Technical calculation · Fan
Fan motor power calculation.
Calculate the fan shaft power and the standard motor to select from the airflow and total pressure in a few seconds.
3D view
How does a fan move air?
Air enters the centre of the impeller through the inlet; the rotating blades throw it outwards and the volute casing delivers it under pressure. The size of the motor changes with the power you calculate.
Preparing the 3D view…
The illustration explains the preliminary calculation; it is not to scale. The view changes as you change the values.
Calculation method
How is fan motor power calculated?
The power a fan delivers to the air is the product of airflow and total pressure. Dividing this power by the fan efficiency gives the shaft power. After the drive loss and the safety margin are added, the next standard motor size up is selected.
Worked example
A direct-coupled medium-pressure fan with 70% efficiency, required to deliver 10,000 m³/h at 2,000 Pa total pressure:
Shaft power: 10,000 × 2,000 ÷ (3,600,000 × 0.70) ≈ 7.94 kW
Selection power: 7.94 × 1.15 ≈ 9.13 kW (15% safety margin)
Motor: next standard size up → 11 kW (15 HP)
Points to watch
Common mistakes when selecting a motor
- Use total pressure, not static pressure. If the dynamic pressure is left out, the motor ends up undersized. Yurtfan selects fans on total pressure.
- Check the cold start with hot gas. Cold air is denser; at start-up the motor is loaded more heavily than in hot operation.
- Add the belt drive loss. With a belt drive, a loss of about 5% must be taken into account.
- Altitude and temperature make air lighter. The Fan Selection Centre applies this correction automatically.
Leave the calculation to our engineers.
Send us your airflow, dust type and plant layout; we will size the fan, filter and duct line together and prepare your quotation.