DTC brushless DC motor by using constant switching frequency

This paper propose direct torque control of constant switching frequency for brushless dc motor DTC-CSF BLDC. It is due to overcome the drawback of conventional DTC such as high torque ripples and variable switching frequency. It is applied by using PI controller to regulate the error of torque producing output error of PI controller, and then compare it with carrier or triangular frequency to generate constant switching frequency. The experiment is implemented by using Altera field-programmable gate array (FPGA) and digital signal processor. Results of experiment show the torque ripples waveforms are maintained in each level of speed and constant switching frequency is proved by the existence of fundamental frequency of 3125 Hz where it is clearly appeared in the frequency spectrum in any variation speed level.