As the efficiency of asynchronous motors is increasingly higher, importance of accurate and precise measurement of losses is of becoming more and more important.
The standardized measurement methods (e.g. as described in IEC standards) for asynchronous motors are designed under consideration of sinusoidal power supply and are widely accepted and used in practice. However, the details or guidelines about precautions to be taken in order to obtain accurate measurement data are not well documented. Therefore, recommendations in this area are highly desirable, to define framework and best practices that can improve both the repeatability and accuracy of the measurement. This work aims to partially address this gap and proposes set of recommendations.
For motors powered by frequency converters, the intrinsic efficiency of the motor alone is particularly difficult to determine. On the one hand, non-sinusoidal voltage and current waves generate additional losses in the motor. Furthermore, the spectrum of the harmonic waves depends directly on the characteristics of the converter (e.g. dv/dt of the pulsed voltages). To overcome this difficulty, this work suggests supplemental conditions to assure better accuracy of the measurement.
