K Rated Transformer are designed to reduce the heating effect of harmonic currents produced by non-linear loads. A standard transformer is not designed for non linear load and will overheat and fail prematurely when connected to these loads. K- Factor is defined as a ratio between the additional losses due to harmonics and the eddy current losses at 50 Hz. It is used to evaluate transformers for non-linear loads. Transformers with a rated K- factor of 4, 7, 13, 20 and 30 are available.