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Abstract
6-1- Conclusion Of The Thesis:-
This thesis demonstrates the dynamic operation of synchronous motor with damper windings, without damper windings and with DTC. The performance characteristics of each case is presented.
The conclusions of the presented work is summarized in the following points:-
1- Dynamic characteristics of synchronous motor with damper winding and without
damper winding are presented and the following results are concluded:-
(a) Damper winding plays a very significant role in reducing amplitude and time of oscillation.
(b) The motor of higher inertia needs longer time to settle at its steady state
condition.
(c) The motor torque required to overcome the friction and windage is very
small thus the change in motor friction coefficient has an unsignificant
effect on dynamic performance of synchronous motor.
(d) Pull in torque is the maximum torque can be suddenly applied to the
motor without losing its synchronism.
(g) But in absence of damper winding the motor takes more time to be
stable, which leads to more heating in motor.
(h) In absence of damper winding, the damping effect is due to iron losses.
2- Direct Torque Control technique are presented and discussed and the following
results are concluded:-
(a) DTC is the newest technique in torque and speed control for Ac drive,
which has a fast dynamic response.
(b) The motor state calculations are updated 40,000 times every second.
(c) The motor operates under motor flux optimization concept, so the motor
flux is automatically adapted to the load torque providing high efficiency.
(d) A smooth circle can be approximated by an equilateral polygon. In fact,
as the number of sides of the polygon increases, the error can be made
as smaller as desired (M.F.Rahman et la strategy).
(e) As the number of sides of the polygon increases, the error can be made as
smaller as desired and also the current wave form can be made sinusoidal
as possible(the proposed pattern).
3- Dynamic characteristics of Synchronous motor using DTC in absence of damper
winding are presented and discussed and the following results are concluded:-
(a) Using DTC technique to control the motor operating voltage or flux to
obtain the same effect as that obtained from using the damper winding.
(b) Using DTC technique instead of damper winding plays a very
significant role in reducing the time and the amplitude of oscillation. It is
observed that the motor with DTC take .75 second to settle at its steady
state condition, while the motor with damper winding take 1.5 second to
settle at its steady state condition at same variation of load.
(c) During Oscillation period at same variation of load, it is observed that
the efficiency of the motor with DTC change from 60 to 90%, while
the efficiency of the motor with damper winding change from 30 to 85 %
which means higher efficiency at dynamic period.
(d) While at sudden variation of field current the improvement due to using
DTC is unsignificant because field winding is low power winding so
oscillation resulting due to its sudden change is much simpler than
resulting due to sudden change in load.
(e) Sudden variation of armature voltage will be recovered by DTC as it is
occurred, So it will be no noticed change.
6-2- Recommendations For Future Work:-
1- Study the dynamic performance of synchronous motor with DTC during starting period.
2- Study the dynamic performance of synchronous motor by controlling voltage and frequancy using DTC.
3- Study the performance of synchronous motor with DTC and field orientation.