Energy efficiency measurements in IM: the non-trivial application of the norm IEC 60034-2-3:2013

Energy efficiency measurements on electric motor, especially squirrel-cage induction motors (IM), are an hot topic for the scientific and industrial communities, as well as for International Standards commissions. The use of induction motor fed by voltage source inverters (VSI) is widespread, and it is progressively substituting the direct connection of the IM to the main supply. The use of inverters introduces some questions about the energy efficiency determination, since inverters introduce additional losses. A proper methods to measure the efficiency of VSI-fed IM in a clear, simple and unequivocal way, is becoming mandatory. To this goal, the IEC 60034-2-3 Technical Specification has been recently emanated. Nevertheless, the number of different technical variables is so high (e.g. voltage amplitude, frequency, modulation technique, and so forth) that the norm cannot be considered a straightforward and ultimate answer to the efficiency measurement. In this paper, some problems regarding the application of the new IEC 60034-2-3:2013 are addressed and some possible solutions are proposed. As a tangible contribution, a proposal for the structure of an automatized energy efficiency measurement is given as well.