Abstract: An electric power conversion apparatus includes: an electric power conversion circuit that allows a DC terminal to be connected to a DC power source via a DC bus line, and performs at least one of converting DC power of the DC power source into AC power to output, or converting AC power into DC power to output; a DC switch turned on when the electric power conversion circuit performs electric power conversion; an AC switch provided on a side of the AC terminal, and turned on when the electric power conversion circuit performs the electric power conversion; a DC voltmeter that measures a potential at a predetermined portion, on a side of the DC terminal; a ground connection portion that connects the DC bus line and ground potential; and a control circuit connected to the electric power conversion circuit, the DC switch, the AC switch, and the DC voltmeter.

Abstract: A disc-shaped grindstone 1 includes a plurality of split grindstones provided in an outer circumferential surface of a disc-shaped base 3. At least a part of the split grindstones include a moving grindstone 6 which is movable in the axial direction of the disc-shaped base 3. Since a part of the split grindstones 4 is the moving grindstone 6 which is movable in the axial direction, the width of the disc-shaped grindstone 1 may be changed in a manner such that the moving grindstone 6 is moved in the axial direction. Accordingly, it is possible to promptly handle a plurality of kinds of grinding targets without replacing the disc-shaped grindstone 1.

Abstract: A disc-shaped grindstone 1 includes a plurality of split grindstones provided in an outer circumferential surface of a disc-shaped base 3. At least a part of the split grindstones include a moving grindstone 6 which is movable in the axial direction of the disc-shaped base 3. Since a part of the split grindstones 4 is the moving grindstone 6 which is movable in the axial direction, the width of the disc-shaped grindstone 1 may be changed in a manner such that the moving grindstone 6 is moved in the axial direction. Accordingly, it is possible to promptly handle a plurality of kinds of grinding targets without replacing the disc-shaped grindstone 1.