The document describes a hands-on lab using a PowerFlex drive to control fan speed using a PI regulator to maintain constant air pressure. The drive is configured to use a constant setpoint as the reference and an analog input for feedback from a pressure transducer. Digital and analog I/O are configured and the PI regulator is tuned by adjusting proportional gain and integral time parameters to control fan speed in response to a simulated pressure demand change using a damper.

1. PowerFlex 70 and 700
Process PI
Hands-On Lab
Equipment List
PowerFlex 70 EC or PowerFlex 700 Series B Demo
Fan Demo (Red or Blue Damper)
Windows 2000 PC with DriveObserver™ software
1203-SSS serial to DPI /SCANport communications adapter
(firmware version 3.003 or later)
Introduction
The PowerFlex drive will use its built-in Proportional – Integral (PI) Regulator to control air
pressure by varying the fan speed. This application scenario involves a fan that must maintain a
constant pressure regardless of the demand. The demo uses a damper in the plenum to simulate
different demand settings.
Before performing this lab, students should complete the PowerFlex 70 or 700 General
Programming Hands-on Lab. They should understand how to access and manipulate numeric, bit
and ENUM parameter data.
A) Connecting the Demo
1. Make connections as shown in the diagram above. You must plug the connector on the chain
into the “Aux Output”.
2. Verify that the PC is connected to the PowerFlex 70 drive as follows:
Connect the nine-pin D-shell connector of the 1203-SFC Serial Cable to Com1 of the computer.
Connect the other end of the 1203-SFC Serial Cable to the 1203-SSS module.
Connect one end of the1202-C10 Cable to the drive and the other to the 1203-SSS module
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2. B) Initializing the Demo
1. Apply power to the drive by pulling out the red emergency-stop button.
2. Reset the drive to the default factory settings, by setting parameter 197 [Reset to Defaults] to 1-
Factory.
Note: To navigate directly to a parameter by number, on the HIM:
Press the ALT button.
Press the
+/–
Param # button.
Enter the parameter number using the numeric keys
Press the button.
Press the Sel button to move the cursor to the parameter value.
3. Resetting the drive will cause a Fault F – 48. Press the button to clear the fault.
C) Configuring the PI Regulator for Process Control
In this lab, you will configure the drive for Process Control to regulate pressure in the fan demo.
Process control uses a Proportional – Integral (PI) Regulator to control the fan motor speed. The
desired pressure (reference) will be a constant setpoint (25% of maximum). The measured
pressure signal (feedback) will come from a transducer in the fan demo. The regulator will
compare the feedback to the reference and generate an output signal, which will become the
speed reference for the drive.
PI Ref Meter
135
PI Fdbk Meter
136
PI Output Meter
PI 138
Regulator
Desired Pressure
Measured Pressure
Fan Speed
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3. Process Control uses the output of PI regulator as the “exclusive” control factor for the speed
reference. No other speed command will affect the speed reference.
Commanded Speed 2
PI Output Meter
PI 138
Regulator
134 [PI Status]
/ Bit 0 [Enable]
124 [PI Configuration]
/ Bit 0 [Excl Mode]
23
Speed Reference
Speed
Reference
Limits,
Logic,
etc...
Process trim control (not used in this lab) adds the output of the PI regulator to a speed command
to create a speed reference.
1. Set parameter 124 [PI Configuration] / Bit 0 [Excl Mode] to a value of 1. This makes
the output of the PI regulator the “exclusive” control factor for the speed reference.
D) Configuring the Reference and Feedback Signals
Configure the drive to use a constant as the PI reference.
PI Ref Meter
135
PI Reference Sel 126
Selector
(set to 0 - PI Setpoint)
PI Setpoint 127
(set to 25%)
PI
Regulator
PI Feedback Sel 128
Selector
(set to 1 - Analog In1)
Analog In1 Value
16
PI Fdbk Meter
136
1. Set parameter 126 [PI Reference Sel] to 0 - PI Setpoint.
2. Set parameter 127 [PI Setpoint] to 25%.
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4. Configure the drive to use Analog Input 1 for the feedback signal. Analog Input 1 receives the
pressure signal from the transducer in the plenum of the fan demo
3. Set parameter 128 [PI Feedback Sel] to 1 - Analog In 1
4. Configure the analog input for either a Red Fan Demo or a Blue Fan Demo
ATTENTION: On a PowerFlex 700, configuring an analog input for 0-20mA operation and driving it
from a voltage source could cause component damage. Verify proper configuration prior to applying input
signals. Make sure the jumper for Analog In 1 (on terminals 17 and 18 of the I/O terminal block) is
installed for a Red Fan Demo and not installed for a Blue Fan Demo.
