An electrical configuration of the inverter portion 14 will now be described below. As illustrated in FIG. 4, the inverter portion 14 includes, in addition to the drive circuit 37 and the control circuit 38, the noise reduction circuit 63 mounted on the circuit board 33 and configured to reduce noise components contained in the direct current power flowing through the busbars 57. In the noise reduction circuit 63, a positive input line 67 is connected to a positive input terminal 66. The positive input line 67 on an output side is connected to a positive output line 68 through a common coil 69. The positive output line 68 on the output side is connected to a positive input terminal of the drive circuit 37. The common coil 69 is configured to suppress a high frequency noise to be transmitted to the drive circuit 37.

In the noise reduction circuit 63, a negative input line 72 is connected to a negative input terminal 71. The negative input line 72 on the output side is connected to a negative output line 73 through the common coil 69. The negative output line 73 on the output side is connected to a negative input terminal of the drive circuit 37.