Which is more power efficient for screw air compressor power frequency or frequency conversion?
Comparison of power saving between power frequency and frequency conversion of screw air compressors and suggestions on selection
In the selection process of screw air compressors, the power saving of power frequency and frequency conversion equipment is the focus of users ‘attention. The following is a professional analysis from four aspects: working principle, energy efficiency differences, application scenarios and selection suggestions:
1. Differences in working principles
-
Power frequency air compressor
Power frequency equipment runs at a constant speed, and the output pressure is adjusted by loading and unloading. Its starting method is usually star delta starting, with a large starting current (about 5-8 times the rated current), which has a great impact on the power grid and equipment. In the unloaded state, the motor still runs at no-load speed, resulting in high energy consumption. -
Variable frequency air compressor
Frequency conversion equipment adjusts the motor speed through a frequency converter to achieve on-demand air supply. Its starting current is low (about 1.2 times the rated current) and has little impact on the power grid and equipment. At low loads, the inverter reduces motor speed and reduces energy waste.
2. Comparison of energy efficiency differences
| characteristics | Power frequency air compressor | Variable frequency air compressor |
|---|---|---|
| Energy consumption regulation | Running at constant speed, the output power cannot be adjusted according to the load, and the energy consumption is high when unloading (about 20%-40% of the full load). | Adjust the motor speed according to the actual air consumption to achieve accurate air supply and extremely low energy consumption during unloading. |
| energy saving effect | The efficiency is higher under constant load, but the energy consumption increases significantly when the load fluctuates. | The energy-saving effect is significant in scenarios with large load fluctuations, and 20%-40% of electricity can be saved in practical applications. |
| initiating impact | The starting current is large and has a great impact on the power grid and equipment. | Small starting current realizes soft starting and has little impact on the power grid and equipment. |
| running noise | The operating noise is high and fluctuates with the change of speed. | Under most working conditions, the operating speed is lower than the rated value, and noise and wear are significantly reduced. |
3. Analysis of applicable scenarios
- Application scenarios for power frequency air compressors
- constant load: If the gas consumption is stable and close to the rated production capacity of the equipment, the power frequency machine can maintain efficient operation, and the difference in energy consumption from the frequency converter can be narrowed.
- Short-term or intermittent use: For scenarios with short running times and small air consumption, power frequency machines may be more economical because they have no inverter losses.
- Cost-sensitive selection: The initial purchase cost is lower than that of the inverter, suitable for users with limited budgets and low requirements for energy conservation.
- Application scenarios of variable frequency air compressors
- Large load fluctuations: If the gas consumption fluctuates with the production rhythm, the frequency converter can quickly adjust the output to avoid energy waste.
- long-term stable operation: In scenarios where continuous gas supply is required, the inverter can maintain efficient operation and reduce comprehensive energy consumption.
- High requirements for atmospheric pressure stability: The frequency converter can achieve precise pressure control to meet the needs of precision manufacturing, food processing and other industries.
4. Selection suggestions
- Priority selection of inverter air compressors
- If the gas consumption fluctuates greatly, the running time is long, or the energy conservation requirements are high, the inverter is a better choice. It has significant energy-saving effect and can extend the service life of the equipment.
- Application scenarios of power frequency air compressors
- In projects with constant loads, short-term use, or cost sensitive, power frequency machines may be considered. However, it should be noted that its energy consumption may be higher than that of inverter motors under long-term operation.
- integrated assessment
- Decisions need to be made based on the entire life cycle costs of the equipment (including energy consumption, maintenance, life, etc.). Although the initial purchase cost of the inverter is high, it can save a lot of electricity bills under long-term operation, and the comprehensive economic benefits are significant.
conclusion：
Inverter air compressor is more energy-saving in most scenarios, especially suitable for large fluctuations in air consumption or long-term stable operation conditions. Power frequency machines are suitable for specific scenarios, such as constant loads or short-term use. In the selection, it is recommended that users comprehensively evaluate energy consumption, cost, maintenance and other factors, and select the equipment that best meets the actual needs.