Method
Air power adjusted by supplied fan, drive and motor efficiencies.
Equations
Pa = V̇ · Δpt
Ps = Pa1000 · ηf
Pin = Psηd · ηm
Symbols and units
| Symbol | Quantity | Unit |
|---|---|---|
| Inputs | ||
| V̇ | Airflow | m³/s |
| Δpt | Fan total pressure | Pa |
| ηf | Fan efficiency | 0–1 |
| ηd | Drive efficiency | 0–1 |
| ηm | Motor efficiency | 0–1 |
| Results | ||
| Pa | Air power | W |
| Ps | Shaft power | kW |
| Pin | Motor input | kW |
Assumptions and limits
- Motor size is not auto-selected.
In practice
- Use the fan total-efficiency at the duty point from the fan selection. The motor rating is chosen separately.
Worked example
The input values are the calculator's own verification test, run through the calculator. They show the working; they are not design values.
Inputs
| V̇ | Airflow | 2 m³/s |
| Δpt | Fan total pressure | 800 Pa |
| ηf | Fan efficiency | 0.7 0–1 |
| ηd | Drive efficiency | 0.95 0–1 |
| ηm | Motor efficiency | 0.9 0–1 |
Results
| Pa | Air power | 1,600 W |
| Ps | Shaft power | 2.28571 kW |
| Pin | Motor input | 2.67335 kW |
A preliminary check for engineer review, not an engineering approval. The project calculation to the applicable codes, authority requirements and specification governs.