A five-phase linear induction machine with planar modular winding

Linear induction motors (LIMs) have become a competitive alternative in electric traction. Three-phase LIM commonly uses double layer overlapping distributed windings. Although this winding configuration results in more sinusoidal magneto-motive force (MMF), hence good machine performance, it has relatively bulky end windings and uses either half-filled slots or overhanging coil sides at the machine end sides. On the other hand, planar concentrated or modular winding will be the simplest and most cost effective alternative for such systems, where the coils are butted closely together and do not overlap. In the available literature, little interest has been given to employ modular windings in induction machines. This is because the MMF produced by a conventional three-phase modular winding contains of two main space harmonics with close magnitude but travel in opposite directions. These two components induce rotor currents with different frequencies yielding additional rotor bar losses and with a resultant limited net torque due to the resulting opposite torque components. In this paper, a five-phase LIM with a planar modular winding is investigated and compared with a three-phase linear machine with a conventional double layer winding and rated at same output thrust. The comparative study is carried out using finite element analysis.