# 11kw ABB drive giving short cct fault



## Safari (Jul 9, 2013)

So am called by an operator.he says he was making his machine on.then he just saw sparks. I find the mpcb in trip position.I measure resistance between phases for the drive input I get 
Resistance (2 ohms).I try to follow up this cct.I find The drive input has the same supply with a three phase transformer.I disconnect the TX.I power up the drive now it has permanent error of short cct.

Apparently 3 days ago it had that same error as per the report.the guys then did a reset on it.they didn't find any short cct

We get Another drive fix it up.return the TX connections now ok.as I leave work I remember I shouldn't have put the TX Connections back.I call a colleuge at work.I tell him that connection could have destroyed that drive.he should remove it.he says that cant be the reason.the drive is 6months old. I fear the next one is on its way.the connection is as shown in the diagram below.

I need the theory behind my reasoning.I think the harmonics from the TX caused all that.is that so?
Btwn
Some person did this wiring.planning to change it tommorrow when I get back to work . Any ideas as the cause of the fault ?


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## JRaef (Mar 23, 2009)

nickson said:


> So am called by an operator.he says he was making his machine on.then he just saw sparks. I find the mpcb in trip position.I measure resistance between phases for the drive input I get
> Resistance (2 ohms).I try to follow up this cct.I find The drive input has the same supply with a three phase transformer.I disconnect the TX.I power up the drive now it has permanent error of short cct.
> 
> Apparently 3 days ago it had that same error as per the report.the guys then did a reset on it.they didn't find any short cct
> ...


Not sure what ABB means by short cct, but that usually means one of the output transistors has failed. If so, it would have nothing to do with that transformer sharing the line side connections with the drive input. Output transistor failures are usually related to heat, an excessive load spike, or regeneration, in that order of likelihood. If the VFD and TX are in the same box, and being that you are near the equator, heat would be my first guess.


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## niteshift (Nov 21, 2007)

Swapping the drive was the right thing to do.
Agreed heat would be my guess too.
ABB drives like/need to be in an air conditioned room.


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## Safari (Jul 9, 2013)

JRaef said:


> Not sure what ABB means by short cct, but that usually means one of the output transistors has failed. If so, it would have nothing to do with that transformer sharing the line side connections with the drive input. Output transistor failures are usually related to heat, an excessive load spike, or regeneration, in that order of likelihood. If the VFD and TX are in the same box, and being that you are near the equator, heat would be my first guess.


Thanks jraef.
The TX is in another panel.it actually feeds an NC press servo feeder.

The panel with drive yes doesn't have a cooling fan apart from the drive inbuilt fan.

Now the drive is 11kw but the motor in use is 5.5kw
Btwn
It's short circuit fault 4


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## Safari (Jul 9, 2013)

I need to quickly add that one of the technicians admitted to reseting the mpcb the first time it tripped. And it sparked at the drive input side.so when I went I didnt get any short apart from reading the TX winding resistances in the drive input side


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## Safari (Jul 9, 2013)

niteshift said:


> Swapping the drive was the right thing to do.
> Agreed heat would be my guess too.
> ABB drives like/need to be in an air conditioned room.


The problem is I feel I haven't found the root cause. And I just installed another drive


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## niteshift (Nov 21, 2007)

When our tech's have to swap out one of the ABB drives, they have to do a "motor I.D. check" which has to do with programing, when installing a new or used drive, don't know if this applies to your drives.


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## JRaef (Mar 23, 2009)

Nickson,
Fault 004 definitely means that there was / is a short on the LOAD side of the drive. Generally, the VFD will trip itself off-line to try to prevent additional damage. But if the fault happens INSIDE of the output components of the drive itself, its ability to control and/or contain that damage is at the same time compromised. So the first time it faulted with that indication, it was trying to prevent further damage, but when he reset it after that, it failed more catastrophically, which, if the transistor was shorting to ground, would get to where the rectifier diodes likely shorted after the second hit, and it tripped the breaker.

In short (pun intended), the drive had an internal meltdown of some sort, it was not going to be related to the transformer being connected or not. Your new drive may eventually suffer the same fate if there is an environmental issue that lead to the first failure, so I would look into it very carefully.


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## DriveGuru (Jul 29, 2012)

I agree with everything JRaef has told you. I would additionally check the motor connections, all it takes is a pinhole against thin tape, you may not visually see evidence of an arc. Also megger the motor and leads, the drive has ground fault protection but it is possible to bypass this protection in group 30. If it is, the next trip to catch it would be Overcurrent, which is current exceeding 300%. The drive being oversized will only help with heat dissipation and possible regeneration. What model is it ACS800 or ACS550? There are some "actual" parameters that can help determine wether you had an IGBT failure , a Gating circuit failure, or both, may even tell you which phase. Short circuit definitely refers to an inverter section failure. Please note that Overcurrent and Short circuit are two entirely separate trips, and are telling you different things.


