U NTIL about ten years ago the only cooling medium utilized for electri cal rotating machinery was air. Ob viously this was occasioned not by the fact that air has any particularly suitable characteristics but because it is the daily common surrounding medium which, of necessity, must be used for open-type machinery. Before that time, the need for construction of machines of con stantly increasing size and speed had brought about the development of closed systems of ventilating. In these, facili ties had been provided for conditioning the cooling air, but this had been primar ily for the purpose of removing dust par ticles. The elimination of the particu larly objectionable oxygen had not been attempted although for some time inert gas had been used in transformers to pre vent oxidation of oil or insulation. Since the use of any medium other than air necessitates a gastight enclosure, it is desirable to use that particular gas or mixture of gases, which offers the most advantages to outweigh the fact that more expensive construction is required. The desirability of using hydrogen for this purpose was first suggested by Doctor W. R. Whitney of the General Electric Company about 18 years ago, and as a re sult a large amount of study and numer ous tests were made to determine the ad vantages of employing this particular gas. The superiority of hydrogen was definitely indicated especially in the case of large high-speed alternators. The difficult problem of a simple and reliable shaft seal, as well as the ability of designers to utilize air cooling satisfactorily on ma chines required by the power industry, de-Paper 40-76, recommended by the AIEE committee on electrical machinery, and presented at the AIEE winter convention, New York, Ν. Y., January 22-26, 1940. PHILIP SPORN is vice-president in charge of engi neering of the American Gas and Electric Service Corporation, New York, N. Y.; F. M. PORTER is a member of the electrical-engineering department of the same organization. F. M. PORTER ASSOCIATE AIEE layed the use of hydrogen in generators until several years ago. In the meanwhile attention was di rected to the hydrogen-ventilated syn chronous condenser, and in 1928 two such machines were placed in service, one of which was the 20,000-kva unit at the Turner station of the Appalachian Elec tric Power Company. This was followed at intervals, by seven others on the sys tems with which the authors are asso ciated, comprising in all a combined ca pacity of 161,000 kva. The successful operation of these machines led to the installation in 1937 of a 50,000-kva hy drogen-cooled generator at Logan, W. Va. This was followed by a 66,667-kva generator placed in service the early part of 1939. An additional condenser was placed in operation in July 1939; still an other in November 1939, and two more generators are in process of installation and will go into service early in 1941, making a combined total of 432,000 kva on the American Gas and Electric Com pany systems. There has thus been obtained an experience with hydrogen,...
