Current nonlinear models of transformers (the EMTP model for example) are inadequate to accurately predict the effects of physical phenomena such as ferroresonance, inrush currents, saturation due to geomagnetically- induced currents, and transformer deration due to power quality problems. Better modeling of complex flux - current relationships is needed. Techniques from nonlinear dynamics and the newly emerging field of chaotic systems are proposed to validate the improved models and gain more insight into the observed phenomena.