Actually it is dead easy to get it adjusted. Just monitor the current going to the " pony " motor. Adjust the pulleys so the current is at or slightly below the rated full load current on the nameplate. The pony motor is then putting out its rated horsepower. Where is it going? Got to be going into the three phase motor. With the three phase " idler " connected to the mains, you won't notice much if any difference in speed. Most four pole motors run at about 1750 rpm when they are being used as a motor. 50 rpm slip. To drive at 1850 rpm,
-50 rpm slip, would take the same horsepower going in as the motor is rated to put out. Actually a bit more to take care of windage and other losses. So the drive ratio is very close to 1 : 1
Dan