Strange AB 525 VFD issue?

[dginbuffalo]

Hello everbody. Trying to hook up a 525 VFD in 2 wire run, 4-20mA speed and a pot that runs the drive in hand mode. For hand mode, there is a switch that is powering terminal 6 of the drive. Basically, it set to run with the 4-20mA signal all the time, unless terminal 6 is energized and then the POT becomes the speed reference.

Now here's the weird part. Drive runs fine in the 4-20mA mode. If I connect the POT wires while the drive is running in 4-20mA mode, and then twist the POT, it varies the drive from where it is up to 60Hz. It's acting like both signals are affecting the speed?? Anybody ever see any weirdness like that before? I checked the wiring and it's per the manual. I "believe" I have all the parameters set right. I think T766 is set to 1 which designates term 6 to use the 2 wire run and then P049 to 5 which designates 0-10vdc POT reference. Kind of bizarre but as always, could be something dumb!

 

[osmanmom]

just guess base on manual instruction,

P047=3,P049=6,P051=5,t065=1,t066=2.

 

[dginbuffalo]

just guess base on manual instruction,

P047=3,P049=6,P051=5,t065=1,t066=2.

Thanks. I'll have to check it out. The way I believe it's setup now is:

P046=2 (DigIn Term Blk)
P047=6 (4-20mA speed source)
P049=5 (0-10v Input)
T066=1 (Speed ref 2 selected--which looks at P049)

The drive starts and runs when either term 2 or 6 is energized.I think with term 6 energized, it will run 0-60Hz with the pot as it should.

With Term 2 energized, it runs based on its 4-20mA from the PLC BUT, as soon as I turn the pot to 100%, the drive ramps to 100% when it should be ignoring the POT selection.

 

[jraef]

Unless you got something crossed up in your wiring of the pot and mA signals. They share a common and are isolated from the rest of the PC board circuitry, but they are not isolated from each other, so if you connected it wrong, they interact.

Sometimes on things like that, if I make a mistake and keep looking for it, I see what I want to see. I find it best to have someone else who has never seen it before, take a look at the wiring and see if they see the problem. It's surprising how often that works, but it's a trick our minds play on us by filling in information that might not agree with what we are expecting to see.

 

[dginbuffalo]

I hear you. I'm hoping something stands out on Monday. Here is circuit. The only thing different is like I explained, the hand switch now goes to terminal 6. The 4-20mA and POT circuit seem pretty straight forward. I need to get the PLC analog out module drawing and check it. It's a 2080-OF2.

 

[Saffa]

I'm not familiar with the powerflex drives but with Altivar drives it's possible to treat references as being summed. Which sounds a lot like what you're seeing.

Not sure if this is possible in the PF drives, but worth a look through the manual to see if this function exists and if so, how to disable it.

 

[dginbuffalo]

I'm not familiar with the powerflex drives but with Altivar drives it's possible to treat references as being summed. Which sounds a lot like what you're seeing.

Not sure if this is possible in the PF drives, but worth a look through the manual to see if this function exists and if so, how to disable it.

I've heard of that function also. I will look through the manual and if that function is possibly enabled. Thanks!

 

[bernie_carlton]

I'm betting that internally the voltage input and the current input wind up going to the same A/D circuit. You might have to isolate the input lines using contacts. Either one or the other closed.

Ahh - a note from the bottom of the input wiring chart page 40 of the manual

Only one analog frequency source may be connected at a time. If more than one reference is connected at the same time, an undetermined frequency reference will result.

 

[dginbuffalo]

I'm betting that internally the voltage input and the current input wind up going to the same A/D circuit. You might have to isolate the input lines using contacts. Either one or the other closed.

Ahh - a note from the bottom of the input wiring chart page 40 of the manual

Oh boy... Thanks for the heads up Bernie. You would've think AB's tech support would have said something on the phone.Grrrrr- I'll talk to them tomorrow. Sounds about right though