I had wanted to add to this another way to trigger a relay to short the inline step-start resistor.
https://www.icmcontrols.com/product/icm102/Simply put it in series with the relay and set the time. Works with a 24v control system or directly on 120 or 240v. Time from 1.5 seconds to ten minutes. These are intended for HVAC systems and thus are both cheap and reliable — $10.00 or so. I like them much better than the charge a capacitor until the pull-in voltage is reached method because it does not chatter, it just switches. I also use these for plate switching delay, providing filament warmup time. Once you set the time, it just works.
Ed
We use these in DIN mount for our motors at work. When you get into the hundreds of HP electric motors ensuring that they stop before you turn them back on is a huge issue.
Especially when you have motors that run on 4160 directly! The backfed current surge can be HUGE. A couple of these in line with the contactors between motor and VFD take care of that problem.
--Shane
WP2ASS / ex KD6VXI
