Benefits of Using Variable Speed Compressors
Many companies gain significant financial benefits from installing variable speed compressors or retrofitting them with a frequency converter. In many cases, the costs of such equipment can be recouped in less than a year.
Application of Variable Speed Technology
Variable speed drive (VSD) technology can be applied to most air compressors with power ratings from 55 kW to over 500 kW.
While VSDs actually save money at high loads, the added cost of such compressors is justified only when the average load on the compressor is less than 75% of the maximum.
Evaluating Compressor Load
You can evaluate the load on the compressor in the following ways:
- By calculating the on and off time of the compressor. Usually, the changes in its operation modes are easy to notice.
- By asking your compressed air equipment supplier or an independent company that can install a monitoring system to take several measurements to evaluate the average load. The monitoring system will do this automatically.
- By determining:
- the type and method of power adjustment of the compressor;
- the average electricity price (UAN/kWh);
- the total power of the compressor (kW);
- the operating time of the compressor.
If the average load is already known, you can estimate the potential savings, which will help determine whether it is worth upgrading the existing compressor or purchasing a new compressor with a built-in VSD.
Advantages of New Compressors with VSD
New compressors with integrated VSD are designed and tested to operate over a wide range of speeds. They are often equipped with special features that may not be available when retrofitting, such as direct-drive motors, eliminating the need for gearboxes.
Upgrading Existing Machines
Upgrading existing compressors can provide good advantages at a lower cost than purchasing new ones. However, caution should be exercised when retrofitting frequency converters to screw and piston machines to ensure proper lubrication levels. All modifications should be carried out only by qualified installers who can set the operating parameters and avoid potential issues. It is also worth noting that upgrades by third-party companies will void the manufacturer's warranty.