Variable Frequency Drive (VFD) for Compressors

Compressors are used in industrial installations to supply compressed air for a wide range of applications, such as pneumatic drives, production processes and automation systems.
Traditionally, a compressor is connected to a storage tank. When the maximum system pressure is reached, the compressor switches off, and switches back on when the pressure drops.

Because the difference between minimum and maximum pressure is relatively large, the system operates with fewer switching cycles.
However, a disadvantage is that the average system pressure is often higher than required for the process.
Higher pressure results in increased energy consumption and additional wear on the compressor system.

With a variable frequency drive (VFD), the compressor speed can be precisely controlled.
Within modern industrial automation, this control is a key component of efficient
drive technology and reliable motor control.

Constant Pressure Control with VFDs

By using a VFD, the compressor can automatically increase or decrease speed based on the actual system pressure and the desired setpoint.
An integrated PID controller ensures stable and accurate pressure control within the compressed air system.

This type of VFD integration enables seamless interaction with
machine control and industrial process control systems.
More technical background on VFDs can be found in the
Fluxcon variable frequency drives wiki.

An additional advantage is that the storage tank can often be smaller,
as the compressor continuously adjusts to actual air demand.

Energy Savings with VFDs on Compressors

Using a VFD allows the average system pressure to be reduced while maintaining a stable compressed air supply.
For example, reducing system pressure from 7 bar to 6 bar can already result in energy savings of approximately 7%.

In addition, leakage losses in the compressed air system are reduced,
which can increase total energy savings to around 10%.

For a calculation example or more information about energy savings with VFDs,
please visit our VFD FAQ.

IE3 Efficiency Directive

Since January 1, 2015, the IE3 efficiency directive for electric motors has been in force.
All motors from 0.75 kW up to and including 7.5 kW must meet IE2 efficiency requirements,
and motors above 7.5 kW must comply with IE3 efficiency or IE2 in combination with a
variable frequency drive (VFD).

Reduced Maintenance Costs with VFD-Controlled Compressors

Because the average system pressure is lower, the compressor operates under reduced load.
This results in less wear, lower maintenance costs and a longer service life.

Suitable VFDs for Compressors

The Fluxcon compact VFD series includes an integrated PID controller.
Based on an analog signal from a pressure sensor, the compressor can automatically maintain a stable desired pressure.