Energy Conservation through Multi Winding Induction Machines

Abstract

Three phase induction motors are employed in Textile mills, Agriculture and in almost all the machine tools. More than 60% of electrical energy generated being consumed by the induction motors. Hence, even a small contribution in the improvement of the power factor and efficiency will be cost effective. The power factor and efficiency of an induction motor is based on the shaft load and in order to improve the same, multi windings are suggested in the same stator. In multi winding induction machines, when one set of windings is connected to a three phase a supply, a revolving magnetic field of constant magnitude is developed in the air gap which is responsible to work as a conventional induction motor to meet the mechanical load and to develop a three phase EMF in the other winding that works as an Induction Alternator (IA).Double Winding Induction Motor (DWIM) also provides an opportunity to load each winding individually to its rated capacity. A small three phase load or a single phase load may be connected to the second set of winding. The dependency of separate supply for this load is eliminated. Hence, improvement in the efficiency, power factor and energy conservation is made possible in these machines. In order to validate the problem statement, a 3-phase, 3.0 kW, 415 V Double Winding Induction Motor(DWIM), a 3-phase, 3.0 kW, 415 V Double Winding Synchronous Reluctance Motor (DWSyRM), a 3-phase, 2.2 kW, 415 V Three Winding Induction Motor (TWIM) have been designed, fabricated and tested. Two controllers have been designed, one for a DWIM to operate the motor in power balancing and maximum efficiency modes of operation and other to operate TWIM at three different voltage levels depending upon the shaft load. In this paper, detailed comparisons of performances of three multi winding machines are presented.