ADVANCED APPLICATION OPTIONS
Dual PID Loop Control
104
Using Dual PIDs to Control Output when Pumping from a Tank or Well
Dual PID control can be used to protect a pumping system from a low water condition when using a tank or
well as the water source.
The VFD uses a pressure transducer (PID 1) on the discharge side of the pump and a level transducer (PID 2)
in the tank. Both PIDs run simultaneously but only one at a time provides speed reference to the VFD.
•
The discharge side is programmed as a standard constant pressure PID loop. Refer to
tion with PID Feedback Control” on page 69
.
•
The level transducer is installed and programmed as an Auxiliary input in inverse mode (PID 2).
When the tank level reading of PID 2 is at or above
PID2 Set Point [ADV2–38]
, normal VFD operation will be
maintained using the PID 1 loop.
When level reading is less than PID 2 setpoint for 2 seconds, VFD frequency reference will be switched from
PID 1 loop to PID 2. When level stays less than
PID2 Set Point [ADV2–38]
, PID 2 output will be decreased to
PID 2
Low Limit [ADV2–41]
. If water level increases and approaches
PID2 Set Point [ADV2–38]
, the VFD speed will be
increased.
If level setpoint is maintained but frequency is not high enough to pressurize the system up to
[SET–21]
+ 1%,
the VFD frequency will be controlled by PID 2 output. During PID 2 operation, if system pressure is equal to
or greater than
[SET–21]
+ 1% for 2 seconds, the VFD will switch speed reference from PID 2 back to PID 1.
When running on PID 2, there are two parameters to switch back to PID 1 or stop VFD:
1.
PID2 Exit Level [ADV2–44]:
If PID2 level reading becomes greater than this setting for 10 seconds,
VFD will switch speed reference from PID 2 back to PID 1.
2.
PID Stop Delay [ADV2–43]:
If VFD has been running at
PID 2 Low Limit [ADV2–41]
and cannot maintain the
level setpoint for this time setting, VFD will stop with the message “Low Level” displayed on the screen.
•
During Low Level stop or at power-up, if level reading is greater than
[ADV2-38]
but less than
[ADV2-
44]
for 10 seconds, VFD will start running with PID 2 output as speed reference.
•
During Low Level stop or at power-up, if level reading is equal to or greater than
[ADV2-44]
for 10
seconds, VFD will start running with PID 1 output as speed reference.
To enable this feature, set the following parameters:
AUX AI Select [ADV2–58]:
Select the terminal (
AVI1, AVI2, ACI
) with the PID 2 transducer connection. Set unit
type and scaling in
[ADV2-59]
to
[ADV2-61]
.
PID2 Output [ADV2–36]:
This setting selects feature options:
•
1_1
P
st
P
PID Off
: When PID2 falls below level setpoint, VFD control is switched from PID 1 to PID 2.
PID2 Type [ADV2–37]:
This parameter should be set to
1_Inverse
for this application.
PID2 Setpoint [ADV2–38]:
Desired tank water level to switch PID control.
PRESSURE
LEVEL
RUNNING
SYNC
SYNC
SYNC
SYNC
SYNC
SYNC
SYNC
RUNNING
RUNNING
RUNNING
RUNNING
RUNNING
STOP
VFD
RUNNING
10 SECONDS
PID2 DELAY TIME
2 SECONDS
10 SECONDS
2 SECONDS
2 SECONDS
2 SECONDS
PID1:
PID2:
2ND PID: 1ST PID OFF MODE
LEVEL
PRES
SURE
ST PT PID1 + 1%
PRESSURE SET POINT
PID2 EXIT LEVEL
LEVEL SET POINT
PID2 LOW LIMIT
Summary of Contents for CERUS X-DRIVE CXD-003A-4V
Page 2: ......
Page 3: ...CERUS X DRIVE INSTALLATION AND OPERATION MANUAL Firmware Version 1 2 Franklin Electric Co Inc ...
Page 96: ...OPERATION Protection Features 96 ...
Page 112: ...ADVANCED APPLICATION OPTIONS Multi Drive Configurations 112 ...
Page 124: ...COMMUNICATIONS BACnet Communication 124 ...
Page 128: ...ACCESSORIES Optional Extension Cards 128 Frame D Frame E Frame F ...
Page 129: ...ACCESSORIES Optional Extension Cards 129 Frame G Frame H ...
Page 132: ...ACCESSORIES Optional Extension Cards 132 ...
Page 234: ...PARAMETER REFERENCE TABLES Parameter Descriptions Motor Menu 234 ...
Page 250: ...GLOSSARY 250 ...