Motor Acceleration Energy Calculator — Quantify Energy Stored at Speed
Calculate the rotational kinetic energy needed to bring a motor and attached rotating load from rest to a target speed. The result shows stored mechanical energy, estimated electrical input energy and average acceleration power.
Acceleration inputs
What acceleration energy represents
As a rotating system accelerates, energy is stored as kinetic energy. The amount depends strongly on total inertia and final angular speed.
Why speed has a squared effect
Rotational kinetic energy is proportional to the square of angular velocity. Doubling the final speed therefore requires four times the kinetic energy for the same inertia.
Why inertia must include the driven load
The motor rotor is only part of the rotating system in many machines. Fans, pumps, flywheels, conveyors and gear trains can contribute substantial reflected inertia.
Average acceleration power
Dividing acceleration energy by acceleration time gives an average power requirement for the modeled energy transfer. Actual motor torque and instantaneous electrical power can vary considerably during the acceleration.
Worked example
For 12 kg·m² at 1,500 RPM, the stored kinetic energy is about 148 kJ. With a 90% simplified efficiency and a 5-second acceleration, the modeled average electrical input power is about 32.9 kW.
Limitations
This page does not determine whether a motor can actually accelerate the load. Torque available over the speed range and the load torque curve must be checked separately.
Frequently asked questions
Does this calculate starting current?
No. It calculates the energy and average power associated with acceleration.
Can the final speed be zero?
No. A zero-speed target produces zero stored kinetic energy and is not a useful acceleration scenario.
Should gearbox inertia be included?
Use the equivalent inertia reflected to the motor shaft where appropriate.