ALTERNATORS. 205 air at the high speed at which the disk is operated, the slots arefilled with a non-magnetic material such as phosphor bronze,finished off smoothly with the face of the disk. The armature conductors are laid zigzag in small straightopen slots in the flat face of the btator core, this face being per-pendicular to the shaft. Fig. 126a shows a cross section of apart of a small Alexanderson alternator. C is the rotor disk,and A the field windings. The armatures are shown at B, and
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Fig. 126a (left).—Section of Alexanderson alternator, showing rotor.Fig. 126b (right).—Front view of armature used in 200 kw. Alexan-derson alternator. the armature conductors, which are carried in laminations, atE. The field flux passes through the iron frame D, the lami-nated armature, and the disk. The slot filled with non-magnetic material is shown at F. The usual air gap is 0.015inch, so that a very slight defect in construction -will causea serious accident. In the radio station at New Brunswick, N. J., there is anAlexanderson alternator having a rated output of 200 kw.generated at a frequency of about 22,100 cycles per second whenthe alternator is running about 2,170 r.p.m. Similar alterna- 206 DYNAMO-ELECTRIC MACHINERY. tors are in use at Tuckerton, N. J., and Marion, Mass. Inthis alternator the rotor disk runs between two laminatedfirmatures, which are cooled by water circulation. The rotordisk of the type of alternator used at New Brunswick is shownin Fig. 120c: this rot

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