MODULATING control
The MODULATING control is an additional mechanical regulation. It continuously changes the flow
rate within the machine's control range.
A control valve, the proportional controller, changes the degree of opening of the inlet valve when
the machine transports compressed air into the air network (LOAD)
The load and power consumption of the drive motor / engine rises and falls with the air demand.
5.8.3 Variable speed drive with frequency converter (SFC)
If the machine runs in the LOAD mode, the ACTUAL value is compared with the TARGET value of
the network pressure. Depending on the pressure differential, the system controls the speed of the
drive motor and, thus, the airend.
The speed of the airend determines the rate of compressed air delivery and the working pressure.
If the compressed air demand rises, the motor speed increases and consequently the volume of air
delivered.
If air demand drops, the SIGMA CONTROL 2 reduces the compressor motor speed and, therefore,
the volume of air delivered.
The network pressure remains constant – within the control range of the frequency converter – re‐
gardless of the fluctuating air demand.
If the network pressure exceeds the TARGET value:
Outside the frequency converter's range of control the machine reverts to the selected control
mode.
DUAL:
The minimum controllable speed is reached and the machine switches to IDLE mode. The drive
engine runs unloaded with low power consumption.
When the preset idling time has elapsed, the machine switches to READY.
VARIO/QUADRO/CONTINUOUS:
The minimum controllable speed is reached and, depending on the air demand at the time, the ma‐
chine switches either to READY or to IDLE. The machine remains in IDLE at least for the duration
of the
venting time, before it switches to READY.
DYNAMIC:
The minimum controllable speed is reached and, depending on the air temperature of the drive mo‐
tor / engine, the machine switches either to READY or to IDLE. The machine remains in IDLE at
least for the duration of the
venting time, before it switches to READY.
If the network pressure falls below the TARGET value:
SIGMA CONTROL 2 runs the motor up to a speed at which air delivery matches the air demand.
The above description is valid only when the
Pressure control option is set to Local mode: in
the menu:10.1.1 Power switching .
The inlet valve opens and the machine delivers compressed air.
The frequency converter varies the speed of the drive motor according to the air demand. The
power consumption of the compressor motor rises and falls according to air demand.
5
Design and Function
5.8
Operating points and control modes
52
User Manual Controller
SIGMA CONTROL 2 SCREW FLUID ≥5.0.X
No.: 9_9450 12 E
Option C1
