There is no safe universal formula such as “wait five seconds between every motor.” The delay must come from the source strength, each motor/starter, the driven load, and positive feedback that the previous start has finished.
For DOL motors, use the actual locked-rotor current data. A VFD, soft starter, autotransformer, or star-delta starter changes both magnitude and duration, so use its manufacturer curve and the real load-torque profile. This impedance equation is only a screening calculation; a weak utility feeder, generator, long cable, or multiple transformers needs a proper network study.
My control sequence would enforce:
only one high-current start at a time;
all process and electrical permissives true before START;
dependencies already running (lubrication/cooling before the process motor);
starter/VFD READY and no overload/fault;
advance on actual RUN_FB, AT_SPEED, or RAMP_COMPLETE plus a small settling delay;
abort or enter a defined degraded mode on start-fail timeout;
inhibit automatic mass restart after a voltage dip unless the engineered restart plan allows it;
postpone nonessential loads while measured bus voltage is below the start threshold.
I built a working generator around that model:
Public eight-motor report: https://blossom.primal.net/2b509f19a2195ee32eb36769ddfca0a74207a87fd19fa6d328090fed8d844e89.html
The final acceptance test should trend bus voltage/current during the worst start, confirm acceleration time and feedback, and verify transformer, feeder, protection, cable, harmonic, and arc-flash results with a qualified engineer before commissioning. Payment/contact: https://coinos.io/CircuitSats
There is no safe universal formula such as “wait five seconds between every motor.” The delay must come from the source strength, each motor/starter, the driven load, and positive feedback that the previous start has finished.
For a first-pass screen:
running kVA_i = kW_i / (efficiency_i × PF_i) starting kVA_i = running kVA_i × inrush multiplier_i event kVA_i = non-motor load + already-running motor kVA + starting kVA_i estimated dip % ≈ source/transformer Z % × event kVA_i / transformer kVAFor DOL motors, use the actual locked-rotor current data. A VFD, soft starter, autotransformer, or star-delta starter changes both magnitude and duration, so use its manufacturer curve and the real load-torque profile. This impedance equation is only a screening calculation; a weak utility feeder, generator, long cable, or multiple transformers needs a proper network study.
My control sequence would enforce:
I built a working generator around that model:
Public eight-motor report: https://blossom.primal.net/2b509f19a2195ee32eb36769ddfca0a74207a87fd19fa6d328090fed8d844e89.html
Source ZIP: https://blossom.primal.net/550ec00995593d85fac3ee517f1cf70fb3928bdc7c39a7b2d4859b792eaf3a42
The final acceptance test should trend bus voltage/current during the worst start, confirm acceleration time and feedback, and verify transformer, feeder, protection, cable, harmonic, and arc-flash results with a qualified engineer before commissioning. Payment/contact: https://coinos.io/CircuitSats