Pump Power Calculator
Determine the power required to drive a pump for a given flow rate and total head.
Required Shaft Power
7.85 kW
Required Shaft Power vs Flow Rate (Q)
Formula
## Pump Power Calculation The power a pump must supply depends on the flow rate, the head it must overcome, and pump efficiency. ### Formulas **Hydraulic power = rho g Q H** (useful work on the fluid) **Shaft power = rho g Q H / eta** (actual input from motor) where rho is fluid density, g = 9.81 m/s^2, Q is volumetric flow rate, H is total dynamic head, and eta is pump efficiency.
Exemplo Resolvido
A pump delivers 20 L/s of water against 30 m total head at 75% efficiency.
- 01Q = 20 L/s = 0.020 m^3/s
- 02Hydraulic power = 1000 x 9.81 x 0.020 x 30 = 5886 W = 5.89 kW
- 03Shaft power = 5.89 / 0.75 = 7.85 kW
- 04Select a motor of at least 7.5 kW (next standard size up).
Perguntas Frequentes
What does total dynamic head include?
Total dynamic head = static lift (elevation difference) + friction head loss in pipes and fittings + velocity head at discharge + pressure head required at the outlet. It is the total energy per unit weight the pump must add.
What is a typical pump efficiency?
Centrifugal pumps typically operate at 60-85% efficiency at their best efficiency point (BEP). Small pumps tend toward 50-65%, large pumps 80-90%. Operating far from BEP reduces efficiency significantly.
How do I account for motor efficiency?
The electric motor also has losses. Total electrical input = shaft power / motor efficiency. Motors are typically 85-95% efficient. Specify the motor based on shaft power, and the electrical supply based on motor efficiency.
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