PURPOSE: To shorten the time until the restart of a compressor when a momentary power stoppage occurs, improve the build-up feeling, and effectively prevent the vibration of a refrigerant pipe on a car body and the liquid return to the compressor.

CONSTITUTION: A compressor 10, a condenser 11, a liquid receiver 12, an expansion valve 13, and an evaporator 14 are connected to a closed loop in sequence by a refrigerant pipe 15 to constitute a refrigerating cycle 9. Loop-like pipes 18, 19 are used as the refrigerant pipe 15 on the discharge side and suction side of the compressor 10. A by-pass route 20 is provided to detour the compressor 10, and an opening/closing valve 21 is provided on the by-pass route 20. A check valve 22 is provided at a position between the branch point of the inlet section of the by--pass route 20 and the condenser 11. When an electric car enters an insulation zone and a momentary power stoppage occurs, the compressor 10 is stopped. When the power is recovered, the opening/closing valve 21 is opened for 1.5sec, then the compressor 10 is restarted.