Two new effects, the existence of the limiting temperature for constant AC losses with the increase of magnetic field and a node point of minimum AC losses, give a clear evidence of predominant two-dimensional nature of dissipation in Bi 2 Sr 2 Ca 2 Cu 3 O x tapes. The effects are explained in the assumption of exponential suppression of Josephson interaction in two types of stacks containing two and three well-connected unit-cells. Superconducting layers of isolated unit-cells are intact in magnetic field which leads to saturation of the temperature of constant losses at non-zero value. The stacks with more than three unit-cells behave in the same way as the ones with three unit cells. Suppression of Josephson interaction in stacks up to separation of superconducting layers, and the increase of eddy current losses in Ag sheath give the node point of AC losses in Ag-sheathed tapes near the temperature of Kosterlitz-Thouless transition of single superconducting layer.