Amplitude-modulated frequency changer

The paper presents an introduction to a novel application of the principles of amplitude modulation to a.c.-a.c. power conversion: these principles represent an analogy in time to the principles on which the pole-amplitude modulation of windings are based. A general method of suppressing one sideband frequency of the modulated public supply is described, and the results of the initial work which has been carried out into the realisation of practical schemes for motor-speed control are described. It is concluded that the amplitude-modulated power supply may well prove to be complementary to the conventional cycloconvertor and may offer the possibility of a range of out put frequencies, most of which are outside the frequencies available from a conventional cycloconvertor.