الفهرس 
cahpter 1Only 14 pages are availabe for public view
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Abstract
Three phase induction motors are the most used motors as they represent 80%
among electric motors used in industrial applications. This is because induction
motors have many advantages like simplicity, ruggedness, low cost, reliability,
compactness and ease of maintenance.
Despite their benefits, induction motors have one major drawback, which
IS that their speed is determined by the frequency of the supply, and various
with torque variation. In some applications, it is required to drive the motor with
constant speed. To overcome this problem, various speed control strategies have
been formulated for the induction machine, depending upon how the voltage-to-
frequency ratio is implemented. These methods work effectively within specific
range of torque variation, and do not work effectively elsewhere.
To overcome this problem, Field Oriented Control, also called vector
control, has been used to control induction motors. It increases torque per
ampere ratio by maintaining the angle between stator field and rotor field at 90°
at any load torque, which reduces the motor current and increases efficiency and
output power.
Dynamic equations for the three phase induction motor have been
determined. Park’s transformation have been applied to transform the three-
phase equations into two-phase in d-q frame of reference. In addition, space
phasor notation for the motor has been presented.
Vector controlled induction motor drives have been presented. There are
two types named direct and indirect. In the direct method, the field angle is
measured from the output of Hall sensors or by integrating the induced emfs
from a set of sensing coils placed near the air-gap and embedded in stator slots.
In the indirect method, the field angle is estimated using dynamic model of the