Hydraulic pump drive power calculator – How to choose a motor?

You've built your own hydraulic power unit, press, or log splitter. You switch on the machine, the cylinder extends to the material, and suddenly... the engine "chokes" and dies, or trips the circuit breakers throughout the workshop. Sound familiar?

This is a classic symptom of using an electric or internal combustion engine with insufficient power for the pump's efficiency and set pressure. With the free calculator from BRhydraulic, you can quickly determine exactly how many kilowatts (kW) and horsepower (HP) your machine needs to operate flawlessly.

Why does the pump draw power from the engine?
A hydraulic pump itself does not create pressure – it only creates oil flow (capacity). Pressure is generated only when the oil encounters resistance (e.g., a weight to be lifted or the resistance of a log in a splitter).
According to the laws of physics, the more liters of oil you want to pump (L/min) and the higher the resistance you need to overcome (bar), the harder the engine has to work to turn the pump shaft. If the resistance exceeds the engine's torque, the drive will stop.
How to calculate the required engine power yourself? (Formulas)
If you prefer to do the calculations on paper, hydraulic engineering uses one very simple and universal formula:
Formula for power in Kilowatts (kW):

P = (Q * p) / (600 * n)

Where:

• P – required engine power in kilowatts (kW)
  
• Q – pump flow rate in liters per minute (L/min)
  
• p – maximum system pressure in bars (bar)
  
• 600 – constant conversion factor
  
• n – overall pump efficiency (for gear pumps, 0.85 is usually assumed, and for piston pumps, 0.90)
  

Conversion to Horsepower (KM / HP):
To convert the result from kilowatts to popular horsepower, simply multiply the result by 1.36:

Power (HP) = P (kW) * 1.36

Remember the safety factor!
The result shown by our calculator is the power needed for the system to operate at given parameters. However, remember that engines need an additional power reserve for so-called starting current and to overcome initial friction resistance with cold oil.

• When purchasing an electric motor, add a minimum of 10-15% reserve to the result.
  
• When selecting an internal combustion engine (e.g., Honda, Lifan for mobile power units), add 20-30% reserve.
  

Complete drives and power units at BRhydraulic
Are you building a power unit from scratch or need to replace a seized pump? Our experts will gladly help you choose a set that won't let you down under load. In the BRhydraulic store, you'll find everything for building power units:

• Solenoid valves: Ensure precise control of oil direction and flow in your system.
  
• Cylinders: A wide selection of ready-to-use cylinders with various strokes and diameters, ready for work in the toughest conditions.
  
• CETOP manifolds: Modular connection plates and blocks facilitating the construction of compact and efficient hydraulic systems.