Moving from IE4 to IE5 can require a substantial reduction in total motor losses, even when the difference in rated efficiency is only a small percentage.

Motor manufacturers need to identify where the required loss reduction can be achieved, including the contribution from stator core materials. For NGOES selection, the question is how much a lower-loss electrical steel grade can contribute under the motor's actual magnetic and manufacturing conditions.

1. What Do IE4 and IE5 Efficiency Classes Mean?

The International Electrotechnical Commission (IEC) classifies IE4 as Super Premium Efficiency and IE5 as a higher motor efficiency class, commonly called Ultra Premium Efficiency. These classifications apply to completed motors, not individual components or electrical steel grades.

The December 2025 edition of IEC 60034-30-1 formally introduced IE5 efficiency limits. The standard specifies efficiency classes for eligible single-speed, line-operated AC motors rated for sinusoidal 50 Hz or 60 Hz supplies. The applicable efficiency limit varies with motor output power, supply frequency, and pole count.

2. IE4 vs IE5: Understanding the Efficiency Gap

IE3, IE4, and IE5 represent progressively higher motor efficiency requirements for comparable rated conditions. At the same mechanical output, a higher efficiency means less electrical input power is converted into losses.

A Small Efficiency Difference Can Mean a Larger Loss Reduction

Consider two motors delivering the same 15 kW mechanical output, one operating at 95% efficiency and the other at 96%.

These are illustrative efficiency values, not the IEC IE4 and IE5 limits for a 15 kW motor.

Parameter	Motor A	Motor B
Mechanical output power	15 kW	15 kW
Assumed efficiency	95%	96%
Electrical input power	15.789 kW	15.625 kW
Total motor losses	789 W	625 W

Improving efficiency by one percentage point reduces total motor losses by approximately 164 W, or 20.8%. Electrical input power, however, decreases by only about 1.0%.

1793843097508-IE4 vs IE5 Motor Efficiency Comparison.webp

Illustration comparing IE4 and IE5 electric motors, highlighting higher efficiency and lower total motor losses at the IE5 efficiency level.

For an actual IE4-to-IE5 comparison, the required loss reduction must be calculated using the applicable IEC efficiency limits under the same rated conditions.

3. How Motor Loss Budgets Change From IE4 to IE5

Motor efficiency is determined by the relationship between mechanical output power and electrical input power. When targeting a higher efficiency class, manufacturers need to reduce the difference between them—the motor's total losses.

Where Motor Losses Occur

Several loss mechanisms contribute to the total.

Loss Category	Main Source	Potential Design Response
Stator winding losses	Electrical resistance in the stator windings	Winding design, conductor size, thermal management
Rotor losses	Rotor currents and related losses, depending on motor topology	Rotor design and electromagnetic optimization
Core losses	Alternating magnetic fields in the stator and, where relevant, rotor iron	Electrical steel selection, flux distribution, lamination design
Mechanical losses	Bearing friction and ventilation losses	Bearing and cooling-system design
Additional load-dependent losses	Stray electromagnetic effects under load	Electromagnetic and structural optimization

The loss distribution varies with motor topology, rating, and operating conditions. An induction motor and a permanent-magnet synchronous motor, for example, have different rotor-loss mechanisms.

How Much Can Electrical Steel Contribute?

Suppose a manufacturer needs to reduce total motor losses by 160 W to meet a higher efficiency target.

If the existing stator core produces 200 W of losses and the selected NGOES achieves a 20% reduction in finished-core loss, the resulting saving would be 40 W. That covers one-quarter of the 160 W target, leaving 120 W to be addressed through other motor design improvements.

These figures are illustrative, not measured IE4 or IE5 motor performance data.

4. What Electrical Steel Can Contribute to IE5 Motor Designs

Non-oriented electrical steel is widely used in motor stator and rotor laminations.

