What is Direct Torque Control?

Direct control torque is a method of optimizing and maintaining normal operation, usually during an AC (AC) motor. There are several programs for this type of control, usually in machines that require consistent and reliable torque. Compared to other methods of controlling AC motors, direct control torque has several advantages and disadvantages, although much of this depends on the program. Certain technological capabilities enable and further amplify this and other frequency inverters – machines usually responsible for controlling the electrical power delivered to a motor.

In essence, the process of direct control torque monitoring involves certain variables in the engine, and adjusting the amount of power to keep these variables within an optimal range. Especially the most important variables measured are voltage and current. From these values, the magnetic flux and the torque of the motor can be deduced. When these measurements are taken, the electrical current supplied to the motor is adjusted, if necessary, to maintain the optimal range of torque and flux.

Applications for direct control torque are numerous in industrial processes, because many machines often require accurate torque over long periods of time. Most often direct torque control will be performed on three-phase AC motors, but other designs can often integrate similar processes. Early trials with direct control torque placed the systems inside locomotives, and direct control torque can now be used in electric car engines.

Benefits of this type of control generally come from consistent measurements and adjustments made to optimize operations. Ideally, any adjustments will be made almost immediately. This can increase the efficiency of the engine’s total and help reduce energy loss. In addition, this type of control can reduce the mechanical resonance of a motor, further increasing efficiency and also cutting down on audible machine noise at low speeds.

Disadvantages of these systems often start with error measurements. There are often measurement errors at low speeds, for example, that can lead to improper adjustments and efficiency losses. Error measurements can also occur at high speeds and over the full range of torques. As a result, high-quality measuring and monitoring equipment is usually required.

High-speed computer technology plays an important role in effective direct control torque. So many quick calculations are required that extremely fast computers and other digital controllers are often crucial to making the right adjustments on time. In addition, speed and position sensors are often needed, especially in low speed applications.

  • Direct torque control can help improve performance and energy efficiency within AC motors.

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