powerflex 400

I have two powerflex 400 drives that I'm currently getting a f12 fault. one drive is running a pump and the other is running a dive belt. If I get this fault I have to clear the fault and open and then close the disconnect before the drive will start. I have to doe this series of events every time in order to get either drive to start. I feel there may be an issue in the disconnects, but its hard to believe that to completely different disconnects are bad. I have spoke with Rockwell with no success. Any help would be appreciated.

As you've probably read, F12 indicates a Hardware Current Overload fault.

Generally a hardware current overload fault really does mean that your loads are pulling more current than the drive can deliver.

Have you measured the usual full load amperes the drive is supplying during operation ? How closely matched to their motor FLA are these drives ?

Does the fault appear immediately when you try to start the drive, or does it appear after the drives have been running the load for a while ?

And is this the same drive you were asking about a few months ago ?

http://www.plctalk.net/qanda/showthread.php?t=99214

If you bring up an old troubleshooting project with a new thread, it's best to link back or refer to the old thread so that you (and the Forum readers) don't have to wade through another round of basic troubleshooting questions. You went through the same experience last year with multiple threads about the same PowerFlex 525 that was overheating.

If I had to guess, you've set up the drive so that you're avoiding the acceleration and deceleration problems on the pump that you were experiencing in November, but the drive is still undersized for the application.

the FLA of the drive is 36 amps and its highest amp draw was 31amps on my meter. I have added a 60sec accel time and the decal is set to coast to stop. This issue seems to happen at immediate start up and can not be cleared operational until the disconnect has been cycled.I change out the control module on the 525 and fixed the issue with it.

What is the FLA rating of the motor ?

Does the drive ever start and run, or does this fault occur every single time you attempt to start the drive ?

If the drive will not start at all, it is probably damaged.

it will start and run this problem is intermittent. the two motors fla is 33,36 amps and both are 30 hp. The drives are also rated at 30hp and continuous amps of 45.5amps

HW OC faults are often caused by intermittent short spikes in current demand, usually because of a load related issue. On the drive belt, I can see that happening if there is a sharp increase in load while running, something like a sudden high step-change in load, a seized bearing or some other jamming condition. But what kind of pump is the other one? If it's a centrifugal pump, that's hard to imagine a load issue that can cause this. But if it's a Positive Displacement pump such as a gear pump, progressive cavity pump, something like that, then yes, it can absolutely happen.

PF400 drives are ALWAYS sized as "Normal Duty" in A-B parlance, what the rest of the world used to call "Variable Torque". That means the drive, although rated for 30HP, is only rated for a maximum of 110% overload for 60 seconds but short intermittent overloads of 180% for only 1 second, which is that Hardware Limit causing the trip you are experiencing. It is intended to ONLY be used on HVAC loads such as centrifugal fans and pumps. That drive should NOT have been used on a conveyor application unless it was over sized, and by how much will depend on what you intend to do with it.

A typical Heavy Duty (Constant Torque) drive rating is 150% overload for 60 seconds, 200% for 3 seconds and a HW Limit of usually 250% for 1 second, essentially 50% more than the Variable Torque rated drive. If that's what you needed from a PF400, you would have to up-size it by at least 2 sizes. So for your 30HP motor, you would need a 50HP PF400, maybe even a 60HP. The same would be true if it is any sort of PD pump. Those are CONSTANT torque loads.

In reality, it would have been better to just buy the right VFD, a PF70,700 or 750 sized for Heavy Duty. Sounds as though someone tried to get away with buying a cheaper drive without fully understanding WHY it is cheaper.

The other remote possibility is that you have an intermittent line fault ahead of the VFD when it is running, coming from something else in the plant or nearby. A brief dip in voltage that is low enough to stop the diodes from conducting into the DC bus (below the Forward Conduction Voltage threshold), can cause a huge current spike coming into the drive, because the transistors on the output are depleting the DC bus caps, but the diodes are not replenishing it for a cycle or 2. So when the line drop is over, the diodes conduct again and the caps re-charge by pulling all the current they need at the Available Fault Current level, albeit for only a cycle or 2, but that is often enough to trigger that fault because that current measurement (for the HW OC fault) is taken at the line side of the DC bus in order to protect the components. If you don't have a Line Reactor ahead of the drive, you need one. The reactor slows the rate of the line anomaly and gives the drive time to react to it better without over doing it.

thank you , I do have a line reactor in front of the drive. I'm working on getting Rockwell onsite at the moment so hopefully I can get this resolved.