To reduce the scale of feeding facilities and expenses for installation investment.

Electric power taken from a feeder 1 via a collector ring 2 is supplied to a driving motor 9 for driving a vehicle and a compressor motor 3 for driving a compressor 4. A pressure switch 6 and a starting switch 7 are arranged in series between the compressor motor 3 and the collector ring 2. The pressure switch 6 is turned on when pressure in an air tank 7 is decreased to a lower limit pressure set value and turned off when the pressure is decreased to an upper limit pressure set value. An arithmetic circuit consisting of an AND circuit 11 and a retaining circuit 18 turns the starting switch 7 on if a regenerative current detector 8 detects that the motor 9 provides regenerative brake to generate a regenerative current when the pressure switch 6 is turned on.