2.2, 3 and 4 kW IE3 Motors: Speed, Pole, Frame and Stock-Based Correct Purchase

IE3 electric motors rated 2.2, 3 and 4 kW are the heart of the most sought-after small-to-medium power band in industry. Pumps, fans, conveyors, geared drives, compressor units and countless general-purpose machines operate in exactly this power range. Because EU EcoDesign rules already make IE3 (Premium efficiency) mandatory at these ratings, the vast majority of new motors sold today are IE3. This means that when buying correctly you must be clear not only on power and speed, but also on efficiency class, frame size and mounting type. In this guide we cover 2.2-4 kW IE3 motors in terms of speed by pole count, IEC frame sizes (90L/100L/112M), mounting options and stock logic, so you can order the right motor correctly the first time in these most-wanted ratings.

Why 2.2, 3 and 4 kW?

These three power values form the backbone of small-to-medium industrial drives. 2.2 kW (about 3 HP), 3 kW (about 4 HP) and 4 kW (about 5.5 HP) are the most commonly encountered ratings in continuously running applications such as pumps, fans and conveyors. The standout features of this band:

• High stock turnover: Being the most demanded ratings, they are sensible to keep in stock and are supplied quickly.
• IE3 mandatory class: Under EcoDesign, IE3 is the minimum standard at these ratings, saving energy in continuous applications.
• Standard IEC frames: Frames 90L, 100L and 112M are standard, so mechanical substitution between brands is easy.
• Mounting variety: B3 foot, B5/B14 flange and B35 foot+flange versions are widely available.

What Does the IE3 Mandatory Class Mean?

IE (International Efficiency) classes are defined in the IEC 60034-30-1 standard. IE1 is standard, IE2 high, IE3 premium and IE4 super premium efficiency. The EU EcoDesign regulation makes a minimum of IE3 efficiency mandatory for most motors of 0.75 kW and above. Therefore a newly purchased motor in the 2.2-4 kW band is expected to be IE3; lower-efficiency IE1/IE2 motors are now non-standard at these ratings.

The advantage of IE3 is lower losses and lower running cost at the same power. To read efficiency and other rated values from the nameplate correctly, our article on reading the IE3 motor nameplate is a good start. For a general stock view of this band, see our IE3 stock guide.

Pole Count and Speed: 2/4/6 Pole

In asynchronous IE3 motors, speed is set by the pole count. 2 pole is preferred for high speed (pump/fan), 4 pole for general purpose, and 6 pole for low speed (mixer/conveyor). Due to slip, actual speed is slightly below synchronous speed.

Frame Sizes (IEC): 90L, 100L, 112M

The IEC frame number gives the shaft centre height (mm) and fixes shaft diameter, foot hole spacing and flange dimensions. Three frames stand out in the 2.2-4 kW band. The same power can fall on a different frame at different pole counts; the frame grows to deliver the same power at lower speed.

As shown, 2.2 kW is frame 90L at 2 pole but rises to frame 112M at 6 pole. Therefore on a replacement motor you must specify not only power but also pole count and frame together. You can find the shaft diameter and frame relationship in our article on shaft diameter and frame table.

Mounting Options: B3, B5, B14, B35

2.2-4 kW IE3 motors come in various mounting types, and choosing the right one is critical for a clean fit to the machine:

• B3 (foot): Bolts to the floor or base through its feet; the most common general-purpose mounting.
• B5 (large flange): Couples directly to a gearbox or pump housing.
• B14 (small flange): Compact flange with threaded mounting holes; small machine connections.
• B35 (foot + flange): Both foot and flange; the highest mounting flexibility. We covered multi-mount from a single stock code in our article on multi-mount universal frame.

Difference From the Band Above

The 2.2-4 kW band is the boundary region where, on moving to 5.5 kW and above, the frame begins to climb to 132 and beyond. If you need higher power, we examined the band above in our article on 11 and 15 kW IE3 motors, and medium-large powers in our article on 18.5 and 22 kW IE3 motors. This way you can choose the right band and frame for your project's power need.

Stock Logic: Why Are These Ratings Always Kept Ready?

Because 2.2, 3 and 4 kW are the most sought-after ratings, keeping the correct pole-frame-mounting combinations in stock is critical to production continuity. When a pump or fan motor fails, stock that can be replaced the same day prevents days-long downtime. The most-wanted combinations are usually 4 pole B3/B5 and 2 pole B3; keeping these variants ready gives a fast-delivery advantage.

Frequently Asked Questions

What frame is a 4 kW 4 pole IE3 motor?

A 4 kW 4 pole (1500 rpm) IE3 motor is typically frame 112M with a 28 mm shaft. The same power at 6 pole (1000 rpm) rises to frame 132S, because a larger frame is needed to produce the same power at lower speed. When ordering, specify power, pole count and frame together.

Is IE3 mandatory at these ratings?

Yes. Under the EU EcoDesign regulation, a minimum of IE3 efficiency is mandatory for most motors of 0.75 kW and above; the 2.2-4 kW band is fully within this scope. Therefore newly purchased motors are expected to be IE3; lower-efficiency IE1/IE2 motors are non-standard at these ratings.

Can I fit a different brand of IE3 motor in the same place?

If the frame number (90L/100L/112M), mounting type and shaft diameter match, different brands are mechanically interchangeable thanks to the IEC standard. Even so, you should compare nameplate values (kW, speed, voltage, efficiency class, mounting) one-to-one with the replacement motor.

