Leeson PWM DC Control: 174299 User Manual download pdf (Page 5)

Regenerative Drives

Most non-regenerative variable-speed DC drives control current ow to a motor in one direction. The

direction of current ow 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

1 2 3 4 5 6 7 8 9 10 ... 34 35

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Leeson PWM DC Control: 174299 User Manual Page 5