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Old April 26th, 2006, 10:30 PM   #1
pid
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Location: ontario
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Exclamation GE drive failed again, it is not cheap!

Hi all,

first we detected 9Amp current in grounding conductor fed to electrical control panel, where did it come from, before we got chance to solve the mystery, now we have another AC drive failed. it is GE AC drive AV300i, mounted on the chassis inside the electrical panel (where 9A is detected from ground cable)

GE AC drives have the power amplifier board mounted on the top of heat sink, that is mounted on the top of chassis.

GE drive is not cheap, and this is the second time the same typies of drive failed. To clarify, here is sequence of event:
-E-stop is trigged
-motor brake (external mechanical brake) is engaged
-motors come to stop
-reset E-stop
-run the cycle from the beginning of step one (no ride through)
-certain drive is inoperable

there is no fault code can be retrived, since the operator panel is blank
,unknown cause indeed, or i am missing some crucial clues that aid diagnosis.

this is the second time the same type of drive failed, inside the same electrical panel(fed with 3 phase, star secondary, ), my feeling is that without identifying the cause of failure, we are set to deal with another drive failure down the road,

I do recognize that drive may leak current if insulation is deterioted, we dozen of drives of AC GE 300i (3-5hp), likely drive is failed by external factors, so what are they?

Does the event of failure occurs at the sudden stop or the drive, or the re-start of drive after the power resume. can we collect clues from damaged power module? has anyone done board level repairing?

I understand there are group of players having profound experience wth troubleshoot drive failure, so come on, what should i do, to prevent another instance of drive failure??

I know lots of you have lots of experience in drive control, please go ahead, let me have it.
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Old April 27th, 2006, 07:02 AM   #2
DickDV
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Location: Kalamazoo MI
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pid, I must say that this sounds strangely similar to a very ugly situation I encountered with small drives last summer. I was lucky tho, only destroyed two drives, the rest kept blowing input fuses.

The key here is that 9 amps in the grounding conductor. You simply have to find out where that is coming from. You said that the panel is supplied from a star secondary transformer which is a good thing as long as the center of the star is grounded.

If you have current flowing in the ground connection to the center of the wye secondary, I think it is safe to conclude that there is leakage current from one or more of the phases to ground somewhere in your system. Note that this leakage is to GROUND, not to NEUTRAL.

Since inverters need to have a ground connection to properly protect the drive output from ground faults, the drive becomes a path for this stray ground current. This current can be higher than the working current of the little drive and destroys the input bridge as it passes thru it. If you check out the failed drives, I would expect to find shorted diodes in the input bridge.

Finding this leakage current path is a classic trouble-shooter's puzzle. It probably is all coming from a one of the three phase conductors and, in a new panel, could very well be a single phase 120V load inadvertently connected phase to ground rather than phase to neutral. Good luck finding it.

I would not blame the drives or search for operating conditions leading to drive failure until I have the ground current issue resolved.

Note that you wouldn't be having this problem if the drives were larger, say 100hp. The leakage current would still be there but the drive's input could handle it without fault or failure.
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Old April 27th, 2006, 08:31 AM   #3
Leadfoot
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I do component repairs on all types of drives both DC and AC. With out knowing exactly what failed in your drive I cannot say for sure where to look for your problem.

DickDV has given you the best way to look for your problems. You will have more failures until you clear the GROUND current.

Is your drive chasis grounded to the supply/building ground?

Is your motor frame grounded to your drive cabinet which should be grounded to your supply/building ground?


First I suggest you measure your input and output voltages to ground with the motor not running and again with the motor running.

FYI,there are numerous repair places that might be able to repair your drive for about 1/2 or less the cost of a new drive. Then you will can get a drive failure analysis from them to help better find the root of your troubles. Even GE repairs them but they have been known to take a long time.
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