{"id":175,"date":"2026-07-08T08:59:16","date_gmt":"2026-07-08T08:59:16","guid":{"rendered":"https:\/\/industrialelectricmotor.net\/?p=175"},"modified":"2026-07-08T08:59:16","modified_gmt":"2026-07-08T08:59:16","slug":"iec-vs-nema-motor-frame-standards","status":"publish","type":"post","link":"https:\/\/industrialelectricmotor.net\/hi\/iec-vs-nema-motor-frame-standards\/","title":{"rendered":"IEC vs NEMA Motor Frame Standards"},"content":{"rendered":"
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Korea Ever-Power \u00b7 Standards Guide \u00b7 IEC 72-1 \/ NEMA MG1<\/span><\/p>\n

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IEC vs NEMA Motor Frame Standards:
\nKey Differences Explained<\/span><\/h1>\n

IEC and NEMA are the two dominant electric motor frame standards in global industrial use, covering the mechanical dimensions, mounting interfaces, and nameplate data conventions that determine whether a replacement motor will physically fit an existing installation. IEC 72-1 governs the metric system used across Europe, Asia, Africa, and most of the world; NEMA MG1 governs the inch-based system used in North America. This guide explains the differences clearly so you can specify correctly and substitute confidently.<\/p>\n

Frame Dimensions<\/span>
\nShaft Height<\/span>
\nVoltage and Frequency<\/span>
\nCross-Reference Guide<\/span>
\nSubstitution Rules<\/span><\/div>\n<\/div>\n<\/div>\n

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IEC Motor Standard<\/div>\n
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Standard:<\/span> IEC 72-1<\/strong><\/div>\n
Units:<\/span> Metric (mm)<\/strong><\/div>\n
Voltage:<\/span> 380 \/ 400 V<\/strong><\/div>\n
Frequency:<\/span> 50 Hz<\/strong><\/div>\n
Frame key:<\/span> Shaft height (mm)<\/strong><\/div>\n
Example:<\/span> 132S, 160M, 200L<\/strong><\/div>\n
Efficiency:<\/span> IE2 \/ IE3 \/ IE4<\/strong><\/div>\n
Markets:<\/span> Europe, Asia, global<\/strong><\/div>\n<\/div>\n<\/div>\n
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NEMA Motor Standard<\/div>\n
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Standard:<\/span> NEMA MG1<\/strong><\/div>\n
Units:<\/span> Imperial (inches)<\/strong><\/div>\n
Voltage:<\/span> 460 \/ 230 V<\/strong><\/div>\n
Frequency:<\/span> 60 Hz<\/strong><\/div>\n
Frame key:<\/span> Number \u00f7 4 = shaft ht (in)<\/strong><\/div>\n
Example:<\/span> 143T, 182T, 256T<\/strong><\/div>\n
Efficiency:<\/span> NEMA Nom \/ Premium<\/strong><\/div>\n
Markets:<\/span> USA, Canada, Mexico<\/strong><\/div>\n<\/div>\n<\/div>\n<\/div>\n

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\"IEC<\/p>\n
Korea Ever-Power Y2 series three-phase motor built to IEC 72-1 metric frame dimensions \u2014 the shaft height, foot hole spacing, shaft diameter, and flange register dimensions are all specified in millimetres and are interchangeable with any other IEC-compliant motor of the same frame designation from any manufacturer worldwide.<\/div>\n<\/div>\n

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Contents<\/div>\n
1. Why Two Parallel Motor Standards Exist<\/a>
\n2. IEC Frame System Explained<\/a>
\n3. NEMA Frame System Explained<\/a>
\n4. IEC vs NEMA Dimension Comparison<\/a>
\n5. Electrical Differences: Voltage, Frequency, Efficiency<\/a>
\n6. Cross-Reference and Substitution Guide<\/a>
\n7. Korea Ever-Power IEC Motor Range<\/a>
\n8. Frequently Asked Questions<\/a><\/div>\n<\/div>\n

