Acyclic (homopolar) dynamos

Except for very low pressures, the so-called homopolar dynamo has so far been a failure from a commercial point of view. This failure is principally due to two conditions: first, the uncertainty as to the magnetic and electrical conditions prevailing in this type of generator; secondly, the difficulties encountered in collecting large currents from a generator running at a high rate of speed. These conditions will be discussed in this paper, and in order that their import may be grasped there will be described in outline the design of, and some results obtained with, a 300-kw. 500-volt turbine-driven acyclic (homopolar) generator built in the shops of one of the large electrical manufacturing companies. The question dealt with is a broad one, too broad to be discussed at length in this paper; the main points only will be taken up and a more thorough discussion left for a later date.