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BRANSOM TECH SERVICES
25 S STOCKTON St. Ste A
Lodi, CA 95240
Phone (209) 367-1403
Fax (209) 3674746
www. BTS ElectricService.com
Support@BTSElectricService.com
Controlling irrigation pump pressure using a VFD and a Pressure Transducer 4-20ma with a DuraPulse
GS2/GS3 Variable Frequency Drive (VFD)
How to setup a DuraPulse VFD to operate in PID Cooling mode using a 4-20ma transducer using FORWARD ACTING
PID. HEATING Mode simply means it slows as pressure builds (reaches a heat and then slows to maintain). So we
also call this Normal PID Mode or simply PID Mode. In other words, we want the VFD to come on full blast or
whatever speed you define as MAXIMUM HERTZ when the 4-20 transducer is at 4 milliamps and slow down as
milliamps rise. CAUTION: Some VFDs are the opposite in this respect so read the manual. We want the motor to
slow as pressure builds (milliamps increases).
In this example, we want a pump to come on 100% until it reaches 35 PSI then trim back and stabilize pressure at
35psi. If the Transducer (0-100psi X 4-20ma) is at 4ma, the pump is at 60hz. If the transducer is at 20ma, the pump is
running at ZERO Hz. The well we are pulling water from is deep so we have that variable working. The water level
can change year to year. Also we are irrigating a vineyard so the distance to each irrigation zone can vary meaning
we might need more Motor Hz to water a zone far away. Since it is drip irrigation, the water lines have to get full in
order to operate all the drippers at the same rate. All of these and more affect line pressure so a PID is the only
solution.
So there it is. You must use a PID loop acting in FORWARD MODE to achieve your goal. You do not have to know
what a PID is or understand how it works. Just set it up and it will work. I am not going to talk about PID Loops
because they are too complicated for normal people. Lucky for you and me, some kindly software engineers put one
in nearly every VFD made and you can use it without too much trouble.
So let’s get started. Buy the right VFD and do the following:
1. Hookup power properly, hookup motor properly, ground VFD properly
2. Turn it on and go to the first settings. Put in motor RPM, Amps and Voltage
3. Go to the Control Settings and tell the VFD how it is to start. Most of the time, a single contact starts it and
stops it. Closed it runs, Open it stops. All irrigation operators support this. So a wire on the common and the
other on a digital input
4. Find the Frequency Control section and setup the drive so that the Frequency Source is ANALOG 4-20ma.
Make sure your transducer is on the right polarity and connected properly. So the NEGATIVE on the analog
common and the POSITIVE on the analog input
5. Setup Limits: Max Freq, Min Freq, Reverse Lockout, Overload settings, Error Settings, etc.
6. Turn on the PID settings. Tell the VFD you want Forward (Normal) Acting PID Loop. More Pressure slows the
motor.
Just a word of warning – run the VFD in manual mode and see what the Transducer does. That confirms it is
working. Setup the Proportional, Integral and Derivative with low initial values. Most VFDs support adjusting
these while it is running. If you have an option to adjust the Process Value using the keypad, make sure that
is turned on so you can fine adjust your pressure.
Frequency Drive Setup and Maintenance
Revision 001
PIDSetupVfdGS3Pump.doc
Saturday, April 11, 2015
BRANSOM TECH SERVICES
25 S STOCKTON St. Ste A
Lodi, CA 95240
Phone (209) 367-1403
Fax (209) 3674746
www. BTS ElectricService.com
Support@BTSElectricService.com
(6 cont.)
Remember that all PID settings affect each other so if you change one, you are changing them all. Ones (1)
and ZEROs (0) will get you started. Once you are in the ballpark, you can adjust the Process Variable and the
Proportional to get the response you want.
The Process Variable is generally expressed as a percentage of the actual signal so prepare for confusion.
7. Now start the VFD. I suggest you have a Signal Generator so you can see what you are doing. In the images
below, I am using a Signal Generator to create the Process Variable. Then adjusting the Integral and
Proportional until I get the right speed for my pump.
I have setup a DuraPulse GS2 drive for this example. My Oyster is a 4-20ma SOURCE!
Here are the
connections. You can
ignore most of it for a
Pump/Irrigation
application. We just
need a dry contact on
the START/STOP
Terminal #1 and the
DCM or +24v if it is in
Sourcing Mode. Make
sure it is grounded
properly.
