Analiza obciąśenia i strat w transformatorach przekształtnikowych układów napędowych

Electric converter drives are nonlinear loads that produce higher harmonics of current. To reduce their influence on quality of electric energy in a power network, medium and high power drives are fed from separate converter transformers. The secondary current of these transformers are non-sinusoidal due to properties of converters and, sometimes, the supply voltage is also distorted. A non-sinusoidal current and voltage with significant content of higher harmonics result in additional power losses and heating of a transformer. As a result, due to thermal effects, the transformed power has to be reduced in comparison to nominal power specified for a linear load. The article deals with analysis of load and losses of transformers feeding frequency converters and controlled rectifiers of steelworks drives. Necessary reductions of transformers nominal power due to non-sinusoidal load current are determined on the basis of harmonic spectra of recorded waveforms of voltages and currents.