1. The document provides instructions for setting up and tuning a PowerFlex 40 drive to control a fan motor using PID loop control to maintain a constant pressure. 2. Key steps include connecting the fan and pressure sensor, enabling the PID controller with a setpoint, and tuning the proportional, integral and differential gains to minimize overshoot and undershoot in response to changes in damper position. 3. The document describes optimizing the PID loop response by adjusting the proportional gain, integral time, acceleration/deceleration parameters, and differential gain while monitoring the feedback and output frequency signals.

1. PowerFlex40 Process PID Lab #7
Background
The PowerFlex 40 drive will be used to operate the fan motor and control air-flow with the built-in PID loop.
Our application scenario is an intake fan that must maintain a constant pressure regardless of the demand. The
damper in the plenum will be used to simulate different demand settings.
Drive Demo Setup
• 1. Position all switches to the OFF position. (Left for IN1, IN2, START, DIR)
• 2. Remove wire access cover from drive, and set logic switch to “SRC” and replace cover.
• 3. Verify that the PC is connected to the PowerFlex 40 drive as follows:
 Connect the PC to the PowerFlex drive as follows:
 Connect 9 Pin D-shell connector to Com1 of the computer.
 Connect cable to the 1203-SCM module.
 Connect RJ45 Cable to the drive and the 1203-SCM module
• 4. Verify that the fan is connected to the PowerFlex 40 drive as follows:
 Connect motor cable of the fan to the external motor connector
 Connect the fan I/O connector to the external I/O connector
 Connect the fan to 120 Vac
• 5. Pull the Power Switch (Red mushroom button) to power the demo.
• 6. Set parameter P041 [Reset To Defaults] to 1 “Factory Rest” to reset all parameter
values to factory default settings.
• 7. Press “Stop” to clear the active fault (F048)
Connecting to the Drive Using DriveExecutive
• 1. Double-click the DriveExecutive icon on the Windows desktop (or in the Windows
Start menu select Programs > DriveTools 2000 > DriveExecutive) to start the
software.
• 2. If a Danger dialog appears, read it and click OK.
• 3. In the menus select Drive > Connect to Drive…
• 4. When the Connect to Drive dialog opens, navigate the tree to the serial driver (in this
case, “Unrecognized Device”).
• 5. Select the drive device (Unrecognized Device) and click OK. The drive window opens.
At this time, DriveExecutive may create a Device Database File.
PID Regulator
Process Control uses the output of the PID regulator as the speed reference. No master speed
reference exists and the PID Output directly controls the drive output. This configuration does
pf40pidlabfan-140914194033-phpapp01

2. 2
not require a master reference, only a desired setpoint, such as a flow rate for a pump. The PID
loop compares the setpoint to the process feedback. The PID loop controls the drive output to
maintain the process steady state to match the setpoint.
Our application will use the Process Control configuration to control pressure in the fan plenum.
Configuring Reference and Feedback Signals
• 1. Set parameter A132 [PID Ref Sel] to 1 “PID Setpoint” to enable the setpoint.
• 2. Set parameter A133 [PID Feedback Sel] to 1 “4-20mA Input”
• 3. Set parameter A137 [PID Setpoint] to a value of 25% (the desired Setpoint).
Defining Control of the PID Regulator
The PID regulator was enabled when you set parameter A132 [PID Ref Sel] to 1 “PID Setpoint”
and parameter A137 [PID Setpoint] to 25.0%
Setting Limits for the PI Regulator
• 1. Set parameter P035 [Maximum Frequency] to a value of 100 Hz. This will allow the PI
Regulator to control the airflow even when the damper is completely closed. If the
frequency is limited to 60Hz, the airflow would not reach the desired level when the
damper is closed.
Checking Switch Settings and Verifying Reference and Feedback Signals
• 1. Start the drive by pressing the Start button on the integral HIM.
• 2. Run the drive in forward. Press the Reverse button on the HIM if necessary. (The fan
in the bottom of the demo should be turning counter-clockwise when looking at it top
perspective.)
• 3. View the drive in DriveExecutive.
• 4. Locate parameter d021 [Analog In 4-20mA]
• 5. View parameter d021 [Analog In 4-20mA] and verify that there is approximately 25%.
• 6. Stop the drive.
Starting DriveObserver
To perform this portion of the lab, you will be used DriveObserver software.
• 1. Double-click the DriveObserver icon on the Windows desktop (or in the Windows Start
menu select Programs > DriveTools 2000 > DriveObserver) to start the software.

