Power conversion unit

A power conversion unit comprising:

• a plurality of semiconductor modules each including a semiconductor switching element;
• a gate drive circuit that drives the semiconductor modules;
• a first substrate having a flat plate shape, the first substrate including a first surface facing a bottom plate of a casing accommodating the semiconductor modules and the gate drive circuit, and a second surface on an opposite side to the first surface;
• and
• a second substrate having a flat plate shape, the second substrate being arranged above the first substrate in parallel with the second surface, wherein
• the semiconductor modules are mounted on the first surface,
• the gate drive circuit is formed on a surface of the second substrate on a side that does not face the second surface,
• the power conversion unit further comprising:
• a connector provided on the second surface and connected to a surface on a side facing the second substrate;
• and
• a heat sink mounted on the first surface, wherein
• the heat sink includes a base having a flat plate shape provided vertically to the first surface and fins fixed to both surfaces of the base,
• the semiconductor modules are arranged side by side on both surfaces of the base, and
• a path through which cooling air passes is formed in a gap between the bottom plate and the first surface.