Powerflex Stall Fault ?

[TwoBlocked]

Been wondering just what was going on with a system. Unfortunately, it's one of those situations where there are too many fingers in the pot, so I've stepped back until called again.

This is a water transfer system with a small priming pump feeding a large pressure pump. Both are centrifugal, and both are on VFDs. The priming pump is a powerflex. There is no pressure indication between the pumps. The priming pump always has at least 5 ft of suction head. How the speed command is determined, I don't know, not sure it matters for my question.

Got called out because the priming pump was tripping on overcurrent. FLC = 38A. Changed parameter A179 to 30A and A182 to 1 (Clim). Tried to operate system and got a Stall Fault. Seemed really odd, since it's a centrifugal pump. How could it stall? Anyhoo, Changed parameter to 37A and it worked ok and left. Later, I heard that on occasion it would still trip out on Stall Fault, but what I did seemed to improve things. In the meantime, someone else got into the program, so who knows what's going on there...

Soooo, It's likely that I will get involved again. Hoping some of you fine folks can educate me on what might be going on. Could it be that the VFD drive sensed a great deal of slippage when reducing the hz to limit the current and called it a stall? Maybe a mechanical issue?

 

[petersonra]

I think you can disable the stall fault. There should be a tech note on how to do so.

It happens when the current limiting causes the VFD to not make it to the desired frequency.

It may be that your load is too much for the drive. Perhaps a bad bearing?

 

[zbang]

I was thinking mechanical, too- bearing, maybe it sucked up some debris, that kind of thing.

 

[petersonra]

I was thinking mechanical, too- bearing, maybe it sucked up some debris, that kind of thing.

Get the millwright out to look at the pump and motor. Could be a loose connection causing the shaft not to be inline.

I would not be trying to do anymore attempts to fix the drive until mechanical issues are ruled out. The problem appears to be that load has increased. That is not an electrical issue.

 

[ptonsparky]

Get the millwright out to look at the pump and motor. Could be a loose connection causing the shaft not to be inline.

I would not be trying to do anymore attempts to fix the drive until mechanical issues are ruled out. The problem appears to be that load has increased. That is not an electrical issue.

So many times it’s mechanical, not electrical. VFD or not.

 

[TwoBlocked]

I think you can disable the stall fault. There should be a tech note on how to do so.

It happens when the current limiting causes the VFD to not make it to the desired frequency.

It may be that your load is too much for the drive. Perhaps a bad bearing?

Found Parameter A186 Stall Fault Time, 5 - Flt disabled.

See, they apparently had been operating the system completely manually through an HMI and came up with "magic" Hz numbers for the VFDs. Now it is being operated with a PID after brining up the pressure manually. Both pumps ramp up the hz according to the same setpoint and manipulated value ( Main pump PSI).

If/when I get back out there, I'll try disabling the fault, and then observe the Hz and Amps. I'll use my temp gun to monitor the bearings.

See, I was thinking when setting a current limit, it would accept the reduced Hz as the command speed, not to continue looking at the external command speed for a stall condition. (Current limiting could have (should have?) been done in the PLC.) Of course there is no notation about it when looking at the current limiting parameters...

 

[TwoBlocked]

Oh, it's a Powerflex 400.