Four Quadrant
Operation
- Motor is driving a hoist consisting of a cage with or
without load, a rope wound on to a drum to hoist the cage
and a balance weight of magnitude greater than that of the
empty cage but less than that of the loaded cage.
- The arrow in the figure indicates the actual directions
of the motor torque, load torque and motion in four quadrants.
- The load torque of the hoisting mechanism is of active
type and assumed to be constant due to negligible friction
and windage for low speed hoist.
- Speed torque curve of the hoist is represented by vertical
line passing through two quadrants. Loaded hoist characteristics
in first and fourth and unloaded in second and third quadrants.
- In the first quadrant the load torque acts in the opposite
direction to that of rotation. Hence to drive the loaded
hoist up, the motor developed torque must be in the direction
of the rotation or must be positive. The power will also
be positive so, this quadrant is known as ‘forward
motoring quadrant’.
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