The difference between frequency conversion screw air compressor and non-frequency conversion

There are many differences between variable frequency screw air compressors and non-variable frequency screw air compressors, which are mainly reflected in the following aspects:

working principle

• Variable frequency screw air compressor: The power supply frequency of the motor is changed through the frequency converter to adjust the speed of the motor, so that the exhaust volume of the air compressor can be adjusted in real time according to changes in actual air consumption. For example, when the air consumption decreases, the frequency converter reduces the motor frequency, the motor speed decreases, and the exhaust volume of the air compressor also decreases, achieving energy-saving operation.
• Non-variable frequency screw air compressor: The motor is directly connected to a fixed frequency power supply, usually 50Hz or 60Hz, and the motor speed is constant. No matter how the air consumption changes, the air compressor runs at a fixed speed, and the exhaust volume is also fixed. When the air consumption is less than the exhaust volume of the air compressor, excess compressed air will be discharged through vent valves and other devices, resulting in energy waste.

energy saving effect

• Variable frequency screw air compressor: It can automatically adjust the exhaust volume according to the actual air consumption. Under partial load conditions, the energy-saving effect is significant. Generally, it can save about 30%-50%, and even in some occasions with complex working conditions and large fluctuations in gas consumption, the energy-saving effect is more obvious.
• Non-variable frequency screw air compressor: Due to the fixed speed, when the actual air consumption is less than the rated exhaust volume, it cannot be automatically adjusted, and it will continue to operate at the rated power, resulting in a large waste of energy.

starting mode

• Variable frequency screw air compressor: Adopt soft starting method, gradually increase the power supply frequency of the motor through the frequency converter, so that the motor and air compressor can start smoothly, with small starting current and small impact on the power grid.
• Non-variable frequency screw air compressor: When starting directly, the starting current is usually 4 – 7 times the rated current, which will cause a greater impact on the power grid and affect the normal operation of other electrical equipment. In order to reduce the starting current, star-delta starting and other methods may be used, but compared with frequency conversion starting, the starting process is still not smooth enough.

operation stability

• Variable frequency screw air compressor: The speed and exhaust volume can be accurately adjusted according to changes in air consumption, making the operating conditions of the air compressor closer to the optimal state, reducing vibration and wear caused by load changes, and making the operation more stable., the service life of the equipment is also relatively long.
• Non-variable frequency screw air compressor: In the case of large fluctuations in actual air consumption, the inability to adjust the exhaust volume in real time may cause large fluctuations in system pressure and affect the normal operation of the gas consumption equipment. At the same time, long-term operation under non-optimal working conditions will accelerate the wear of the equipment and reduce the stability and service life of the equipment.

Prices and maintenance costs

• Variable frequency screw air compressor: Due to the addition of control equipment such as frequency converters, its purchase price is usually about 20%-30% higher than that of non-variable frequency screw air compressors of the same specification. However, in terms of maintenance costs, due to more stable operating conditions and less wear, the maintenance costs are relatively low. The main maintenance items include regular replacement of conventional components such as lubricating oil, air filters, and oil filters.
• Non-variable frequency screw air compressor: The purchase price is relatively low, but due to long-term operation at fixed speed and large energy waste at partial loads, its comprehensive operating cost may be higher in the long run. At the same time, due to relatively large equipment wear, the maintenance cycle may be short, and maintenance costs will increase accordingly. Wearing parts, such as piston rings, valves, etc., may need to be replaced more frequently.

To sum up, variable frequency screw air compressors have obvious advantages in terms of energy conservation and operating stability, and are suitable for occasions with large fluctuations in air consumption; while non-variable frequency screw air compressors are suitable for relatively stable air consumption and energy conservation requirements. Not high occasions. Users can choose the appropriate air compressor type according to their actual needs and operating conditions.