We claim the ornamental design for an electrical generator, as shown and described.
FIG. 1 is a top, front, left isometric view of an electrical generator showing the new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a right side elevational view thereof;
FIG. 5 is a left side elevational view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The ornamental design which is claimed is shown in solid lines in the drawings. Any broken lines in the figures illustrate portions of the electrical generator that form no part of the claimed design.