Electrical Engineer

1, if it's big enough.

You can use any size generator your sweet heart desires to do whatever you are trying to do. It will do something. It may not do what you want but I don't understand what you want to do. So doing something qualifies as a success for me.

Better yet, hire somebody (consulting with a salesman can count as hiring them) that understands your goal, conditions and the electric load.

Good Luck.

It depends on the type of load and the starting method of the motor, and on the capability of the prospective generator. About 180 kW for a rough first estimate.