The variable speed drives market remains a key component and beneficiary of the boom in all aspects of automation and energy saving which am becoming of ever greater importance throughout the world. The words of Harry Ward Leonard, first uttered on the 18th November 1896 in his paper ＇Volts vs. Ohms speed regulation of electric motors＇ still bold true: ＇The operation by means of electric motors of elevators, locomotives, printing processes, travelling cranes, turrets on men-of-war, pumps, ventilating fans, air compressors, horseless vehicles, ann many other electric motel, applications too numerous to mention in detail, all involve the desirability of operating an electric motor under perfect and economical control at any desired speed from rest to full speed＇.