The magnetic amplifier is a device employing saturable reactors as its basic element. The theory or magnetic amplifiers is developed from the standpoint of rectangular hysteresis loops that are simplified in such a manner as to eliminate the problems of nonlinearity. The saturable reactor may be connected in either series or parallel combinations and their operation analyzed on the basis of voltage, current, and flux waveforms. The characteristics or the saturable reactor circuits may be enhanced by the addition of feedback. Feedback is accomplished either by magnetic means using additional windings, or by self-saturation in which rectifiers are used to secure feedback. The result is a device in which a small amount of power can effectively be used to control larger amounts of power. / Master of Science