WE CLAIM:
1. A power conversion device comprising:
a power conversion unit to convert an input power and output the converted power;
a reactor connected to an input side of the power conversion unit;
a controller to control electronic components included in the power conversion unit;
a first unit, an interior of a housing thereof being divided by a partition into a closed section into which outside air does not flow and an open section into which the outside air flows, the closed section containing the electronic components, the first unit comprising a heat sink exposed to the open section and releasing heat transferred from the electronic components;
a second unit, an interior of a housing thereof being divided into a first space and a second space by a partition having an opening, the second unit being adjacent to the first unit, the second unit containing in the first space a blower for blowing air from the second space toward the first space, the blower having an impeller at least partially exposed to the second space from the opening; and
a third unit adjacent to the second unit and containing the reactor,
wherein a first vent is formed in a part at which a housing forming the open section contained within the first unit and a housing forming the second space contained within the second unit contact each other,
a flow inlet into which the outside air flows is formed in the housing forming the open section contained within the first unit,
a second vent is formed in a part at which a housing forming the first space contained within the second unit and a housing of the third unit contact each other, and
a flow outlet is formed in the housing of the third unit and discharges air flowing in from the second vent.

2. The power conversion device according to claim 1, further comprising a
fourth unit into which the outside air does not flow, the fourth unit containing the
controller.
3. The power conversion device according to claim 2, further comprising:
a switch housed in the fourth unit and connected to the input side of the power
conversion unit; and
a smoothing circuit housed in the fourth unit and connected to an output side of the power conversion unit, wherein
the blower is driven by an output of the power conversion unit smoothed by the smoothing circuit.
4. The power conversion device according to claim 1, wherein
the partition of the first unit and the partition of the second unit are horizontal,
a vertical direction upper part of the first unit is the closed section, and a vertical direction lower part of the first unit is the open section,
a space of a vertical direction upper part of the second unit is the first space, and a vertical direction lower part of the second unit is the second space, and
the power conversion device is to be disposed on a roof of a vehicle.
5. The power conversion device according to claim 4, further comprising:
a fourth unit into which the outside air does not flow, the fourth unit containing the controller, wherein
a direction in which the first unit and the second unit are adjacent to each other is orthogonal to a direction in which the second unit and the third unit are adjacent to each other, and
the fourth unit is adjacent to the first unit and the third unit.