Powerflex 70 Output & Commanded frequency

raholter

Member
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Join Date
Oct 2013
Location
alabama
Posts
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I am going from a PLC (RSLogix 5000) to a Drive (Powerflex 70) to a motor. In the PLC I calculate the frequency for the motor to run at and then I send it to the drive. At the drive I am able to see the commanded frequency parameter has the correct value that I want, however, the out put frequency from the drive to the motor is always greater than what I want by at least double. I checked my PI controller to see if it was enabled and it is not. Then I checked to see if slip compensation was enabled and it also is not. Also, I checked to see if I was pulling the correct reference and it was (Speed Ref A Sel was set to 22, DPI Port 5). I can't think of anything else that could be influencing my output frequency.

Any help will be appreciated.
Thanks.
 
I've done that and I know that the frequency or scale factor that the plc sends to the drive is correct, but I am having issues with the drive output frequency being twice that of the commanded frequency.
 
My maximum frequency is 120 Hz and my plc is sending around 4200 as the speed reference. So, my commanded frequency is 15.46 Hz, but my output frequency of the drive is in the high 28-30Hz.
 
Do you have Drive Executive? If so connect to the drive with it running and look in Diagrams, you should be able to drill down and find your problem. If you are still stuck then post a Drive Executive backup file (.DNO) preferably taken whilst the drive is running?
 
Last edited:
Dmargineau, parameter 053(Motor cntl sel) is 4(FVC vector) and I do have an encoder feed back. feedback type is quadrature, ppr is 1024, and there is no feedback filter.
 
Well...It looks like we are finally getting somewhere...:D
The reason the PF70 Output Frequency is different than the Commanded Reference is the chosen control mode.
When in Vector control mode, when compared to the V/Hz one(strictly Speed Regulation), the PF70 on-board processor is using both the Speed Reference and the Torque Reference when "deciding" the inverter's Output Frequency since, within the FVC mode, the VFD is actually regulating current while "adjusting" the frequency accordingly in order to maintain the torque settings (which are prevalent to the speed ones!).
Refer to Page 3 of http://www.ab.com/support/abdrives/powerflex70ec/PF70EC_ControlBlockDiagramsSm.pdf
in order to determine what other setup paremeters "cause" the mismatch between the commanded speed reference and the "resulting" Output Frequency.
 
Have you checked that parameter 88 is set to 1 (Speed Reg).

I assume you have checked that the encoder really is 1024 ppr and that is what is entered in the drive.

Have you done an auto-tune?

Have you used the start-up wizard? It would be worth running through that just to make sure all parameters are set correctly.
 
Ok, output current is 0.5 amps and my torque current is 0.15 amps. If I change to V/Hz mode or change speed/torque mode from speed reg. to zero torque will that lower my output torque to 0.35 amps?
 
The question here is:
What type of VFD control does your application require???!
If you need Speed Control only use V/Hz control and your Reference Command will "go straight" to the Speed Regulator/Frequency Output.
If your application needs Torque Control with Speed Regulation, choose the Flux Vector Control Mode, however" you will generate the corresponding "difference" between speed reference and output frequency due to the required torque settings.
 

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