ABSTRACT
An induction machine (IM) is built with 1-, 2-, 3-(or 6-) phase ac primary stator windings and a cage or wound rotor. In the latter case, the rotor winding is of a 3-phase ac type, and is connected through copper sliprings and brushes to an external source (PWM converter) that provides variable voltage and frequency. The so-called wound rotor or doubly fed induction machine is thus obtained. Also linear induction motors (LIMS) with aluminum-slab-on-iron or ladder secondary, or with two (3)-phase ac secondary winding on board of mover, have also been built for niche applications.
