Guys,
What is a 4 quadrant drive? Is it similar to a vector drive?
4 Quadrant Operation is simply the way to refer to a graph of torque versus speed.
A 4 quadrant drive (inverter) can turn the motor either forward or reverse, as well as decelerate in either direction (in other words there are no limitations dependent on motor direction).
A load that has a high inertia and must move in both directions while changing directions rapidly requires four-quadrant capability from the drive.
There are many applications requiring four quadrant drives and they are pretty common.