The problem being solved: several large motors restarting together after a dip pulls 6-8x full-load amps EACH at across-the-line start. Stacked inrush drags the bus down, contactors drop out below their holding voltage (around 65-70% of nominal), VFDs trip on undervoltage, and you get the cascade that turns a blink into a full line shutdown.

Practical fixes, in order of cost:

1. Time-staggered starts. Cheapest fix there is: a PLC sequence or even three off-delay timers that allow one motor block per 5-15 seconds. Rule of thumb - do not release the next start permit until the previous starter's inrush has ended, which you verify with a current switch or simply by timer set longer than the manufacturer's stated acceleration time.
2. Feedback-interlocked sequencing (the robust version). Instead of blind timers, permit the next start only when the previous motor signals 'running' - auxiliary contact plus current above setpoint, or speed switch. Timers lie during a weak grid; measured current does not.
3. Soft starters or VFD ramps on the big ones. A soft starter cuts inrush to roughly 2-3x FLA and often removes the need for staggering entirely among itself; VFDs are gentler still since they accelerate against a current limit. Worth it for anything above ~50 hp that starts frequently.
4. Support the bus. Capacitor banks help with steady-state sag but not much with motor inrush dynamics; if the utility feed is genuinely weak, that becomes an engineering study, not a controls trick.

One detail people miss: write the restart priority into the sequence. After a blackout you do not want every motor racing to self-restart - essential loads first, comfort loads last, and stagger everything in between. That priority list belongs in the PLC program, not in an operator's head.