Troubleshooting PowerFlex 755 Drive Setup: Minimum Speed Issue with Potentiometer Input

09-07-2024
forqnc
10 comments
895
156

Question:

Hello everyone, I am currently facing an issue with my first PowerFlex 755 drive setup. When I start the drive, it runs at the minimum speed of 5Hz, even though parameter 2 indicates that the command speed reference is coming from my potentiometer. This is a new setup, and the motor spins freely. The configuration is simply Stop/Start with adjustable speed from the potentiometer. I would appreciate any assistance in identifying what I may be overlooking. I have made changes to parameters as detailed in the PDF. Thank you in advance for any help provided.

Top Replies

Determine if your vehicle is in Automatic mode by checking the HIM. It may currently be in manual mode.

10-07-2024
DarrylR

Watch HIM showcase Auto.

11-07-2024
forqnc

When troubleshooting control issues, don't forget to check the safety inputs as well. If you're not using them, make sure to keep the jumper installed for the drive to function properly. This step is crucial for ensuring the safe operation of the equipment.

11-07-2024
DarrylR

Is it possible to utilize analog input on the primary control board instead of the supplemental I/O module? It appears that there may be an issue with the reference signal, causing the drive to operate at the minimum set speed.

12-07-2024
rkukl

Have you verified the jumpers as outlined in Manual Publication 750-IN111B-EN-P from March 2022 on page 4?

12-07-2024
rkukl

Hey there, it sounds like you've got a tricky situation on your hands. One thing that comes to mind if your PowerFlex 755 is running at minimum speed despite settings from your potentiometer is to double-check the calibration of the potentiometer itself. Also, an overlooked A/D calibration can sometimes be the culprit as well. It might also be worth examining the frequency at which your drive input command is set, as an incorrect frequency could affect the speed. Lastly, a simple firmware update could rectify the issue. Don't forget that technical support from the manufacturer is often just a phone call away. They might also have a solution to your issue.

31-12-2024
Ryan Brooks

Sounds like a bit of a headache. It could be various things, but one thing to double-check is the continuity of the potentiometer wiring. Sometimes, a poor connection or a short can cause this sort of issue. Also, confirm if parameter 36 - Low Speed Select, is set appropriately, sometimes, this might limit the motor's speed. And finally, make sure your speed reference source, under parameter 39 Speed Reference 1 Select, is set correctly for the potentiometer. Hope you sort it out!

12-01-2025
Gregory Hughes

Hey there! It sounds like you’re off to a good start, but I’d suggest double-checking a few things. First, ensure the potentiometer is correctly wired and functioning, as a faulty connection might limit your control. Also, verify that the drive's minimum speed setting isn't hardcoded to 5Hz—sometimes those parameters can be slightly misleading. Lastly, it might be worth reviewing the control mode settings (like PRV or AMN) to make sure everything aligns with your desired setup. Good luck, and I hope you get it running smoothly soon!

04-03-2025
Anthony Lewis

More Replies →

What is the purpose of setting parameter 300 and how does it impact performance?

12-07-2024
robertmee

DarrylR pointed out the importance of checking the control wiring and ensuring the safety inputs are being used to operate the drive effectively. We have implemented the Safe Off Torque board as requested by the customer, with wiring instructions of +24VDC to SP+ and SE+ and 0VDC to SP- and SE-, while removing the jumper as advised. rkukl suggested exploring the option of using an analog input on the main control board instead of the add-on I/O module to resolve the issue of the drive not responding to the reference speed and running at minimum speed. Additionally, parameter 300 is set to Hz for optimal performance. For further troubleshooting, it is recommended to refer to the manual publication 750-IN111B-EN-P for checking the jumpers and ensuring they are correctly set to Current mode on the 22-Series I/O module. Thank you to all for the valuable responses and guidance provided.

12-07-2024
forqnc

I have not yet utilized the STO board in conjunction with a PF755. Assuming that is not the root of the issue, it is important to check your motor control mode settings (P0/35). It appears that autotune may have been activated for a permanent magnet motor configuration. If your motor is not PM and you have adjusted the control mode, have you performed a new autotune session? Is the application speed-regulated? During troubleshooting, other settings such as torque control or position control may have been unintentionally adjusted. To track the active control mode, monitor P0/313. The control specifications per mode are outlined in P0/309-312. Consult the control block diagrams in Appendix B of (750-pm001-en-p) to identify any potential limitations. Access these diagrams with live data if you are online in CCW. There are various paths that can be followed between P0/2 and P0/1.

13-07-2024
clintm

I am embarrassed to admit that I am back with an update for any viewers who may find themselves facing a similar situation in the future. After finally arranging a teams meeting with my Distributor, I shared my screen to show him the parameters I had configured. During the meeting, he examined parameter 420 Drive O/L, which was set to its default value of 3. His assessment confirmed my suspicions - the drive was restricting the Output Frequency due to a potential mechanical or other issue. Despite the motor spinning freely when turned by hand, I decided to release the belt tensioner and remove the belts for further inspection. It was during this process that I noticed the motor wiring, which had not been correctly connected. Upon checking the wiring, I discovered that the first phase wire from the drive had come loose from the wire nut. After re-terminating the wire and verifying all other connections, I tested the drive again and found that everything was running smoothly. It turns out that the motor had lost a phase and the drive was simply doing its job to limit the output. This experience taught me a valuable lesson - always double-check the basics when troubleshooting new equipment. I appreciate all the responses and assistance I received during this process. Thank you.

13-07-2024
forqnc

Forqnc shared an update on a successful troubleshooting session during a team meeting with a distributor. After verifying the parameters on screen, they discovered that a default setting on parameter 420 Drive O/L was limiting the Output Frequency due to a potential mechanical issue. Upon further inspection, they found a loose phase wire on the motor, which was causing the drive to limit the output. This experience taught them to always double-check the basics when encountering problems with new equipment. They now keep an aluminum coupling on their desk as a reminder to "trust but verify" information provided by others. It's crucial to thoroughly check all components to avoid issues like the one they faced with the DC tach generator and gearbox system.

14-07-2024
joseph_e2

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Frequently Asked Questions (FAQ)

FAQ: 1. Why is my PowerFlex 755 drive running at the minimum speed of 5Hz even though the potentiometer input is set as the command speed reference?

Answer: - The issue could be related to the drive configuration or parameter settings. Ensure that the potentiometer input is correctly configured and that the drive parameters are set up to accept the potentiometer signal for speed control.

FAQ: 2. What should I check if my PowerFlex 755 setup is not responding to changes from the potentiometer for speed control?

Answer: - Verify the wiring connections between the potentiometer and the drive, ensure that the potentiometer is functioning properly, and double-check the parameter settings related to analog input configuration on the PowerFlex 755 drive.

FAQ: 3. How can I troubleshoot a PowerFlex 755 drive setup where the motor spins freely at startup instead of following the potentiometer input for speed control?

Answer: - Check the wiring connections, confirm that the drive is receiving the correct signal from the potentiometer, and review the drive's parameter settings to ensure that the analog input is properly assigned for speed control.

FAQ: 4. Where can I find detailed information on configuring the PowerFlex 755 drive for potentiometer input control?

Answer: - Refer to the PDF documentation provided with the drive for specific instructions on setting up potentiometer input control. Additionally, you may consult the manufacturer's technical support or online resources for guidance on configuring the Power

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