Result
Preliminary calculation: This tool is for quick sizing and information. Electrical installation designs and cable and protection selection must be done according to the relevant standards and by an licensed electrical engineer. Results are approximate.
Formula
P₂ / P₁ = (Q₂ / Q₁)³E_inverter = Σ ( P_full × (Q_i)³ / η_inv × hours_i )When the speed of centrifugal fans and pumps is reduced, power falls roughly in proportion to the cube. With throttling by valve or damper, the power gain is very small. That is why air handling unit fans with variable load, circulation pumps and cooling tower fans are ideal candidates for an inverter.
- The pressure sensor and control algorithm must be set correctly
- A dv/dt filter may be needed depending on motor and cable length
- Inverters generate harmonics; power factor correction and filters should be considered
Frequently asked questions
Does an inverter save energy in every system?
It is effective in fan/pump systems where the load varies and the speed can be reduced. There is no gain at constant load.
Does the cube law always apply?
Under ideal conditions. When static pressure, minimum flow requirements and equipment efficiency change, the actual gain is lower.
How do I adjust the calculation?
Enter the flow rates and durations of your actual load profile; set the existing system's power ratio according to your measurement.