Electrical and mechanical differences between NEMA/IEEE and IEC ac low voltage random wound induction motors

The primary standard for low voltage, random wound, induction motors in North American countries is National Electrical Manufacturers Association (NEMA) MG 1-2011. In some other countries, the governing standard is International Electrotechnical Commission (IEC) 60034-1:2010. This paper compares performance, design and construction details of NEMA and IEC three phase, low voltage, random wound alternating current (AC) induction motors. Not only are there obvious mechanical mounting and dimensional differences, but design practices and electrical design norms are different as well. Users must recognize and provide for these variations as they manage projects in different parts of the world. Although testing standards have been fundamentally harmonized between IEEE, CSA and IEC in recent years, efficiency requirements in various countries are not uniform. Obtaining motors in compliance with common standards such as IEEE 841 or API 610 becomes difficult when considering IEC motor designs. This paper discusses the challenges that arise when trying to apply a NEMA based standard to an IEC motor design and vice versa.