Measurement of stray load loss of d.c. machines

For many years the standard practice, in calculation of conventional efficiency of d.c. machines, has been to include stray load losses as equal to 1% of the output. This assumption may be true for large, compensated d.c. machines but it is known to be small for smaller, uncompensated, general-purpose, industrial-type machines of open design. An A.I.E.E. Committee on Rotating Machines was formed to investigate whether the present practice of assigning 1% for the stray load loss is justified or not. They reached a conclusion, reported in 1949, after investigating 243 stray loss tests on different motors ranging from 1/2 hp to 50 hp, that the present practice should be continued until a new method is available which gives a direct measure of these losses...In this article, an attempt is made to measure stray load losses directly by a short circuit test --Introduction, page 1-2