LINEAR INDUCTION MOTOR


A linear induction motor by its simplest definition is simply an induction motor with its stator rolled out flat open. It is not very difficult to construct and the working is quite easy to understand much like other induction machines. But constructing one on one’s own is indeed a valuable experience. It is a kinky feeling to see a a simple assembly of coils rolling on a track when supply is given to it.

We constructed a two pole linear induction motor for our laboratory project. While others were contented with designing just an induction motor we decided to go ahead and take the gamble. So did it pay off? The answer is both yes and no.

The first thing we had to do was to find out what a LIM really is. After a day of googling we had somewhat an idea of what we were going to do. It was during this period that we realised that a linear induction  is not the same as magnetic levitation and our fantasies of creating our own miniature maglev train would not work out unless we were able to allocate a few crores for our project and obtain super-conducting magnets for the purpose. So our maglev died before it was born. But we still went ahead with the much less exotic idea of a motor running on wheels.

The next phase was the hunt for the raw materials. I say hunt because the city is an hours travel from our college. Every time we had to go there to get something. We would return and just as we neared the college someone would remember something that was missed. It was the fact that Ismail had a bike helped us not to  lose our heads in this process.

The stator needs to be of laminated construction to minimise eddy current losses. But where would we go for a laminated core in this cursed place. So it was decided to use just a crude iron piece. The slots were made and our stator was made. We got the tracks, coils and everything ready in a span of two days. Now began the real fun!!

We decided to settle down for a two  pole winding because it was the simplest and needed the minimum no of slots. It needed 9 slots. Actually it is analogous to a 6 slot 2 pole induction machine. The only difference being that the end slots are half-filled. The coils were wound, the track was laid out and we eagerly carried our machine to the lab. We gfave supply and as we expected the machine did not display even a stirring of life. Had Mr. Karthik Vel not been there our tryst with destiny would have ended there. But that man whom I hated so much during my lab sessions appeared like a savior. He was excited by our idea and came forward to help us. He suggested that we check for shorts which was the first thing we should have done. And lo there was a short everywhere. Our coil had been cut by the sharp edges of the stator. So we rewound the machine with proper precautions and ran it again eagerly. And it ran!

Our cute little vehicle moved slowly down the track. It is impossible to describe what I exactly felt that moment. Everything seemed bright and beautiful that evening. Then fate intervened. We decided to increase the number of turns and change the alignment of wheels with the intention of perfecting it. All changes were made and we were so confident that we didn’t even test the machine before the appointed day of the demo. And the D-Day arrived. Supply was given and our machine instead of moving attracted the magnet track and refused to move an inch. The hours that followed were terrible. We tried all sorts of changes and finally brought our set up to the original working version. Now the machine did move or shall I say tried to move. There were all sorts of problems. The bearings were worse than before now and the machine was attempting to turn. The iron piece had been permanently magnetised by repeated excitations. Thus our great experiment had a tragic end. We were left wondering what if we had just left the setup undisturbed after our first trial?

But it’s all in the game. If we had done so we would never have known what could have gone wrong with the machine. It is said that only the person who risks the greatest failure can attain the greatest victory.

Our lecturer is pleased with our attempt and wants us to improve on it. We are looking forward to the hunt again. But that will come later. Now it is time to prepare for my exams.

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Comments
One Response to “LINEAR INDUCTION MOTOR”
  1. Adarsh Balakrishnan says:

    hello,
    I too had a similar experiance doing the same project. It is indeed a pleasure to convey that we too were succesfull. Infact we were heavily aided by our guide who had a sound knowledge in the same. Sheer curiosity makes me request you to forward the project report to my E-MAIL.

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