Situation:

An international motor manufacturer is developing a next-generation drive motor for highly dynamic test rigs. This application requires magnets with precisely specified magnetic strength, extremely high resistance to demagnetization, and significantly reduced sensitivity to eddy currents in rapidly changing magnetic fields.
The motor operates under an extreme regime:

• speed changes from +3000 rpm to –3000 rpm within 0.1 seconds,
• with very high peak currents and strong flux fluctuations,
• where even minimal deviations in magnetic properties can lead to vibrations, power loss, or thermal issues.

The design therefore requires a very homogeneous magnetic field and minimal eddy current losses in the rotor.

Complication:

The end magnets in the rotor must individually fall within very strict tolerances. Key requirements include:

• Magnetic moment accuracy within ±1–2%,
• Temperature stability above 150–180 °C,
• High coercivity (HcJ) to prevent flux distortion and demagnetization during rapid field changes,
• Minimal eddy current losses, essential due to extremely fast magnetic field reversals.

Eddy currents arise when a solid magnet block is exposed to rapidly changing magnetic flux. These currents cause:

• heat generation,
• power loss,
• phase delay in the magnetic field (lag),
• and mechanical damping.

For this application, such effects are unacceptable.

Question:

The customer asked Bakker Magnetics to provide a complete quality control and selection solution, consisting of:

1- Measuring the magnetic moment of each individual magnet with high precision.
2- Sorting magnets by magnetic moment into predefined classifications.
3- Packaging per selected group, including serial numbers and full traceability.
4- Developing a production method in which the magnet is constructed from small insulated segments.
— This interrupts electrical conductivity between segments.
— As a result, eddy current losses are significantly minimized during rapid acceleration and deceleration phases.

Solution:

1. Advanced magnetic moment measurement system

Bakker Magnetics developed a custom measurement system based on:

• a fluxmeter with Helmholtz coil setup,
• highly stable reference magnets,
• a reproducible fixture for precise positioning,
• automated data processing and serial numbering.

Each magnet is:

• measured individually,
• assigned a unique ID,
• linked to a database containing measurement data (moment, direction, temperature stability data, and batch information).

The magnets are then automatically sorted into precisely defined classes.

2. Segmentation and electrical isolation against eddy currents

Because eddy currents increase exponentially with the mass of conductive material, Bakker Magnetics developed a segmented magnet construction:

• each segment is thinner and electrically insulated,
• segments are bonded together with a heat-resistant, electrically insulating adhesive layer,
• tolerances on segment thickness and flatness were tightened to minimize magnetic air gaps.

This construction reduces eddy current losses by several tens of percent and enables thermal stability under extremely dynamic operating conditions.

3. Traceability and rotor integration

The customer receives:

• a clear overview of each magnet group,
• the corresponding measurement values,
• and a recommendation for optimal placement per rotor position (matching magnetic moments to prevent imbalance).

This allows the motor manufacturer to configure a rotor with exceptionally homogeneous magnetic properties.

Result:

Through the combination of:
– highly accurate magnet selection,
– segmented magnet construction,
– strongly reduced eddy current losses,
– and magnets with high coercivity and efficiency,
the customer is able to produce a motor that responds extremely quickly and precisely, with minimal thermal and magnetic losses.

As a result, the motor manufacturer has secured a unique position in the world of highly dynamic test systems, particularly for automotive development, e-drivetrain testing, and mechatronic systems where precision and speed are critical.