Discussion on “some features affecting the parallel operation of synchronous motor-generator sets,” at New York, March 23, 1906

W. L. Waters: In the operating of synchronous motor-generators, my own experience has, unfortunately, not shown quite such simple results as those indicated by Mr. Taylor. One installation of synchronous motor-generators will work very well; the machines will divide their load properly, and the load can be changed from one machine to another by means of the field rheostat, while another installation which is apparently very similar will give considerable trouble, even after the machines are lined up and the connections correctly made. Suppose a 500-kw. machine is running on full load and a second machine is thrown in, then this second machine might take 40% of the load or it might take 60%; and as further load comes on the machines, it may be divided proportionately between them, or it may not. The results obtained from the machines seem to be different every time they are thrown together. The reason for this is not particularly clear, but it has been suggested that the explanation is to be found in the different condition of the outside circuit and of the load at the time. Most of these machines carry a load which is by no means balanced. The distribution system being three single-phase circuits rather than three phase. The result of this is that there may be very bad conditions of unbalancing, both of load and power-factor, between the different phases, and that these conditions may vary widely from time to time.