Gardner Denver L23, Original Operating And Service Manual

Page: 25 / 64

5 Assembly and Operation
23
Regulated Speed Operation
Speed control is achieved with the help of a software PI
controller which adjusts the speed according to the
need for compressed air.
The controller attempts to hold the system pressure
between the
CUT-OUT POINT and TARGET PRESSURE
values set in the control system (see Section 9.5.3).
Automatic Operation
•
If the system pressure reaches the preset maximum
value, the speed of the electric motor (- 3 - Fig. 4) is
regulated down to adjust the delivered quantity to
match the actual compressed air consumption.
•
If the minimum motor speed is reached and system
pressure continues to rise, power is cut to the
solenoid valve (- Y1 - Fig. 4) and the suction
regulator is closed. The reservoir pressure is
relieved to approximately 22 PSI.
•
In this way no additional compressed air is delivered
to the distribution system.
•
If system pressure does not sink to the target
pressure within the rundown time programmed, the
system is shut down.
•
If the target pressure is reached before the motor
rundown time expires, voltage is applied again to
the solenoid valve (- Y1 - Fig. 4).
•
The system will now change to ON-LOAD.