Variable frequency drives-technology and applications

Variable frequency AC motor drives are recently making a tremendous impact in the industrial automation of nations. The rapid evolution of the technology could be possible because of many innovations in power semiconductor devices, power converter topologies, microprocessors, application specific IC´s, control and computer-aided design techniques. The paper gives a brief but comprehensive state-of-the-art review of AC machines, power converter circuits and power semiconductor devices. The control and estimation issues with particular emphasis of induction motor drives are discussed. Finally, a few selected drive applications are reviewed. Variable frequency drives are expected to have increasing influence on a nation´s industrial productivity, energy conservation, environmental protection and urban pollution problems in the coming decades.