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The given work was aimed to experimental studies of a plasma channel expansion in a vacuum-arc discharge between the CuCr50 electrodes; with the anode temperature calculated in this stage. Time dependences of an arc channel diameter have been obtained using a high-speed multiframing image analog camera. In addition, plasma expansion velocities V have been determined for different discharge electric currents. It has been demonstrated that V under the experiment conditions does not depend on the current value, nor it does on the presence or absence of the external axial magnetic field. The experiments show that when the electrodes differ in size, the arc discharge initiated in the center of the cathode expands with time until it reaches the size of a smaller electrode while keeping a cylindrical form. The obtained data on V were used for calculation of the anode temperature. Variations of the power supply and of the heating zone sizes with time as well as evaporation loss have been taken into account in the adopted model. It was shown that in the high-speed expansion mode, an anode spot appeared by insignificant heating of the anode. In the low-speed expansion mode, high heating of the anode is possible, with anode intense evaporation taking place. The anode temperature in stage of discharge gap fill by plasma during electric current commutation has been calculated.