Pump Motor kW Calculator for Water

Pump Power Formula:

\[ kW = \frac{Flow\ Rate \times Head \times Specific\ Gravity}{367 \times Efficiency} \]

Flow Rate:

m³/h

Head:

meters

Specific Gravity:

dimensionless

Efficiency:

decimal (0-1)

Pump Motor Power:

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1. What is Pump Motor Power Calculation?

The pump motor power calculation determines the required kilowatt (kW) rating for a pump motor based on the flow rate, head, specific gravity of the fluid, and pump efficiency. This is essential for proper pump selection and energy efficiency.

2. How Does the Calculator Work?

The calculator uses the pump power formula:

\[ kW = \frac{Flow\ Rate \times Head \times Specific\ Gravity}{367 \times Efficiency} \]

Where:

\( Flow\ Rate \) — Volumetric flow rate in cubic meters per hour (m³/h)
\( Head \) — Total dynamic head in meters (m)
\( Specific\ Gravity \) — Density ratio compared to water (dimensionless)
\( Efficiency \) — Pump efficiency as a decimal (0-1)
367 — Conversion factor (9.81 m/s² × 3600 s/h ÷ 1000 W/kW)

Explanation: The formula calculates the power required to move a fluid against gravity and friction losses, accounting for the pump's efficiency.

3. Importance of Pump Power Calculation

Details: Proper pump sizing ensures energy efficiency, prevents motor overload, and extends equipment life. Undersized pumps can't meet demand while oversized pumps waste energy and increase costs.

4. Using the Calculator

Tips:

Flow Rate: Typical range 5-500 m³/h for most applications
Head: Total dynamic head including static head and friction losses
Specific Gravity: 1.0 for water, higher for denser fluids
Efficiency: Typically 0.5-0.9 (50%-90%) depending on pump type and size

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between kW and horsepower?
A: 1 kW ≈ 1.34 hp. The calculator provides results in kilowatts (kW), the standard metric unit for power.

Q2: How do I account for motor efficiency?
A: This calculation gives pump shaft power. For motor input power, divide by motor efficiency (typically 0.85-0.95).

Q3: What if I have imperial units?
A: Convert flow rate to m³/h (1 US gpm ≈ 0.227 m³/h) and head to meters (1 ft ≈ 0.3048 m) before calculation.

Q4: What's a typical pump efficiency?
A: Centrifugal pumps typically range from 40-85% efficiency, with larger pumps generally more efficient.

Q5: Does this account for NPSH requirements?
A: No, this is only for power calculation. Net Positive Suction Head (NPSH) must be checked separately.