Laminated NdFeB Magnets

Eddy current loss is a key challenge in high-speed and high-frequency permanent magnet motors. An alternating magnetic field induces eddy currents inside NdFeB magnets. These currents generate extra heat and may increase the risk of irreversible demagnetization. Laminated NdFeB Magnets are a proven solution for reducing eddy current losses under suitable operating conditions.

What Are Laminated NdFeB Magnets?

Laminated NdFeB Magnets are made by cutting a sintered NdFeB magnet block into multiple thin layers. These layers are then bonded together with electrically insulating adhesive. This laminated structure divides a large conductive region into smaller, electrically isolated sections. It helps prevent large eddy current loops and reduce eddy current losses under demanding operating conditions.

What Problems Does the Laminated Structure Solve?

Restricting eddy current paths and reducing eddy current losses are the main purposes of laminated magnets.

The laminated structure reduces the effective conductive area and uses interlayer insulation to restrict current loops. This helps lower eddy current losses inside the magnet. It can also provide several engineering benefits:

Reduced Magnet Heating: Lower eddy current losses help reduce heat generated inside the magnet.
Improved Thermal Management: Less eddy current heating helps reduce the motor’s thermal load.
Lower Demagnetization Risk: Lower temperatures can improve thermal stability and reduce the risk of irreversible demagnetization.
Design and Cost Optimization: Magnet grades and material costs can be optimized while meeting magnetic performance, temperature, and demagnetization resistance requirements.

Custom Laminated NdFeB Magnets

The performance of custom NdFeB magnets depends on the application. Standard products may not meet the specific requirements of every motor design. Customization should focus on the following factors.

Magnet Grade and Number of Layers：

Select a suitable NdFeB grade based on operating temperature, target air-gap flux density, and demagnetization resistance. UH-series grades may be considered when they meet the requirements of the application. The number of layers and individual layer thickness must also be determined.

Layer thickness and layer count affect eddy current losses, the volume of magnetic material, and manufacturing costs. The design must balance loss reduction with magnetic flux output and overall cost.

Insulation Method and Temperature Resistance：

Interlayer insulation is essential for reducing eddy current losses. Depending on the application, suitable options include epoxy bonding systems, insulating coatings, and other qualified materials. These options differ in temperature resistance, insulation performance, and bonding strength. Selection should consider the actual operating temperature and long-term service conditions.

For high-speed rotors, interlayer bonding strength and structural reliability also require careful evaluation. The laminated assembly must withstand centrifugal forces and vibration during operation.

Geometry and Magnetization Direction：

Laminated NdFeB Magnets can be customized in block, arc, and other shapes according to customer drawings. Their geometry should match the magnetic circuit and available installation space.

The magnetization direction must be designed in coordination with the magnetic circuit, field distribution, and lamination direction. For radial or multipole magnetization, the orientation of each layer and the insulation structure must be evaluated. This helps balance eddy current reduction with the required magnetic performance.

Surface Protection：

Suitable epoxy coatings or other corrosion protection methods can be selected according to the operating environment. The coating must be compatible with the insulation system and bonding materials. Its effects on insulation performance, bonding strength, and dimensional tolerances should also be considered.

For high-temperature or high-humidity applications, the long-term stability of the surface protection system and the complete laminated assembly should be verified.

Typical Applications of Laminated NdFeB Magnets

New Energy Vehicles: Higher motor speeds and power density increase the importance of magnet thermal management. Magnet temperature can be a key factor in maintaining an adequate demagnetization safety margin.

Robotics: Compact joint modules often operate continuously within limited spaces. Heat generated around the magnets can affect available torque and operating margins.

Industrial Automation: Variable-speed drives and precision motion control systems have specific requirements for energy efficiency and temperature rise.

Aerospace: Cooling options may be limited in some aerospace applications. Reducing eddy current heating can help reduce the need for additional cooling capacity.

Premium Home Appliances: Compact designs and energy efficiency requirements make magnet losses an important factor in managing overall product temperature.

Frequently Asked Questions (FAQ)

Do Laminated NdFeB Magnets Have Lower Magnetic Performance Than Solid Magnets?

Not necessarily. Lamination does not automatically reduce the intrinsic magnetic properties of the NdFeB material. However, insulation layers reduce the volume of magnetic material and may affect the overall magnetic flux output.

Does Lamination Affect the Mechanical Strength of Magnets?

It can. Interlayer bonding strength, insulation materials, and assembly processes all affect structural reliability. Centrifugal forces are especially important in high-speed rotating applications.

Should All High-Speed Motors Use Laminated NdFeB Magnets?

No. The decision depends on operating frequency, eddy current losses, temperature rise, and cost requirements. Electromagnetic analysis should be used to determine whether lamination is beneficial for a specific motor.

How Long Does the Insulation Layer Last? Can It Degrade or Fail?

Yes. Insulation layers may degrade due to high temperatures, vibration, thermal cycling, or adhesive aging. Service life depends on material selection, manufacturing quality, and operating conditions.

What Other Methods Can Reduce Eddy Current Losses in Magnets?

Increasing the number of magnet segments is one effective method. Other motor design changes can also help, including optimizing pole-slot combinations, increasing the air gap, reducing stator slot opening width, and using skewed slots. Laminated magnets offer a way to address losses directly within the magnet. They may be particularly useful when changes to the overall motor design are limited.