# AB Powerflex 4



## gnuuser (Jan 13, 2013)

if you want them repaired you have to ship them back.
i replace them often at work on our conveyor systems

if the fan is belt driven you need to set the parameters to ramp up and ramp down speed to prevent belt damage.

if the fan is direct drive you also need to install current clamping circuits to prevent feedback to the vfd if power goes down as it will fry them quickly (this sounds like what happened to yours)


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## varmit (Apr 19, 2009)

If the display is dead on a Pflex 4, throw the drive away, unless it is under warranty, and replace it. These are not repairable. Even if they were repairable, it would not be economical due to the low initial cost of the drive.

If this drive is on a fan, be sure that "stop mode" is set to "coast".


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## eric7379 (Jan 5, 2010)

I run into this all the time. 

Like Varmit said, throw it away and buy a new one. 

I have priced the repair cost of one before, and the cost was about 75% of what a new one would cost. :no::no:

Power Flex 4's are throw away drives.


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## Peewee0413 (Oct 18, 2012)

Check if the fan is bad too. If the fan failed it may have fried your VFD. If it did, think about installing a reactor. Can help sometimes. Like he mentioned, if your setting is ramp to stop it may cause unwanted problems. Has it randomly faulted in the past during shut down? Is it the VFD screen or the remote screen? Good luck....


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## Cow (Jan 16, 2008)

Same as everyone else said, if no display, toss it. It's only a PF4. I usually oversize the drive a little when I use the PF4's. What size are motors on those big ass fans? 5hp? We've done a few of them but I can't remember....


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## Chris Kennedy (Nov 19, 2007)

Couldn't get up to the fan, VFD rated 460V 1hp. Ohmed out the motor leads and got 17.8Ω T1-T2, T2-T3 and T1-T3 so motor appears good.


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## Peewee0413 (Oct 18, 2012)

Was it set to ramp to stop previously?. I have heard it can destroy a VFD.


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## gnuuser (Jan 13, 2013)

it can without clamping or current shunt.
and the reason being that cutting power to a motor results in the collapse of the magnetic field in the stator and like a pickup coil in a small gas engine,
the collapsing field can generate a tremendous surge feeding back through the motor leads.(both stator and rotor)
if you don't have an adequate clamping the feedback will fry the vfd

you wouldn't believe how long it took us to convince our (non electrician) boss:wallbash:


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## Peewee0413 (Oct 18, 2012)

The VFD is equipped with safety, but it can cause damage before it sees the surge.


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## Jlarson (Jun 28, 2009)

I'd get a new one from big ass. Don't go changing their settings or hacking reactors into their panel.


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## JRaef (Mar 23, 2009)

If the PF4 is not even powering up, _*and you are sure it's not just a blown fuse or a tripped CB ahead of it*_, that means the power supply for the electronics is fried and that will mean there is damage to the the entire control board (the power supply is part of the board). The repair cost will be close to or more than the replacement cost as others have said. Just replace it.

As to why it happened? No way to know. But a really common thing that happens on fans like the BAFs is that something about the air flow is making the fans spin backward when they are off, then the VFD is told to run in the Fwd direction. When that happens, it has to first overcome the inertia of the fan's reverse rotation before is can accelerate it to the correct direction, so the VFD goes into overload until that can happen. It should trip out the drive before damage happens, but people sometimes get tired of the nuisance and disable protection features, or if just repeated enough times the damage can be incremental.


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## Jabberwoky (Sep 2, 2012)

I'm curious what the parameter settings for P037 Stop Mode and A096 Flying Mode En were if you have a paper copy of them for that drive.


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## Chris Kennedy (Nov 19, 2007)

Jlarson said:


> I'd get a new one from big ass. Don't go changing their settings or hacking reactors into their panel.


Thats an idea I will pursue, thanks.


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## Peewee0413 (Oct 18, 2012)

JRaef said:


> If the PF4 is not even powering up, and you are sure it's not just a blown fuse or a tripped CB ahead of it, that means the power supply for the electronics is fried and that will mean there is damage to the the entire control board (the power supply is part of the board). The repair cost will be close to or more than the replacement cost as others have said. Just replace it.
> 
> As to why it happened? No way to know. But a really common thing that happens on fans like the BAFs is that something about the air flow is making the fans spin backward when they are off, then the VFD is told to run in the Fwd direction. When that happens, it has to first overcome the inertia of the fan's reverse rotation before is can accelerate it to the correct ......
> 
> Ways around that. Parameter change. "Dc injection prior to startup." Raise ramp rate.


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## gnuuser (Jan 13, 2013)

then these are whats needed to prevent the fans from turning while they are off.
http://www.warnerelectricacmotorbrake.com/


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