Hookup your 4-20ma
Transducer at ACM
(Analog Common) and
AI2 (Analog Input #2)
Once you have this
done, the power
hooked up, and the
motor hooked up, you
are ready to turn on
the drive and get
started.
Frequency Drive Setup and Maintenance
Revision 001
PIDSetupVfdGS3Pump.doc
Saturday, April 11, 2015
BRANSOM TECH SERVICES
25 S STOCKTON St. Ste A
Lodi, CA 95240
Phone (209) 367-1403
Fax (209) 3674746
www. BTS ElectricService.com
Support@BTSElectricService.com
After setting up PID
(setting 7.00)
as Forward (normal)
Acting
Start Motor and it
ramps up to 66Hz
We can adjust this
MAX to any speed we
want for the
application.
4-20ma Source at 4ma
4-20ma Source at
7.3ma
Motor starts to slow
down
Stabilizes at 63.5 HZ
Frequency Drive Setup and Maintenance
Revision 001
PIDSetupVfdGS3Pump.doc
Saturday, April 11, 2015
BRANSOM TECH SERVICES
25 S STOCKTON St. Ste A
Lodi, CA 95240
Phone (209) 367-1403
Fax (209) 3674746
www. BTS ElectricService.com
Support@BTSElectricService.com
4-20ma Source at
8.3ma
Motor continues slow
down
Stabilizes at 56.5 HZ
4-20ma Source at
9.7ma
Motor continues slow
down
Stabilizes at 46.4 HZ
Frequency Drive Setup and Maintenance
Revision 001
PIDSetupVfdGS3Pump.doc
Saturday, April 11, 2015
Phone (209) 367-1403
Fax (209) 3674746
www. BTS ElectricService.com
Support@BTSElectricService.com
BRANSOM TECH SERVICES
25 S STOCKTON St. Ste A
Lodi, CA 95240
4-20ma Source at
10.2ma
Motor continues slow
down
Stabilizes at 43.0 HZ
This simulates
overshoot
4-20ma Source at
12.1ma
Motor shut down,
Line plugged or
if the 4-20 transducer
is damaged
Stabilizes at 00 HZ
ERR on keypad Display
We can tie this ERR to
an output
Settings for my GS2 in this example
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
480
3.3
60
1725
1725
5.00
6
1.00
1.01
1.02
1.03
1.04
1.05
1.06
1.07
1.08
1.09
0
10
10
0
0
10
30
0
0
0
2.00
2.01
2.02
2.03
2.04
2.05
2.06
2.07
2.08
2.09
0
0
0
1.5
20
1.5
20
12
Frequency Drive Setup and Maintenance
Revision 001
3.00
3.01
3.02
3.03
3.04
3.05
3.06
3.07
3.08
3.09
1
0
0
3
4
5
4.00
4.01
4.02
4.03
4.04
4.05
4.06
4.07
4.08
4.09
3
0
0
100
0
0
6.00
6.01
6.02
6.03
6.04
6.05
6.06
6.07
6.08
6.09
1
0
0
0
0
0
0
0
150
0.1
9.00
9.01
9.02
9.03
9.04
9.05
9.06
9.07
9.08
9.09
1
1
0
0
0
0.5
0
0
PIDSetupVfdGS3Pump.doc
Saturday, April 11, 2015
Phone (209) 367-1403
Fax (209) 3674746
www. BTS ElectricService.com
Support@BTSElectricService.com
BRANSOM TECH SERVICES
25 S STOCKTON St. Ste A
Lodi, CA 95240
5.01
5.02
5.03
5.04
5.05
5.06
5.07
5.08
5.09
5.10
5.11
5.12
5.13
5.14
5.15
0
0
0
0
0
0
0
8.00
8.01
8.02
0
1
1.10
1.11
1.12
1.13
1.14
1.15
1.16
1.17
1.18
1.19
1.20
1.21
1.22
10.00
10.01
10.02
10.03
10.04
10.05
0
0
0
0
0
0
0
0
2.10
7.00
7.01
7.02
7.03
7.04
7.05
7.06
7.07
7.08
7.09
7.10
7.11
7.12
7.13
7.14
7.15
7.16
7.17
7.18
7.19
7.20
7.21
7.22
7.23
7.24
7.25
7.26
7.27
7.28
2
100
0
100
0
0
44.7
0
0
0
0
0
0
0
1.9
0.3
0
60
0
110
60
3
3.10
3.11
3.12
3.13
3.14
3.15
3.16
3.17
3.18
3.19
3.20
3.21
3.22
3.23
3.24
3.25
3.26
3.27
3.28
3.29
3.30
3.31
0
1
0
0
10
5
4.10
4.11
4.12
4.13
4.14
4.15
4.16
4.17
4.18
0
100
6.10
6.11
6.12
6.13
6.14
6.15
6.16
6.17
6.18
6.19
6.20
6.21
6.22
6.23
6.24
