Mechanical & Drives
Inertia, kinetic energy and run-up time
Inertia of a rotor or roller, stored energy and acceleration time.
Calculating…
How it's calculated
Solid: J = ½ × m × r²
Hollow: J = ½ × m × (ro² + ri²)
E = ½ × J × ω²
t = J × ω ÷ T
High-inertia loads such as fans, flywheels, large rollers and centrifuges take a long time to start and stop. That affects motor starting, VFD ramp times, braking resistor sizing and how long you must wait for rundown before opening guards.
Accelerating torque is motor torque minus load torque, and inertia reflected through a gearbox is divided by the ratio squared.