We claim the ornamental design for a wireless power transmitter, as shown and described.
FIG. 1 shows a perspective view of a wireless power transmitter;
FIG. 2 shows a front view thereof;
FIG. 3 shows a left side view thereof;
FIG. 4 shows a right side view thereof;
FIG. 5 shows a rear view thereof;
FIG. 6 shows a top view thereof;
FIG. 7 shows a bottom view thereof;
FIG. 8 shows a left side view thereof in a fully extended position; and,
FIG. 9 shows a left side view thereof in a fully retracted position.
The dashed lines are for the purpose of illustrating portions of the wireless power transmitter and form no part of the claimed design. The dotted lines on the surface portions indicate contour and not surface decoration.