Refrigerating machine

摘要

A refrigerating machine having a compressor driven by a motor. The motor incorporates an armature with an iron core having a cage type conductor and a permanent magnet which is magnetized so as to enable the motor to operate as a synchronous motor. A bypass passage is provided between a discharge side of the compressor and a suction side of the compressor, a shut-off valve is provided for opening and closing the bypass passage, a pressure detecting device is provided for detecting a discharge pressure from the compressor and a current detector is provided for detecting a value of drive current for the compressor. The shut-off valve is opened and closed in accordance with the discharge pressure and the value of the drive current.