The Effect of IE3 on Running Cost

At continuously running ratings such as 2.2-4 kW, the efficiency class matters far more than the purchase price; because the energy paid over a motor's lifetime is many times the initial investment. IE3 motors run with lower losses than IE1/IE2, which means measurable energy savings throughout the year on a continuously running pump or fan. Moreover, lower losses mean less heating and therefore longer insulation life.

• Continuous operation: On a motor running long hours per day, the efficiency difference adds up significantly.
• Lower heating: Fewer losses, lower winding temperature and longer life.
• Payback: The extra cost of a high-efficiency motor is quickly amortized in continuous duty.

So in the 2.2-4 kW band, IE3 is not just a requirement but also a smart investment.

Rated Torque and Correct Selection by Load

Power (kW) and speed (rpm) together determine the rated torque (Nm) the motor produces. At the same power, a lower-speed (higher-pole) motor produces higher torque; therefore, to choose a motor suited to the load, you must evaluate not only power but also torque. Rated torque is found with the formula M = 9550 × kW / rpm.

As the table shows, a 4 kW 6 pole motor produces about three times the torque of a 2 pole motor of the same power. That is why higher-pole motors are preferred in high-torque applications such as mixers and extruders.

Points to Watch in Drive (VFD) Use

2.2-4 kW IE3 motors are often used with a frequency drive; in pump and fan applications especially, speed control provides large energy savings. However, several points require attention in drive operation:

• Winding insulation: du/dt voltage spikes from the drive stress the winding; an inverter duty winding should be preferred.
• Cooling at low speed: If it will run at low speed for long periods, external forced cooling is considered.
• Bearing current: Bearings should be protected with grounding and, if needed, insulated bearings.
• SF validity: The service factor is usually voided in drive operation; the motor should be selected for rated load.

Pre-Order Checklist

When ordering a 2.2-4 kW IE3 motor, the following information must be clear to get the right motor the first time. Missing information leads to wrong replacement and delay:

• Power (kW): 2.2 / 3 / 4 kW.
• Poles/speed: 2/4/6 pole, target speed.
• Frame: 90L / 100L / 112M.
• Mounting: B3 / B5 / B14 / B35.
• Voltage/frequency: 380-400 V / 50 Hz (50/60 Hz compatibility if needed).
• Efficiency class: IE3 (mandatory).
• Protection class: IP55 standard, IP65/IP66 if needed.

When this list is completed fully, the correct IE3 motor is supplied quickly and without error.

Shaft Diameter and Mechanical Compatibility Details

When replacing 2.2-4 kW IE3 motors, the most often overlooked detail is shaft diameter and foot dimensions. Even if the frame number is the same, if the shaft diameter and key (keyway) dimensions do not match correctly, the coupling or pulley will not seat on the motor. Therefore on a replacement motor, the shaft dimensions should be checked alongside the frame.

As shown, although 100L and 112M have the same shaft diameter (28 mm), their foot hole spacings differ; therefore both dimensions must be verified for mechanical compatibility. In a coupled drive, the wrong shaft diameter requires an adapter and can cause alignment problems.

50/60 Hz Compatibility and Export Projects

2.2-4 kW IE3 motors are often used in export machinery and multi-country facilities; in this case the line frequency becomes critical. A motor labelled to run on a 50 Hz grid delivers a different speed and power on a 60 Hz grid. Therefore in export projects the motor must be selected to suit the target country's frequency.

• 50 Hz: Europe, Turkey, most of Asia; 1500 rpm synchronous at 4 pole.
• 60 Hz: North America, some countries; the same motor turns about 20% faster at 60 Hz.
• Dual-frequency compatibility: Some motors are labelled for both 50 and 60 Hz; provides flexibility for export machinery.

A frequency change affects not only speed but also power, torque and cooling; therefore the target grid should be clarified from the start. Correct frequency compatibility secures trouble-free operation of the export machine in its destination country.

Should the Transition From IE3 to IE4 Be Considered?

Although IE3 is the mandatory class in the 2.2-4 kW band, in continuously running, long-hour applications the higher class IE4 (super premium) efficiency can also be considered. IE4 motors run with lower losses than IE3, meaning extra energy savings at high running hours. However, the extra cost of IE4 only amortizes over a sufficiently long running time.

• Continuous operation: On pumps and fans running long hours per day, IE4 payback accelerates.
• Short operation: In low-hour or intermittent applications, IE3 is usually sufficient and economical.
• Mechanical compatibility: In the IE3-to-IE4 transition, frame, foot and shaft dimensions usually stay the same; mechanical substitution is easy.

The decision should be made by the application's annual running hours and energy cost. On a continuously running critical drive, IE4 can offer lower total cost in the long run; but for most standard applications, IE3 is both a mandatory and a sufficient choice.

Reading the IE3 Motor's Rated Values Correctly

In selecting a 2.2-4 kW IE3 motor, reading the rated values on the motor nameplate correctly is the foundation of error-free purchasing. The nameplate shows power (kW), speed (rpm), voltage and connection, rated current, power factor (cosφ), efficiency class (IE3) and the percentage efficiency value. These values directly determine the motor's suitability for the application and the panel and protection selection. Rated current in particular is critical for thermal protection and cable sizing, while power factor matters for compensation and grid loading.

Source the Right IE3 Motor from Stock

Knowing the right pole count, frame and mounting for 2.2, 3 and 4 kW IE3 motors saves time on both replacements and new purchases. As HEM Motor we offer these most-wanted ratings from manufacturer stock with fast delivery. To determine the motor that fits your need and to request a tailored quote, get in touch; our technical team will clarify the right power-pole-frame-mounting combination for you.