Discussion on “heat-tests on alternators” at Milwaukee, Wis., May 28, 1906

C. P. Steinmetz: This paper is very interesting, as it deals with a problem of machine testing and manufacture that is becoming more and more serious, and will probably in the future be a proper subject of investigation by our standardizing committee. The investigation and measurement of the temperature-rise of a machine under load have been made by loading the machine to full load, and then running it a sufficiently long time to reach stationary temperature. The size and number of machines has increased so fast that even by relegating these heat-tests to the night time, when not much power is used for operating the factory, the amount of power required to make the tests exceeds that available. In the last few years, with the development of hugh alternators, the amount of power required by a single alternator has risen beyond the available power of most manufacturing plants; it is not very uncommon now to find two or three alternators in a factory, of sizes varying from 5 000 to 8 000 kw., waiting to be tested. With such hugh machines, the time required to reach stationary temperature is from 20 to 24 hours, or more. Few facilities are available now really to make a full-load heat-test of these machines; therefore it has become necessary to determine the heating at full load without being required to put full load on the machine.