# Powerflex 700 and a Generator



## Introyble (Jul 10, 2010)

My first thought and correct me here at any point


Powerflex 700 is AC drive

Second thought ~ Must be an AC motor

Third thought ~ Maybe the AC motor is also a generator???

Fourth thought ~ those smart people at AB figured out that AC drives and motors regenerate their own power usage?????


Fifth thought ~ must be a drive that captures its own power consumption

AKA Regenerative Drive???????


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## Introyble (Jul 10, 2010)

Oh, btw, :laughing:

Yes AC drives have a DC bus or DC link.


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## JRaef (Mar 23, 2009)

glen1971 said:


> Have a group of Powerflex 700 drives that were recently replaced with Powerflex 700 drives as part of an MCC repalcement and now when the system transfers to the generator, the motors won't continue running...
> 
> One thing I did notice was when the generator took the load, the drive DC voltage spiked to just over 700... They are on a 480 volt system, and normal DC was around 670...
> 
> ...


Yes, the drive will regen for a moment or two, but 700VDC is not yet even close to the DC Bus Over Voltage trip threshold of the drive, which is 850VDC.

I take it from the lack of mentioning it, the drive is not displaying a fault then? if so, then most likely whatever is giving the VFD a run command is dropping out. That would also explain the DC bus spike, because you likely have it set to decel on a stop command, and as far as it knows, it is getting a stop command.

Check that first, sometimes it's the easy things.


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## JRaef (Mar 23, 2009)

Introyble said:


> My first thought and correct me here at any point
> 
> 
> Powerflex 700 is AC drive
> ...


No the PF700 is not a regen drive, it will not pump the power back into the line. All drives are capable of keeping an induction motor excited and allowing regen, that's what we call Dynamic Braking. But the energy has to be dumped off into a resistor bank, or back into the motor (as heat). There are drives that CAN pump the kinetic energy back into the line, but they are essentially two drives back-to-back and therefore twice as expensive so you REALLY have to want it. But the PF700 is not one of them.


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## Introyble (Jul 10, 2010)

JRaef said:


> No the PF700 is not a regen drive, it will not pump the power back into the line. All drives are capable of keeping an induction motor excited and allowing regen, that's what we call Dynamic Braking. But the energy has to be dumped off into a resistor bank, or back into the motor (as heat). There are drives that CAN pump the kinetic energy back into the line, but they are essentially two drives back-to-back and therefore twice as expensive so you REALLY have to want it. But the PF700 is not one of them.


I'll take your word on that. I wasn't certain if the 700 was a regen..... Sounded like it should be :laughing: Yes, thank you, I understand how a brake works.


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## glen1971 (Oct 10, 2012)

JRaef said:


> Yes, the drive will regen for a moment or two, but 700VDC is not yet even close to the DC Bus Over Voltage trip threshold of the drive, which is 850VDC.
> 
> I take it from the lack of mentioning it, the drive is not displaying a fault then? if so, then most likely whatever is giving the VFD a run command is dropping out. That would also explain the DC bus spike, because you likely have it set to decel on a stop command, and as far as it knows, it is getting a stop command.
> 
> Check that first, sometimes it's the easy things.


 
No it wasn't displaying the faults.. The system was working before and I had all the parameters set up to work.. They had someone else change the MCCs and VFDs out and now they don't like to restart with a transfer of power to the generator. They had their electrician looking into it, and couldn't figure it out.. 
I don't think that the start command is dropping out, as the PLC didn't change... Cycling the 480 volt power at the VFD or cycling the On/Off in the field will restart the drive to whatever speed the PLC is telling it to...
Thanks for your help!


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## Jabberwoky (Sep 2, 2012)

Because there are no faults you'll have to check what JRaef asked. Verify your start/stop command and check your speed command. Does cycling the 480V effect the control circuit or is it just line power for the drives?


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## Cow (Jan 16, 2008)

Did someone install a phase fail relay that monitors facility power?

Does the PLC stay powered up during a power transfer? UPS?


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## glen1971 (Oct 10, 2012)

Jabberwoky said:


> Because there are no faults you'll have to check what JRaef asked. Verify your start/stop command and check your speed command. Does cycling the 480V effect the control circuit or is it just line power for the drives?


It would cycle the control power in the circuit, as there is a 480-120 control xfmr on each drive...PLC is still calling for them to run via an interposing relay in the PLC. Switches are all ON/OFF, not pushbutton start/stops...

I'm gonna try and get there next week and do some looking and check into it more for myself.. I find it odd that they worked before and now not after they go to emergency power..Guessing a wiring problem, or there is one or more parameter that was missed...


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## glen1971 (Oct 10, 2012)

Cow said:


> Did someone install a phase fail relay that monitors facility power?


There has always been one in place.. On the old system, it was an Omron relay.. I am assuming they are taking it off the transfer switch somewhere.. 

The problem comes whenever the system switches to generator.. Whether it is due to a utility loss or to performing a test...


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## JRaef (Mar 23, 2009)

Check parameter 168, which is the Auto Re-Start function. If it is left in the default state of Disabled, it will not resume operation if the Run command is left on after a power loss until the Run command is opened and re-closed. Enabling that means it will not require that cycling of the run command. Could be that the old system had that enabled but not recorded, then when the new ones were installed and someone followed the recorded settings, they left it disabled. That sort of thing happens a lot.

