Demagnetization severely cripples permanent magnet motors, initiating a cascade of failures centered on a catastrophic drop in efficiency. The consequences manifest across four key dimensions:
1. Collapse of Output Performance
Drastic loss of load capacity and torque, leading to stalling under heavy loads.
Failure to start normally despite inrush currents reaching 2-3 times the rated value.
Severe torque ripple and unstable operation in cases of partial demagnetization.
2. Degradation of Electrical Characteristics
Highly unbalanced phase currents (>10% imbalance) and elevated no-load current.
Significant reduction (>15%) and distortion (clipping, noise) of the back-EMF waveform.
High energy waste: power factor below 0.8 and energy consumption increase of 8-15%.
3. Dangerous Physical Deterioration
Thermal Runaway: Rapid temperature rise (stator >+30°C) creates a vicious cycle: Demagnetization → Overheating → Further Demagnetization, risking magnet damage above 150°C.
Mechanical Vibration: High-frequency vibration (at 2x/6x line frequency) due to magnetic field distortion.
System Failure: Causes weak acceleration and short range in EVs, or poor precision and lag in servo drives.
4. Long-Term Reliability & Safety Risks
Accelerated insulation aging and risk of winding short circuits from continuous overcurrent.
Potential loss of speed control at high speed poses a safety hazard.
Progressive damage from local to complete demagnetization, resulting in total motor failure and costly repair (rotor/permanent magnet replacement).
In essence, a demagnetized motor transforms from an efficient device into a high-consumption, overheating, and unreliable liability, demanding immediate attention to prevent irreversible damage and safety incidents.
Post time: Jan-20-2026