Drive power query

[jasonf987]

Hi gents,

We have a number of ABB AC drives in my mill. Having had a recent shut for 4 weeks we are now experiencing a number of drive related problems a few days after starting up
eg: Power Caps blowing, control cards being damaged and needing to be changed etc.

With consistant powering down and then powering up again on the drives will the capacitors take excesive load due to charging & discharging and then cause them to fail?

Should a UPS on the supply reduce the possibility of similar issues reoccuring?

Has anyone experienced similar issues in the past?

 

[DickDV]

This should not be caused by being down for a period of time. I would first check for power surge/quality problems.

 

[davidbeach]

Were they outside their operating environmental requirements when put back into operation? In particular, were temperature and humidity within acceptable bounds? If there were condensation on any of the components during warm up you would have had trouble.

 

[waross]

I agree with David Beach.
In addition, there may be a build up of dust or other contaminants on the boards and caps that attracts a little moisture when cold and then flashes when the power comes on.
Another issue is that after a shutdown, with the plant not running the power tends to be above normal when the drives are energized.
I suspect a combination of all of the above.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[jasonf987]

Thanks all for your replies,

the drives are in a controlled environment, which includes air conditioning, air purification and room pressurization.

We monitored the power quality on start up and there were no surges which occurred, while the supply was within the required range.

 

[controlsdude]

Check phase to phase and phase to ground if caps are blowing and environmental conditions are good. Some manufacturers ground one side of the caps and if your phase to phase floats above a certain level it will blow the caps.

In manuals
Unbalanced or ungrounded distribution systems
If phase to ground voltage exceeds 125% of normal line to line voltage . .......


Either clip the caps off the ground or correct the power unbalance or check your grounding.

Did you have power worked on during the shutdown?

 

[jraef]

A common problem is icing of the capacitors. If at any time during your shutdown the controlled environment was left uncontrolled and it dipped below freezing, it could have caused damage.


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
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[ozmosis]

How old are your drives?
VFD's do not last forever and it is possible coincidence that these are failing now. If they are 10+ years old then maybe it is time for an upgrade.

 

[7anoter4]

I encountered the caps blowing phenomenon a time ago with a harmonics filter supplied by AEG.I think the problem was the resonance. It is possible the system-utility or local VFD or soft start or else-produces voltage harmonics and a resonance may occur.
Our ABB caps were provided with fuses [Is-Limiter] so the blowing was avoided. See:

http://library.abb.com/GLOBAL/SCOT/...71A41257227003849CB/$File/DS Is-Limiter E.pdf

 

[7anoter4]

I a large power station many control cards were damaged- mainly on the entering block. The problem was lightning transients. See:

http://www.lightningsafety.com/nlsi_lhm/lpts.html#bonding

The phenomenon was minimized by correct grounding, employing optocouples and surge suppressors.