Also check that you don't have a Restart Delay time programmed into 167.


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## Tsmil (Jul 17, 2011)

I wish the AB tech reps in my area were as knowledgable as you seem to be, JReaf. It's for that very reason we don't use AB unless specified by the customer.


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## Jabberwoky (Sep 2, 2012)

JRaef said:


> Check parameter 168, which is the Auto Re-Start function. If it is left in the default state of Disabled, it will not resume operation if the Run command is left on after a power loss until the Run command is opened and re-closed. Enabling that means it will not require that cycling of the run command. Could be that the old system had that enabled but not recorded, then when the new ones were installed and someone followed the recorded settings, they left it disabled. That sort of thing happens a lot.
> 
> Also check that you don't have a Restart Delay time programmed into 167.





> Cycling the 480 volt power at the VFD or cycling the On/Off in the field will restart the drive to whatever speed the PLC is telling it to...


It sounded to me like the auto restart was working when he cycled 480V. I guess that depends on which powers up first the drive or the control.


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## John Valdes (May 17, 2007)

Tsmil said:


> I wish the AB tech reps in my area were as knowledgable as you seem to be, JReaf. It's for that very reason we don't use AB unless specified by the customer.


Seems to be the same case here also.
I know of exactly one guy that is the expert on AB drives. For all of Upstate SC.
Maybe it has something to do with the vendors/distributors for AB.
Here in Upstate SC, you can only deal with Graybar and a couple other supply houses for AB products.

A supply house does not seem to be the best home for AB (frankly any power transmission supplies) and its products.
On the other hand, supplying/stocking distributors for other brands seem to have more technically knowledgeable people than supply house do.

Just because they carry AB products for industry, does not mean they can actually help you with any technical issue locally.

Motor/Drive/Gearing shops and PT houses employ people that actually know the products, go to the training and work with the products everyday.
The guy that sells you operator interface (PB's etc.....) is usually not my first choice when I need manufacturer help or support.

I have been out of this business for a few years now, so Jareaf might have more info in this regard.
In particular, who and how do you pick your distributors?


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## Tsmil (Jul 17, 2011)

No options here. Only 1 authorized distributor. Their rep is ok for most but for real trouble they bring in someone from Rockwell. Even then we are still crossing our fingers. 
We have a powerflex 700, 100hp. Replace it every year. Little while ago went through 3 in 3 months. No reason found.


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## JRaef (Mar 23, 2009)

Rockwell actually has a very strict policy when it comes to the quality and capabilities of authorized distributors. And yes, Rockwell Automation (A-B) is the only remaining major mfr that has a strict policy of "Exclusive APR" for their distributors, *A*rea of *P*rimary *R*esponsibility. So in any given market area, there can be only one. Legally they cannot stop someone else from bring it in the back door from an authorized branch somewhere else, but those selling outside of their APR are not given any factory support. Unfortunately there are companies out there that CLAIM they are A-B distributors because they can back door any part number you give them or buy through the grey market for surplus parts, but they get no training, no support no return policy etc. from RA. It's something that RA cannot stop without restricting trade, but unfortunately it is the local customer that suffers. Sorry about that.

That said, once a company already HAS the line, it is a very arduous process of changing. So when a company that was once good enough to land the A-B line starts to flounder, it can take years to go through the legal process of firing them and giving their business to a better distributor. Then sometimes in a downturn of the economy, there IS NO better distributor in an area and the RA people have to work with what they have. We have that situation going on in our area right now.

But all authorized RA distributors are required to have a trained and qualified VFD specialist, a PLC specilaist, a Motion Specialist, a Component Specialist, an MCC Specialist and a Services Specialist, and they are NOT supposed to be the same person. The VFD, PLC, Motion and MCC Specialists are required to attend training 4 times per year, 2 at the factory and 2 locally. So it's distressing to hear that some people are getting poor service from them, someone is slacking off, or it might be the issue I mentioned above, tenure...

Gaybar, by the way, is as far as I know not an authorized RA distributor anywhere in the US. There are a few locations that, because of what are called "integrated supply" contracts with major national industrial companies, are stocking A-B components that their IS companies need, so they often claim they are A-B distributors. But it is not an authorized direct relationship with RA, they actually are required to buy their parts from the authorized A-B distributor in that APR.

So maybe this is a little TMI / behind the scenes stuff, but it bothers me when I hear people are getting bad service. When I was on the other side, I would have felt like you do. I expect the best when I buy premium.


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## glen1971 (Oct 10, 2012)

*Got it figured out...*

Thanx for all the replies.. 

They tagged me up with a Rockwell guy today and we got it figured out.. There was a few issues... 
All the VFDs weren't configured the same.... Power Loss Level/Times/Action.. Restart on Power Up...

Then we extended the Transfer Time on the Generator from 3 seconds to 10 seconds to allow the HMIs to fully power down.. We had to set 184 to Continue to help the drives disipate the DC Bus Voltage quicker (VFD regeneration).. While doing our tests, we had one drive go down on Undervoltage and one on Overvoltage, so we changed the Auto Restart Tries to 2 and the time to 5 seconds...

Apparrently they have heard of this happening a few times before.. Hope this helps someone else...


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## JRaef (Mar 23, 2009)

Thanks for the follow through!

I'm putting that one "in the vault" for future reference... inch:


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