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1. Why Two Parallel Motor Standards Exist<\/h2>\n

Electric motor standardisation developed independently on either side of the Atlantic during the early twentieth century. In the United States, the National Electrical Manufacturers Association (NEMA) published the first edition of its motor frame standard in the 1950s, establishing inch-based dimensions tied to the 60 Hz, 460 V North American power system. In Europe and the rest of the world, the International Electrotechnical Commission (IEC) developed an independent metric system tied to the 50 Hz, 380\u2013400 V international power infrastructure.<\/p>\n

Although both standards define the same basic set of dimensions \u2014 shaft height, shaft diameter, shaft extension length, foot hole spacing, and flange register diameter \u2014 they do so in different units with different numerical values, and they add different supplementary requirements for electrical performance, nameplate data, insulation testing, and efficiency classification. The result is that an IEC motor and a NEMA motor of nominally similar output power are not mechanically interchangeable without adapter plates or shaft machining, even when their frame designations might appear to be at similar positions in their respective series.<\/p>\n

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Geographic Coverage Today<\/div>\n
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IEC 72-1 (metric):<\/strong>
\nEuropean Union, United Kingdom, Australia, New Zealand, India, China, Japan, South Korea, Southeast Asia, Middle East, Africa, South America. Covers approximately 85 percent of global new motor installations.<\/span><\/div>\n
NEMA MG1 (imperial):<\/strong>
\nUnited States, Canada, Mexico, and some Latin American countries where North American electrical infrastructure is installed. Covers approximately 15 percent of global new motor installations.<\/span><\/div>\n<\/div>\n<\/div>\n<\/div>\n

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2. IEC Frame System Explained<\/h2>\n

IEC 72-1 assigns frame designations using the shaft height (the distance in millimetres from the underside of the motor foot to the shaft centreline) as the primary identifier. This makes the shaft height immediately readable from the frame designation: an IEC frame 132 motor has a shaft height of 132 mm; frame 160 has shaft height 160 mm; frame 200 has shaft height 200 mm. Within each shaft height, a letter suffix indicates the stator core length: S (short), M (medium), or L (long). Longer core lengths accommodate larger winding volume and therefore higher power output at the same shaft height.<\/p>\n

\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
IEC Frame<\/th>\nShaft Height H (mm)<\/th>\nShaft Dia. D (mm)<\/th>\nFoot Hole A (mm)<\/th>\nFoot Hole B (mm)<\/th>\nTypical Power (4P)<\/th>\n<\/tr>\n<\/thead>\n
IEC 71<\/td>\n71<\/td>\n14<\/td>\n112<\/td>\n71<\/td>\n0.18\u20130.37 kW<\/td>\n<\/tr>\n
IEC 80<\/td>\n80<\/td>\n19<\/td>\n125<\/td>\n100<\/td>\n0.37\u20130.75 kW<\/td>\n<\/tr>\n
IEC 90<\/td>\n90<\/td>\n24<\/td>\n140<\/td>\n100<\/td>\n0.75\u20132.2 kW<\/td>\n<\/tr>\n
IEC 100<\/td>\n100<\/td>\n28<\/td>\n160<\/td>\n112<\/td>\n2.2\u20133.0 kW<\/td>\n<\/tr>\n
IEC 112<\/td>\n112<\/td>\n28<\/td>\n190<\/td>\n114<\/td>\n3.0\u20135.5 kW<\/td>\n<\/tr>\n
IEC 132<\/td>\n132<\/td>\n38<\/td>\n216<\/td>\n140<\/td>\n5.5\u201311 kW<\/td>\n<\/tr>\n
IEC 160<\/td>\n160<\/td>\n42<\/td>\n254<\/td>\n178<\/td>\n11\u201318.5 kW<\/td>\n<\/tr>\n
IEC 180<\/td>\n180<\/td>\n48<\/td>\n279<\/td>\n203<\/td>\n18.5\u201330 kW<\/td>\n<\/tr>\n
IEC 200<\/td>\n200<\/td>\n55<\/td>\n318<\/td>\n228<\/td>\n30\u201345 kW<\/td>\n<\/tr>\n
IEC 225\u2013315<\/td>\n225\u2013315<\/td>\n60\u201385<\/td>\n356\u2013508<\/td>\n254\u2013406<\/td>\n45\u2013200+ kW<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

