The difference between power frequency screw air compressor and permanent magnet

The differences between power frequency screw air compressors and permanent magnet screw air compressors are mainly reflected in the aspects of driving motors, energy-saving effects, control methods, maintenance costs and noise levels. The following is a detailed comparison:

1. Principle of driving motor

• Power frequency screw air compressor：
  Adopt ordinary induction motor, fixed speed (such as 50Hz/60Hz), and fixed output pressure and flow. The starting method is star triangle buck starting, which has a large starting current and obvious impact on the power grid.
• Permanent magnet screw air compressor：
  Use permanent magnet synchronous motor + frequency converter drive, adjustable speed (stepless speed change). Permanent magnet materials are magnetically stable, require no external excitation, and are more efficient. The start is soft start, the current is stable, and there is no impact on the power grid.

2. energy saving effect

• power frequency machine：
  The energy efficiency is acceptable at full load, but the efficiency is greatly reduced at low load, and there is no-load energy consumption (usually accounting for 30%-50% of the rated power).
• permanent magnet machine：
  • full load: Energy saving by more than 39.7% compared with power frequency machines.
  • Light load (<20%): Maintain 95% operating efficiency, automatically sleep when no load, and almost zero energy consumption.
  • frequency conversion adjustment: Adjust the speed according to the actual air consumption to avoid invalid operation.

3. Control method and accuracy

• power frequency machine：
  Start and stop are controlled by pressure switches, and the pressure fluctuates greatly (more than ±0.2MPa), and frequent start and stop accelerate equipment aging.
• permanent magnet machine：
  PID closed-loop control, stable pressure (±0.01MPa), continuous gas supply, and extends equipment life.

4. Maintenance costs and longevity

• power frequency machine：
  • Bearings require regular lubrication and are costly to maintain.
  • Hard starting aggravates mechanical wear and has a relatively short life (generally 8-10 years).
• permanent magnet machine：
  • Bearing-free design, maintenance-free.
  • Soft starting reduces mechanical impact and has a life span of more than 15 years.

5. noise and vibration

• power frequency machine：
  The noise is as high as 85dB(A) and the vibration is obvious, requiring additional damping measures.
• permanent magnet machine：
  The noise is as low as 65dB(A), the operation is smooth, and it is suitable for silent scenes (such as laboratories and hospitals).

6. Price and application scenarios

• price：
  Permanent magnet machines have high initial investment (30%-50% more expensive than power frequency machines), but the long-term energy conservation returns are significant.
• applicable scenarios：
  • power frequency machine: Scenarios with stable gas consumption and low requirements for noise and energy conservation (such as small factories).
  • permanent magnet machine: Scenarios with large fluctuations in gas consumption, precise pressure control and low energy consumption (such as electronics, medicine, precision manufacturing).

summary

Selection suggestions: If long-term stable gas supply is needed and the budget is limited, power frequency machines can be optional; if energy conservation, low noise and precise control are pursued, permanent magnet machines have more advantages.