How to choose a screw air compressor?

When choosing an air compressor, especially when customers want to purchase a screw compressor, it is inevitable to encounter a power frequency screw compressor and a variable frequency screw compressor, because permanent magnet variable frequency screw compressor is now a popular choice of variable frequency screw compressor. Therefore, here is a brief introduction to the differences between power frequency screw compressor and permanent magnet variable frequency screw compressor.

1、 Power regulation method

The power frequency screw air compressor adjusts the intake volume and load of the unit by changing the opening of the intake valve, achieving power regulation. The permanent magnet variable frequency screw air compressor adjusts the speed and load of the unit by controlling the frequency and voltage output by the frequency converter, achieving power regulation. It can be seen that there is a significant difference in the power regulation methods between the two.

2、 Power loss

The power frequency screw air compressor needs to reduce voltage through a transformer to convert the grid voltage into the operating voltage of the unit, which will result in electrical energy loss. The permanent magnet variable frequency screw air compressor does not require a transformer and directly converts the grid voltage into the unit's operating voltage, which can avoid energy loss caused by transformers. Therefore, from the perspective of power loss, permanent magnet variable frequency screw air compressors have higher energy efficiency.

3、 Efficiency

The power frequency screw air compressor, due to the need to reduce voltage through a transformer and control the opening of the intake valve, will experience certain energy loss and relatively low unit efficiency. The permanent magnet variable frequency screw air compressor, due to the use of advanced permanent magnet synchronous motors and more intelligent control methods, can achieve efficient operation.

4、 Application scope

Power frequency screw air compressors still occupy a large market share in some areas where the load is relatively constant, such as air compressors, refrigeration units, and so on. The permanent magnet variable frequency screw air compressor is more popular in some fields that require high energy consumption, environmental protection, and accuracy, such as precision instrument manufacturing, automotive painting, food manufacturing, and so on. It can be said that there are also certain differences in the application scope of the two.

In summary, the differences between power frequency screw air compressors and permanent magnet variable frequency screw air compressors are mainly reflected in power regulation methods, power losses, efficiency, and application scope. Choosing different types of screw machines is crucial for different fields and needs. 

The permanent magnet variable frequency screw air compressor is commonly referred to as VSD due to its variable speed drive. Due to the fact that VSD's permanent magnet variable frequency screw air compressor can automatically adjust its operating speed to accurately match the compressed air demand in real time. Generally speaking, choosing a permanent magnet variable frequency screw air compressor based on the scale and type of application can reduce these energy costs by 35% to 50% in production practice. With the passage of application time, a considerable amount of money can be left.

But in reality, when purchasing, it is not necessary to choose a permanent magnet variable frequency screw air compressor. Although variable frequency technology may sound like an ideal choice, it is not always suitable for any solution! Variable frequency air compressor is an ideal choice for enterprises with fluctuating demand during the production process. Specific situations that require the selection of permanent magnet variable frequency screw air compressor include:

The demand for compressed air varies significantly in different job positions for quality inspection;

The demand fluctuates with shifts, working days (i.e. weekends), or seasonal fluctuations; Or production requires tight pressure bands;

If the need for compressed air is consistent in the production process, or if these changes are not significant, then choosing to use a power frequency screw air compressor may be a suitable choice.

If there is a large amount of compressed air and fluctuations in demand, a solution can be considered by combining the power frequency screw air compressor and the variable frequency compression screw air compressor. The power frequency screw air compressor provides basic load, and one or more variable frequency compressors are "fine tuned" to meet the changes in demand:

Although variable frequency compressors have a high initial investment cost, they repay the increased investment through energy conservation, and the greater the change in demand, the greater the potential energy savings.

The working pressure range of variable frequency compressors is much narrower than that of power frequency compressors. They operate at lower conveying pressures while maintaining the minimum working pressure required for the air system. They can also provide more stable discharge pressure for all compressed air applications throughout the facility.

The net pressure of the variable frequency compressor can be set to be lower than the no-load pressure of the power frequency compressor.

The variable frequency compressor can start/stop at full system pressure without the need for unloading, which is both time-saving and labor-saving, without loss of idle time or emission losses that occur during normal operation.

JOY MACHINERY always adheres to the corporate vision of "building a leading brand of oil-free air compressors in the world", and hopes to provide high-quality, clean and safe air for food, beverage and other production enterprises on the road of oil-free air compressor research and development, production and sales. Source protection, and also contribute a little bit to people's health and safety.

JOY MACHINERY oil-free air compressor series is widely used in the food and beverage processing industry due to its clean air source and continuous and stable gas transmission. If you have any needs, please contact us! JOY Machinery (Shanghai) Co., Ltd. has a professional design team with rich experience and welcomes customization. Diversified products can meet most applications and meet your one-stop shopping needs. The air compressor series includes power frequency screw air compressors, variable frequency screw air compressors, permanent magnet variable frequency screw air compressors, two-stage compression screw air compressors, integrated screw air compressors, laser cutting air compressors, medium and high pressure air compressors. Air compressors, oil-free water-lubricated screw air compressors (special oil-free screw air compressors for the medical industry), diesel-moving screw air compressors, electric-moving screw air compressors and other products.

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