The IEC mounting code (IM designation) specifies the mounting arrangement: IM B3 (foot horizontal), IM B5 (flange horizontal), IM B35 (foot and flange), IM V1 (foot vertical shaft down), and so on. The same mounting code system applies across all IEC frame sizes and all manufacturers.<\/p>\n<\/div>\n

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3. NEMA Frame System Explained<\/h2>\n

NEMA MG1 assigns frame numbers (such as 143T, 182T, 213T, 256T) where the first two or three digits encode the shaft height and the letter suffix indicates the T-frame series (the current standard since the 1960s) and mounting type. The shaft height in inches is calculated by dividing the first two digits of the frame number by 4: frame 143T has a shaft height of 14 \u00f7 4 = 3.5 inches (88.9 mm); frame 256T has a shaft height of 25 \u00f7 4 = 6.25 inches (158.8 mm). The third digit (3 in 143T, 6 in 256T) relates to the axial distance between the shaft end and the bolt hole pattern, not directly to the core length.<\/p>\n

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NEMA frame history note: before 1964, NEMA used U-frame designations (such as 143U) which are physically larger than the current T-frame for the same power rating. If replacing a U-frame motor, confirm whether the installed base uses T-frame or U-frame dimensions. Korea Ever-Power does not manufacture U-frame motors; all Y2 series motors are built to current IEC 72-1 dimensions which align more closely with T-frame than U-frame NEMA motors.<\/p>\n<\/div>\n

\n\n\n\n\n\n\n\n\n\n\n\n
NEMA Frame<\/th>\nShaft Height (in)<\/th>\nShaft Height (mm)<\/th>\nShaft Dia. (in)<\/th>\nTypical Power (4P, 60 Hz)<\/th>\n<\/tr>\n<\/thead>\n
NEMA 56<\/td>\n3.50 in<\/td>\n88.9<\/td>\n5\/8 in<\/td>\n\u2153\u2013\u00be hp<\/td>\n<\/tr>\n
NEMA 143T<\/td>\n3.50 in<\/td>\n88.9<\/td>\n7\/8 in<\/td>\n1\u20131.5 hp<\/td>\n<\/tr>\n
NEMA 182T<\/td>\n4.50 in<\/td>\n114.3<\/td>\n1\u215b in<\/td>\n2\u20133 hp<\/td>\n<\/tr>\n
NEMA 213T<\/td>\n5.25 in<\/td>\n133.4<\/td>\n1\u215e in<\/td>\n5\u20137.5 hp<\/td>\n<\/tr>\n
NEMA 256T<\/td>\n6.25 in<\/td>\n158.8<\/td>\n1\u215d in<\/td>\n10\u201315 hp<\/td>\n<\/tr>\n
NEMA 324T<\/td>\n8.00 in<\/td>\n203.2<\/td>\n2\u215b in<\/td>\n20\u201330 hp<\/td>\n<\/tr>\n
NEMA 365T<\/td>\n9.00 in<\/td>\n228.6<\/td>\n2\u215e in<\/td>\n40\u201360 hp<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/div>\n

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4. IEC vs NEMA Dimensional Comparison<\/h2>\n

The following table places comparable IEC and NEMA frames side by side, showing why the two systems are not dimensionally interchangeable even at nominally similar shaft heights. The shaft diameters, foot hole spacings, and shaft extension lengths all differ, meaning that an IEC motor cannot be directly bolted onto a NEMA motor mounting without modification.<\/p>\n

