480V VFD problem
480V VFD problem
(OP)
In one of our projects, we have a bunch of 480V VFDs in LV MCCs, which have not been used for the past 6 years. What are the steps required to ensure that these VFDs can be made operational? I understand that there are some issues regarding the DC capacitors. Please advise, if you have experience of a similar situation. Thanks.





RE: 480V VFD problem
Most manufacturers have that information on their home-pages.
Gunnar Englund
www.gke.org
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Half full - Half empty? I don't mind. It's what in it that counts.
RE: 480V VFD problem
RE: 480V VFD problem
If you need to hire people to do the job and send them across the globe, it will cost a lot more.
Replacing the capacitors is not a simple task. Most modern VFDs are compact builds and it is usually a lot easier to reform than change capacitors.
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: 480V VFD problem
Keith Cress
kcress - http://www.flaminsystems.com
RE: 480V VFD problem
RE: 480V VFD problem
There are a few guys available "locally" in other parts of the world that have the equipment and knowledge to do this. It is not rocket science.
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: 480V VFD problem
My point is, if you have an obsolete MCC and the supplier is telling you the VFD is still valid, it's highly likely that it is only a technicality and the VFD is long in the tooth as well, so even if you reform them and re-use them, they will be very very expensive to maintain in short order. Might be worth considering selling it off as surplus and starting fresh with modern product to take advantage of modern options.
"Will work for (the memory of) salami"
RE: 480V VFD problem
Bill
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"Why not the best?"
Jimmy Carter
RE: 480V VFD problem
An alternative you could attempt is trying around a 1500ohm, 500W resistor in series with each phase of the AC source. Temporarily replace the cables between the disconnect and the VFD with these resistors and turn-on power until either the drive DC bus reaches >600VDC or it doesn't charge and is proven to have failed. Almost any electrician could handle doing this.
RE: 480V VFD problem
This isn't by chance in Las Vegas is it?
"Will work for (the memory of) salami"
RE: 480V VFD problem
jraef...this is at FT McMurray..Alberta....
Luckily the equipment vendor is providing us full support on the VFD lineup....the only new fabrication will be the Incomer, since the present MCC had MLO................
RE: 480V VFD problem
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: 480V VFD problem
"Will work for (the memory of) salami"
RE: 480V VFD problem
Can you give us a description of your reforming procedure?
Thanks.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: 480V VFD problem
Keith Cress
kcress - http://www.flaminsystems.com
RE: 480V VFD problem
While you're there, go 5.8 miles North-West of Tar Island and zoom in on Mildred Lake. Zoom in close until you see four photo icons just west near the highway. Three of the icons have photos of the old red/orange drag-line. I was on the commissioning crew when drag-line was brand new and started for the first time back in the '70s. The machine was supplied with a 25,000 Volt trailing cable. Four 3000 HP motors drove the 20 large DC generators that supplied the motors.
The bucket was around 80 yards and hung from a 400 foot long boom that reached 212 feet in the air.
The motor line-up was 10 x 1050 HP DC motors and 10 x 1300 HP DC motors.
It was an awesome sight when the factory tech made a mistake and eight of those generators flashed over with a "ring of fire" around the commutator.
Bill
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"Why not the best?"
Jimmy Carter
RE: 480V VFD problem
Mildred lake is the Syncrude base-plant site.
Bill
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"Why not the best?"
Jimmy Carter
RE: 480V VFD problem
If you have access to the Rockwell Knowledge Base (or are willing to register for free) it is in article 18015, at least the part about the DC. The AC option is from my previous experience / mistakes...
"Will work for (the memory of) salami"
RE: 480V VFD problem
The resistor will limit current (both direct current and ripple current, so no sweat) and the voltage will grow slowly (RC time constant) until the contact opens. Start with the relay set to 30-40%, then increase to 60-70% after a few hours and finally increase the setting to full DC link voltage and let the system stay there for a few hours. The capacitors will discharge when the relay opens. The relay then closes and cycles on/off to keep capacitor voltage fairly constant.
The beauty with this method is that you are alway current limiting and that not much bad can happen. Also, if there is a bad capacitor, you will notice that the relay doesn't operate at all. And, best of all, you can go fishing while you are waiting for the process to finish!
This Resistor/Relay method was built inte all of the earlier Siemens VFDs. They later used an SCR bridge+resistor and now, I don't know how it is made.
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: 480V VFD problem
However before you power up ensure that the insides of the VFDs are thoroughly cleaned .Clear all residual dust or moisture inside . Otherwise some of the control cards are likely to fail. Also for the capacitors, initially you can raise the voltage gradually through a 3-phase variac.
There is no way to check whether the VFDs shall be operational or not without powering it up. Once it is powered up, if any problem persists, you would get to see the error codes and you'll have to act accordingly as per the OEM troubleshooting chart.