Hysteresisgraph (BH tracer)

Selection criteria

Field range, temperature-controlled measurement, accuracy.

Supply chain

Hysteresisgraphs (BH tracers) are a niche led by German makers (Magnet-Physik, Brockhaus) and a few Chinese instrument makers. Motor makers with significant magnet spend benefit from their own tracer to check incoming lots independently.

Buyer FAQ

What does a hysteresigraph measure?

It drives a closed magnetic circuit and records the full demagnetisation curve of a permanent-magnet sample: remanence Br, coercivities HcB and HcJ, and maximum energy product (BH)max — at room temperature or, with a heated pole set, at operating temperature.

Why test at temperature for motor magnets?

NdFeB loses coercivity as it heats up. A grade that passes at 20 °C may demagnetise at 120–150 °C under a stall or short-circuit current. Test HcJ at the motor's maximum magnet temperature and keep a margin above the worst-case demagnetising field.

Which standards apply?

IEC 60404-5 (permanent magnet materials, measurement in a closed circuit) and its Chinese equivalent GB/T 3217; sample size and shape must suit the electromagnet's pole gap.

Where it is used