Selecting SmCo magnets for high-speed motors

1. Describe the working conditions

Provide the continuous magnet temperature and short-duration peak, including heat exposure time and cycling. The magnet temperature is the relevant input; an ambient or housing temperature alone does not define it.

Specify the required field or flux and the measurement position. Review the reverse magnetic field and load line with the motor designer, including the operating conditions the component must withstand. These inputs establish the basis for comparing grades.

2. Compare materials under matching conditions

Remanence (Br), normal coercivity (Hcb), intrinsic coercivity (Hcj) and maximum energy product ((BH)max) describe different aspects of magnetic performance. Use the grade table with its test temperature rather than treating a single value as a complete motor specification.

XGS 35H and XGS 35 illustrate why this matters: their published 20 °C remanence and energy-product ranges match, while their intrinsic-coercivity minimums differ. A higher Hcj minimum is relevant to the demagnetization assessment, but it does not establish the working temperature of every rotor geometry.

For more severe thermal environments, examine the dedicated high-temperature grades and their hot measurements. The XGS 26-T550 entries at 20 °C and 550 °C should not be interchanged.

3. Connect the magnet to the rotor design

The component drawing should define arc or segment profile, axial length, interfaces, tolerances and magnetization direction. For an array or assembled rotor, identify the arrangement of magnetic elements and the required magnetic output of the assembly.

Hangda’s company presentation includes a high-speed motor Halbach-array design and production examples labelled as high-speed and ultra-high-speed motor rotors. These support a discussion about magnetic-circuit and component development, alongside the material selection.

Retaining components, assembly clearances and balancing requirements must be addressed in the rotor design. Material energy product is not a rotor-speed rating, and the magnet supplier’s scope should be separated from complete-motor design approval.

4. Make the sample answer a defined question

Agree what will be checked before the first sample: dimensional characteristics, magnetic properties, field or flux, and any thermal-exposure evaluation. Establish measurement positions, temperatures and acceptance limits so that supplier inspection and system testing are comparable.

Use the sample results to settle the production specification. Include drawing revision, quantity, inspection documentation and packaging requirements in the order discussion.