Device for regulating the operating pressure of an oil-injected compressor installation

Device for adjusting the operating pressure of an oil-injected compressor installation including a compressor element (2) driven by a motor (4) having an adjustable rotational speed, controlled by a control module (13), and including an air inlet (5) and a compressed air outlet (7) to which is connected an oil separator (10) connected to a compressed air pipe (11) supplying compressed gas, said device (15) comprising a controlled inlet valve (16) connected to the air inlet (5) and a blow-off mechanism (17) connected to a blow-off pipe (18) which connects the oil separator (10) to the inlet valve (16) and is closeable by a blow-off valve (19), said inlet valve (16), blow-off valve (19) and control module (13) comprising electrically controllable components and being connected to an electronic control unit (22) arranged to adjust the operating pressure (Pw) in the oil separator (10), said oil pressure being measured by an operating pressure sensor (23) that is connected to the electronic control unit (22);

• wherein said inlet valve (16) comprises a butterfly valve driven by a stepping motor (20) having an accompanying electronic stepping motor card (21);
• wherein said electronic stepping motor card (21) includes a micro step modus;
• wherein said control unit (22) includes an operating pressure controller (27) configured as a PID controller having an output signal representing a desired inlet flow (102) of the compressor element (2), on the basis of which the rotational speed of the motor, the inlet pressure (Pi) at the air inlet (5) and the exhaust flow (Qb) are adjusted;
• wherein the control unit (22) includes an inlet pressure controller (28) which is configured as a PID controller with a reinforcement (K), wherein the reinforcement (K) is a function of the position of the inlet valve (16) or of the relation between the absolute pressure following the inlet valve (16) at the air inlet (5) of the compressor element (2) and the absolute pressure on the inlet side of the inlet valve (16).