Selected motor power: N=(Q/3600)*P/(1000*η)*K
Where air volume Q is in m3/h, total pressure P is in Pa, power N is in kW, η is the total pressure efficiency of the fan (according to relevant fan standards, the total pressure efficiency shall not be less than 0.7, the actual estimated efficiency can be smaller, or 0.6, small fans take the smaller value, large fans take the larger value), and K is the motor capacity coefficient, see the table below.
1. Centrifugal fan
2. Axial flow fan: 1.05-1.1, take the larger value for small power and the smaller value for large power.
The selected motor power N = (Q/3600) * P / (1000 * η) * K
The formula for calculating the power P (kW) of a wind turbine is P = Q * p / (3600 * 1000 * η0 * η1).
Q—Air volume, m3/h;
p—Total air pressure of the fan, Pa;
η0—the internal efficiency of the fan, generally taken as 0.75~0.85, with lower values for small fans and higher values for large fans.
η1 — Mechanical efficiency:
1. Direct connection between fan and motor, take 1;
2. The coupling connection should be 0.95~0.98;
3. Use a V-belt connection with a diameter of 0.9~0.95.
4. Use a flat belt drive and take 0.85.
How to calculate the motor current:
I = (motor power / voltage) * c
The unit of power is KW
Voltage unit: kV
C: 0.76 (product of power factor 0.85 and power efficiency 0.9)
Here's an explanation of the formula for calculating the fan shaft power: N = QP/1000 * 3600 * 0.8 * 0.98
Q is the flow rate, measured in m³/h, and p is the total air pressure, measured in Pa (N/m²).
Note: The basic unit of power is W. In dynamics, W = Nm/s.
The unit of QP is Nm/h = W * 3600.
The power of a fan shaft is generally expressed in kW.
1000 is the conversion of W to kW.
3600 converts hours to seconds.
The above calculations yield the output power of the fan itself. The fan shaft power refers to the input power of the fan, which is also equal to the output power of the motor. The fan output power divided by the conversion efficiency gives the fan shaft power.
0.8 is the estimated internal efficiency of the fan.
0.98 is an estimated mechanical efficiency value.
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