Estimates the time for a motor and its connected load to accelerate from standstill up to rated speed, from the total (motor + load, reflected to the motor shaft) moment of inertia and the average net accelerating torque available during run-up — the rotational analogue of F=ma.
Standards followed
Rotational form of Newton's second law: t = J×ω / T_avg, ω = 2πN/60
What it can do
- Acceleration time from moment of inertia, rated speed, and average net accelerating torque.
- Grading band from VERY FAST to VERY SLOW as a quick sanity check.
Example problem
J=2.5 kg·m², rated speed 1480rpm, average net accelerating torque 180 N·m.
- ω = 2π×1480/60 ≈ 155.03 rad/s
- t = 2.5 × 155.03 / 180 ≈ 2.15 s
≈2.15 s — NORMAL band.
The average accelerating torque is the net torque (motor torque minus load torque) averaged over the entire run-up — it is not the motor's starting or breakdown torque alone, and estimating it accurately usually requires either a torque-speed curve integration or manufacturer/drive software data for anything beyond a rough screening estimate.