To avoid the stop of a vehicle even if either of the positive and negative power supply voltage lines for feeding power to a current sensor is broken.

An IGCT voltage line 15 for feeding an IGCT voltage V2 is OR-connected to a positive power supply voltage feed line 11 feeding the positive power supply voltage Va to the current sensor 20 from a control unit 10 via diodes D1, D2 set in a forward direction to the current sensor 20 side for each of the feeding lines 11, 15 make connection to the current sensor 20. Furthermore, an earth line 16 is OR-connected to a negative power supply voltage feed line 12 feeding the negative power supply voltage Vb via diodes D3, D4 set in a reverse direction to the current sensor 20 side for each of the negative power supply voltage feed line 12 and the earth line 16 to make connection to the current sensor 20.