Patent ID: 7121813

Claim:
A reverse rotation preventing structure of a centrifugal compressor, wherein the centrifugal compressor compresses a low-temperature and low-pressure refrigerant sucked through a suction port into a high-temperature and high-pressure refrigerant and discharges the high-temperature and high-pressure refrigerant through a discharge port, the reverse rotation preventing structure comprising: a suction pipe that extends from the suction port; a discharge pipe that extends from the discharge port and that discharges fully compressed refrigerant; a fluid passage pipe that connects the suction pipe and the discharge pipe, to convey fully compressed refrigerant to the suction port from the discharge pipe, wherein an opening and closing of the fluid passage pipe is controlled by a bypass valve mounted on the fluid passage pipe, based on a power-down detecting signal; and a power-down detector that detects a power-down of the centrifugal compressor and generates the power-down detecting signal so that the fully compressed refrigerant is allowed to flow to the suction pipe through the fluid passage pipe, wherein the bypass valve opens without delay upon power down of the centrifugal compressor, to prevent reverse rotation of the centrifugal compressor.