Precautions for the Use of Permanent Magnet Motors

Guidelines based on IEC 60034 Standards and Magnetic Property Requirements

The Critical Demagnetization Zone

Protecting the permanent magnets is essential for maintaining motor life and efficiency.

1.1 Temperature Management

Neodymium Iron Boron (NdFeB) magnets are highly sensitive to heat.

• Irreversible Damage: Temperatures above 150°C will cause non-reversible demagnetization.

• Safe Operation: It is recommended to keep the operating temperature ≤ 80°C.

  
  

1.2 Current Surge Protection

• Threshold: A reverse surge current exceeding 2 times the rated value will cause immediate demagnetization.

• Requirement: Systems must utilize a soft start mechanism combined with strict current limiting protection.

Strong Magnetic Hazard Management

The powerful magnetic fields of these motors pose physical risks during handling.

• Safety Distance: Maintain at least a 2-meter safety perimeter during disassembly and assembly.

• Tool Safety: Prohibit the use of metal tools to avoid magnetic suction and high-speed "shooting" accidents.

• Environmental Hazards: Open flame cutting is strictly prohibited, as magnets release toxic gases at high temperatures.

Operational Control Principles

Adhering to these "iron laws" ensures stable performance and hardware longevity.

3.1 Cooling Priority

• Water Cooling: Water conductivity must be ≤ 50 μS/cm to prevent electrolytic corrosion.

• Air Cooling: Air inlets must stay ≤ 40°C, and dust filters should be cleaned weekly.

  
  

3.2 Anti-Dragging and Back-EMF

If a frequency converter fails while the load continues to spin, the motor acts as a generator.

• Risk: Output voltage can exceed 1000V, leading to winding breakdown.

• Solution: A dedicated braking unit is required.

  
  

3.3 Preventing Loss of Step

• Vector Control: Must be enabled if the load changes by more than 30% of the rated torque.

• Restriction: V/F control is strictly prohibited for variable load scenarios.

Maintenance and Insulation Protocols

Unauthorized maintenance often leads to catastrophic failure.

• Rotor Integrity: Do not dismantle the rotor. Magnetization requires professional "Wan'an" level equipment; user disassembly will likely scrap the motor.

• Insulation Testing: Perform monthly checks to ensure winding-to-ground insulation is ≥ 100MΩ. In humid environments, the use of moisture-proof paint is mandatory.

• Bearing Selection: Ceramic bearings are compulsory. Ordinary steel bearings will absorb magnetic powder, increasing wear by 60%.

Special Scenario Responses

• High Temperature: Install PTC sensors set for an emergency stop at >130°C.

• Corrosion: Use IP65-rated casings and stator epoxy impregnation.

• Vibration: Ensure rotor dynamic balance accuracy reaches ≤ G1.0 level.

Fatal Error Warnings

• Demagnetization equals Scrap: Replacing magnetic steel costs approximately 70% of a new motor and results in a permanent loss of energy efficiency.

• Liability Waiver: Per GB 755-2008, manufacturers are exempt from liability for accidents caused by unauthorized repairs or disassembly.

Conclusion: The Ultimate Law

Guard the permanent magnet motor temperature red line, prevent current shocks, and prohibit non-standard disassembly to maintain peak performance.

Damage to permanent magnets is irreversible; a single instance of severe overheating or overcurrent will declare the motor dead.