Screw compressor

A method for controlling a vertical screw compressor comprising the steps:

• providing a vertical screw compressor comprising a compression chamber, including an inlet and an outlet, that is formed by a compression housing in which a pair of meshed helical compressor rotors in the form of screws are rotably mounted, rotor shafts of said meshed helical compressor rotors extending parallel to one another along first and second rotational axes, respectively, wherein a non-return valve is provided at the inlet of the compression chamber, a drive motor is provided with a motor chamber formed by a motor housing, in which a motor shaft is rotatably mounted that drives at least one of the aforementioned pair of meshed helical compressor rotors, wherein the compression housing and the motor housing are connected directly to one another to form a compressor housing, wherein the rotor shafts of the compressor rotors extend at an angle with or transverse to a horizontal plane during normal operation of the vertical screw compressor, and wherein the drive motor is an electric motor with a motor rotor and a motor stator;
• cooling and lubricating both the drive motor and compressor rotors by providing a fluid to the vertical screw compressor in a single cycle where all of the fluid first flows from a head of the compressor housing and then to a base of the compressor housing, wherein the fluid is driven through the drive motor and the compressor rotors under a compressor pressure generated by the screw compressor, and
• providing a cooling circuit for the fluid for cooling both the drive motor and the compression chamber, wherein the cooling circuit comprises cooling channels that are provided in the motor housing and of the compression chamber itself, and wherein the cooling channels at least partially extend along an axial direction in a way such that the fluid does not get into an air gap between the motor rotor and the motor stator.