Since 1926, the National Electrical Manufacturers Association (NEMA) has set standards for electric motors used in North America. NEMA regularly updates and publishes MG 1, which assists users in the proper selection and application of motors and generators. It contains practical information about the performance, efficiency, safety, testing, fabrication, and fabrication of alternating current (AC) and direct current (DC) motors and generators. The International Electrotechnical Commission (IEC) sets standards for electric motors for the rest of the world. Similar to NEMA, IEC publishes standard 60034-1, a guide for electric motors for the global market.
Do you know the difference between the NEMA standard and the IEC standard in addition to the metric and imperial systems? China’s motor standard uses IEC (European standard), and NEMA MG1 is the American standard. Fundamentally, both are the same. But it’s also a little different in some places. NEMA standards and IEC standards differ in terms of motor power usage coefficient and rotor temperature rise. The power utilization factor of the NEMA motor is 1.15, and the IEC (China) power factor is 1. The way of marking other parameters is different, but the essential content is the same.
Let’s take a look:
1. Metric motors are more beautiful and conform to oriental aesthetics, but imperial motors have more types.
NEMA standard motor
IEC standard motor
2. Different comparisons
Generally speaking, the main difference is that the mechanical size and installation are different, and IEC is stricter about sealing; in terms of electrical Nema requirements, there is a long-term overload coefficient of 1.15 and UL’s common high insulation requirements.
| Difference | IEC | Nema |
| Size Standard | Metric | American market/imperial system (including threaded holes for junction box outlet) |
| Global market share | 70% | 30% |
| Implementation standards | IEC60034, 60071 | Nema MG1 |
| Common shells | Cast aluminum or cast iron | cast iron or cast steel |
| Common protection levels | IP44 and above | IP20 and above |
| Common greases | Lithium grease | Polyurethane based grease |
| Common motor junction box locations | top | left or right |
| Motor seal | Seal (higher) | Common water-slinging ring seals (lower)/high-end seals |
| Motor drainage | No clear request | Common requirements include drainage holes or vents |
| Motor starting current and torque | IEC-N/NE/H/HEIEC-N≈Nema A/BIEC-H≈Nema C | Nema A, B, C, D [common nema B]The starting current and starting torque are clarifiedThe higher ABCD rises, the greater the current and the greater the starting torque. Nema D has no corresponding IEC standard |
| Frequency | 50hz | 60Hz |
| Wiring | Common 6-pole wiring board (star connection) | Common 9-pole terminal board (double star connection) |
| Allowed supply voltage deviation | Area A±5%, Area B±10% | Standard ±10% |
| Allowable power supply frequency deviation | Area A±2%, Area B±3%~5% | Under rated voltage, frequency ±5% |
| Motor working system | More detailed definition, S1….S10 | The definition is slightly simpler |
| Motor overload capacity | Standard 1.0 | Allows long-term 115% overload (ie: factor 1.15) |
| Energy efficiency testing methods | EC60034-2-2 B1Currently EU access IE3 | IEEE 112-2017 B CSA390:10(R2019) The current North American access is equivalent to IE3 |
| Insulation requirements/certifications | Lower/common CE | Underrated voltage, frequency ±5% |
Although NEMA and IEC have many similarities, there are a few fundamental differences between the two motor standards. NEMA’s philosophy emphasizes a more robust design for broader applicability. Ease of selection and breadth of application are two fundamental pillars in its design philosophy. IEC, on the other hand, focuses on applications and performance. Selecting IEC equipment requires a higher level of application knowledge, including motor loading, duty cycle, and full load current (FLC) – used when selecting an IEC contactor. Additionally, NEMA designs components with safety factors that may have service factors as high as 25%, while IEC focuses on saving space and cost.
What about NEMA?
NEMA has not yet provided a defined standard for IE5 in the North American market, although some manufacturers are selling VFD-powered motor drive pairs as “ultra-high efficiency.” The same concept applies to achieving IE5 equivalent efficiency levels with variable speed drives at full load and part load. Integrated motor drives using ferrite-assisted synchronous reluctance technology are another solution that provides IE5-level efficiency and simplifies setup while eliminating costly wiring and installation time.
Why is energy efficiency a hot topic?
There are many reasons why government licensing of electric motors exists. Electric motors and motor systems account for approximately 53% of global electricity consumption. Motors can remain in use for 20 years or more, so the energy used by inefficient motors accumulates over the life of the product, causing unnecessary stress on the grid and avoiding CO2 emissions. By focusing on selecting the best motor, OEMs can design their equipment to improve overall system efficiency, resulting in reduced environmental impact and cost savings to pass on to customers. In addition to lowering greenhouse gases and energy bills, efficient motors can improve air quality, reduce equipment downtime, and increase end-user output.
Is it worth upgrading?
The difference between the purchase price of a motor and a drive is only a few percent, relative to the energy used to run the device over its lifetime. For low voltage motors, when replacing, the payback time is typically 2-3 years. When considering new investments, the typical payback time for an IE efficiency rating is less than one year.