\"IEC<\/p>\n

\n\n\n\n\n\n\n\n\n\n\n
IEC Frame<\/th>\nIEC Shaft Ht (mm)<\/th>\nNearest NEMA Frame<\/th>\nNEMA Shaft Ht (mm)<\/th>\nShaft Ht Difference<\/th>\nDirect Bolt-On?<\/th>\n<\/tr>\n<\/thead>\n
IEC 90<\/td>\n90 mm<\/td>\nNEMA 143T<\/td>\n88.9 mm<\/td>\n\u22121.1 mm<\/td>\nNo<\/td>\n<\/tr>\n
IEC 112<\/td>\n112 mm<\/td>\nNEMA 182T<\/td>\n114.3 mm<\/td>\n+2.3 mm<\/td>\nNo<\/td>\n<\/tr>\n
IEC 132<\/td>\n132 mm<\/td>\nNEMA 213T<\/td>\n133.4 mm<\/td>\n+1.4 mm<\/td>\nNo<\/td>\n<\/tr>\n
IEC 160<\/td>\n160 mm<\/td>\nNEMA 256T<\/td>\n158.8 mm<\/td>\n\u22121.2 mm<\/td>\nNo<\/td>\n<\/tr>\n
IEC 180<\/td>\n180 mm<\/td>\nNEMA 286T<\/td>\n177.8 mm<\/td>\n\u22122.2 mm<\/td>\nNo<\/td>\n<\/tr>\n
IEC 200<\/td>\n200 mm<\/td>\nNEMA 324T<\/td>\n203.2 mm<\/td>\n+3.2 mm<\/td>\nNo<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

Even where shaft heights are within 2 to 3 mm of each other, foot hole spacings (A and B dimensions) differ substantially between IEC and NEMA, and shaft diameters are specified in different tolerancing systems (metric h6 in IEC versus inch tolerances in NEMA). A direct bolt-on substitution of an IEC motor into a NEMA mounting or vice versa is not possible without machining work or an adapter plate.<\/p>\n<\/div>\n

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5. Electrical Differences: Voltage, Frequency and Efficiency<\/h2>\n
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Supply Voltage and Frequency<\/div>\n

IEC motors are rated for 380\u2013400 V, 50 Hz three-phase supply (the standard across the IEC world). NEMA motors are rated for 460 V (or 230\/460 V dual-voltage), 60 Hz three-phase supply (the North American standard). Running an IEC motor on 60 Hz supply increases synchronous speed by 20 percent (a 4-pole motor runs at 1,800 rpm instead of 1,500 rpm) and increases iron losses, requiring derating. Running a NEMA motor on 50 Hz supply reduces synchronous speed by 17 percent and may require re-rating. Dual-voltage NEMA motors (230\/460 V, 60 Hz) cannot be simply connected to a 380 V, 50 Hz IEC supply without a frequency difference issue even when voltage is acceptable.<\/p>\n

Power output at 50 Hz on a 60 Hz NEMA motor: derate to approximately 83% of nameplate rating<\/div>\n<\/div>\n
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Power Units: kW vs Horsepower<\/div>\n

IEC motors are rated in kilowatts (kW). NEMA motors are rated in horsepower (hp). Conversion: 1 hp = 0.746 kW. Common cross-references: 1 hp \u2248 0.75 kW; 2 hp \u2248 1.5 kW; 5 hp \u2248 3.7 kW; 10 hp \u2248 7.5 kW; 20 hp \u2248 15 kW; 50 hp \u2248 37 kW. The IEC preferred power series (0.18, 0.25, 0.37, 0.55, 0.75, 1.1, 1.5, 2.2, 3.0, 4.0, 5.5, 7.5, 11 kW\u2026) does not align exactly with the NEMA hp series (0.5, 0.75, 1.0, 1.5, 2.0, 3.0, 5.0, 7.5, 10\u2026 hp), so there is rarely an exact power-for-power substitution at the same frame size.<\/p>\n

Quick reference: select IEC motor at the next standard kW above the hp \u00d7 0.746 kW equivalent<\/div>\n<\/div>\n
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Efficiency Classification<\/div>\n

