Electric Motors
VFD Energy Savings Calculator
VFD Energy Savings Calculator is meant for one defined electric motors case. Run a separate case when the equipment, period, or connection changes.
Check Estimated power after speed reduction
Avoid mixing nameplate, measured, and billing values in VFD Energy Savings unless that mix is intentional.
Where VFD Energy Savings fits
The displayed estimated power after speed reduction answers one bounded question: calculate estimated power after speed reduction from original fan power and speed fraction. Treat it as a case record rather than a general approval.
Keep VFD Energy Savings tied to the motor nameplate, supply system, duty cycle, and starting condition.
Testing original fan power
Using the sample values, Original fan power = 15 kW; Speed fraction = 0.8, the primary result is 7.68 kW.
This VFD Energy Savings one-input test is a scale check, showing direction and sensitivity without turning the changed case into a recommendation.
If the changed speed fraction comes from a real measurement, keep the original VFD Energy Savings run so the source of the difference remains clear.
Unit handling for VFD Energy Savings
Only the entries shown on VFD Energy Savings feed estimated power after speed reduction. If another correction factor matters, keep it in the notes or make a separate run.
The formula uses Original fan power, and Speed fraction to produce Estimated power after speed reduction. Unit mistakes usually show up as an answer that is off by a factor of 10, 100, or 1,000.
When your notes point to Motor Acceleration Time, open it after saving this baseline so the two cases do not get mixed.
Source notes for VFD Energy Savings
Collect Original fan power, and Speed fraction from the same operating case before reading estimated power after speed reduction.
- Original fan power
- Enter original fan power in kW. Default shown: 15 kW.
- Speed fraction
- Enter speed fraction. Default shown: 0.8.
Interpreting VFD Energy Savings
Read estimated power after speed reduction together with the input values, not as a standalone fact. The same number can imply different decisions under a different equipment rating or operating period.
Changing original fan power while leaving speed fraction fixed is a useful way to see which assumption controls the answer.
Use VFD Motor Speed for that neighboring calculation rather than adding unstated assumptions here.
What VFD Energy Savings leaves out
The cube law applies to suitable variable-torque loads.
- Drive settings
- Starting current
A numerically valid VFD Energy Savings result can still be wrong if the field condition, connection type, tariff period, or equipment rating does not match.
Common VFD Energy Savings questions
What should be recorded with the answer?
Save the VFD Energy Savings inputs, unit basis, operating case, and result note so estimated power after speed reduction can be reproduced later.
What does a Check inputs message usually mean?
On VFD Energy Savings, Check inputs usually means a required entry is missing, outside its allowed range, or creating an undefined operation.
Which value should be rounded first?
Keep speed fraction at source precision during VFD Energy Savings; round estimated power after speed reduction only where presentation or purchasing requires it.
Can the default values be used as a recommendation?
No. The VFD Energy Savings defaults only demonstrate the form. Replace them with measured or rated values for the actual electric motors case.
Why might a real measurement disagree?
A field reading for VFD Energy Savings can include losses, tolerance, temperature effects, waveform distortion, or instrument limits that the worksheet does not model.