We measured total AC losses in a YBCO tape conductor using a calorimetric method for which the validity was proven by simultaneous electric and calorimetric measurements of the losses in the same part of the conductor. Our data is accurate to 5x10^-5∼5x10^-2 J/m/cycle at 64.1 Hz. The data can be reduced to one curve plotted against a corrected abscissa of the external magnetic field plus the internal magnetic field. The AC loss in different phases of transport current and external magnetic field varies with the phase. Our finding demonstrates the possibility of reducing loss in the case of tri-axial superconducting cables.