To accurately calculate the core loss of medium frequency transformer（MFT） under nonsinusoidal excitation

we comparatively study several correction methods based on original steinmetz equation（OSE）.Firstly

the correction methods are comparatively analyzed from the correction principle.Secondly

Square waveform is a typical voltage waveform for MFT

and triangular waveform is close to the sinusoidal one.Equations of the correction methods for these two voltage waveforms are derived.Finally

measurement system for hysteresis loop of the core is set up

and coefficients of OSE for a nanocrystalline ring core are fitted in the medium frequency range.Thereby

the calculated values of each correction methods are compared with the measured values of the core loss density under square and triangular waveform excitations.It is found that the error of the coefficient Steinmetz equation（Wc SE） is the minimum.When calculating the core loss of nanocrystalline in the medium frequency range

Wc SE is the most accurate.The research results can provide a reference for the accurate calculation of the core loss of medium frequency transformer at its design and optimization stage.