9A current inside conductor

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powerelectronic

powerelectronic

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we inherited this system, has problem from day one, please help :!:
situation:
Electrical control panel is fed with 3 ph 3 wires 480Vpp power from transformer, there run L1,L2,L3 and bare conductor, bare conductor is attached to the housing of electrical panel.

Now current is detected read out from bare conductor of 9 Amp, is that normal?

so again:
9A is read out inside transfomer bare conductor inside the electrical panel, there are L1,L2,L3 plus bare conductor feeds the control panel from transformer secondary(star)

Questions:
why 9A in the bare conductor? does it matter? :shock:
what is the proper setup of grounding and bonding between transformer star and electrical panel? :shock:
Are there any guideline governing the threshold for objection current inside electrical control panel? ie. NEC :shock:

Thanks in adv for your input :idea:
 
The system that you are describing sounds a little odd. Is there a Neutral? It sounds like there are multiple Neutral to Ground connections. If the transformer is bonded, then make sure that the first panel has both a Neutral bar and a Ground bar. The Neutral bar must be insulated from the case.

The Neutral can only be connected to the ground at one place, either at the transformer or at the first disconnect. 250.30

Eric Stromberg, P.E.
 
Eric
If the transformer is bonded
Click to expand...
would you please explain what "bonded" means?

Eric
make sure that the first panel has both a Neutral bar and a Ground bar. The Neutral bar must be insulated from the case.
Click to expand...
inside electrical panel, there are L1, L2, L3 bus, there are neither neutral bus nor ground bus, inside panel there are three ph AC drives, and single phase motors inside the electrical panel,

since there is no load from neutral to ground, would you explain that neutral is needed? i guess what is the function of neutral when 3 wires is used?

Please teach me. :arrow:
 
If there are single phase motors inside the panel, then how are they connected if there is no Neutral?

You said this is a 480 Volt system. It would help to see a picture of this. I've never tried to upload pictures to this forum either, so i don't know what's involved. You can email me the pictures at

eric@XXXXXX

Eric

Moderators note. I removed the email address. If you wish to contact Eric please do so by the PM feature of this forum.

Thanks, Bob
 
so i don't know what's involved. You can email me the pictures at
Click to expand...

Done that.

If there are single phase motors inside the panel, then how are they connected if there is no Neutral?
Click to expand...
allow me to clarify....from the L1,2,3 power bus, there are 3 ph motors, then there is one 460/230v transformer
 
situation

situation

transformer1-2.jpg


6 conductors, one bare conductor between transformer and electrical panel,

2 conductor per phase-double the current. not sure what the bare conductor do?

it is 3 phase, 3 wires systems, there is no neutral, but does it require neutral for grounding and bonding?

ultimatly how to remove 9A in conductor?

how to test out to see where the 9A comes from?
 
Hi Eric.
each one contains single conductor, two sets of L1,2,3, feed into each side of control panel, drives on mounted on one side of metal wall, pid controllers are on the othe side of the same metal wall,
bare conductor is attached to the panel, (see pictures for details)

There are 9A current seen from bare cable, why, :?:
in your opinion what is the proper ground and bonding? :?:
 
480 is an extremely deadly working space to be in. In situations where someone can get hurt, for lack of knowlege or experience, it is forum policy and better advice to refer them to those qualified to work with 480.

When a user joins the forum on todays date, or when the person asks "what is the bare wire" or "what is bonding" they certainly are not familiar enough with 480 to be anywhere near the inside of that equipment.

Phase to Ground is the most deadly voltage because more people are exposed to it in their homes, but 480vac is certain to terminate any mistakes. This voltage has killed at a distance, from behind objects, overhead, and under floors.

Because of the late hour, see the timestamp, the forum moderators and most everyone else are sleeping. This is not the normal responses to the Original Post.

The left coast and rest of the world should remember how agitated the other animals get when they smell a DIY (Due-It-YourSelfer).

I've seen how they get riled up, come out swinging and beating on their keyboards like a troop of screaming monkeys. During these hunting parties and angry parades, when someone gets bit, everyone joins in to get their share of fresh meat.

Tomorrow when the animals wake up, and log in to their morning news, it won't be me that gets beat for letting a DIY eat from the table.
 
Thank you for providing words of cautions, as we are interested in searching for answers that could explain what cause the 9A current in bonding cable?