3. 3
• 2. In the menus, select File > New. The sampling dialogue will open.
• 3. Select a sampling period of 300 milliseconds, and then click OK.
Adding Traces
• 1. If the Add Trace dialog is not already open, select Chart >Add trace s…
• 2. DriveObserver will display the node that is currently using by DriveExecutive.
(Otherwise, you will need to use the Add Node button to select a drive.)
• 3. From the drive Linear List, select the following parameters from the linear list of the
node by clicking the checkbox in front of each desired parameter: d001 [Output Freq]
and d021 [Analog In 4-20mA], A137 [PID Setpoint] .
• 4. Click OK.
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.
Tuning the PID Regulator
The PID regulator in the drive must be adjusted for the specific fan that you are connected to.
These adjustments need to be made to optimize how the drive reacts to changes in the connected
load.
Understanding Gain Settings
This section will help you get a feeling for how to adjust the drive gain values. Use
DriveExecutive to make changes while you watch the [Output Freq] and [Analog In 4-20mA]
signal in DriveObserver. Do not forget to change the damper position after each parameter
setting change.
The Proportional component affects how the regulator reacts to the magnitude of the error. To
adjust the response, use parameter A134 [PID Proportional Gain]. The default value is 0.01.
The Integral component affects how the regulator reacts to error over time. To adjust the
integration rate, use parameter A135 [PID Integral Gain]. The default value is 0.1. This
parameter is scaled so that when it is set to 2.0, the process will integrate from 0-100% of
[Maximum Frequency] in 2.0 seconds when the process error is 100%.
The Differential component affects the rate of change of the PID output. A136[PID Differential
Gain]. Differential Gain (in 1/seconds) used by the PID regulator. This parameter is scaled so
that when it is set to 1.0, the process response is 0.1% of [Maximum Frequency] when the
process error is changing at 1% / second Optimizing the PID Regulator

4. 4
Using DriveObserver, you should be able to adjust the gain settings in the PowerFlex 40 drive
until you have a graph that looks like the one below. A properly tuned PI regulator will
minimize overshoot (and ringing) while avoiding excessive undershoot. When properly tuned,
your chart should look something like this when the damper is changed from fully open to fully
closed.
1. Parameter A134 [PID Prop Gain] is set to a default of 0.01. This equates to 1% output change for
100% feed back change. Adjust A134 [PID Prop Gain] to a value of 2.0 and verify the operation
of the PID regulator by varying the position of the damper from fully open to fully closed on the
fan.
2. Parameter A135 [PID Integral Time] is set to a default of 2.0 seconds. This adjusts the integral
term every 0.1 seconds. Adjust A135 [PID Integral Time] to a value of 0.2 and verify the
operation of the PID regulator by varying the position of the damper from fully open to fully
closed on the fan.
3. Adjust the acceleration and deceleration parameters and observe the effects on loop response.
Change the accel and decel to 0.1 sec. Now change the damper on the fan from fully open to
fully closed. Retune the PID loop if necessary.
4. Parameter A136 [PID Differential Gain] is set to 0 default. Adjust this and observe the effect on
the process response when making changes to the damper from fully open to fully closed on the
fan.
5. Parameter A138 [PID Deadband]. This parameter setting allows a deadband that is +/- of the
Setpoint. I.E. if A138 [PID Deadband] is set to 5.0 and Setpoint is set to 25.0. This allows the
feedback to change from 20 to 30 without the PID regulator acting on the error.
6. Parameter A139 [PID Preload]. This parameter will be pre-loaded into the integral component of
the PID at any start or enable.