Method for controlling compressor discharge pressure

A method for controlling compressor discharge pressure in a compressor, the compressor comprising a compression module driven by a prime mover, the compression module having a discharge port through which a compressed fluid is discharged with a discharge pressure, and an inlet through which uncompressed fluid is flowed into the compression chamber, the flow of fluid through the inlet controlled by an inlet valve repositionable by an actuator driven by motor means, the method comprising the steps of:

• A) running a discharge pressure control routine, comprising the steps of:
• i) calculating the difference between the actual discharge pressure and a predetermined setpoint discharge pressure;
• ii) computing the required change in valve position to achieve the setpoint discharge pressure, the period of time the motor means must be energized to produce the change in valve position, and the direction the valve must be moved to produce the setpoint discharge pressure;
• and
• B) running an actuator position control routine, comprising the steps of:
• i) energizing the motor means in the required direction for the computed period of time;
• and
• ii) braking the motor means by energizing the motor means in a direction different than the required direction for a braking time interval.

A method for controlling discharge pressure in a compressor, the compressor comprising a compression module driven by a prime mover, the compression module including an inlet valve positionable between an open position and a closed position and positions therebetween by a linear actuator that is driven by a motor movable in first and second directions, a discharge port having a discharge pressure sensor proximate the discharge port, said compressor having a setpoint discharge pressure and an actual discharge pressure sensed by the discharge pressure sensor;

• an electronic control module, in signal receiving relation with the discharge pressure sensor, and in signal transmitting relation with the motor and the inlet valve position sensor, the electronic control module including a logic routine comprised of a discharge pressure control routine;
• the method comprising the following steps:
• A) running the discharge pressure control routine, the control routine comprised of the following steps:
• i) sensing the actual discharge pressure;
• ii) calculating the difference between the actual discharge pressure and the setpoint discharge pressure;
• iii) determining whether the inlet valve is in the open position and the setpoint pressure is greater than the actual pressure and if either the inlet valve is not in the open or the setpoint pressure is less than the actual pressure, executing the steps of:
• a) calculating the distance the inlet valve needs to be repositioned to produce the required discharge pressure, and the direction the valve needs to be moved;
• b) transmitting at least one energizing pulse from the electronic control module to the motor to move the motor in a first direction;
• and
• c) after the last at least one energizing pulse is transmitted to the motor, transmitting a braking pulse from the electronic control module to the motor to move the motor in the second direction;
• vi) if the inlet valve is fully open and the setpoint discharge pressure is greater than the actual discharge pressure, changing the discharge pressure by effecting the prime mover speed by executing the steps of:
• calculating the change in prime mover setpoint speed;
• and calculating a new prime mover setpoint speed.