Locked-Rotor Restart Batch

Plan a staggered (batched) re-acceleration of induction motors after a voltage dip: per-motor locked-rotor current, residual bus voltage, per-batch limit, number of batches and total staggering time (IEC 60947-4-1 / motor re-acceleration practice).

Inputs

Pre-fault system voltage (pu) pu

System / source reactance Xₛ pu

Bus floor for re-accel U_min pu

Locked-rotor current factor K_lr × Iₙ (pu)

Number of identical motors —

Batch interval t_gap s

Results

Note — Simultaneous re-acceleration of many motors pulls the bus below the re-acceleration floor, so motors are started in staggered batches. Each batch inrush is limited to (U_sys − U_min)/X_s so the bus stays at/above U_min. The total staggering time is (N−1)·t_gap. This is a single-busbar approximation in per-unit; it ignores load torque, acceleration heating and the 27/59 / protection coordination — confirm against the relay and motor data.