Permanent magnet motors deliver high efficiency, but their magnets can lose strength if operated beyond design limits. Demagnetization causes current to rise and torque to fall.
What Causes Demagnetization
- Sustained overheating beyond the magnet grade limit
- Excessive load or stall conditions
- High-frequency drive settings that overheat the rotor
Warning Signs
Rising current for the same load, reduced output and motor overheating suggest weakened magnets.
Prevention
- Size the motor correctly for the load
- Keep cooling airflow unobstructed
- Respect drive frequency and temperature limits
- Monitor motor temperature
Summary
Demagnetization is largely preventable through correct sizing and temperature management, which also extends motor life.