Simulation of a 5-Pole Linear Induction Machine using Finite Element Method showing the Source Independence of the Peak-to-Peak Thrust Ripple

Abstract

In this paper, it has been shown that in a Linear Induction Machine (LIM), the thrust ripple that arises due to the magnetic asymmetry, does not depend on whether the machine is being fed from a current source or a voltage source. When a LIM is supplied from a balanced 3-phase voltage source, the LIM draws unbalanced currents from the supply due to the open magnetic circuit of the machine. This unbalance causes a ripple in the developed thrust. The thrust ripple increases with increase in speed of the LIM. However, when the LIM is being fed from a 3-phase balanced current source, there will be no unbalance in the line currents. This paper shows that even in such a scenario, there is no change in the amount of ripple in the developed thrust at any given speed. The thrust ripple is independent of how much current the LIM draws from the supply, how much terminal voltage is applied or the nature of the source from which the LIM is being supplied. This means that thrust ripple of a LIM is unique, and its variation depends only on the speed of the machine.