DC drives are thyristor based phase controllers
employed for controlling the speed and/or torque of DC motors.
These are employed in very high power applications,
such as locomotives, where high power capability of the thyristors
and the simplicity of the design can make them a more attractive
proposition than transistor based controllers.
The precise speed and torque control with
power regeneration capability given by the DC systems helps
user build a accurate control system with a greater price