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:

1. 100 horsepower single stage delivers 436 CFM @ 125 psig

2. 100 horsepower two-stage delivers 513 CFM @ 125 psig

Variable Speed Compressors at Energy Machinery

At Energy Machinery, we offer 24-hour field service and certified technicians are available with for troubleshooting and repairs, turnkey instructions, and planned maintenance programs.

We are an authorized warranty repair center for Gardner Denver, Champion, and Cooper Cameron compressors.

Take a look at our variable speed air compressors below. If you need help finding the right one for your business, contact us today and a representative will reach out to you quickly!



Compressed air can be damaging to applications that require moisture-free air.  Atmospheric air that enters an air compressor intake contains water vapor.

While in the air compressor, heat from compression and pressurization forces water vapor to condense into liquid droplets.

These droplets travel downstream and can ruin your products, air tools, cylinders, and air motors

Refrigerated air dryers take the moisture-laden air from the air compressor discharge and lower the temperature condensing the water vapor to water and separating it from the air before it goes downstream damaging product and equipment.

How Does a Refrigerated Air Dryer Work?

Compressed air enters the air dryer at a temperature of around 100F.  The air enters an air to air heat exchanger.

In this heat exchanger, the incoming air is pre-cooled by the outgoing cold air.  The air then enters a refrigerant to air heat exchanger which cools the air to around 35F.  

At this lower temperature, the moisture in the air is condensed and separated out of the air and is expelled from the unit.  

Lastly, the air travels through the previously mentioned air to air heat exchanger allowing the incoming warm air to reheat the colder air leaving the air dryer.

The compressed air leaving the dryer has a pressure dew point between 35°F to 50°F.

2 Types of Refrigerated Air Dryers

1. Non-cycling
2. Cycling

Non-cycling refrigerated air dryers

Non-cycling refrigerated air dryers operate with the refrigeration compressor running continuously, regardless of the inlet load.  

Minimal energy savings is realized from 100% down to 0% inlet air load.

Cycling Air Dryers

Cycling refrigerated air dryers automatically cycle the refrigeration compressor on and off in response to inlet load conditions as the inlet air load is reduced the refrigeration compressor cycles off, providing energy savings.  

This is done through some type of thermal mass that holds the temperature once the air compressor cycles off

Contact Us for Your Application

Need help deciding on the best one for your application?  Contact us today and a product expert will get back to you immediately!