Electric Motor Standards

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The concept of standard is used for AC motors which are designed in conformity with international or national standards within a given country or area. The standards generally applied to ÀC motors can be divided into two main categories: IEC/EN and NEMA. 

The IEC/EN Standard
The IEC/EN standards cover what is usually referred to as‘IEC’ motors (Europe, Asia).  In this standard, metric units (SI units) such as metre (m) are applied.

The International Electrotechnical Commission (IEC) sets standards for motors used in many countries around the world. IEC 60034 standards contain recommended electrical practices that are developed by the participating IEC countries. Mechanical dimensions and tolerances of AC motors are specified by the IEC 600 72 and EN50347 standards.

NEMA
The NEMA standards covers AC motors in the USA and Canada and other countries related to the US. Imperial (US) units such as inches are applied. The National Electrical Manufacturers Association (NEMA) sets standards for a wide range of electrical products, including motors. NEMA is primarily associated with motors used in North America. The standards represent general industry practices and are supported by manufacturers of electrical equipment. The standard for motors is found in NEMA Standard Publication No. MG1. Some large motors may not fall under NEMA standards