Energy Machinery, Inc. | May 5, 2019

Variable Speed Compressors

Rotary screw air compressors controlled by VSDs (variable speed drives) are one of the best energy efficient industrial innovation introduced in the past few years.

The style of air compressor control can reduce energy wasted by compressors running in the unloaded condition exponentially.

Variable speed air compressors are ideal for plants that have fluctuating demand.

Some examples of this demand include Single shift seasonal type businesses that have higher production levels for a couple of months out of the year, or 24/7 operations, that have varying demands between shifts.

Variable Speed Air Compressor Benefits

Reduced energy consumption
Quieter than a fixed speed when running at a lower RPM
Consistent plant pressure increased component lifetime
Low inrush current during motor starts
May qualify for energy incentives

Single State vs. Two Stage Variable Speed Air Compressors

The main difference between single and two-stage air compressors are the number of compression stages.

Single stage air compressors compress air from atmospheric pressure to operating pressure in one stage.

A two-stage compressor uses two stages to compress the air.

The first-stage compresses the air to around 30 psig after which it is cooled before entering the second stage.

In the second stage, the air is compressed from 30 psig to operating pressure usually around 100 or 125 psig. This allows for the compressor to reach operating pressure more efficient

Example:

100 horsepower single stage delivers 436 CFM @ 125 psig
100 horsepower two-stage delivers 513 CFM @ 125 psig