Comprag DV75 Bedienungsanleitung Seite 12

The system is controlled by an electronic controller
within programmable pressure limits by automatically loading and unloading the compressor
in relation to air consumption.
Main operating mode: Upon start-up, the frequency inverter accelerates the compressor over
15 seconds to the maximum permitted frequency. Pressure builds up to the specified target val-
ue. When it is reached, the compressor maintains the set pressure by varying the current signal
coming from the frequency inverter. If the consumption of compressed air increases, the frequency
coming from the frequency inverter also increases and thus the rotation of the main motor shaft. If
the consumption of compressed air decreases, the frequency coming from the frequency inverter
also decreases. However, the compressed-air pressure remains constant. When the off button is
pressed, the frequency inverter lowers the frequency over 15 seconds to the minimum permitted
frequency and switches off the compressor.
Unloading: If air consumption is less than the air delivered by the compressor, the net pressure
increases. When the net pressure reaches the upper limit of working pressure (unloading
pressure), the solenoid valve (3) is de-energized. The damper (5) of the intake valve (1) closes
the air inlet opening by a spring force:
1. The control pressure present in the chambers of the intake valve (1) and the unloading
valve (7) is vented into the atmosphere via the solenoid valve (3).
2. The damper (5) of the intake valve (1) closes the air inlet opening.
3. The unloading valve (7) is opened by the air-oil separation tank pressure. The pressure
from the air-oil separation tank (4) is released towards the air inlet.
4. The pressure is stabilized at a low value, air output is stopped (0 %) and the compressor
runs unloaded.
Loading: When the net pressure decreases to the loading pressure, the solenoid valve is energized:
1. The control pressure is fed from the air-oil separation tank (4) via the solenoid valve (3) to
the unloading valve (7).
2. The unloading valve (7) closes the air blow-off opening. The damper (5) moves backdown
and causes the intake valve (1) to open fully.
Air output is resumed (100 %), and the compressor runs loaded
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v-Log (2) which keeps the net pressure
Version 1.4