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## micromind (Aug 11, 2007)

If you megger the motor, disconnect it from the VFD first. Applying megger voltage to the output of a VFD will ruin it quickly.


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## Safari (Jul 9, 2013)

micromind said:


> If you megger the motor, disconnect it from the VFD first. Applying megger voltage to the output of a VFD will ruin it quickly.


Yes I did that. Megger value turned out fine (infinity).motor cable was also meggered turned out ok.


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## Safari (Jul 9, 2013)

DriveGuru said:


> I agree with everything JRaef has told you. I would additionally check the motor connections, all it takes is a pinhole against thin tape, you may not visually see evidence of an arc. Also megger the motor and leads, the drive has ground fault protection but it is possible to bypass this protection in group 30. If it is, the next trip to catch it would be Overcurrent, which is current exceeding 300%. The drive being oversized will only help with heat dissipation and possible regeneration. What model is it ACS800 or ACS550? There are some "actual" parameters that can help determine wether you had an IGBT failure , a Gating circuit failure, or both, may even tell you which phase. Short circuit definitely refers to an inverter section failure. Please note that Overcurrent and Short circuit are two entirely separate trips, and are telling you different things.


The drive is ACS355 I've checked all the parameters in group 30 
3017 earth fault is enabled
3005 motor Therm protection is set to FAULT 

Did megger the motor and the cable turned out fine.


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## Safari (Jul 9, 2013)

niteshift said:


> When our tech's have to swap out one of the ABB drives, they have to do a "motor I.D. check" which has to do with programing, when installing a new or used drive, don't know if this applies to your drives.


Yes we check the motor winding and insulation resistance. Also do the programming. I
Don't know if this is what you meant if not please elaborate. Thanks.


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## DriveGuru (Jul 29, 2012)

nickson said:


> The drive is ACS355 I've checked all the parameters in group 30 3017 earth fault is enabled 3005 motor Therm protection is set to FAULT Did megger the motor and the cable turned out fine.


If the output is clear of shorts, the root cause is most likely temperature related, voltage related or age. I would double check the current limit in group 20. Make sure the drive isn't running into overload(unlikely the way it's sized)(during Acceleration as well). If current goes above the drives rating duty cycle has to be taken into consideration. Also make sure the drive isn't regenerating(watch the buss voltage in actuals while its decelerating(also unlikely due to sizing). Is there by chance a contactor or disconnect between the drive and motor? How long is the cable run to the motor? What is the age of the drive? If you don't know the age what is the serial number? What is the ambient temperature of the enclosure it's mounted in? If you open up the 355, there should be MOV's tied across the input, If you had an over voltage on the input these will more than likely be in pieces. Plus since you were able to get to a point to start it and then trip, that also means the input bridge was good and the buss was charged. Many times if an output semi shorts, the next time power is applied you blow the precharge circuit, and subsequently the input bridge.


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## Safari (Jul 9, 2013)

DriveGuru said:


> If the output is clear of shorts, the root cause is most likely temperature related, voltage related or age. I would double check the current limit in group 20. Make sure the drive isn't running into overload(unlikely the way it's sized)(during Acceleration as well). If current goes above the drives rating duty cycle has to be taken into consideration. Also make sure the drive isn't regenerating(watch the buss voltage in actuals while its decelerating(also unlikely due to sizing). Is there by chance a contactor or disconnect between the drive and motor? How long is the cable run to the motor? What is the age of the drive? If you don't know the age what is the serial number? What is the ambient temperature of the enclosure it's mounted in? If you open up the 355, there should be MOV's tied across the input, If you had an over voltage on the input these will more than likely be in pieces. Plus since you were able to get to a point to start it and then trip, that also means the input bridge was good and the buss was charged. Many times if an output semi shorts, the next time power is applied you blow the precharge circuit, and subsequently the input bridge.


The motor is rated 10.9A.I have set the Max current limit at 19A 

I watched the bus voltage during decelarating. It still remains at 556v .doesn't change much 

Fuses are installed at the input side of the drive.output goes directly to the motor

The cable to the motor is 4meters.

I have the serial number of the drive just see the pic.can you get year of manufacture from that?

Ambient temp is 33 'Celsius.inside the enclosure is 38'Celsius


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## Safari (Jul 9, 2013)

Just remembered the Torque values were 300% Max and -300% min.these are default values.


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## niteshift (Nov 21, 2007)

nickson said:


> Yes we check the motor winding and insulation resistance. Also do the programming. I
> Don't know if this is what you meant if not please elaborate. Thanks.