For a Red Fan Demo:
Set parameter 320 [Anlg In Config] / Bit 0 [Analog In 1] to 1 (Current)
Set parameter 322 [Analog In 1 Hi] to 20.0 ma
Set parameter 323 [Analog In 1 Lo] to 4.0 ma
For a Blue Fan Demo:
Set parameter 320 [Anlg In Config] / Bit 0 [Analog In 1] to 0 (Voltage)
Set parameter 322 [Analog In 1 Hi] to 10.0V
Set parameter 323 [Analog In 1 Lo] to 0.0V
E) Defining Control of the PI Regulator
This example configuration requires the PI regulator to be on at all times. It also requires some
digital inputs to control parts of the regulator.
1. Set parameter 125 [PI Control] / Bit 0 [PI Enable] to a value of 1. This constantly enables the PI
regulator.
2. Set parameter 363 [Digital In 3 Sel] to 0 - Not Used.
3. Set parameter 364 [Digital In 4 Sel] to 27 - PI Hold.
4. Set parameter 365 [Digital In 5 Sel] to 28 - PI Reset.
The digital inputs now control parameter 125 [PI Control].
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5. F) Setting Limits for the PI Regulator
Parameters govern the range of the PI regulator output. In this example, the drive will operate
from zero to maximum speed. The example application may require a maximum speed higher
than 60 Hz, in order to achieve the desired airflow when the damper is fully closed. Different
applications require different limits. Some applications require unidirectional (only positive)
operation. The example application does not.
1. Ensure that parameter 131 [PI Lower Limit] has a value of -100% and parameter 132 [PI
Upper Limit] has a value of 100%. These are the default values.
2. Ensure that parameter 124 [PI Configuration] / Bit 4 [Zero Clamp] is off. This is the default
setting.
3. Set the value of parameter 82 [Maximum Speed] to 100 Hz.
G) Verify the Drive Setup
1. Make sure the In 6 switch is in the right (on) position.
2. Start the drive, and run in forward. An “F” on the HIM indicates forward operation.
3. Go to parameter 134 [PI Status]. Verify that the switches, In 4 – In 5 on the demo, affect the
control as programmed in Section E. Bit 1 [PI Hold] should respond to digital input 4, and bit 2
[PI Reset] should respond to input 5.
4. Ensure that the reference and feedback signals are present. View the values in parameters 135 [PI
Ref Meter] and 136 [PI Fdback Meter].
Note: If parameter 136 [PI Fdback Meter] does not read 25% when the damper is all the way
open, you need to increase airflow. Remove equipment from around the bottom of the fan demo
that may be blocking airflow. If that does not work, raise the demo off the table.
5. Stop the drive.
H) Configuring an RSLinx Serial Driver
1. Double-click on RSLinx icon on your desktop (or in the Windows Start menu select Programs >
Rockwell Software > RSLinx > RSLinx) to start RSLinx. We need to start RSLinx the first time
so that we can configure a serial driver.
2. In the menus, select Communications > Configure Drivers. The Configure Drivers dialog box
will open.
3. Look in the list of Configured Drivers. If you see a driver whose name begins with “AB_DF1”,
select it and click Delete.
4. In the Available Drivers selection box, select “RS-232 DF1” and click Add New.
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6. 5. When prompted for a name, click OK. The Configure RS-232 DF1 Devices dialog box will open.
Make sure that:
•Set the “Comm Port” to the communications port on your PC (COM1 for this lab)
• Set the “Device” to 1770-KF2/1785-KE/SCANport
6. Set the baud rate to the baud rate of your adapter (38400 for this lab).
7. Click OK to close the dialog box.
8. Verify that the driver that you just configured is listed in the Configured Drivers list with a status
of “Running”.
