A modular, hybrid HVDC transformer, located in the turbine nacelle has been proposed for the offshore wind industry to improve efficiency and redundancy while reducing costs. The injection of harmonics by the transformer power electronics however, complicates the core loss calculations of such a transformer. The standard Steinmetz Equation is no longer valid and the alternative loss equations proposed in the literature are significantly more complicated. Therefore, many in the industry still use the Steinmetz Equation with the signal's Fourier Transform. However, the literature suggests this to be inaccurate without quantifying it. This paper will therefore compare the accuracy of this approach to a prominent alternative presented in the literature, the improved Generalised Steinmetz... Equation.