ABSTRACT
D.c. brush or d.c. commutator machines have traditionally been used in variable speed drives in the range of low (a few watts) to medium, 10 MW, power ratings at low speeds. The popularity of d.c. brush motors in variable speed drives is primarily due to the lower cost of a single-stage (rectifier) PEC required for two-quadrant operation (one direction of motion). Four-quadrant operation, however, implies rather involved PEC configurations and controls.
