Comparison of Application Capabilities of U and T Rated Motors

The inception of the T-frame line in the mid 1960´s as the new standard integral horsepower induction motor has frequently raised the question among users as to the relative application capability of these motors to previous U-frame motors with which users have good application familiarity. This question has been asked and answered in numerous technical presentations and conferences. The aspects of the topic that have aroused most interest are: 1) insulation systems, temperature rating standards, and relative insulation life expectancy, 2) effect of overloads, 3) effect of over- and undervoltage, 4) effect of unbalanced voltage, and 5) bearing and shaft sizes.