Core Axial Lengthening as Effective Solution to Improve the Induction Motor Efficiency Classes

Starting from 2011, in order to reduce electricity consumption and carbon dioxide emissions, the European Minimum Energy Performance Standard will impose minimum efficiency values for electric motors introduced into the European market. The new European standard requirements will impose nontrivial efforts to manufacturers, particularly for small-and medium-sized producers. In this paper, the axial lengthening of the magnetic core is considered as an effective solution to improve the induction motor efficiency class. In fact, this design solution does not require changing stator and rotor laminations, and it can be considered as a "no tooling cost" (NTC) solution to improve the rated efficiency. Starting from standard-efficiency totally enclosed fan-cooled machines, one size has been selected, and a 'lengthened' motor prototype has been designed and analyzed using a very fast and reliable design procedure based on a coupled analytical-finite-element approach. The experimental results confirm the accuracy of the proposed design method and validate the proposed NTC solution to get higher efficiency induction motors.