Sleep & wake-up mode:
Sleep mode & wake-up mode facility has provided to avoid unnecessary
utilization of power when required pressure level has reached in
pipe & there is no discharge from pipe. In this condition PLC will
observe the present pressure & motor RPM & will forced the drive
in sleep mode. When water discharge will take place through pipe
pressure start reducing in pipe, this will detect by PLC & when
pressure falls below the preset level PLC will restart the drive
to maintain the pressure in pipe which is called the wake-up mode of drive.
Dry run of the pumps:
If water level of the tank falls below the suction level,
level transmitter located inside the tank will give the
feed back to the PLC & PLC will shut down all the running
pumps to avoid the dry run of the pumps. By using level
signal one relay will be activated & through one of the
relay contact i/p will be given to PLC & through another
relay contact manual operations of the pumps will be also
stopped.
Alarms alerts:
If any fault generates in VFD, by using VFD relay contact
input will be given to PLC & after detecting alarm from
drive, PLC will stop the system to avoid accident. Also
from over load relay auxiliary contact of each star-delta
starter one input will given to PLC to acknowledge the
trip indication of star-delta starter & to take the
necessary action. To give the alarm annunciation signal
to operator one Hooter & indicator will be connected on
the panel. Input signal to the hooter & indicator will
be given by combining all the alarm signals from star-delta
starter & VFD. One relay will be activated if any one
alarm will be occurred & by using contact of this relay
Hooter will be activated. If operator want to reset the
generated alarm one switch will be provided on the panel.
System status display:
To give the online status information of the system to the
operator, status indicator will be provided on the panel.
With this operator will come to know that which pump
is running on VFD, which auxiliary pump is running & so on.
Operator interface unit:
OIU is connected to the PLC. In addition to the system status
indication OIU will be used to show the system status in
alphanumerical format. Also with the help of OIU the
necessary parameter from PLC such like sleep mode,
wake-up mode set points, drive set point, second star-delta
& third star-delta start & stop set point, friction loss
compensation set point can be edited as per user demands.
Manual operations:
If VFD will fail or as per operator requirement operator
will put the system in manual mode. For change over from
Auto to manual & Manual to Auto one selector switch will
be provided on panel. In manual mode first pump of the
series will come on VFD & remaining two pumps can be started
on star-delta as per requirement. In manual mode all the
operations will be performed manually by using buttons
provided on panel & PLC will get bypass.
