Reduction in capacity of polyphase motors due to unbalancing in voltage

It is well-known that polyphase motors of both induction and synchronous types overheat when supplied from circuits in which the ideal conditions of voltage balance and phase angle are not maintained. In order to determine definitely the performance under other than ideal conditions, and to ascertain the points at which overheating commences, a series of tests was run under varying conditions of voltage unbalance, unsymmetrical angular relations between phases, and combinations of these two.