Speed Control Methods for Constant Torque Drive

Constant torque drives are those drives where the torque required to drive the load remains constant throughout the operation. Examples of constant torque drives include conveyors, mixers, pumps, and compressors. In order to control the speed of such drives, various speed control methods are employed. Some of these methods include:

1. Field Control
In this method, the field winding of the motor is varied in order to control the speed of the motor. The field winding can be varied either by varying the current flowing through it or by varying the number of turns in the winding. This method is not very popular for constant torque drives as it can cause instability in the motor.

2. Armature Voltage Control
In this method, the voltage applied to the armature winding of the motor is varied in order to control the speed of the motor. This method is very effective for constant torque drives as it provides good speed regulation and does not cause instability in the motor.

3. Shunt Armature Control
In this method, the resistance of the shunt winding in the motor is varied in order to control the speed of the motor. This method is not very popular for constant torque drives as it can cause instability in the motor.

4. Mechanical Loading System
In this method, the speed of the motor is controlled by varying the load on the motor. This method is not very effective for constant torque drives as it does not provide good speed regulation.

Preferred Speed Control Method for Constant Torque Drive

Out of the above-mentioned methods, armature voltage control is the preferred speed control method for constant torque drives. This is because:

- It provides good speed regulation
- It does not cause instability in the motor
- It is easy to implement and maintain
- It is cost-effective

Therefore, for constant torque drives, armature voltage control is the most preferred speed control method.