High-efficiency drives using permanent-magnet motors

The concern for energy conservation opens up a very large market for adjustable speed drives of medium to large rating. This paper advocates the increased use of neodymium-based permanent magnet motors in these drives based on their potential for a higher efficiency than can be achieved with induction motors. Typically, it is estimated that the losses of the permanent magnet motor can be made less than 60% of those of an induction motor of the same frame size. The result is a saving in electric energy costs which may compensate for the higher initial cost of the motor in less than a year of operation