Motor control unit with thermal structure

Claim 1

A motor control unit comprising a first semiconductor module circuit for converting an alternating current into a direct current, a second semiconductor module circuit consisting of switching elements for converting said direct current into an alternating current of optional voltage and frequency, a control circuit for controlling the semiconductor module circuits, a unit case accommodating said circuits and being substantially rectangular in cross section, vertically high and laterally thin with respect to a perpendicular installation surface and comprising front, right-side, left-side and back surfaces, and a plurality of heat sinks disposed outside said unit case at the back thereof, at least one printed circuit board mounted with said semiconductor modules and a hollow, laminar heat plate which is filled with a hydraulic fluid, said at least one board and said plate being disposed in parallel with the right- and left-side walls of said unit case, one part of said heat plate being disposed inside said unit case and the other part thereof extending to the outside of said unit case, and the heat dissipating installation surfaces of semiconductor modules being in contact with said heat plate inside said unit case and said heat sinks being in contact with said heat plate outside said unit case, thereby transferring and dissipating heat generated inside the unit case to the heat sinks outside said unit case, wherein said plurality of heat sinks comprise two heat sink structures disposed on opposite sides of said heat plate, each of said heat sink structures including a substantially flat plate base and a plurality of fins extending from said substantially flat plate base, wherein substantially the entire surface area of the other part of said heat plate is in contact with said heat sink structures, wherein said plurality of fins extend outwardly away from said heat plate to an extent bounded by a projected area of a laterally thin side of said substantially rectangular unit case, and further wherein said plurality of fins on one side of said heat plate are longer in length than said plurality of fins on the opposite side of said heat plate.