Sep.16,2026
For an Electric Motor Core Parts Manufacturer, lamination thickness is one of the most important design and purchasing variables in a motor stator or rotor core. It affects iron loss, efficiency, operating temperature, production cost, mechanical strength, and the final motor performance.
Engineers and purchasing teams searching for this topic usually need more than a basic definition. They want to know how thickness changes hysteresis and eddy current loss, how to select a suitable gauge, how to verify supplier data, and how to avoid paying for a specification that does not improve the motor.
When an alternating magnetic field passes through a solid steel core, it induces circulating electrical currents inside the material. These currents are called eddy currents. They generate heat and consume power without producing useful mechanical output.
A motor core is therefore built from many thin electrical steel sheets instead of one solid steel component. Each sheet is insulated from the next by a coating. This interrupts the current path and reduces the amount of energy lost as heat.
For a similar material and operating condition, eddy current loss is approximately proportional to the square of lamination thickness. A simplified relationship is:
Pe is proportional to t squared times f squared times B squared divided by rho
This means that reducing thickness can have a significant effect at high frequency or high flux density. For example, changing from a 0.50 mm lamination to a 0.25 mm lamination can reduce the theoretical thickness-related eddy current component substantially, assuming the material, insulation, frequency, and flux density remain comparable.
Hysteresis loss is caused by repeated changes in the magnetic direction of the steel. It depends mainly on the electrical steel grade, grain structure, magnetic processing, flux density, and frequency.
Reducing thickness does not automatically reduce hysteresis loss to the same degree as eddy current loss. A thinner sheet can still have high total core loss if the steel grade has poor magnetic properties or if the stamping process creates excessive stress.
For purchasing decisions, lamination thickness should therefore be reviewed together with:
Thin laminations improve electrical performance, but they are more sensitive to handling, stamping, burr formation, distortion, and stacking errors. A supplier must control the full production process rather than simply using a thinner steel coil.
Important manufacturing controls include:
Thickness alone is not a complete material specification. Two laminations with the same thickness can produce different losses because their chemical composition, rolling process, annealing treatment, coating, and magnetic properties are different.
A practical material specification should include:
Thickness selection should match the motor's electrical frequency. Standard industrial motors operating near 50 Hz or 60 Hz may use a different thickness from high-speed motors, inverter-driven motors, traction motors, and aerospace motors.
At higher frequency, eddy current loss increases rapidly. In these applications, thinner electrical steel may provide a stronger efficiency benefit. However, high-frequency motors may also experience additional losses caused by:
A thinner lamination cannot compensate for an overloaded magnetic circuit. If the stator teeth or rotor core operate close to saturation, the motor may still have high core loss and poor temperature performance.
Review the following design factors before selecting thickness:
For standard induction motors, moderate-speed permanent magnet motors, pumps, fans, and compressors, a medium lamination thickness may provide the best balance between efficiency and manufacturing cost.
Purchasers should compare the expected energy savings with the additional cost of thinner material, more complex stamping, slower production, and higher inspection requirements.
A balanced specification commonly considers:
High-speed motors and inverter-fed motors are more sensitive to high-frequency losses. In these designs, thinner laminations may reduce core loss, but the decision must be confirmed with electromagnetic simulation and prototype testing.
Purchasing teams should ask the supplier whether the quoted material has been tested under the actual operating frequency instead of relying only on a standard 50 Hz or 60 Hz material loss value.
Large stator and rotor stacks can experience greater mechanical stress during assembly, transportation, balancing, and operation. Very thin laminations may require improved stacking support and tighter process control.
For large motor cores, evaluate:
Small motors often use compact parts with narrow teeth, small slots, and tight dimensional tolerances. A thinner sheet may reduce loss, but it may also increase burr risk and scrap rate.
For these parts, the best solution may be a slightly thicker lamination with better steel quality, improved stamping precision, and a more reliable stacking process.
Before comparing materials or suppliers, record the actual operating conditions. A test result has limited value if the frequency, flux density, temperature, and waveform do not match the motor design.
Check the supplier's material certificate and compare it with the approved drawing and purchase specification.
Measure several locations on multiple laminations. A single measurement cannot represent an entire production batch.
Do not remove the insulation coating before measurement unless the test procedure specifically requires it. Removing the coating can make the measured value different from the supplied part and can damage the lamination surface.
Burrs can connect adjacent laminations and create a low-resistance path for circulating currents. Damaged insulation coating can have a similar effect.
The nominal stack height does not equal the effective magnetic steel height because insulation coatings, air gaps, burrs, and assembly tolerances occupy space.
Use a standard Epstein frame, single-sheet tester, ring sample, or other qualified test method as appropriate. The method must be documented because different test methods can produce different results.
A supplier offering thinner steel is not necessarily offering a lower-loss motor core. Compare the measured core loss at the operating frequency and flux density required by the motor.
Supplier comparison should include:
The purchase price per kilogram is only one part of the total cost. A thinner lamination may increase tool wear, stamping time, inspection time, scrap, and assembly complexity.
Use a total cost comparison that includes:
A supplier may provide an excellent prototype but fail to maintain the same performance in mass production. Ask for evidence that the process is stable over time.
Useful supplier questions include:
Using a thickness chosen for a 50 Hz motor in a high-frequency inverter motor can lead to excessive core loss and temperature rise. Always evaluate the complete electrical waveform and operating range.
A certificate for the raw steel coil does not prove that the finished stamped core has the same performance. Stamping stress, burrs, coating damage, and stacking gaps can increase loss after processing.
Excessive burrs can electrically connect adjacent sheets. This reduces the benefit of lamination insulation and may cause local hot spots. Burr limits should be written into the drawing or quality agreement.
Thickness can vary across the sheet and along the coil. Measure multiple locations and multiple parts from each production batch.
Thinner material may reduce eddy current loss, but it can also increase cost, deformation, tooling difficulty, and assembly risk. The best thickness is the one that meets the motor performance target at the lowest reliable total cost.
If the actual stack contains more air gaps or coating thickness than expected, the effective magnetic steel area decreases. The motor may require a higher magnetic flux density to produce the same torque, increasing core loss.
Punching and forming can create residual stress around slots and teeth. This stress can reduce magnetic performance even when the raw material specification is correct.
Complete a first article inspection and a controlled production trial before approving a new lamination supplier. Confirm dimensions, burrs, coating condition, stack height, core loss, and assembly behavior.
Set the motor efficiency, temperature rise, speed, torque, frequency, and expected service life. These targets determine whether a lower-loss material or thinner lamination can create measurable value.
Compare the expected performance of at least two practical gauges. Review core loss, stacking factor, magnetic saturation, mechanical strength, stamping yield, and total cost for each option.
Use electromagnetic simulation to estimate tooth loss, back iron loss, rotor loss, harmonic loss, and temperature rise. Include the actual steel loss curve where available instead of using a generic material model.
Produce prototype laminations using the intended material and stamping process. Assemble the core with the intended stacking and compression method, then measure no-load current, input power, temperature rise, torque, and efficiency.
Release the final thickness only after the prototype results meet the design target. Record the approved material grade, test conditions, tolerances, inspection plan, and change control requirements in the purchase specification.
Continue checking thickness, burrs, coating resistance, stack height, and core loss during mass production. A stable monitoring plan helps prevent gradual quality decline caused by tool wear, material substitutions, or process changes.
When the design requires reliable dimensions, low core loss, and consistent mass production, work with an experienced Electric Motor Core Parts Manufacturer. Onlink can support motor core lamination sourcing and production evaluation from material selection through stamping, inspection, stacking, and delivery.
