Screw Rotary Air Compressors -Fixed Speed vs. Variable Speed 

There are two kinds of industrial Screw Rotary Air Compressors with fixed speed and variable speed air compressors. Both kinds of Screw Rotary Air Compressors have different ways in how they operate. what are the differences between the two?

Fixed Speed compressor with direct drive

The motor of  Screw Air Compressors will run at a constant RPM unless turned off. If the factory needs some air during the plant time, the inlet valve will open up for loading. If they don’t need air, the inlet valve closes. The machine will unload.  It doesn’t actually ramp the motor up and down.

Y-Δ: Star-delta starting is a starting method of asynchronous motors. - it will have an impact on the grid at the moment of starting, The maximum instantaneous current can reach 6-7 times the rated current. If the capacity of the grid is not enough, it will cause the circuit breaker to trip for protection.

Product highlights of the DM-G Fixed Speed Screw Rotary Air Compressors

l lYE3 series air compressor special high-efficiency asynchronous motor, protection grade IP54;

l Dream customized air end, new type 5:6 asymmetric toothed semi-permanent rotor, 6~8 bearings, air volume increased by 5~10%.

l Plum-shaped elastic coupling, high transmission efficiency, low noise

l High-efficiency and low-noise internal rotor axial flow fan, motor IP54 protection grade, F grade insulation, sufficient air volume, high air pressure, and good cooling performance.

l Siemens contactor, man-machine communication interface, simple operation and stable operation

l l Stable and reliable control system

l The control system has voltage detection, three unbalance detection, overpressure, overtemperature, overload, overrun alarm high report

l Alarm function, real-time protection of the unit, automatic monitoring of operating conditions, automatic loading and unloading, sleep, reset

l No special person is required to supervise functions such as start.

l Chinese and English switching display interface, multi-unit control can be realized

Variable Speed Screw Rotary Air Compressors with inverter motor

A variable speed air compressor is a different story. It will actually use a variable speed, or VFD drive, which allows the motor to actually ramp up and down, allowing for energy savings. If the variable speed air compressor needs to, it can go down to a 50% flow, and in turn, it can also go all the way up to a 100%. for example, A 132KW compressor could go down to the equivalent of a 66 kw compressor , saving energy in the long-run.

l Ultra-efficiency permanent magnet synchronous motor-, protection grade IP54, temperature-resistant magnetic steel of 180℃, low-temperature rise design, low-temperature rise design, motor temperature rise is less than 60k, the service life of the motor is longer.

l Customized high-performance vector control inverter, perfectly matched with the motor, low frequency and large torque, can output 180% of rated torque

Inverter control start - it will have an impact on the grid at the moment of starting, The maximum instantaneous current can reach 3-4 times the rated current. If the capacity of the grid is not enough, it will cause the circuit breaker to trip for protection.

anent magnet variable speed air compressors are widely used in the industry. Compared with fixed speed air compressors, what are the differences between the two?

1. The air pressure is more stable:

1. Because the variable speed screw air compressor uses the stepless speed regulation characteristics of the frequency converter, it can start smoothly through the controller or the PID regulator inside the frequency converter; it can also be adjusted quickly for occasions with large fluctuations in air consumption response;

2. Compared with the upper and lower limit switch control of power frequency operation, the air pressure stability is improved exponentially.

2. Start without impact:

1. Since the frequency converter itself contains the function of a soft starter, the maximum starting current is within 3 times of the rated current. Compared with the power frequency starting which is generally more than 6 times of the rated current, the starting impact is small.

2. This impact is not only on the power grid, but also on the entire mechanical system, which is also greatly reduced.

3. Variable air flow control:

1. The air compressor driven by industrial frequency can only work at one displacement, and the variable frequency air compressor can work at a relatively 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.

2. When the air consumption is low, the air compressor can be automatically dormant, which greatly reduces the energy loss.

3. The optimized control strategy can further improve the energy-saving effect.

4. Low noise:

1. Most of the working conditions of the frequency conversion system work at lower than the rated speed, the mechanical noise and wear of the host machine are reduced, and the maintenance and service life are prolonged;

Permanent magnet variable speed air compressors have more advantages in energy saving and efficiency than fixed speed air compressors.

Conclusion of Main differences

1. Motor

l Asynchronous motor for fixed speed air compressor

l Inverter control motor for variable speed air compressor

2. Inverter control panel for variable speed air compressor

3. Control panel design has a little difference.