Evaluation of power transformer loses measurements methods under nonlinear load conditions

Efficiency of the transformer is in the range of 95-99%, which means that up to 5% of the energy is wasted in the losses of the power transformer. The efficiency of power transformers is defined as the ratio between output and input power. Input power is the sum of the output power and transformer losses. Measurement of the power transformer losses under nonlinear load conditions can be done only when the load is connected, i.e in real working conditions. Connection of the instrumentation is on the input and the output terminals of the measured system. The measured system is considered as a two-port network in which the losses are dissipated. Several connections were proposed for measurements of power transformer losses under nonlinear conditions using digital instruments and different measuring methods: Difference of Input and Output of Powers, called Power In-Out Method, and Voltage and Current Difference. The topic of this article is to discuss and evaluate accuracy in measurements of the transformer losses with those methods. We are not focused on digital process, A/D conversions, etc., we are focused on algorithms and methods of measurement and their response to the instrumentation errors. Significance of assessment of measuring errors is due to the fact that the errors are propagating through calculations and produce errors in the measuring results. Analyses are done with algebra of penetration of errors used in calculations and measuring algorithms.