Improvement in DC Motor Performance by Asymmetrical Triggering, Part I: One-Quadrant Drive

The static Ward-Leonard drive suffers from two major disadvantages: 1) poor power factor when the phase-controlled converter supplying the motor is operated at a delayed triggering angle, and 2) the problems associated with discontinuous armature current when the machine is lightly loaded. If asymmetrical triggering technique is judiciously applied to a converter-controlled dc drive, it improves not only the power factor but also the overall performance of the drive. It reduces the ripple content of the armature current and the value of the extra inductance necessary to achieve current continuity for low-current operation.