They“r right, a softstart is a much better system, but this is actually build because it will overload the fuses and powerlines in no time when it starts up, so it will start in star delta and save you from building a HUGE power outlet.
7500watt is about 32 amps and the start current is maybe arr 150amps (cant remember the right formular to this) if it starts up normally, but this system makes it to start up with maybe a third of that.