Servo characteristics of a rectifier-driven motor

THERE ARE A significant number of applications of d-c motors in which either the armature power, field excitation, or both, are supplied by one or more controlled rectifiers. In one type of servomechanism system, the speed of the motor is controlled through the armature power by a controlled rectifier; in another type, the motor speed is controlled by the action of a controlled rectifier upon the field excitation. Previous papers^1,2 have been written wherein an analysis is made of the case where the armature power is supplied by a controlled rectifier under steady-state conditions. To the engineer interested in employing the d-c motor and controlled-rectifier combination as a prime mover in a closed-loop control system, the steady-state analysis is significant but not necessarily sufficient.