Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)

Department / School

Electrical Engineering


This thesis presents a project in the design and study of a voltage regulator for generators on an AC network computer. The entire unit consists of two main parts: the part with sensing and amplifying circuits and the part with power drive devices. In the sensing and amplifying circuits, tubes such as 5651, 12AX7, and 12AU7 are used. The variation of AC voltage of a generator in a network system, as simulated by a variac on the analyzer, is sensed, after being rectified, by a grid of 12Ax7 while the grid voltage on the other half of the tube is maintained constant by tube 5651. The subsequent variation of plate voltages of both halves is then fed, through a voltage amplifier 12Ax7 stage, to a twin triode 12AU7 stage which serves as a current amplifier. The power drive circuit consists of a 27 volt DC shunt motor, two C11B trinistors, or silicon controlled rectifiers as they are commonly called, and their associated gating circuits. The gating of the trinistor is studied and saturable core reactors are used. Plate currents of both halves of 12AU7 flow through DC control windings of the saturable reactors respectively. The DC voltage for the motor is obtained from an AC source through the inverse-parallel connection of trinistors which makes bi-directional rotation of the motor possible. The motor, being coupled through a reducing gear to the variac on the analyzer, will drive the variac in a proper direction so as to maintain a constant voltage output from the variac. The dynamic response of the regulator unit is tested with the aid of an X-Y plotter.

Library of Congress Subject Headings

Voltage regulators
Automatic control


Includes bibliographical references



Number of Pages



South Dakota State University