A power conversion unit comprising: a circuit connection section that includes a positive conductor having an external positive terminal, a negative conductor having an external negative terminal, and an alternating-current conductor having an external alternating-current terminal; a first power semiconductor module that is connected to the positive conductor, the negative conductor, and the alternating-current conductor; a second power semiconductor module that is connected to the positive conductor, the negative conductor, and the alternating-current conductor; and a capacitor (121, 122) that is connected to the positive conductor and the negative conductor; wherein the first power semiconductor module includes a first direct-current terminal (111p, 111n) and a first alternating-current terminal, the first direct-current terminal (111p, 111n) having a first positive terminal connected to the positive conductor and a first negative terminal connected to the negative conductor, the first alternating-current terminal being connected to the alternating-current conductor; wherein the second power semiconductor module includes a second direct-current terminal (112p, 112n) and a second alternating-current terminal, the second direct-current terminal (112p, 112n) having a second positive terminal connected to the positive conductor and a second negative terminal connected to the negative conductor, the second alternating-current terminal being connected to the alternating-current conductor; wherein the external alternating-current terminal, the first power semiconductor module, the second power semiconductor module, the capacitor (121, 122), and an external direct-current terminal (131b, 132b) including the external positive terminal and the external negative terminal are arrayed on a straight line extending in the longitudinal direction of the circuit connection section and are electrically connected to the circuit connection section; wherein the external alternating-current terminal is disposed at one longitudinal end of the circuit connection section; and wherein the external direct-current terminal (131b, 132b) is disposed at the other longitudinal end of the circuit connection section; characterised in that the distance between the first alternating-current terminal and the first direct-current terminal (111p, 111n) and the distance between the second alternating-current terminal and the second direct-current terminal (112p, 112n) are greater than the transverse length of a flat plate of the circuit connection section. a circuit connection section that includes a positive conductor having an external positive terminal, a negative conductor having an external negative terminal, and an alternating-current conductor having an external alternating-current terminal; a first power semiconductor module that is connected to the positive conductor, the negative conductor, and the alternating-current conductor; a second power semiconductor module that is connected to the positive conductor, the negative conductor, and the alternating-current conductor; and a capacitor (121, 122) that is connected to the positive conductor and the negative conductor; wherein the first power semiconductor module includes a first direct-current terminal (111p, 111n) and a first alternating-current terminal, the first direct-current terminal (111p, 111n) having a first positive terminal connected to the positive conductor and a first negative terminal connected to the negative conductor, the first alternating-current terminal being connected to the alternating-current conductor; wherein the second power semiconductor module includes a second direct-current terminal (112p, 112n) and a second alternating-current terminal, the second direct-current terminal (112p, 112n) having a second positive terminal connected to the positive conductor and a second negative terminal connected to the negative conductor, the second alternating-current terminal being connected to the alternating-current conductor; wherein the external alternating-current terminal, the first power semiconductor module, the second power semiconductor module, the capacitor (121, 122), and an external direct-current terminal (131b, 132b) including the external positive terminal and the external negative terminal are arrayed on a straight line extending in the longitudinal direction of the circuit connection section and are electrically connected to the circuit connection section; wherein the external alternating-current terminal is disposed at one longitudinal end of the circuit connection section; and wherein the external direct-current terminal (131b, 132b) is disposed at the other longitudinal end of the circuit connection section;