Note: If the Status is “Conflict”, other software may be using the serial communication port or
you may have two RSLinx serial drivers programmed for the same serial port:
Delete duplicate drivers
If another serial software package, such as DriveExplorer, is running, close it.
Then stop and re-start the RSLinx serial driver.
9. Click Close, to close the Configure Drivers dialog.
10. In the menus, select Communications > RSWho…. The RSWho dialog will open.
11. You should see both a computer (Workstation) and the connected drive device
(AB_DF1-1, Data Highway Plus).
Note: At this time, the drive device may be depicted by a question mark icon labeled
“Unrecognized Device”. The serial driver will work.
If this is not the case, verify that you have properly connected the PC to the drive using the 1203-
SSS adapter and that power to the drive is on. If you check all these things and the connected
drive device still does not appear, verify your device driver settings and try other baud rates (i.e.
9600, 19200, 38400) and computer communication ports (i.e. COM1, COM2).
12. Close RSLinx.
I) Starting DriveObserver
To perform this portion of the lab, you will use DriveObserver software.
1. Double-click the DriveObserver icon on the Windows desktop (or in the Windows Start menu
select Programs > DriveTools > DriveObserver) to start the software.
2. In the menus, select File > New. The sampling dialogue will open.
3. Select a sampling period of 300 milliseconds, and then click OK.
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7. J) Adding Traces
1. If a file is not already open, select File > New.
2. If the Add Trace dialog is not already open, select Chart >Add traces…
3. In the Add Trace dialog, click the Add Node button.
Navigate from the Workstation, through the AB_DF1 driver to the drive (address 01) and double-click
on the icon for the AB DPI object (the drive).
4. Back in the Add Trace dialog, select the following parameters from the linear list of the node by
clicking the checkbox in front of the desired parameters: 1 [Output Freq], 136 [PI Fdback Meter]
and 127 [PI Setpoint].
5. Click OK.
K) Recording Data
1. Start the drive by pressing the ‘Start’ button on the integral keypad.
2. In the DriveObserver toolbar, click the Record button. DriveObserver now displays new
data.
3. If you want to stop recording data, click the Stop button.
TIP: Double clicking the parameter in the table beneath the chart will open a dialog so
that you can change the color, minimum & maximum values, line format, etc. For this
exercise, you may wish to set the Analog Input and the PI Setpoint to a scale of 0-
100%.This will allow you to verify that they are equal
L) Operating the drive
1. Turn the digital input switches (In 4 and In 5) to the left (off). Leave the In 6 switch in the right
(on) position.
2. Turn the damper vertical to maximize the airflow in the plenum.
3. Start monitoring data on the computer.
4. Start the drive.
5. Adjust the damper in the plenum to restrict airflow.
Note the reaction of the drive. The drive should increase fan speed in order to overcome the
airflow restriction, as it tries to keep the pressure feedback constant at 25%.
6. Change damper position to increase airflow.
Note the reaction of the drive. The drive should decrease fan speed in order to compensate for the
reduced airflow restriction, as it tries to keep the pressure feedback constant at 25%.
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8. M) Tuning the PI Regulator
1. The proportional component affects how the regulator reacts to the magnitude of the error.
Manipulate the value in parameter 130 [PI Prop Gain]. Try values of 0.5, 1.0, 2.0 and 5.0 (the
default value is 1.0). Note the different reactions of the parameter 137 [PI Error Meter] signal,
when you change the damper position. The proportional term of the regulator adjusts the regulator
output based on the amplitude of the error (the difference between the reference and feedback). If
the error is large, the correction is large.
2. The integral component affects how the regulator reacts to error over time. Manipulate the value in
parameter 129 [PI Integral Time]. Try values of 0.5, 1.0, 2.0 and 5.0 (the default value is 2.0).
Note the different reactions of the parameter 137 [PI Error Meter] signal, when you change the
damper position. The integral term of the regulator adjusts the regulator output based on the
duration of the error. When the error persists for a longer time the regulator puts out a larger
correction.
Varying the values in these parameters will change how quickly the system responds to damper position
changes (how responsive it is). It also changes how much the system over-shoots the reference while
responding (how well damped it is).
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