Method of and apparatus for preventing overheating of electrical motors for compressors

Claim 1

A compressor system including apparatus for preventing overheating of an electric motor for a compressor, comprising a rotary screw compressor, an electric motor of the closed type having a rotary shaft connected to a rotary shaft of said screw compressor for driving said compressor, and a sealing case for housing said electric motor, an oil separator connected to an outlet port of said compressor, a condenser, the top portion of which is connected to an upper portion of said oil separator, said condenser also connected to an inlet suction port of said compresser by means including: a high pressure receiving vessel, an electromagnetic valve, an expansion valve, an evaporator, and a liquid separator, which are respectively connected in series in said order, and a liquid return line including a check valve connected between said liquid separator and said evaporator; a first oil return line including an oil pump and an oil cooler, connecting said oil separator and said motor, a second oil return line connecting an oil ejection port of said compressor with said first oil return line at a point downstream of said oil pump and oil cooler, a branch liquid line connected downstream from said electromagnetic valve and upstream of said expansion valve, said line including a throttle valve, and connected to an upper portion of the sealing case for said motor, and means connecting the downstream end of said motor case with a second gas suction port of said compressor, said second gas suction port located in a gear blade groove space of said screw compressor at a position where the screw blades of said compressor in meshing engagement with one another have at least partially compressed gas entering said screw compressor through said inlet suction port.