NEW DEVELOPMENTS IN VARIABLE SPEED DRIVES.

DC drives are almost always understood to mean rectifier fed variable speed DC drives. These consist of a suitable DC motor and a controllable thyristor rectifier interposed between the motor and the AC supply. The principal features of the variable speed DC drive are relatively low rectifier costs and high efficiency, good dynamic control, a uniform control concept for most applications, good speed regulation even at low speeds, high accuracy speed setting, accurate torque control and high starting torque. The article compares AC and DC drive systems.