DISADVANTAGES: The major disadvantage of the DTC drive
is the steady state ripples in torque and flux. The pulsations in
flux and torque affect the accuracy of speed estimation. It also
results in higher acoustical noise and in harmonic losses.
IMPROVEMENTS IN DTC METHOD: Generally there are two
methods to reduce the torque and flux ripple for the DTC
drives. One is multi level inverter; the other is space vector
modulation (SVM). In the first method, the cost and the
complexity will be increased, in the second method, the torque
ripple and flux ripple can be reduced, however the switch
frequency still changes.