# AB Powerflex 700 Ride thru power fail



## gottspeed (Mar 8, 2010)

Hi, I'm trying to set a Powerflex 700 to continue running a motor after a brief power fail (10-20 seconds) so there is time for the generator to start and transfer switch to change to backup power.

I see in the manual on page 43 under 'Power Loss Mode' that you can set the drive to react with Coast, Decel, Continue, Coast Input, etc.

http://literature.rockwellautomation.com/idc/groups/literature/documents/um/20b-um002_-en-p.pdf

I'm concerned that the drive will start from square 1 on a power fail, that is reboot and wait for the user to clear the AC Power Loss fault. Although the PLC is on UPS, the drive won't be. So the PLC will maintain the run command, but I know on some other drives it will show setup mode after power restore.

Anyone know how to handle this?


----------



## JRaef (Mar 23, 2009)

There are other parameters that address this. 168 enables it to Start At Powerup, which means that if the Run command (and all other permissive conditions) are satisfied, and a Restart Delay time (167) is expired, then it will re start automatically. 

You also want to enable the "Flying Start" feature (169), which lets the drive look at the spinning motor, match its output frequency and catch the motor running on the fly. Otherwise, if the drive turns on at zero speed and starts ramping up, but the motor is already faster than that, the first thing that happens is that the motor slows down and/or regenerates

if the power loss is long enough to cause a Fault (185) then you have to decide on whether or not you want it to automatically try to reset the fault and restart, then if yes, how many times to try, how long to wait before retrying etc. etc.

RTFM...


----------



## glen1971 (Oct 10, 2012)

Some of the ones I've worked on where a brief voltage loss is more of a nuisance than it is anything else... Here's what I've changed:
169 - Flying Start - Enabled
184 - Power Loss Mode - Continue
185 - Power Loss Time - 60 seconds
186 - Power Loss Level - 0 vdc

That keeps most of the fans and pumps running through any bumps we've had.. There is one more trick that I used (against AB's recommendation) that has helped a couple of the more remote sites ride through some longer dips, mainly just to have it so an operator doesn't need to drive up and hit a reset to make it start..


----------



## gottspeed (Mar 8, 2010)

Thank you so much for your advice guys, this beats getting out to the plant and ****ing around on their time.

Again, much appreciated.


----------



## KennyW (Aug 31, 2013)

What do you mean wait for the user to clear the fault? You said its on a plc. Presumably the plc

1) knows when you lose non-ups power and/or the status too the genset transfer switch

2) knows the drive is faulted

3) is capable of resetting the drive faults. 

Setting the drives as recommended is good but from a systems perspective my priority would be that that the controlling plc be aware of power losses and genset transfers, and manage these events accordingly. 

Just a slightly different perspective.


----------



## glen1971 (Oct 10, 2012)

KennyW said:


> What do you mean wait for the user to clear the fault? You said its on a plc. Presumably the plc
> 
> 1) knows when you lose non-ups power and/or the status too the genset transfer switch
> 
> ...


None of the VFDs I have been working with are set up for remote fault resets from the PLC... Without having the VFD fault displayed on the PLC/SCADA I don't know that I'd want to be just resetting them blindly.. I would assume that type of programming is in use, but not in the fields I'm working with..


----------



## gottspeed (Mar 8, 2010)

glen1971 said:


> There is one more trick that I used (against AB's recommendation) that has helped a couple of the more remote sites ride through some longer dips, mainly just to have it so an operator doesn't need to drive up and hit a reset to make it start..


What was that one unrecommended trick?


----------



## glen1971 (Oct 10, 2012)

I removed the undervoltage from the fault list on a few locations that usually gets longer outtages (1-3 minutes).. They all restart after a dip, so long as the PLC is still issuing a run command.

Parameter 238, bit #1...


----------