6.25
6.26
6.27
6.28
6.29
6.30
6.31
6.32
6.33
6.34
6.35
6.36
6.37
150
150
2
0.5
150
400
42
0
0
0
0
0
0
0
9.10
9.11
9.12
9.13
9.14
9.15
9.16
9.17
9.18
9.19
9.20
9.21
9.22
9.23
9.24
9.25
9.26
9.27
9.28
9.29
9.30
9.31
9.32
9.33
9.34
9.35
9.36
9.37
9.38
9.39
9.40
9.41
9.42
9.99
9.99
9.99
9.99
9.99
9.99
9.99
9.99
9.99
9.99
9.99
9.99
9.99
9.99
9.99
60
0
0
0
0
0
1.07
2
8
Some Notes on my settings:
In the GS3 Series, when using a PID, you can make some adjustments while the drive is running
note
– such as 703, 704 & 705. These do not exist in the GS2 drives
P4.00
Be sure you have polarity correct NEG(-) to Term2 / POS(+) to Term25
P6.16
This motor will be damaged when running below 42hz so we set it here
P4.04
Mark Pumps FORWARD ONLY so you don't unscrew the impeller
note
There is a Dip Switch that does not matter unless you are using Sinking or Sourcing inputs
This is the slowest the pump will run under PID Control
P6.16
Frequency Drive Setup and Maintenance
Revision 001
PIDSetupVfdGS3Pump.doc
Saturday, April 11, 2015
BRANSOM TECH SERVICES
25 S STOCKTON St. Ste A
Lodi, CA 95240
P7.00
P7.02
P7.25
P7.27
Phone (209) 367-1403
Fax (209) 3674746
www. BTS ElectricService.com
Support@BTSElectricService.com
Activate PID Loop and choose FORWARD ACTING if you want drive to slow down as Milliamps
(pressure) rises
Set this to KEYPAD. Then you can adjust the PV Ratio value from the keypad for fine tuning
speed.
This is a percentage of the Max RPM in case you want to keep your pump from going full
speed on startup
If 4-20ma Signal is lost, the pump automatically goes to 47hz which equals ~35psi
P7.28
What to do if the 4-20ma Sig is lost. (see P7.27)
The run screen allows you to select what you see Motor Hz and PRESSURE when pressed.
DISPLAY This can be changed while the drive is running
My thanks to Dwight Busalacchi for making these 2 white papers a priority for me.
Dwight is a grape grower in Lodi California and is shifting the paradigm of irrigation with his state-of-the-art watering
controller and soil moisture analyzer. Go to http://miovigneto.com/
Good luck setting up your motor and send me an email if you have any questions or corrections. It is easy to make a
mistake on these but very hard to damage the drive. So don’t worry about it much. If I made a mistake here, please
feel free to correct my mistake and let me know. Some settings are going to be different just because it is using a PID
Loop to control the motor.
As long as you hook up the drive to the right voltage and the motor is wired for the right voltage, you will not
damage the drive
I can be reached at:
Jerry Bransom
Bransom Tech Services - Engineering & Contracting
******
dba BTS Electric Service – Commercial & Industrial Electrical Contractor
dba California Robotics and Automation – Industrial Automation and Material Handling
25 S. Stockton St. Suite A
Lodi, CA 95240-2978
(855) 762-6899 (855-ROBOT-99)
(209) 367-1403 x102
(209) 367-4746 fax
support@btselectricservice.com
www.btselectricservice.com
www.calrobot.com
Frequency Drive Setup and Maintenance
Revision 001
PIDSetupVfdGS3Pump.doc
Saturday, April 11, 2015