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

Adjustable speed induction motors (IMs) drives based on voltage source inverters (VSIs) have become rather popular and widespread, owing to their capability of enabling a substantial improvement of energy utilisation, compared to fixed speed motors directly connected to the main supply. Since inverters produce additional losses in the drive, some concerns about the determination of the overall energy efficiency of the system obviously arise. Therefore, a proper method to assess the efficiency of VSI-fed IMs in a systematic and standardised way is becoming mandatory. To fulfil this task, the IEC 60034-2-3 Technical Specification has been recently issued. However, many details are still under definition, due to the manifold aspects of a standardised measurement procedure, such as the inverter topology, the DC bus input voltage level, the output voltage amplitude and frequency and the modulation technique. Therefore, in its current form, the specification 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 automated energy efficiency measurement procedure is provided as well.