Induction machine can also be called asynchronous machine, which is the object to be controlled in this
project. The induction machine is composed of a stator and a rotor as shown in Fig. 2.2(a). The stator is
fixed while the rotor rotates inside with a small air gap between them. The rotors of almost 90% induction
machine are squirrel cage rotors [9], which contain conductor bars and end rings as shown in Fig. 2.2(b).
The rotor cage is a closed conductor as the conductor bars are all short-circuited by the end rings. The
rotor is mounted on the shaft with two bearings [9]. Normally one of the two shaft ends is used for driving
the load while the other one for mounting the shaft position or the speed measurement devices. The stator
is made up of several pole pairs. Each pole pair has three windings placed symmetrically in space as
illustrated in Fig. 2.2(a). Based on the arrangement of the three windings, the flux linkages(~
A, ~
B and
~
C)generated by the windings have 120°displacement in space.