Readers are encouraged to share their views on issues affecting the electric power engineering profession. Send your letters to Mel Olken, editor in chief, m.olken@ieee.org. Letters may be edited for publication.
Early Three-Phase Power
The History article in the September/ October 2007 issue of IEEE Power & Energy Magazine titled "Early Three-Phase Power" by Gerhard Neidhöfer was very interesting. This is the first time I have ever read such a concise summary of all the early three-phase work conducted both here and abroad.
The comments on p. 98 regarding an initial reluctance to accept three-phase distribution in situations where lighting was required reflects a concern in that era about the operation of an unbalanced three-phase system. A book titled Polyphase Electric Currents by Prof. Silvanus P. Thompson and published in 1895 discusses the problem of unbalanced three-phase circuits. It describes a solution to this in the form of a three-phase incandescent lamp having three filaments (called "wicks" at that time) joined in a common connection inside the bulb, and using three external terminals. This device was first shown by Michael von Dolivo-Dobrowolsky in 1891, and it was apparently considered such an elegant solution to this problem that similar lamps were eventually made by the Edison-Swan Company. In addition, a three-phase arc light having three carbons in a 120-degree configuration was demonstrated in 1894. The arc was said to display a "gyratory movement."
Thomas J. Blalock
I greatly enjoyed the article "Early Three-Phase Power" in the September-October 2007 issue of IEEE Power & Energy Magazine. I was especially surprised to learn that Nikola Tesla in the United States focused on two-phase ac and overlooked the advantages of three-phase ac, leaving three phase to be developed by Haselwander, Dolivo-Dobrowolsky, and Wenstrom in Germany and Switzerland. I knew of the ac-versus-dc battle between Tesla (funded by Westinghouse) and Edison, but not the two-phase versus three-phase battle, and the WWI bias in the US against giving due credit to German and Swiss inventors.
Jerry Goerz
