Patent ID: 8360738
Filing Date: 2013-01-29
Classification: F04B,F04C

Abstract:
1. Device for adjusting operating pressure of an oil-injected compressor installation including a compressor element driven by a motor having an adjustable rotational speed, controlled by a control module, and including an air inlet and a compressed air outlet to which is connected an oil separator connected to a compressed air pipe supplying compressed gas, said device comprising: a controlled inlet valve connected to the air inlet and a blow-off mechanism connected to a blow-off pipe which connects the oil separator to the inlet valve and is closeable by a blow-off valve, said inlet valve, blow-off valve and control module comprising electrically controllable components connected to an electronic control unit and arranged to adjust the operating pressure in the oil separator, said operating pressure being measured by an operating pressure sensor that is connected to the electronic control unit; wherein said inlet valve comprises a butterfly valve driven by a stepping motor having an accompanying electronic stepping motor card; wherein said electronic stepping motor card includes a micro step modus; wherein said control unit includes an operating pressure controller configured as a PID controller that generates an output signal representing a desired inlet flow of the compressor element to adjust the rotational speed of the motor, the inlet pressure at the air inlet and the exhaust flow; wherein the control unit also includes an inlet pressure controller configured as a PID controller that applies a PID algorithm using a deviation of the inlet pressure to generate a signal used to determine an angular velocity of the stepping motor, wherein a reinforcement used in the PID algorithm is adjusted to provide a proportional action for the PID controller responsive to a deviation of the inlet pressure, wherein the reinforcement is a function of the position of the inlet valve or of the relation between the absolute pressure following the inlet valve at the air inlet of the compressor element and the absolute pressure on the inlet side of the inlet valve.