Three major problems EXIST with both CONVENTIONAL methods of motor control and VFD control: 

1. When a motor is directly coupled and run at a low speed, it becomes very inefficient. You could GO with a high torque motor that is significantly larger than the standard and would have the same results most of the time. 
2. Typical motors do not cool themselves well at extremely low speeds. The added heat buildup in the windings can cause premature motor failure. Check with the motor MANUFACTURER for more details. 
3. The third issue is load inertia, which is larger than that of the motor. 

The effects of all of these things increase greatly with a sloppy transmission SYSTEM. A speed reducer or gearbox should be employed to solve this problem. It will match the inertial changes and increase efficiency. Speak with a technical resource about sizing the gearbox to meet your application needs.

Three major problems exist with both conventional methods of motor control and VFD control: 

The effects of all of these things increase greatly with a sloppy transmission system. A speed reducer or gearbox should be employed to solve this problem. It will match the inertial changes and increase efficiency. Speak with a technical resource about sizing the gearbox to meet your application needs.