The "motor I.D." probably does not pertain to your application, for multiple drives running synchonously.
The drives do like/need a steadystate incoming voltage, such as a Reactor provides for, like this, but sized for your needs.


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## DriveGuru (Jul 29, 2012)

nickson said:


> The motor is rated 10.9A.I have set the Max current limit at 19A I watched the bus voltage during decelarating. It still remains at 556v .doesn't change much Fuses are installed at the input side of the drive.output goes directly to the motor The cable to the motor is 4meters. I have the serial number of the drive just see the pic.can you get year of manufacture from that? Ambient temp is 33 'Celsius.inside the enclosure is 38'Celsius


Personally I like to set my current limit at nameplate current if the application allows, but if you're not exceeding the ratings it's a mute point. From my experience the current limit doesn't work as well on that model as it does on the 550 or 800, but there is also a considerable price difference on those drives. That buss voltage is pretty low compared to what I'm used to, you must be running close to 400v on the input, that drive is rated for a 650v nominal buss, so again you should be ok there. I read that someone mentioned line reactors, these offer minimal input protection to the drive itself, they will limit capacitor inrush current a little bit due to input voltage fluctuation, but their main purpose Is to stop the drives high frequency noise from getting back to your incoming and effecting other equipment. Cable length is good, so you shouldn't be running into trouble with reflected wave phenomena. Temperature is border line, the drive is rated at 104 degF. , I would consider installing a fan to exhaust heat from the cabinet, or better yet adding air conditioning. The drives serial number puts it built in the 43rd week of 2013, so your local ABB rep may be able to get it replaced under warranty, hurry though time is ticking. I hope this helps.


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## JRaef (Mar 23, 2009)

Well from the sounds of it you have done a relatively thorough check of the system to eliminate outside issues, which might leave only one remaining cause, bad luck. You got a bad drive. It's unusual, but it happens. 

But lets not completely rule out environment just yet. 38C is right on the ragged edge of acceptability were it not for the fact that your drive is over sized, which would be the correct strategy to compensate for that. So I agree it does not appear to be temperature at first look. But could it have BEEN hotter at some point? For a transistor failure to take place, it only has to overheat once and for a very short time, as in minutes or even less, depending on how hot it got. I recently did some trouble shooting on a system with multiple drive failures, all in the same 3 boxes. Factory failure analysis all showed thermal damage, yet all of the boxes were air conditioned, with the AC units showing 70F as the temperature setting. But I installed some thermal indicator stickers that permanently change color when heated, they came back showing that the internal temperature got to 128F (over 50C) at some point during the month I had them in there. Turned out that the operators were opening the doors to look at things inside multiple times per shift. When they did, the AC power was cut, but the power to the drives was not. So the box was filling with hot summer (110F) air when the doors were open, the drives were still running, then it would take a few minutes for the AC unit to cool it down again when the doors were closed. That period of time was letting the internal temp get to well above the drives max rating. I'm not suggesting yours it the same, but just that a single observation of temperature is not always going to eliminate that possibility.

Also, what about humidity? Drives can't take more than 95% and non-condensing. High humidity, followed by a drop in temperature, makes warm metal surfaces, such as heat sinks, condense the moisture, which can get to the power deveicesvand short them out internally.


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## Safari (Jul 9, 2013)

Yes jraef can't rule out temp.temperatures go high in the afternoons.I took those temp readings around 10am.so there is a possiblity that temp was the main cause....


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## Safari (Jul 9, 2013)

Just to give an update on the drive. I managed to ask the first technician who attended to the drive 3days before failure.

He says he got an earth fault alarm on the drive.used the meter to be sure that it was so and indeed found continuity between phase and earth. What he did surprised me he said he disconnected the earth cable so there was no earth and allowed the machine to operate.

He then instructed the lady who was coming in the morning shift to find an alternative cable and replace.

Apparently the lady on finding the machine was operational didn't bother to do anything. 

If I ever explain this to the boss they both will loose this job.

Atleast I can talk to the guy and let him know the mistake he did.

But the she is very rude. She won't listen.

Atleast thats how the drive failed.


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## JRaef (Mar 23, 2009)

Yes, that will do it for sure. All he did by removing the ground connection was to remove the ability for the protection circuit to see it and prevent further damage. That created a VERY dangerous situation in that if your ground fault was high resistance, and someone came along and touched the machine while providing a lower resistance to ground, they could have been severely injured or killed. He was lucky. Not replacing the cable may not have been the actual cause of the failure only in that the damage to the transistors may have already been done by then, but it continued that severe safety risk.

They both owe you their livelihoods, but make sure it never gets out that you knew what they had done and didn't report it, some management types might want to make an example out of you too.


