Derating of polyphase induction motors operated with unbalanced line voltages

The results of tests are presented which indicate the need for a severe reduction in the rating of motors when operated with unbalanced line voltages. Varying amounts of positive-and negativesequence applied voltages are considered. Also, results of one method of calculating reduced motor rating are presented, and are compared with measured values. As data are conservative in that only the most unfavorable conditions for unbalance are examined.