The ornamental design for a poweradapter, as shown and described.
FIG. 1 is a perspective view of a power adapter showing our new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left view thereof;
FIG. 5 is a right view thereof;
FIG. 6 is a top view thereof;
FIG. 7 is a bottom view thereof;
FIG. 8 is another perspective view thereof;
FIG. 9 is a usage state reference drawing; and,
FIG. 10 is an enlarged view of the bottom view.
The broken lines represent portions of the structure that form no part of the claim. The power adapter is shown with a symbolic break in its length. The appearance of any portion of the article between the break lines forms no part of the claimed design.