Adjustable speed AC drives—A technology status review

The technology of solid-state adjustable speed ac drives was launched in the 1960's. Since then many innovations in devices, circuits, control theory, and signal electronics have made a considerable contribution to this technology. With the heritage of past experience, and the projection of present trends, an almost certain prediction can be made that adjustable speed ac drives will find widespread applications in industry before the end of this decade. The paper reviews the present status of ac drives technology in which the salient technical features of ac machines, converters, controls, and performances of the integrated drive systems have been discussed, and wherever possible, the appropriate trend of the technology has been indicated.