This paper is not intended to be a theoretical discussion of the principles of unipolar machines; neither is it a purely descriptive article. It is rather a record of engineering experiences obtained, and difficulties overcome, in the practical development of a large machine of the unipolar type. For those who are interested in the design and development of electrical machinery there may be many points of verv considerable interest in this record. Some of the conditions of operation, with their

more »

... attendant difficulties, proved to be so unusual that it is believed that a straightforward story of these troubles, and the methods for correcting them, will be of some value as a published record. Two theoretical questions of unipolar design have come up frequently: (1) whether the magnetic flux rotates or travels with respect to the rotor or the stator; and (2) whether it is possible to generate e.m.fs. in two or more conductors in series in such a way that they can be combined in one direction, without the aid of a corresponding number of pairs of collector rings, to give higher e.m.fs. than a single conductor. To the first question the answer may be made that in the mach ne in question, it makes no difference whether the flux rotates or is stationary; the result is the same on either assumption. To the second it may be said that when the theory of interlinkages of the electric and magnetic circuits is properly considered, it is obvious that the resultant e.m.f. is equivalent to that of one effective conductor, and thurefore it is not practicable to obtain higher e.m.fs. than represented by on, conductor, without the use of collector rings or some equivalent device. It 1811