Analysis of discontinuous current in a 12-pulse thyristor DC motor drive

The discontinuous current magnitude in a 12-pulse DC drive is determined in terms of the significant parameters including motor internal inductance, the interphase inductance, and the firing delay angle to the drive power converters. It is shown that there are two significant ranges of firing angle advance in discontinuous current. In range 1, from 0 to 15° advance, the current is discontinuous in both converters and the DC motor. In range 2, from 15 to 30° of firing angle advance, the current is discontinuous in both converters but continuous to the DC motor. Further firing angle advance causes continuous current in both converters and the motor. Both firing angle ranges of discontinuous current are analyzed to determine the magnitude of average output current as a function of the significant parameters