LEESON PWM DC Control: 174299 - Manual (Page 5)

V
Regenerative Drives
Most non-regenerative variable-speed DC drives control current flow to a motor in one direction. The
direction of current flow is the same direction as the motor rotation. Non-regenerative drives operate
in Quadrant 1, and also in Quadrant 3 if the drive is reversible (See Figure 1).
Motors must stop before reversing direction. Unless dynamic braking is used, non-regenerative drives
cannot decelerate a load faster than coasting to a lower speed.
Regenerative drives operate in two additional quadrants: Quadrant 2 and Quadrant 4. In these
quadrants, motor torque is in the opposite direction of motor rotation. This allows regenerative drives
to reverse a motor without contactors or switches, to control an overhauling load, and to decelerate a
load faster than it would take to coast to a lower speed.
MOTOR
TORQUE
NOTE: ARROWS IN SAME DIRECTION = MOTOR ACTION
ARROWS IN OPPOSITE DIRECTION = REGENERATIVE ACTION
MOTOR
ROTATION
Figure 1. Four Quadrant Operation