Four-Switch Inverter-Fed Direct Torque controlof Three Phase Induction Motor

In this paper, four-switch inverter fed direct torque control three phase Induction Motor drive is presented. A triangular wave is used as dither signal of minute amplitude (for torque hysteresis band and flux hysteresis band respectively) in the error block. This method minimizes flux and torque ripple in a Four-Switch inverter fed induction motor drive while the dynamic performance is not affected. The optimal value of dither frequency and magnitude is found out under free running condition. This four switch based inverter fed direct torque control of three phase induction motor is simulated using MATLAB/SIMULINK software. The simulated results are presented. It shows that the proposed method reduces torque ripple by 60% (peak to peak) compared to the case without dither injection, results in low acoustic noise and increases the switching frequency of the inverter. INDEX TERMS: Balanced voltage vectors, direct torque control (DTC), four-switch/six-switch threephase inverter (FSTPI/SSTPI), induction motor (IM) drive, vector selection table.