| Abstract |
General theory of electrical machines neglects the existence of the iron loss. As a consequence, all the
high performance control schemes are characterised with certain amount of detuning, caused by the
iron loss. Impact of iron loss on operation of field oriented induction machines has been recently
subjected to detailed scrutiny and appropriate methods of iron loss compensation have been
developed. As far as direct toque control (DTC) of induction machines is concerned, it appears that a
corresponding study has never been done. This paper discusses two aspects related to the problem of
iron loss in DTC of induction machines: detuning effects and means for compensation. A detailed
simulation study is at first performed and the influence of iron loss on accuracy of the DTC scheme is
evaluated. It is shown that the net consequence of the iron loss existence is a difference between the
torque reference and the average motor output torque, that may be substantial. On the other hand,
accuracy of stator flux magnitude and position estimation, being based on stator voltage and current
measurement, is not affected by the iron loss existence. On the basis of the results of the detuning
study, an iron loss compensation method is developed. The method can be used in an extremely
simple form for a variety of induction machines, that consists of deduction of a constant, iron loss
related, torque component from the initial torque estimate. |
