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.
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480V VFD problem 2
- Thread starter cherryg
- Start date
Skogsgurra
Electrical
Have a look at
Most manufacturers have that information on their home-pages.
Gunnar Englund
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Half full - Half empty? I don't mind. It's what in it that counts.
Most manufacturers have that information on their home-pages.
Gunnar Englund
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
- Thread starter
- #3
Looking at high labor rates, and time for shipping equipment for testing and installation at site, won't it be more prudent to replace the capacitors right away? Please share your thoughts. One issue may be the certification of the equipment.
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1
- #4
Skogsgurra
Electrical
It all depends on the situation. If you are in an industry with an operational electrical department, the cost for forming the capacitors will be low.
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
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Half full - Half empty? I don't mind. It's what in it that counts.
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
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
And the capacitors you buy may need to be formed...
Keith Cress
kcress -
Keith Cress
kcress -
- Thread starter
- #6
Unfortunately, the LV MCC lineup has been phased out by the manufacturer (though not the VFD itself). We may have to ship the sections to a third party inspecting firm, who can be contracted to reform the capacitors. If these are irreversibly damaged., we may then opt for replacement of the capacitors as a last resort. Rest of the VFD section will need to be checked too.
Skogsgurra
Electrical
480 V - sounds like USA. Where are you?
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
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Half full - Half empty? I don't mind. It's what in it that counts.
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
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
I cannot imagine anyone who has phased out an MCC but not the VFDs inside. The product life cycle of a modern VFD is a fraction of the product life cycle of an MCC.
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"
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"
LionelHutz
Electrical
Depending on the size of the VFD's, it might be cheapest and simplest to just power them up and replace any that fail.
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.
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.
- Thread starter
- #12
waross...this was a newly (then) procured equipment, which was never used. The project was shelved and all the equipment went into preservation.
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................
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................
/hijack Now you have my curiosity up Bill.. What is that place?? Staring at it I can't begin to figure it out. Looks like a sand based oil field? /hijack
Keith Cress
kcress -
Keith Cress
kcress -
If you are in Google Earth, search Tar Island AB. You should see Highway 63 to the west. Find the interchange leading to Tar Island. On the west side of the interchange is the Voyageur site. This was to be an 11 Billion dollar heavy oil up-grader project that was started and then was aborted and finally cancelled. It may not be this site, a number of projects were impacted by the economic slowdown.
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
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
--------------------
"Why not the best?"
Jimmy Carter
Officially, we tell everyone to disconnect the control boards (usually ribbon cables) so that nothing turns on, then apply DC at the rated voltage, ramped up or increased in 4 steps, over at least 2 hours. But for 460V drives it's hard to get hold of a DC power supply that can handle 635VDC (or more if it's a 575V drive). So you can use a Variac applied to two of the AC terminals, but it must be ramped very slowly starting from zero over the course of 4-6 hours, no steps (or many many small steps) because the ripple current (since you essentially do not yet HAVE caps), can damage the caps. I have seen some instructions that just say to use a transformer to drop the AC input in one step for 2 hours, but I would not use that method on something un-powered for more than 2 years. I have seen it kill caps too, ripple current is a killer.Waross said:
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"
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1
- #20
Skogsgurra
Electrical
A much easier way of doing it is to hook up a resistor (can be one or more incandescent lamps) and an overvoltage relay whose "coil" is connected to the DC link (possible via a voltage divider) and whose output contact is wired in series with the resistor and opens when the set voltage is reached.
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
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
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
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
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