Methods of improvement the thrust force developed by linear induction motors

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Methods of improvement the thrust force developed by linear induction motors

El-Hosainy Ismaeel, M. / Ahmed, F.I.

In this paper, the theory of improvement the thrust force developed by linear induction motors (LIMs) using additional coils inserted into the primary circuit, is presented. Design considerations of these coils are determined so that the optimum thrust force is developed by the LIM. The theory is presented by using a generalized 3-dimensional models. The paper shows a use of a single additional coil properly designed and inserted into the primary circuit, will the thrust force developed in almost all the speed range of the LIM. This paper introduces the theory of the starting coil schemes, for the first time, for LIMs. These schemes considerably increase the thrust force developed by the LIM. By using these coils, an increase of about 66 % of the ampere turns of the winding, and without increasing the iron weight, can increase the thrust force, in almost the whole slip range by more than 3 times its original value before inserting these coils. The paper shows that the starting coil schemes are more effective in the completely-filled slots LIMs than in the half-filled endslots LIMs. The paper also presents a very simple formula for finding out the optimum positions of the starting coils in the primary circuit of the LIM, inn order to yield the maximum thrust performance.