The word "bare conductor" is used to just illustrate the setup, present open-ended question (not assume anything), and inform you with facts. we start our days early. it is up to you evaluate the setup.


any thought will help :arrow:
 
Ramsy,
Good point,
My assumption is that, anyone who is even thinking of getting in a panel like this wouldn't be doing so unless fully qualified.

I await the moderator's decision.

Eric Stromberg, P.E.

(incidently, how does one post a picture to the forum?)
 
hi eric
good morning.
I'm always open to new ideas and correcting those that I have wrong . Great forum for learning and expanding electrical code background.

this is hypothetical question about 9 A current, using real life set up. we will have qualified contractor to work on it,.

picture worthes thousand words, the FAQ provides methods to upload picture, what i did it was to follow the instruction, and spend lots of time (you can tell by the time stamp of the post)to experiment it before getting it up. however the picture takes about 5 sec to appear.
 
eric stromberg said:
I await the moderator's decision.
Click to expand...
If a member's profile states that he or she is an electrician, the Forum Moderators are not going to treat the person as a DIY. We had this discussion in an exchange of private messages a year or two ago. We decided that it was not our place to dig into a member's background, to see if they are "qualified" to do the work concerning which they have posted a question.

If any other member suspects that the OP might be treading into unsafe territory, that the OP might be attempting work that is dangerously beyond their knowledge, skill, and experience, then you may feel free to decline to post an answer, and you may feel free to issue a cautionary statement. But the Moderators are not going to close the thread, unless there is clear evidence that a DIY is masquerading as an electrician in an effort to circumvent the Forum rules. I don't see any such evidence in this thread.
 
eric stromberg said:
(incidently, how does one post a picture to the forum?)
Click to expand...
You must first upload the picture to a publicly accessible web site. I use www.photobucket.com. Once the picture is there, you open the picture from that web site, copy its location from the browser's address block, and paste it into your reply.

If you want to look for other possible web sites for hosting your picture, look at any picture that is posted here. Hit the "quote" button, as though you planned to reply to the other person' comments. You will be able to read the web address of their picture within the quoted text.
 
Chief Charlie b

Thank you for the energizing statement, I respect your decision, fully understand the reasoning behind it as well.

I look forward to exchanging ideas with so many great minds of this professional forum. Allow me to borrow the quote: the road for success is always under contruction.

Regarding the issue of 9A in the conductor, no doubt, this is complex issue. I want to thank Eric, who is making the wave, for giving constructive comment that help me put matter into perspective.
 
AC drive FAILED, it is not cheap

AC drive FAILED, it is not cheap

Proudly to be part of this forum.

With the 9A in ground mystery remains unsolved, 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??

dave
 
Re: AC drive FAILED, it is not cheap

Re: AC drive FAILED, it is not cheap

Do these VFDs have dynamic braking? If not you should probably add it. the energy in the rotating system needs to go somewhere when you trip the estop. if the motor is still rotating, it goes back into the drive. if there is no place to dissipate the energy, it can damage the thyristors.

Many VFDs use the power from the dc bus in the VFD to power the operator panel. If the operator panel is blank that is a sign something is wrong with the power section. Do you have semiconductor fuses in the drive that might have opened?

How is the e-stop wired? Generally it is not the best of ideas to open up the line to the VFD itself. The fastest way to stop a motor in such a circumstance is usually to make the drive brake to a stop on e-stop using max decel. generally you do this by placing a contact from the estop relay in series with the run signal so that on an estop the VFD will brake to a stop (assuming the decel time is set to a reasonably fast setting). If not you may need to do some re-wiring to make the thing go into max decel when the estop trips.

Obviously it is impossible for me to know enough about what you are doing to make a serious recommendation, but it might be worth having a look at some of these ideas.
 
When I look at the picture of the feeder conductors to the panel, the source of the 9A in the bonding conductor jumps out at me.

You have a bare conductor that goes back to the supply transformer, presumably bonded to the enclosure of the transformer and the panel. There are almost certainly _other_ electrically continuous paths between these two enclosures; possibly conduit runs, building steel, really good grounding electrodes, etc. So the bare conductor is almost certainly part of a closed loop.

The supply conductors are in separate conduit runs, so they will have 'loop area' between them, and will produce a considerable magnetic field in the space surrounding them.

That bare conductor is the secondary of an unintentional transformer, a shorted secondary.

As far as diagnosing your drive failures, I do not have enough experience to hazard a guess. The only times that I've had to deal with drive failures have been when our in house power electronics has not been up to snuff and we blew output IGBT devices. Have you confirmed that the supply is actually grounded?

-Jon
 
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