Abstract :
According to legend, the American industrialist Henry Ford once said: "If you need a machine and don\´t buy it, then you will ultimately find that you have paid for it, but don\´t have it". As time passes, inefficient industrial machines consume more and more costly energy and begin eating away at budgets. In developed economies, it is estimated that electric motors account for about half of the total energy consumed. Variable speed drives (VSDs) can reduce the energy bill on many motor-driven systems by more than their own capital cost in a relatively short period, often in less than a year. As energy prices continue to soar, the return on investment on a VSD application increases in proportion to the bill.
