Screw compressor

A screw compressor for refrigeration circuits, comprising:

• a containment body comprising:
• a suction chamber and a suction port for a fluid to be compressed;
• a delivery chamber and a discharge port for said compressed fluid;
• a containment seat for two helical compression rotors placed side by side, said containment seat being interposed between said suction chamber and said delivery chamber, said containment seat comprising an inlet opening and an outlet opening for said fluid;
• two helical compression rotors placed side by side, each with a helical relief configured to engage with the helical relief of the other compression rotor to define one or more compression chambers for said fluid;
• an electric motor to actuate said helical compression rotors;
• lubrication means with a lubricating fluid for said helical compression rotors;
• filtration means of the compressed fluid for the separation of said lubricating fluid from the compressed fluid;
• an inverter connected to said electric motor;
• an electronic control unit configured to control and manage said inverter;
• a low-pressure sensor positioned at said suction port and connected to said electronic control unit;
• a high-pressure sensor positioned at said discharge port and connected to said electronic control unit;
• an adjustment spool configured for adjusting a width of said outlet opening;
• a fluid actuator configured to move said adjustment spool, said fluid actuator being controlled by said electronic control unit;
• a current meter configured to measure electric current absorbed by said electric motor during the compressor operation;
• said electronic control unit being configured to:
• measure an outlet pressure (Hp) of the fluid via said high-pressure sensor and measure an inlet pressure (Lp) of the fluid via said low-pressure sensor;
• calculate a compression ratio (Pr) between the outlet pressure (Hp) and the inlet pressure (Lp);
• measure electric current (Ivi) absorbed by said electric motor, the electric current (Ivi) being measured by the current meter connected to the electronic control unit;
• command said fluid actuator so as to move the adjustment spool to a balance wherein the electric current (Ivi) absorbed by said electric motor is as low as possible depending on the compression ratio (Pr);
• determine an optimal intrinsic volumetric ratio (Vi-opt), wherein the optimal intrinsic volumetric ratio corresponds to a position of the adjustment spool which determines a minimum absorption of the electric current (Ivi-min) absorbed by said electric motor;
• periodically or continuously measure a rotation speed (nr) of said electric motor and periodically or continuously measure said outlet pressure (Hp) and said inlet pressure (Lp) to periodically calculate said compression ratio (Pr);
• command said fluid actuator to move said adjustment spool so as to automatically maintain said optimal intrinsic volumetric ratio (Vi-opt).