motor efficiency classes
Understanding Motor Efficiency Classes: IE2, IE3, and IE4
IEC efficiency classes (IE1, IE2, IE3, IE4, and IE5 in the same family of standards) classify how much of the electrical input becomes shaft power on a defined test — IEC 60034-30-1 for most 50/60 Hz mains-fed induction motors in the industrial kW band. The class is printed on the nameplate. It is not a brand, not a frame number, and not the same thing as a household energy label.
Rated kW on the plate is output. Electrical input is output ÷ efficiency. A 7.5 kW motor at 90% efficiency draws about 8.3 kW from the grid at full load; the same shaft at 87% draws more. That is why plants compare IE2 vs IE3 on long-running pumps and fans. The percentage is rating-specific (kW, poles, 50 or 60 Hz). This page does not invent a table of η% — use the two nameplates or a test report.
JWMotor’s general-purpose map is: Y2 for IE2, YE3 for IE3 (the usual new-install and replacement quote), YE4 for IE4 when the spec or energy policy names super-premium. Minimum legal class depends on the country and the rating. We quote the class you print on the order, not a slogan.
IE class does not pick poles, voltage or mounting. A YE3 and a Y2 in the same kW can still be the wrong shaft or B5 instead of B3. Send the plate (kW, poles, V, Hz, frame, IE) to contact JWMotor. For a running-cost sketch, use nameplate efficiencies in the numbers — do not copy a blog’s average η.
Class vs JW series
How to choose a class
- Read IE on the installed plate if you must stay like-for-like
- New general-purpose S1 → YE3 (IE3) unless the spec says otherwise
- High hours or IE4 named → YE4
- Energy maths uses plate η, not this page’s adjectives
Terms
- IE1 / Standard
Older standard-efficiency band. Many regions no longer allow new IE1 for general-purpose mains motors in the regulated kW range. You still see IE1 on installed machines. Replacement is usually YE3 unless the spare must stay like-for-like IE2.
- IE2 / High (Y2)
High efficiency. JW Y2 is the IE2 series. Use it when the project or the spare policy still names IE2, or when you are matching an installed IE2 nameplate and must not change class.
- IE3 / Premium (YE3)
Premium efficiency. Default quote for new IEC three-phase S1 motors in most industrial specs JW sees. Same shaft-height family as other IEC metric motors; still confirm D, key and flange.
- IE4 / Super premium (YE4)
Super-premium. Worth the conversation on high hours (process pumps, fans). Not automatic: first match kW, poles and mounting, then whether the buyer will pay for IE4.
- η (efficiency)
η = shaft power ÷ electrical input, as a percentage at the stated load. Class is a band; the number on the plate is the one you use for energy maths. Do not mix 50 Hz and 60 Hz figures for the same kW.
- Not covered here
IE codes on this page are for mains industrial induction motors under IEC 60034-30-1. They are not EV traction classes, not generator efficiency, and not an appliance energy star.
What IE class is not
Not a substitute for kW, poles or shaft height. Not a household energy label. Not a wind-turbine or EV efficiency standard. JW will not print a fake η% to win the keyword.
FAQ
Is IE3 the same as YE3?
YE3 is JW’s IE3 general-purpose series. IE3 is the class. Other makers also sell IE3. Match kW, poles, volts and mounting; do not order “IE3” without those.
Can I drop an IE3 YE3 onto an IE2 machine?
Often yes if H, shaft, flange, kW and poles match. Speed is still set by poles and frequency, not by IE class. Confirm the datasheet shaft Ø.
Do you publish efficiency % on this page?
No. η depends on the exact rating. Read it from the two nameplates or the test report. Inventing a % would be the wrong number for your motor.
IE4 vs IE3 — when does JW quote YE4?
When the specification or energy policy names IE4, or hours are high enough that the buyer wants super-premium. Otherwise YE3 is the usual industrial quote.
Does a VFD change the class?
The nameplate class is still the mains-test class. Inverter supply is a different thermal and insulation discussion — JW YVF2 when the motor is inverter-duty, not a silent swap of a standard YE3 without checking the plate.
What do I send for a quote?
IE class if printed, kW, poles, voltage, frequency, mounting, frame, and a photo of the plate.
Get a quote
Request a quote with rated kW, voltage, frequency, pole count, mounting (foot or flange), and whether you need a drop-in IEC replacement or a VFD-rated winding.
Request a quote