Chicago Pneumatic CPF 175 Instruction Manual page 19

The principle of the pressure regulation by variable speed
Pressure
Controller
required
• Pressure regulation for low rates of flow
For an air consumption rate lower than the minimum rate of flow
for the machine, the pressure is adjusted by the machine's time-
delayed START/STOP controls.
Since the operation element cannot function below a certain speed
(corresponding to the minimum output), the compressor conti-
nues to run and compress at the minimum speed until the pressure
reaches the limit called "Indirect shutdown ".
Once this threshold has been reached, the motor will stop, the
machine will go into stand-by mode after a certain period of
inactivity and the full drainage process will be carried out.The
pressure then drops towards the indicated pressure and, at the end
of the minimum time delay (since reaching the no-load pressure),
the drive allows the motor to restart. The pressure then rises again
and the cycle starts over (fig. 20d).
To avoid pumping the system - frequent stop / start - drainage
time may be increased
(cf. notice AIRLOGIC).
Chicago Pneumatic Compressors
62 305 799 65
Fig. 20a
Motor
Drive
Frequency speed
• Energy saving
For demand of compressed air within the machine's flow range -
min flow to max flow, the frequency converter or the variable
speed drive feed the motor in order to ensure that it turns at the
speed required to supply air demand both for pressure and flow.
It is used to adjust the power supply to the motor (and thus the
machine) to the exact power requirement for the compression of
the air, without a drainage stage being necessary.
COMMENT :
Energy savings are increased if machine maintenance is carried
out in accordance with the maintenance instructions and
frequency.
Compressor
unit
Pressure sensor
Tank
System
11/2008
Page 19