PowerFlex 700

[bryan372002 0]

Had a AB PowerFlex 700 blow up on me. checked all wiring, megged the moter. any Ideas what could cause this and is common ? I have had the same happen with a toshiba drive for no apparent reason

[Ken Moore 23]

Incoming line surge. Do you have reactors or isolation transformers upstream of the drive?

[Ken Roach 194]

I agree, drive failures are not always apparent. The handful of drives I'd had fail in an energetic fashion were polite enough to do so immediately after I or the user made an obvious mistake. These included, but are not limited to, shorting the DC bus terminals and powering up the drive with the MOV jumpers mis-installed. The questions Tech Support is going to ask you include: Did the drive fail the first time it was powered up ? Did it fail on powerup, or during operation ? Is the power distribution system a high-resistance ground, ungrounded, or B-phase grounded system ? If so, were the User Manual directions regarding MOV and capacitor jumpers followed ? Is the drive installed in a high-humidity environment ? Any corrosive gases or dusts in the atmosphere ? Did you run a megohmmeter test with the drive connected to the motor ? That will almost always damage a drive. Rockwell Automation may be able to offer you a failure analysis of the drive. It won't be able to say "at 11:41 AM a voltage spike of 860 VAC was applied for 66 milliseconds" but it will be able to tell you which components failed and what was likely to cause those failures.

[JeffKiper 9]

We have some of the sharpest mind around that I have ever had the pleasure of talking, or communicating with. Close to what the same question. Has anyon else noticed tha when a DC SCR fails it only takes out the SCR, replace it and you are on the move again. Now lets shift gears to a AC drive, when it has a TRIAC fail it takes out multiple boards. Is this just me or have others noticed this as well? Sorry I don't intend on High jacking this thread.

[OkiePC 14]

My first install of a PF700 resulted in an immediate explosion. Luckily, the feeder CB was ten feet away. I had inadvertently connected input power to the output terminals. That one was hard to explain to the boss... Makes me think though, that extreme regeneration might be another possible cause? Edited 10 Sep 2008 by OkiePC

[Kiwi Nate 0]

We had 3 PF go in a week. Same machine, same motor. Luckily for us it was all arranged through the drive distributor, we were just the poor old customer. They put it down to the line contactor always switching on and off as the operators started and stopping the machine. From memory, we changed it so that once we had zero speed on the motor, we then switched off the line contactor. Never had a problem since.

[BigDave 0]

What type of power system do you have. Is your 480 a grounded system or ungrounded? There is MOV's on the Powerflex 700 drives, if your system is ungrounded you want to remove the jumpers. The powerflex manual will show you were these jumpers are at. If these jumpers are not removed and the nominal line-to-line voltage exceeds 125% it will cause the VFD to "Blow up". This doesn't happen right away you need the nominal voltage to exceed 125% because of this you could run for awhile thinking you are ok than all of a sudden boom. If your system is grounded and the jumpers are there the only things I can think of that would cause the VFD to blow up is what has already been stated, line or load contactor dropping out while the vfd is still outputing power and wiring the line to the output terminals.

[TimWilborne 108]

One thing that hasn't been mentioned, besides the line reactors, is circuit protection. As convenient as a circuit breaker is, it does not provide adequate protection for most drive as they can allow a tremendous amount of energy through while they mechanically react. Almost all drives require current limiting fuses.

[bryan372002 0]

Thanks for all the input Guys. still not sure what happened. It is a 480v grounded system with surge protectors on the incoming power for the main cabinet of this machine. we have still however lost various components due to stom surges, and the grounding is good as far as i can tell. far as contactors being turned off while load is present, while it is not impossible I would say it is unlikely. I checked everything I have the correct equipment to check with, replaced the drive and has been running with no problems for weeks. I sent the drive out for repair so maybe i'll get a failure report.

[BobLfoot 301]

Please post back if the failure report sheds any light. We can all learn from something like this.

[jstolaruk 9]

As Ken mentioned, line reactors on the drive input would be a good investment. Standard with any VFD design/installation I do now.