Lessons Learned - Powerflex 40 Drive Won't Start

recondaddy

Member
Join Date
Apr 2006
Location
Atlanta, GA
Posts
77
I'm currently on a project start-up and am keeping a running list of lessons learned. I've learned so much on this forum from you incredible folks, and I want to contribute whenever I can.

Today's challenge: Stubborn Powerflex 40

Here's the setup: I have a Powerflex 40 in a remote vendor panel. I am sending it a speed reference over ethernet, but the start command is coming from inside it's own panel. So, parameter 36 (Start Source) is set for "2" (2-Wire), and parameter 38 (Speed Reference) is set for "5" (Comm Port).

Here's the challenge: Assuming the stop input on the drive's I/O block is high (as required to enable the drive), and the speed reference is being successfully provided to the drive, why does it refuse to ramp up when the start command goes high?

The run light on the drive "blips" ever so teasingly, but no glorious turning of conveyors.

Here's the reason: Though I didn't really have to, I added the drive to the I/O tree of my ControlLogix program. In doing so, the four input words and two output words for the drive were added to my tag database. The first two input words (0 and 1) are for ENBT overhead, while the second two words (2 and 3) are for Logic Status and Feedback, respectively. The two output words are for Logic Command and Speed Reference, respectively.

Now, one would think that with parameter 36 (Start Source) being set for 2-wire control, the Logic Command word in the PLC would be inconsequential, right? Wouldn't it be reasonable to assume that it would be ignored? Apparently, that's only true in my world.

As it turns out, the stop bit of the Logic Command word was set to "1", so while the relays inside the vendor panel were commanding the drive to start, my PLC program was telling it to stop. Hence the "blip" of the run light on the drive and its refusal to ramp up.

CHECK THAT LOGIC COMMAND WORD (PF40:O.Data[0])!!

Hope this helps someone.
 
It's been my experience that AB drives will stop when they receive a stop command from anywhere no matter what the start device is set to. On some drives you can mask out some functions from digital in or comms but, I don't think you can mask the stop command. I imagine this is for safety reasons.
 

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