1793842893889-Electrical Steel Stator Core Loss and Motor Performance.webp

Laminated electrical steel stator core and motor windings illustrating the role of NGOES in motor magnetic performance and core loss.

Core Loss at the Relevant Magnetic Conditions

Electrical steel core-loss data is measured under specified conditions of magnetic flux density and frequency. A grade with lower loss at one test point may not retain the same advantage at another.

Flux density also varies across motor teeth and yokes, making the relevant operating range important when comparing candidate grades.

HWHG's Electrical Steel Grade vs. Actual Core Loss guide discusses the relationship between material specifications and measured losses.

1790740647706-HWHG Electrical Steel Coils .webp

HWHG Non-Oriented Electrical Steel for High-Efficiency Motors

Magnetic Performance Beyond Core Loss

Magnetization characteristics affect the motor's magnetic circuit and magnetizing current. Changing to a lower-loss grade may also alter the flux density achievable under a given magnetic field, particularly when the existing core geometry is close to its design limits.

Lamination Thickness

Thinner laminations can reduce the eddy-current contribution to core loss under otherwise comparable conditions. They also increase the number of laminations required for the same stack height, potentially changing cutting and assembly costs.

These trade-offs are covered in HWHG's Electrical Steel Lamination Thickness guide.

5. Core Manufacturing Trade-Offs When Targeting IE5

Cutting and assembly can increase core losses beyond those indicated by the original NGOES material test.

Manufacturing Effects on Finished-Core Loss

Residual stress and deformation near cut edges affect magnetic behavior, while burrs may create electrical contact between adjacent laminations. Interlocking, welding, and clamping can introduce additional local stress.

Processed-lamination or finished-core measurements can reveal losses introduced during manufacturing.

Material Cost vs. Achieved Loss Reduction

Lower-loss NGOES may carry a higher purchase cost. Thinner gauges and different material specifications can also affect cutting, stacking, and material utilization costs.

The comparison is between the additional material and manufacturing cost and the reduction in motor losses achieved.

6. Electrical Steel Procurement for IE4 and IE5 Motor Production

A motor efficiency target does not specify the electrical steel grade, magnetic properties, or coil dimensions required for production. Motor OEMs need to define these requirements from the electromagnetic design and manufacturing process.

Specify the Required Magnetic Performance

The purchasing specification should identify the required NGOES grade or magnetic performance range.

Core-loss values need their corresponding test frequency and magnetic flux density. Magnetization characteristics may also be specified where they affect the intended magnetic circuit.

Define the Manufacturing Format

For NGOES purchased in coil form, the material specification may include:

Nominal thickness and applicable tolerance.
Required coil width.
Electrical insulation coating requirements.
Agreed surface and edge conditions.
Coil dimensions and handling requirements.
Order quantity and inspection documentation.

Changes in thickness or material grade may require adjustments to existing stamping tools or stack designs.

Verify Material Performance and Supply Consistency

For motor OEMs using multiple coil lots, consistent magnetic properties, thickness, and insulation coating are important for maintaining approved production specifications.

Material identification and inspection records allow procurement and quality teams to check these properties across deliveries.

Sourcing NGOES for Higher-Efficiency Motor Cores

HWHG manufactures non-oriented electrical steel for motor applications, supported by advanced rolling, annealing, and digitalized production systems. These processes support control of strip thickness, magnetic properties, and insulation coating quality during manufacturing.

For IE4 and IE5 motor projects, customers can submit their required NGOES grade, magnetic specifications, coil dimensions, and purchasing quantity for material availability review.

Technical References

IE4 vs IE5 Motors: Efficiency Differences and Electrical Steel Requirements

How to Identify Manufacturing-Related Core Loss Increases in Motor Stators

Electrical Steel for Servo Motors: Magnetic Requirements and Stator Core Performance

UAV Motor Core Loss: How ESC Harmonics Affect Electrical Steel Performance

Send Your Drawing or Specs, Get a Fast Material Quote