LARGE-SIGNAL NONLINEAR MODEL OF ANISOTROPIC TRANSFORMERS FOR NONSINUSOIDAL OPERATION .2. MAGNETIZING AND CORE-LOSS CURRENTS

No-load currents and voltages of saturated single-phase transformers are computed based on given lambda-i and harmonic core-loss characteristics. First, the induced voltage and instantaneous magnetizing current are calculated for given sinusoidal or nonsinusoidal terminal voltages. Subsequently, the harmonic components of the magnetizing current are obtained from a Fourier analysis and the associated flux linkage time function can be determined and used to compute the flux density components within each mesh of the transformer core grid structure. These harmonic flux density amplitudes can then be employed to calculate the harmonic core losses based on measured harmonic iron-core loss and newly defined phase-factor functions. The core losses are then used to calculate the harmonic components of the core-loss current. The no-load current is obtained from the sum of the magnetizing and the core-loss current components. The calculated sinusoidal or nonsinusoidal no-load current will be expanded into its harmonic components; thus, taking skin effects into account, the ohmic losses caused by all harmonics of the no-load current can be calculated. Finally, the waveform of the no-load current and the calculated losses are compared with measurements for various voltage waveshapes.