IEC vs. NEMA: a comparison of the different rating structures and application considerations as applied to motor controllers (600 volts and below)

The selection and application of International Electrotechnical Commission (IEC) rated devices is considerably different from the selection and application of National Electrical Manufacturers Association (NEMA) rated devices. Insights into these different characteristics and different selection/application requirements are provided so that if confronted with a proposition for consideration of IEC rated devices, there will be some basis for making the type of comparison that needs to be made to form an engineering judgment. Many of the comparisons made between IEC and NEMA rated devices are general and apply to the complete product lines. However, the primary comparisons and majority of text are confined to motor controllers for three-phase, single-speed, full-voltage, nonreversing, squirrel-cage induction motor applications at 460 V AC