NEMA vs. IEC Efficiencies

Since 1926, the National Electrical Manufacturers Association (NEMA) has set standards for motors used in North America. NEMA regularly updates and publishes MG 1, a book that assists users in the proper selection and application of motors and generators. It contains practical information concerning performance, efficiency, safety, testing, construction and the manufacture of alternating current (AC) and direct current (DC) motors and generators. The International Electrotechnical Commission (IEC) defines the standard for electric motors for the rest of the world. Similar to NEMA, IEC publishes Standard 60034-1, the motors guide for the global market.

While there are many similarities between NEMA and IEC, there are few fundamental differences in the two motor standards. The NEMA philosophy emphasizes more robust designs for broader applicability. Ease of selection and breadth of application are two of the fundamental mainstays within its design philosophy. IEC, on the other hand, is focused on application and performance. Selecting IEC devices requires a higher level of knowledge about the application, including motor load, duty cycle, and full load current (FLC) when selecting an IEC contactor. In addition, NEMA designs components with a safety factor and may have up to 25 percent service factor while IEC is focused on space and cost savings.

IEC efficiency standards
Standard IEC/EN 60034-30-1 on efficiency classes of line-operated AC motors was published by the IEC in 2014. This standard defines four IE efficiency classes for single speed electric motors. Compared with IEC/EN 60034-30: 2008, it significantly expands the range of products covered with the inclusion of 8-pole motors and introduces IE4 efficiency performance class for electric motors. More recently, the technical standards have been updated per IEC/TS 60034-30-2, which are for variable speed AC motors not covered in the IEC/EN 60034-30-1 and apply to frequency converters only. They apply to synchronous and permanent magnet motors. The purpose of IEC/TS 60034-30-2 is to create a level playing field between established and new, innovative, motor technologies to enable fair competition and market development.

What about NEMA?
NEMA has no defined standard available yet for IE5 in the North American market, although some manufacturers are marketing a VFD-driven motor-drive pair as “ultra-premium efficiency.” The same concept applies in which IE5-equivalent efficiency levels are achieved through variable speed drives at full and partial loads. An integrated motor-drive using ferrite assisted synchronous reluctance technology is another solution that will provide an IE5 level of efficiency and simplify the setup while eliminating expensive wiring and installation time.

So why is efficiency such a hot topic?
Government mandates on motors exist for many reasons. Motors and motor systems account for approximately 53% of global electricity consumption. Motors can stay in use for 20 years or longer, so the wasted energy used by an inefficient motor accrues over the lifetime of a product, leading to unnecessary strain on power grids and avoidable CO₂ emissions. Simply by focusing on the selection of an optimal motor, OEMs can design their equipment to improve overall system efficiencies, leading to reduced environmental impact and cost savings, which can passed to their customers. In addition to lowering greenhouse gasses and energy bills, an efficient motor can result in improved air quality, less equipment downtime and increased output for the end user.

Is it worth upgrading? Savings and payback
The purchase price of a motor and drive is just a few percent compared to the energy spent to run the equipment over its lifetime. For low voltage motors, the payback time is typically 2-3 years in the case of a replacement. When considering a new investment, the typical payback time for a higher IE efficiency class is less than one year.