The difference between permanent magnet frequency conversion and power frequency of screw air compressor

Detailed explanation of the difference between permanent magnet frequency conversion and power frequency in screw air compressor

The driving methods of screw air compressors are divided into two types: permanent magnet frequency conversion and power frequency. The main differences are reflected in working principle, energy efficiency, stability, noise and maintenance costs. The following is a specific comparison:

1. working principle

• permanent magnet variable frequency
  Driven by a rare earth permanent magnet synchronous motor, a frequency converter is used to adjust the motor speed to achieve on-demand adjustment of the exhaust volume.
  characteristics: No slip, no excitation loss, high efficiency, less heat.

• power frequency
  It is driven by a fixed-speed motor, and the exhaust volume is controlled through mechanical transmission, and the speed is constant.
  characteristics: The structure is simple, but the speed cannot be adjusted, and the exhaust volume is fixed.

2. Energy efficiency and energy conservation

• permanent magnet variable frequency
  • Adjust motor speed in real time according to air consumption to avoid no-load operation and save energy30%-40%。
  • National first-level energy efficiency standards are efficient at full load and light load.
• power frequency
  • The motor continues to run constantly, running at full speed even at low air consumption, resulting in high energy consumption.
  • The energy efficiency level is low and long-term operating costs increase.

3. Stability and response speed

• permanent magnet variable frequency
  • soft start: The starting current is small (≤1.2 times the rated current) and has no impact on the power grid.
  • fast response: Adjust the air pressure in real time through PID regulator for high stability.
• power frequency
  • hard start: The starting current is large (6 times the rated current), which has an impact on the life of the equipment.
  • response lag: When the air pressure fluctuates, the adjustment is slow and the stability is poor.

4. noise and vibration

• permanent magnet variable frequency
  • Low-speed operation reduces engine noise5-10 decibels。
  • Inverter fans further reduce aerodynamic noise.
• power frequency
  • Fixed high speeds cause high noise and vibration.
  • Additional sound insulation measures are needed, increasing costs.

5. Maintenance costs and longevity

• permanent magnet variable frequency
  • low maintenance cost: Permanent magnet motors have no bearings, do not require lubrication, and have a low failure rate.
  • long life: Soft starting reduces mechanical impact and has high equipment durability.
• power frequency
  • Frequent maintenance: Wear parts such as bearings and lubricants need to be replaced regularly.
  • to have a shorter lifespan: Frequent start-ups and stops and hard starts accelerate equipment aging.

6. applicable scenarios

• permanent magnet variable frequency
  • recommended scene: Industrial environments with large fluctuations in gas consumption, 24 hours of operation, and high requirements for air pressure stability (such as automobile manufacturing, electronics, food, etc.).
• power frequency
  • applicable scenarios: Small workshops or homes with stable gas consumption, short operating time, and cost-sensitive.

Summary comparison table

Selection suggestions：

• prioritypermanent magnet variable frequency: If long-term operation, energy conservation and noise reduction or air pressure stabilization are required.
• selectpower frequency: Only applicable to scenarios with stable gas consumption and limited budgets.