Powerflex running with no commanded frequency

[tachypsychia]

Hi all,

Replaced an older Lenze drive with a powerflex 40 after it let some magic smoke out.

Not my first rodeo with powerflexes (525s, 755s, 7000s) but first with a 40.

I have two speeds (41.5hz, 90hz) to run and use the DIN on pin 5 and 6 to control it.

Problem is, when the drive is enabled and in run, after cycling to either speed 1 or 2 and back to a stop, the motor will creep ever so slightly forward. There is no command being given, as far as I can tell. If I look at the commanded frequency at d001/d002 however, it does some major glitching like it IS being told to go to a speed, then being told to go back to zero.

See video of glitch drivehere https://imgur.com/a/t4evEZi
Video of motor/belt speed: https://imgur.com/a/S5e0mq8


What I've looked at:

Defaulted the drive back out even though it was new from box and tried again. No change

Changed P38 from 0 (poteniometer) to 1 (Internal Freq). Documentation says if I have A051/A052 turned to 4 (use preset freqs at A070-77) it will override whatever is being used here. I thought that the pot might be commanding it to a slow speed. I changed the internal frequency to 0 to prevent this. No change.

I did the same above to P38 to 4 (preset freq) Now I needed to change A070 to 0 (no DIN) then A071 and A072 to my requested frequencies. I really thought this one would do it, but again no dice.

I did some googling and then tried playing with P37 (Stop Mode) from 0 to 1 (ramp to coast). This actually made things worse as it slowed and down much slower but STILL kept creeping along.

I'm not sure exactly what I'm missing but SOMETHING is telling it to run when I do not have a commanded frequency, yet the drive is enabled.

I'm considering swapping my enable to an XIO Stop Stop command instead since that seems to be the only way to get it to stay truely stopped.

This one is really stumping me, would appreciate some help!!!

 

[Steve Bailey]

The following is specifically directed at what you're observing on the drive's discrete inputs. What type of signal are you using to command the speed on the DIN lines? My preference would be a contact closure between the terminal and DC common, but sometimes people use transistor outputs. These can leak enough current in the off state to look like they are still on when commanded off. If you're using PLC DC outputs, also make sure DC- on the PLC module is connected to DC common on the drive. Also make sure the source/sink selection on the drive is correct for the type of DC output on the PLC. (PLC sourcing output to drive sinking input or PLC sinking output to drive sourcing input.)

 

[tachypsychia]

Tried a quick swap of my Run input (terminal 2) with Stop which is jumpered (terminal 1)
The jumpered enable doesnt reset since it needs a momentary input with a 3 wire setup (P36 to 1)

I might try a two wire setup and see if that makes a difference but I ran out of time to troubleshoot. Ideally I need 3 wire so I can use DC braking Auto to stop. Two wire defaults to coast to stop only =-(

 

[tachypsychia]

The following is specifically directed at what you're observing on the drive's discrete inputs. What type of signal are you using to command the speed on the DIN lines? My preference would be a contact closure between the terminal and DC common, but sometimes people use transistor outputs. These can leak enough current in the off state to look like they are still on when commanded off. If you're using PLC DC outputs, also make sure DC- on the PLC module is connected to DC common on the drive. Also make sure the source/sink selection on the drive is correct for the type of DC output on the PLC. (PLC sourcing output to drive sinking input or PLC sinking output to drive sourcing input.)

The DIN lines are fed from a SLC 5/03 Isolated Relay Output 1746-A10

I have the Output 0/4 going to DIN5/6 and the DC- side going to terminal 4 (common) on the drive. It is set to SINK on the drive as well. I appreciate the input!

Addendum: I have a baldor VFD connected in the same manner on a nearby motor that I wired up last week and it works without issue (Same output relay card, DC- to common on the drive, digital input for 2 speed control). Only difference seems to be the drive? I have the option of editing the code, but want to address the cause not the symptoms.

Also updating the first post with a video of the speed the drive is turning the belts.

 

[padees]

The 1746-A10 is a 10 slot chassis...


My dumb guess is something may be leaking and could possibly be giving (2) speed references to the drive at the same time.

 

[tachypsychia]

The 1746-A10 is a 10 slot chassis...


My dumb guess is something may be leaking and could possibly be giving (2) speed references to the drive at the same time.

Apologies, it's a 1746-OX8 not a chassis!

I'll put a scope on it tomorrow and see if there is any noise. Thank you!

 

[Steve Bailey]

Is anything connected to DIN 3 or DIN 4 (terminals 7 & 8)? Try jumpering them off to make sure you're not picking up stray voltage on either of them. If A053 is also set to 4 alng with A051 and AO52, DIN 3 adds additional preset speeds. If A053 is left at default, DIN 3 being on makes the keypad pot the frequency command source. If A054 is left at default, DIN 4 being on is a jog command.

 

[chelton]

What is the value of d012 when this is occurring? You should be able to narrow down where the speed source is coming from.

 

[jaden]

I have seen this in a classroom setting. Perhaps, try an AutoTune, Parameter A127 to see if that helps.

 

[tachypsychia]

Is anything connected to DIN 3 or DIN 4 (terminals 7 & 8)? Try jumpering them off to make sure you're not picking up stray voltage on either of them. If A053 is also set to 4 alng with A051 and AO52, DIN 3 adds additional preset speeds. If A053 is left at default, DIN 3 being on makes the keypad pot the frequency command source. If A054 is left at default, DIN 4 being on is a jog command.

I did these earlier in the day yesterday. I have only terminals 5 and 6 plugged in, and the A053 and AO54 set to 0 as I thought the jog command might have been part of the problem. I also set the jog frequency to 0 just in case.

What is the value of d012 when this is occurring? You should be able to narrow down where the speed source is coming from.

d012 shows 01. But.. thats just the display of what P36 and P38 are right? I didn't think that would change regardless of having a frequency command.
I currently have it as pot, but have had it at 4 for preset frequencies and it didnt change.

I have seen this in a classroom setting. Perhaps, try an AutoTune, Parameter A127 to see if that helps.

I'll give that a shot this morning!

One other oddity i'll add that is making me think that it is somehow the drive or a combination of parameters is that I pulled all external wiring from the drive except the jumpered stop terminal.
I applied control voltage to terminal 2 to put the drive in run.
I used the pot to ramp up the VFD, then back to 0
The motor still turns slowly after ramping down. So without any external signals on the VFD, I'm beginning to wonder if I have a questionable drive.

 

[tachypsychia]

I give up trying to figure it out with a 3 wire setup.

I made it 2 wire and added a second input that turns on via the PLC when either speed command is sent and off when not. This is the only way I could get the drive not to run.

Terminal 1 - Enable command from PLC (control power/MCR)
Terminal 2 - Run command from PLC output on when either DIN is on

/shrug