# What is Quadrant Diagram, Explain The Quadrant Diagram For Hoist Drive System, Sign Convention Of Speed Torque

Hello guys, welcome back to my blog. In this article, I will discuss the sign convention of speed and torque, what is quadrant diagram, working of quadrant diagram for the hoist system, etc. Each and everything I will try to explain in a simple way.

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### Sign Convention Of Speed Torque

The power is positive for motoring operation and power is negative for braking operation. The speed is considered to be positive for upward movement or motor running in an anti-clockwise direction. The speed is considered to be negative for downward movement or motor running in a clockwise direction.

The torque is said to be positive if it accelerates and torque is said to be negative if it deaccelerates.

### Quadrant Diagram For Hoist Drive System

The above diagram shows a quadrant diagram for the hoist drive system. The motor always operates in two modes i.e., motoring and braking. In motoring operation, electrical energy is converted into mechanical energy whereas, in braking operation, mechanical energy is converted into electrical energy.

The hoist drive system operates in four quadrants such as, in quadrant one - forward motoring, in quadrant two - forward braking, in quadrant three - reverse motoring, and in quadrant four - reverse braking.

In quadrant one - In quadrant one, the weight of loaded cage is greater then the weight of counterweight, the load torque is running in a direction which is opposite to that of rotation. In order to pull up the loaded cage, a motor must produce the torque in the anti-clockwise direction. Here, the speed is positive. The power developed is also positive because it is motoring operation.

In quadrant two - In quadrant two, the weight of the cage is less than the weight of the counterweight. So the cage is pulled up, in order to limit the speed to the safe value, the motor must produce braking torque in a clockwise direction. The load torque is in an anticlockwise direction. Here, the speed is positive whereas the power developed is negative.

In quadrant three - In quadrant three, the weight of the cage is less than the weight of the counterweight. In order to pull up the counterweight, the motor must produce torque in a clockwise direction. The load torque is in an anti-clockwise direction. Here, the speed is negative and power developed is positive.

In quadrant four - In quadrant four, the weight of the cage is more than the weight of the counterweight. Here the loaded cage is pulled down, in order to limit the speed to a safe level, the motor must produce the torque in the anti-clockwise direction. Here, both speed and power developed is negative.