Allen Bradley PF755 Fault Code 77 - IR Volts Range

[pawPLC]

Hi,

I am having issues matching a 50HP submersible pump w/ a PF755 VFD (480V 3-Phase, 65(ND)/52(HD)). The failures occur at the static AutoTune stage as we have new drives installed to use w/ an existing pump. We are seeing a 'Code 77, IR Volts Range' fault. The distance between the drive and the pump is on the order of 50 metres, possibly longer.

Background: The application involves lowering the submersible pump into a hot-water drilled hole(thru Ice) to a depth of 50-100 metres. The pump recovers spent water from the drilling application and returns about 90% of the drill output to a surface rodwell used as a supply for the drilling operation. The PF755 VFD operates at the surface and is not submerged.

The feedback for the PF755 is completely open-loop using Induction FV motor control (P35). Currently, we are simply trying to tune a newly installed VFD w/ the pump motor via the static method (no rotational or inertia tune). The pump/motor complement is NOT submersed at this time (see pics). I have attached a CCW export for your reference.

At this point we are a little stuck and are looking for suggestions and or troubleshooting tips that we could leverage in getting the VFD and pump matched. The F77 error occurs across multiple PF755 and both a primary and spare pump.

Thanks so much for all your help, -- pawPLC.

----

The motors nameplate info is attached but here is a summary:

-- Motor NP Volts: 460 VAC

-- Motor NP Amps: 67.70 Amps

-- Motor NP Hertz : 60 Hz

-- Motor NP RPM : 3450 RPM

-- Motor NP Power : 50 HP

-- Motor Poles : 2

 

[kamenges]

Based on the saved motor voltage at the time of the fault and the rated motor current the motor resistance just feels a little low. It calculates out to something like 0.064 Ohms. Again, that might be right for a 50HP motor but it feels a bit low.

Is there a reason you are using encoderless induction flux vector control for this application? Do you expect to need torque control of the motor at some point? Unless this is a pretty special pump application I would use volts/hertz control, enter the motor nameplate info and call it a day. But if the autotune failed the way it did that seems to me to be an indication that something else is unhappy. I would get some more detailed motor data and make sure the motor resistance is correct.

Keith

 

[pawPLC]

hi Keith,
Thanks for getting back to me.

Not a specialized pumping application. We just thought that FVC gave us better control and stability of the pump then something simpler. It is a very odd situation in that we have a primary and a spare pump and they are both reacting the same to an autotune from two separate PF755 drives.
e.g., we get the same response from either drive connected to either pump.

You are right, it isn't very satisfying that the autotune fails. We might try Induction SV next and if that still fails then try VHZ mode as our last resort.

We do not have another cable as we are in a remote base camp or we certainly try that.

Thank You, --pawPLC

 

[MikeyN]

Hello and welcome to the forum! You will need to remove those attachments as it is against forum policy to post copyrighted material like that. Something that people have done in the past is to include a URL link to the KB article in their posts.

 

[plvlce]

Hello and welcome to the forum! You will need to remove those attachments as it is against forum policy to post copyrighted material like that. Something that people have done in the past is to include a URL link to the KB article in their posts.

The editing window for posts is short enough by the time that by the time you posted it was far too late, he will already not be able to do so.

 

[pawPLC]

OH!

Thank You Mikey (and others), for calling this to my attention.

Could one of the board's administrators remove the articles, at their earliest convenience?

I apologize for violating any protocol here. --pawPLC.

 

[5618]

The post with some copyrighted material has been removed. I want to preserve the comments from OP from that post. Thanks for the follow-up letting us know what you found.

Update.

We did some further testing yesterday w/ the setup and found that a phase had dropped on the load side of the PF755. Follow-up investigations revealed a mangled slip ring setup leading to the cable spool in the picture. We are in the process of repairing that now and will re-test.

For those interested in the material, see answer IDs QA14252 and QA15094 (access = TechConnect) with information on Fault77 in PowerFlex 750 (and related model) drives.

 

[robertmee]

Submersible centrifugal pump? Run it in V/Hz and don't look back.