IEC motors use the international efficiency classification system (IE1 Standard, IE2 High, IE3 Premium, IE4 Super Premium) defined in IEC 60034-30-1. NEMA motors use a different classification scheme: NEMA Nominal Efficiency and NEMA Premium Efficiency (defined in NEMA MG1 Table 12-12). NEMA Premium Efficiency is approximately equivalent to IEC IE3 at most power ratings, though the test methods and specific efficiency values differ at some points in the range. The IEC and NEMA efficiency classes are not numerically interchangeable and should not be directly compared without consulting both standards.<\/p>\n<\/div>\n<\/div>\n<\/div>\n

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6. Cross-Reference and Substitution Guide<\/h2>\n

Substituting an IEC motor for a NEMA motor (or vice versa) requires checking four things independently: shaft height (does it match the coupling or driven machine), foot hole pattern (does it match the baseplate), shaft diameter and extension length (does it fit the coupling or pulley), and electrical rating (does the motor work on the available supply). All four must be verified \u2014 a match on one or two dimensions is not sufficient for a successful substitution.<\/p>\n

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Substitution Checklist: IEC Motor Replacing NEMA (or Reverse)<\/div>\n
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\u2713 Shaft height<\/div>\n

Measure the existing motor shaft height from the foot underside to shaft centreline. Find the IEC frame whose shaft height matches within \u00b12 mm to avoid a height difference at the coupling.<\/p>\n<\/div>\n

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\u2713 Foot hole pattern<\/div>\n

Measure A (longitudinal foot hole spacing) and B (lateral foot hole spacing) on the existing motor. Compare with the IEC frame A and B dimensions. If they differ, a new baseplate or adapter plate is needed.<\/p>\n<\/div>\n

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\u2713 Shaft diameter and extension<\/div>\n

The existing coupling bore or pulley bore must match the new motor shaft diameter. If not, bore the coupling or fit a shaft adapter sleeve. Shaft extension length must allow full coupling engagement.<\/p>\n<\/div>\n

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\u2713 Electrical supply compatibility<\/div>\n

Confirm the IEC replacement motor rated voltage and frequency match the available supply. For North American 460 V 60 Hz installations, specify a 460 V 60 Hz wound IEC motor or use a step-down transformer if using a standard 380 V 50 Hz IEC motor.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n

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7. Korea Ever-Power IEC Motor Range<\/h2>\n

Korea Ever-Power manufactures all electric motors to IEC 72-1 metric frame standards. All Y2 series motors are dimensionally interchangeable with any IEC-compliant motor from any manufacturer at the same frame designation. The full three-phase motor range<\/a> covers IEC frames 71 through 315 in 2-pole, 4-pole, 6-pole, and 8-pole configurations at 380 V 50 Hz as standard.<\/p>\n

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\"Korea<\/p>\n

CNC Frame Machining<\/div>\n<\/div>\n
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\"Korea<\/p>\n

CE and ISO Certified<\/div>\n<\/div>\n
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\"Korea<\/p>\n

Global IEC Markets<\/div>\n<\/div>\n
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\"Korea<\/p>\n

Worldwide Delivery<\/div>\n<\/div>\n<\/div>\n<\/div>\n

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8. Frequently Asked Questions<\/h2>\n
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Is a NEMA 145T motor the same as an IEC 90 motor?<\/div>\n<\/div>\n
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No. NEMA 145T (shaft height 3.625 inches = 92.1 mm) and IEC 90 (shaft height 90 mm) have similar but not identical shaft heights \u2014 the difference of 2.1 mm means the shaft centreline heights differ, which will cause coupling misalignment if one is substituted for the other on the same baseplate without shimming. More critically, the foot hole spacings (A and B dimensions) are different between NEMA 145T and IEC 90, meaning the motor cannot be bolted down to the same baseplate without modification. The shaft diameter also differs: NEMA 145T uses a 7\/8 inch (22.2 mm) shaft while IEC 90 uses a 24 mm shaft. These are three separate incompatibilities requiring modification before a NEMA-to-IEC substitution is possible.<\/p>\n<\/div>\n<\/div>\n

