Electrical & Mechanical Power Calculator
Calculate apparent power, active power, reactive power, and mechanical shaft power in single and three-phase systems. Enter the speed to see the motor torque, and send the results to ONX Control engineers to request a suitable solution for your application.
Electrical Inputs
Basic CalculationMechanical Output Parameters
Shaft SidePower Results
Electrical + MechanicalDerived Results
Auxiliary DataEngineering Expert Window
Cos φ and efficiency are not the same: The power factor indicates how much of the apparent power drawn from the grid is converted into active power. Efficiency shows how much of the active electrical power is converted into mechanical shaft power.
Transitioning from mechanical power to torque: As the shaft speed decreases, a higher torque is required for the same power. Therefore, a gearbox plays a critical role in applications requiring high torque at low speeds.
What is the Difference Between Electrical and Mechanical Power?
In motors, the power drawn from the grid is not directly mechanical power. First, apparent power is calculated, then active electrical power is found using the power factor. In the final stage, the mechanical power obtained at the shaft is calculated considering the motor efficiency.
In three-phase systems, apparent power is generally calculated as S = √3 × V × I, and active power as P = √3 × V × I × cosφ. Mechanical shaft power is found by multiplying active power by efficiency: Pmech = P × η.
This tool developed by ONX Control helps you make a quick preliminary evaluation in motor, drive, and mechanical load selections by calculating apparent power, active power, reactive power, mechanical shaft power, and torque together.
Frequently Asked Questions
Are Cos φ and efficiency the same?
No. Cos φ is the power factor and represents the portion of apparent power converted into active power. Efficiency is the conversion ratio of active electrical power to mechanical power.
Why does 3-phase power calculation include √3?
Because balanced three-phase system power expressed with line voltage and line current includes a √3 multiplier due to the geometric relationship between the phases.
How is mechanical power converted to torque?
If mechanical power in kW and speed in rpm are known, torque is approximately calculated as T = 9550 × P(kW) / n(rpm).
Is this tool sufficient for motor selection?
It is very useful for preliminary evaluation. However, for the final selection, duty cycle, starting regime, overload capacity, cooling, and mechanical load profile should be additionally examined.
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