Four quadrant operation of a Drive on v

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Four quadrant operation of a Drive on v. Motor operates in two modes –

Four quadrant operation of a Drive on v. Motor operates in two modes – Motoring and Braking v. In motor it converts electrical energy to mechanical energy – Supports its motion v. In braking it works as generator converting mechanical energy to electrical energy – Opposes its motion

In quadrant – I • Developed power is positive • Machine works as motor

In quadrant – I • Developed power is positive • Machine works as motor • Supplying mechanical energy • Forward motoring

In quadrant – II q q q Developed power is negative Machine works as

In quadrant – II q q q Developed power is negative Machine works as Generator Supplying electrical energy Forward braking Opposing the motion

• In quadrant – III Developed power is positive Machine works as motor

• In quadrant – III Developed power is positive Machine works as motor Supplying mechanical energy Reverse motoring Direction of rotation reversed

• In quadrant – IV Developed power is negative Machine works as Generator

• In quadrant – IV Developed power is negative Machine works as Generator Supplying electrical energy Reverse braking Opposing the motion

• For better understanding , let us consider operation of a hoist in

• For better understanding , let us consider operation of a hoist in four quadrants • A hoist consists of the rope wound on a drum coupled to a motor shaft • One end of the rope is tied to a cage(bucket) which is used to transport man or material from one level to another • Other end of the rope has a counter weight • Weight of the counter weight is higher than the weight of an empty cage but lower than the fully loaded cage

• In quadrant – I Movement of the cage is upward CCW -

• In quadrant – I Movement of the cage is upward CCW - Positive motor speed Developed power is positive Forward motoring operation

In quadrant – II • Cage is empty • Movement of the cage is

In quadrant – II • Cage is empty • Movement of the cage is upward • Since the counter weight is heavier than an empty cage , it is able to pull up • In order to limit the speed of the within a safe limit , motor must produce braking torque in CW direction • Since speed is positive and developed power is negative , it is forward braking operation

In quadrant – III • Empty cage is lowered • Since the empty cage

In quadrant – III • Empty cage is lowered • Since the empty cage has a lesser weight than the counter weight , motor must produce torque in clockwise direction • Since the speed is negative and developed power is positive , operation is reverse motoring

In quadrant – IV • Movement of the cage is downward • Since the

In quadrant – IV • Movement of the cage is downward • Since the weight of the loaded cage is higher than that of the counter weight , it is able to come down due to gravity itself • In order to limit the speed of the cage within a safe limit , motor must produce torque in CCW direction • As both power and speed are negative , drive is operating in reverse braking mode