VSD or FixSpeed: comparing compressor control
Choose control using the load profile. A constant process and variable demand require different operating comparisons.
Record the load profile
Record shift flow and pressure, shutdowns, weekend operation and seasonal changes. Note the number of compressors and their sequencing. A monthly average can hide long low-load periods and brief peaks.
Compare operating ranges
VSD adjusts speed within its permitted range to match supply to demand. With FixSpeed, assess loaded, unloaded and stopped operation. Consider station-wide control rather than a label on one unit. Request power and capacity data for each relevant duty point.
Do not promise savings without inputs
Compare at identical pressure, air-quality and availability requirements. Motor kW alone do not describe station consumption. Enter a justified average input power in Optimize. Diesel starting methods are unrelated to VSD/FixSpeed selection for an electric compressor.
What to prepare
- Flow and pressure profile
- Capacity and power range for each model
- Part-load losses
- Multi-compressor control
- Consistent TCO comparison basis
This guide helps assemble inputs. Check the complete datasheet for the specific model’s conditions.