Technology Archives - SOLLANT- Top Manufacturer of Air Compressor, Generator, Drilling Rig in China

Fixed Speed VS Variable Speed Compressor

sollant — Sun, 12 Apr 2020 15:11:19 +0000

What are the working principles of fixed speed and variable speed compressors?

Power frequency air compressors are also called fixed speed air compressors. In any case, as long as the air compressor is started, the speed will always be constant.

The motor uses a 3-phase asynchronous motor. The motor speed of different powers is generally in the range of 2930-2970 ( 380v50hz).

The variable speed(VSD) air compressor uses a 3-phase permanent magnet synchronous motor, which is used in conjunction with a frequency inverter to adjust the motor speed according to the pressure feedback signal to achieve the purpose of energy-saving.

What is the difference between fixed speed vs variable speed compressor?

Working Pressure:

The variable speed(VSD) air compressor uses the step-less speed regulation characteristics of the frequency converter, and can start smoothly through the PID regulator inside the frequency converter; it can quickly adjust the response to the working environment with relatively large fluctuations in air consumption;
Air pressure stability is much better than a fixed-speed air compressor.

Machine Start:

The frequency converter of the air compressor has the function of a soft starter. The maximum starting current is within 1.2 times the rated current, and the starting impact is small. The starting current of a power frequency air compressor is generally more than 6 times the rated current.
The start-up impact of variable frequency air compressors is much smaller than that of industrial frequency air compressors.

Air Flow Control：

The air compressor is driven by fixed speed can only work at one displacement. The variable speed air compressor can work in a wide range of displacement. The frequency converter adjusts the motor speed in real-time according to the actual air consumption to control the air displacement.
When the air consumption is low, the variable inverter can be automatically dormant, which greatly reduces the energy loss.
The optimized control strategy can further improve the energy-saving effect.

The Voltage Adaptability of AC Power:

Due to the over-modulation technology adopted by the inverter, sufficient torque can be output to drive the electric motor even when the AC power supply voltage is slightly lower. When the voltage is slightly higher, the voltage output to the motor will not be higher;
For the occasion of self-generation, the variable frequency drive can show its advantages better;
According to the characteristics of the motor’s VF (variable speed air compressors work below the rated voltage in an energy-saving state), the effect is obvious for sites with the low grid voltage.

Machine Noise：

Most of the working conditions of the frequency conversion system are lower than the rated speed, the noise and wear of the main engine are reduced, and the noise is lower than that of the fixed speed system.

Price:

Because the fixed speed air compressor does not have a frequency converter, the production cost and price are usually cheaper than the variable speed air compressor.

Let Us See More Simple and Clear:

Variable Speed Feature

Energy-saving, reduce production energy consumption
Extend the service life of the machine
Stable airflow, suitable for intermittent operation
Air compressor unit runs more quietly
Automatically adjust the motor speed

Fixed Speed Feature

Low machine cost
Motor speed is not adjustable
Airflow always maintains the same standard
Under the same requirements, it is suitable for 7*24 hours of uninterrupted operation

Do I Need a Fixed Speed or Variable Speed Compressor?

Choose a Fixed Speed Drive for This Condition:

The fixed speed mainly relies on two points to control the start and stop (high-pressure stop, low-pressure start).

If there is no high requirement on the air pressure used, and the selected air compressor produces air volume close to the required air volume, it is the remaining amount. When the volume is not large, it is recommended to use the power frequency.

At this time, regardless of the power frequency conversion air compressor, in order to ensure the air volume demand, it will basically run at full load.

At this time, the power frequency conversion consumption is the same, and the frequency conversion air compressor is still more With the addition of a frequency converter, there is an additional component that can be easily damaged and repaired, and the power saved in long-term use is negligible.

In some cases, VSD is the correct solution. If your power supply costs are high, the compressor runs for many hours a day, and your needs vary greatly, then VSD makes sense.

Finally, VSD needs a clean, dry installation area and a good power supply.

Therefore, the frequency conversion air compressor is not necessarily the best choice. You must choose the appropriate air compressor according to your own use situation and the characteristics of the air you use.

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Screw Compressor VS Piston Compressor

sollant — Sun, 12 Apr 2020 12:55:03 +0000

Which Is Better? —Screw Compressor VS Piston Compressor

Screw air compressors and piston air compressors are the two most common models in the air compressor market. Practitioners of air compressors often use these two models as a comparison to advertise and promote to users.

Piston air compressors entered the market early and had a large market share; screw air compressors entered the market late, but with a high degree of intelligence.

However, it is a trend that screw air compressors replace piston air compressors, and it has been steadily proceeding. In the near future, more screw air compressors will be used in industrial production, and the market share of screw air compressors will continue to increase.

