Comparison of IEC, Nema and UL Motor Control Equipment Standards

In the U.S., the traditional motor control equipment nas been designed to National Electrical Manufacturers Association (NEMA) standards. In Europe, the motor controllers most commonly in use have been designed to International Electrotechnical Commission (IEC) standards. The application philosophy has differed greatly between the two standards. In addition, physical characteristics, performance tests and device markings have been defined differently between the two standards. To properly evaluate either device, the criteria underlying their design and application must be understood. The major differences between the standards are reviewed and other differences that have developed between the products outside the realm of the standards are illustrated.