In article , NONONOmisc07
@bigfoot.com says...

Some 3p starters are pretty
sophisticated electronic circuits that bring them up slowly.

The same question for a starter like this.



While not technically correct, I refer to it as a one shot inverter or
speed control. In the AC line are some SCRs or Triacs and a control
circuit to drive them. They ramp the speed of the motor up slow and when
it gets near full speed a relay usually pulls in to put the full voltage
to it. Most often used in motors of 50 HP and up. We had them on some
200 hp motors where I worked. Big motors are like a dead short on the
lines so in order to keep the inrush current down, the ramp up starters
are used.