Considerations about direct torque control and encoder-less operation of induction motor drives

The paper presents the principle of direct torque control and encoder-less operation of the induction machines. Direct Torque Control - or DTC - is the most advanced AC drive technology developed by any manufacturer in the world. Comparative to vectorcontrol, direct torque control (DTC) techniques need no axis transformation and the electromagnetic torque and the stator flux are estimated and directly controlled by applying the appropriate stator voltage vector. Aditionally, it is possible to estimate the rotor speed without the use of an encoder.