Comparison of rotary screw air compressor vs piston selection compressed air has played a vital role in the daily operations of most companies. The demand for compressors is obvious, but which compressor to choose?

The screw-type or the piston type can make it work best in the equipment, which is a question worth discussing. This first needs to consider the similarities and differences between the two compressors before choosing the most suitable one.

Compressors have been widely used in various gas fields, but air compression is the most widely used part. At present, stationary screw air compressors account for approximately 40% of the air compression market share, while piston air compressors account for 21% of the market share (calculated in US dollars).

What is the difference between rotary and piston compressor？

Different structure

The organization structure of the screw air compressor consists of the oil screw main engine, electric motor, oil and gas separator, oil pipeline system, cooling system, gas pipeline system, and electrical control system.

The piston compressor is composed of a compressor main unit, cooling system, regulating system, lubrication system, safety valve, electric motor, and control equipment.

Different features

The screw air compressor has the advantages of low vibration, no need to fix on the foundation with anchor bolts, low motor power, low noise, high efficiency, stable exhaust, and no wearing parts.

Under normal circumstances, the compressed gas of the piston compressor does not contain oil, and there is no need to add a degreasing device.

The disadvantage of this machine is that the motor power is too large, the exhaust pressure is not stable enough, the exhaust temperature is high, the noise is too large, the maintenance workload is large, and the maintenance cost is high.

The fault is different

Screw air compressor failure is very few, just regular maintenance, replacement of air filter, oil filter and oil-gas separator, can be normal operation.

Due to incomplete oil scraping and poor sealing of piston air compressor, oil often runs to packing device or even piston ring, resulting in oil in compressed gas.

In addition, the exhaust temperature is high, sometimes as high as 200 ℃; the cooling effect is not good due to the blockage of cooling; the piston ring is stained with oil, which is especially easy to wear; the valve flap leaks; the cylinder is worn, etc.

Which is better rotary or piston compressor？

4.Performance Comparison:

Reliability

Piston air compressors have low reliability, many parts, many vulnerable parts, large maintenance, poor operation reliability, short life span, and the interval between overhauls is generally about 8,000 hours.

The screw air compressor has high reliability, few parts, no wearing parts, small maintenance, reliable operation, long life, and the interval between overhauls can reach 40,000 to 80,000 hours.

Dynamic Balance

Piston type has unbalanced inertial force, machine running vibration and noise are big, small machine or above needs to install the foundation.

The screw type has no unbalanced inertial force, the machine can work steadily and at a high speed, is small in size, light in weight, and can achieve basic operation.

Pressure Stability

The reciprocating air compressor has a discontinuous exhaust, causing airflow pulsation, unstable pressure, and easy to cause pipeline vibration. A large-capacity air tank is required.

The rotary screw air compressor has a uniform exhaust, no airflow pulsation, stable pressure, and no need for large-capacity air tanks.

Air Quality

Reciprocating air compressors have poor air quality and high exhaust oil content, which cannot meet the higher requirements of users, and post-processing costs are high.

The oil-injected screw compressor can also achieve good air quality, and the exhaust oil content is only between 1-5 ppm, which meets the higher requirements of users and reduces post-processing costs.

Price-Piston VS Screw Air Compressor

Piston-type air compressors have low production requirements and low prices. Screw-type air compressors require high production technology, and their prices are more expensive than piston-type air compressors.

Stress Adaptability

Piston air compressors are suitable for a wide range of pressures and can reach the required pressure regardless of the flow rate, up to 350Mpa in industry.

The oil-injected screw air compressor is limited by the rigidity of the rotor and the bearing, so it cannot be used in high-pressure occasions, and the exhaust pressure generally does not exceed 3 Mpa.

Capacity Adaptability

The piston type has strong adaptability and a wide range of displacement, which is not affected by pressure.

Rotary compressors cannot be applied to miniature occasions because they rely on gap sealing gas. Generally, rotary compressors have superior performance only when the volumetric flow is greater than 0.2m3/min.

Operation and Maintenance

The piston air compressor has a low degree of automation and must be operated by someone on duty. The screw air compressor has a high degree of automation. The operator does not need to undergo long professional training and can realize unattended operation.

Conclusion:

Based on the above, if you consider the price, the piston air compressor is the best choice; in order to reduce the maintenance cost and production cost of the air compressor, increase economic benefits, facilitate equipment management, protect the environment and reduce pollution.

And use high-efficiency high-reliability screw compressors to replace piston-type air compressors and the construction of an advanced and economical air compressor station is an inevitable trend of increasing development and strength.

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