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Can Korea Ever-Power supply motors wound for 460 V 60 Hz for North American installations?<\/div>\n<\/div>\n
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Yes. Korea Ever-Power can supply Y2 series motors wound for 460 V 60 Hz (or dual-voltage 230\/460 V 60 Hz) for North American market installations on IEC metric frames. The motor would retain its IEC 72-1 metric frame dimensions \u2014 so all mounting dimensions remain metric \u2014 but the electrical specification matches the North American supply standard. This is the most practical approach for North American facilities that want to standardise on IEC metric frame motors for dimensional interchangeability while using the local 60 Hz supply. Please enquire through the Korea Ever-Power technical team<\/a> with your required power rating, frame size, pole count, and supply specification.<\/p>\n<\/div>\n<\/div>\n

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Which is better: IEC or NEMA for a new machine design?<\/div>\n<\/div>\n
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For any new machine designed for sale or installation outside North America, IEC is the correct choice. IEC motors are available from a wider range of manufacturers globally, cover a broader power range in smaller increments, and meet the energy efficiency regulations of the European Union, China, Australia, and most other markets that are mandating IE3 minimum efficiency. For machines designed exclusively for North American customers using North American electrical infrastructure (460 V 60 Hz), NEMA MG1 motors are the more straightforward specification because they match the local electrical supply standard without any derating or frequency conversion. For a machine that will be exported globally, design to IEC and specify dual-voltage winding (230\/460 V for US market variants) \u2014 the IEC frame dimensions are then consistent worldwide while the winding is adjusted for the local supply.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n

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Korea Ever-Power \u00b7 IEC Frame Motors \u00b7 Worldwide Supply<\/div>\n

Need IEC Frame Motors for Your Application or Export Market?<\/h2>\n

Korea Ever-Power Y2 series: full IEC 72-1 compliance, frames 71 through 315, IE3 standard, available in 380 V 50 Hz and 460 V 60 Hz windings on request. Global export with CE and ISO certification.<\/p>\n

View IEC Motor Range<\/a><\/p>\n<\/div>\n<\/div>\n

Edited by Cxm<\/p>\n<\/div>","protected":false},"excerpt":{"rendered":"

Korea Ever-Power \u00b7 Standards Guide \u00b7 IEC 72-1 \/ NEMA MG1 IEC vs NEMA Motor Frame Standards: Key Differences Explained IEC and NEMA are the two dominant electric motor frame standards in global industrial use, covering the mechanical dimensions, mounting interfaces, and nameplate data conventions that determine whether a replacement motor will physically fit an […]<\/p>","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_et_pb_use_builder":"","_et_pb_old_content":"","_et_gb_content_width":"","footnotes":""},"categories":[28],"tags":[],"class_list":["post-175","post","type-post","status-publish","format-standard","hentry","category-industrial-electric-motor"],"_links":{"self":[{"href":"https:\/\/industrialelectricmotor.net\/hi\/wp-json\/wp\/v2\/posts\/175","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/industrialelectricmotor.net\/hi\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/industrialelectricmotor.net\/hi\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/industrialelectricmotor.net\/hi\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/industrialelectricmotor.net\/hi\/wp-json\/wp\/v2\/comments?post=175"}],"version-history":[{"count":1,"href":"https:\/\/industrialelectricmotor.net\/hi\/wp-json\/wp\/v2\/posts\/175\/revisions"}],"predecessor-version":[{"id":178,"href":"https:\/\/industrialelectricmotor.net\/hi\/wp-json\/wp\/v2\/posts\/175\/revisions\/178"}],"wp:attachment":[{"href":"https:\/\/industrialelectricmotor.net\/hi\/wp-json\/wp\/v2\/media?parent=175"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/industrialelectricmotor.net\/hi\/wp-json\/wp\/v2\/categories?post=175"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/industrialelectricmotor.net\/hi\/wp-json\/wp\/v2\/tags?post=175"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}