Motor soft Starter. How does it work?

A motor can demand up to 8 times it's rated current when it's starting under load. This starting current surge is normally very brief. Anything that will slow the surge down should do the job for you. An inductor will slow down this current surge. If it's slowed down enough your generator can keep up. You can certainly start with a 75 turn coil and see how it works. If it doesn't do the job, add more turns. You don't want to go overboard as the coil will impede the current flow of an AC circuit and could cause your motors to over heat. Add about 25 turns if the 75 turn coil doesn't work. Keep adding until things seem to run right. You might not be able to reduce the starting current to equal the run current. The motor needs some extra current to start.