Nominal bus voltage for Kinetix 5500 @490VAC ?

Ken Roach

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Anyone out there using Kinetix 5500 drives with a nominal 480V input ?

This should be a basic electricity question, but I don't know what's going on.

I have four of them in the field that are getting 3-phase 490V but the DC bus voltages are showing 750V DC when the drives have precharged and are idle.

I was expecting about 1.44 x 490 = 690 V on the DC bus. My recollection from when we wired these up in our shop is that it was definitely under 700V, but now they're in the field and we're getting bus regulator faults and weird voltages.

So: anyone running these at 480V input who can go look at their DC bus voltage display for me ?
 
Ken
Have you actually measured the source voltage ?
that dos seam high I think the buss loader(Brake Resistor ) turns on at 760 on most systems.
It would look to me like you have a transformer bank that is tapped high I have seen that where they had a large motor load and they taped the transformer high to compensate for the voltage drop and later removed the heavy load and didn't set the taps back
 
Do you have line reactors installed Ken and, if you do, are they 3% or 5%?

Shop transformers are pretty small; in the field transformers are large kVA (>150) and have low impedance (< 3%).

490 VAC line seems a bit high and the K5500 highest accepted DC input voltage (common bus follower) is 747 VDC for 480 VAC nominal input; you are a 'hair' above it.

Had to install or replace 3% line reactors with 5% several times for field supply power issues after passing with flying colors 'in-house'...:D
 
I currently have access to four Kinetix 6500 units (sorry, no 5500's). Verified readings from meter is input ˜493 volts leg to leg, DC bus ˜712 volts. That's "at rest" and the DC bus readings from my Fluke scope essentially match what Studio 5000 gives me.
Don't know if that's of any help...
 
Had an issue with an ABB VFD where the DC bus voltage would jump up and fault out the drive. After many hours on the phone with ABB tech they determined the drive was faulty. Sent a replacement drive and same thing. They are baffled as well as everyone else.

During lunch break everything was running fine, all equipment in the plant was shut down except this new equipment. After lunch when everyone was back to work, I noticed as soon as they fired up a roll form line a hundred feet or so away, the DC bus on the VFD shot up and faulted out the drive.

The problem was a DC induction welder on that line that was never properly isolated. The DC voltage spike in the drive was the same exact voltage the welder was running at.

Needless to say, they didn't want to pay to properly solve the issue and I ended up pulling the drive and installed a line starter.

Their maintenance guy was always wondering why they go thru a lot of AC motors.

After my report, the manufacturer of the new equipment promptly voided the warranty.
 
Thanks for all the input, guys !

I'm dealing with secondhand information on this one, unfortunately. We're running all of these servos as standalone, no DC common bus links. They're physically independent axes that run individually, so there's no benefit to common bus.

Everyone I've talked to says that our shop supply is a delta configuration and so is the customer site, so I expected them to remain the same. The customer is a huge new building so I can see why they are tapped a little high: only a fraction of their loads are online now.

I'm going to go there myself to see how the system is grounded; I agree that this might be an issue with the ground screws still being installed on the Kinetix drives, the more I look at it. You're supposed to disconnect those if you've got an ungrounded delta, but we've supposedly got an ungrounded delta in our shop and didn't have the same problem.
 
This sounds like very dirty power to me. You can read 490VAC and many facilities are that high today but that will not explain the high voltage. somewhere around 700-710 seems right for clean sinewave power. A scope on the power will likely reveal a bunch of noise and pulses riding on top of the AC. Need to get rid of it, better at the source, but, if nothing else, than at the input to the drive with a 5% reactor.

I would definitely recommend checking for floating or corner-grounded power. If present, you must disconnect the CE noise suppression network in the drive. You also will probably need to shut off the output ground fault as you will get nuisance faults with floating power.

If you do have floating power, you can kill two birds with one stone by installing a drive isolation transformer instead of that reactor. Be sure it has a grounded wye secondary. It will fix the floating power issues and act as an excellent noise filter as well.
 
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