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## DriveGuru (Jul 29, 2012)

Wow...very very lucky. If you had an ACS550 or an 800, they actually measure the ground resistance before allowing the IGBT's to fire(if the protection is enabled in group 30). I don't believe the 355 has that circuitry, just a ct wrapped around all 3 leads sensing ground fault current, so once you fire once there is short circuit current. The rest is exactly as JRaef explained. Again...wow


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## Safari (Jul 9, 2013)

JRaef said:


> Yes, that will do it for sure. All he did by removing the ground connection was to remove the ability for the protection circuit to see it and prevent further damage. That created a VERY dangerous situation in that if your ground fault was high resistance, and someone came along and touched the machine while providing a lower resistance to ground, they could have been severely injured or killed. He was lucky. Not replacing the cable may not have been the actual cause of the failure only in that the damage to the transistors may have already been done by then, but it continued that severe safety risk.
> 
> They both owe you their livelihoods, but make sure it never gets out that you knew what they had done and didn't report it, some management types might want to make an example out of you too.


Somehow iam happy I got to know the root cause.atleast I can rest knowing it was purely negligence.the guy is fresh from school so the one who allowed him to work shifts is to blame.

He even wrote a report on what he did and somehow it was never read. But he is lucky that report book is already filled up and now we have another book.

Jraef atleast he wrote a report
If they didnt read it then am not to blame.......


Thank-you for your input all through

Its now 0144hrs here .am in nyt shift

Let me get back to work


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## Safari (Jul 9, 2013)

DriveGuru said:


> Wow...very very lucky. If you had an ACS550 or an 800, they actually measure the ground resistance before allowing the IGBT's to fire(if the protection is enabled in group 30). I don't believe the 355 has that circuitry, just a ct wrapped around all 3 leads sensing ground fault current, so once you fire once there is short circuit current. The rest is exactly as JRaef explained. Again...wow


Yes "wow" I know.  it could have been avoided.fresh from school he is.

I will let him read all these posts.


Thanks too for your input drive guru. 

Hey one thing
How do you determine the year and date of manufacture from the serial number?


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## DriveGuru (Jul 29, 2012)

The first digit is the factory code where it was built, next 2 are the year, next 2 are week, numbers after that represent build number for example 4523rd drive built that week.


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## Zana (Jul 25, 2014)

If you're getting a short circuit fault, you most likely would need to replace an actual circuit board in the drive to correct the issue. Which is why most people just swap out drives. If it was an ABB ACS800, then you could have changed out the motor side converter card and fixed the issue. However, as someone who has done that many many times, it's a real pain in the ass. Not to mention the individual converter cards cost about $1200 a piece on that model.


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## Zana (Jul 25, 2014)

nickson said:


> Just to give an update on the drive. I managed to ask the first technician who attended to the drive 3days before failure.
> 
> He says he got an earth fault alarm on the drive.used the meter to be sure that it was so and indeed found continuity between phase and earth. What he did surprised me he said he disconnected the earth cable so there was no earth and allowed the machine to operate.
> 
> ...


Wow, what the hell. lol...earth fault is easy to fix, too. The guy who did that should be educated or fired.


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## Safari (Jul 9, 2013)

Zana said:


> Wow, what the hell. lol...earth fault is easy to fix, too. The guy who did that should be educated or fired.


Educated.

For some reasons haven't met him since that incident. We are on parallel shifts.but tommorrow afternoon I should be able to get him.


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## DriveGuru (Jul 29, 2012)

Zana said:


> If you're getting a short circuit fault, you most likely would need to replace an actual circuit board in the drive to correct the issue. Which is why most people just swap out drives. If it was an ABB ACS800, then you could have changed out the motor side converter card and fixed the issue. However, as someone who has done that many many times, it's a real pain in the ass. Not to mention the individual converter cards cost about $1200 a piece on that model.


 There is nothing in an acs800 called a "motor side converter card". ????? He has a 355, which more than likely has the IGBT's soldered in, ABB won't sell those to service partners let alone end users. Choice is send it to ABB or **** can it.


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## Zana (Jul 25, 2014)

DriveGuru said:


> There is nothing in an acs800 called a "motor side converter card". ????? He has a 355, which more than likely has the IGBT's soldered in, ABB won't sell those to service partners let alone end users. Choice is send it to ABB or **** can it.


Actually there is.

http://wiki.hevs.ch/gridlab/index.php5/Hardware/ABB_ACS800-11

You can select between both from the control panel.


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## DriveGuru (Jul 29, 2012)

Zana said:


> Actually there is. http://wiki.hevs.ch/gridlab/index.php5/Hardware/ABB_ACS800-11 You can select between both from the control panel.


Actually there is not, you should get your information from more reliable sources, I would suggest starting with ABB.com. 
Drives 101: 
1) The input section is called a "converter" as it converts incoming AC voltage to DC 
2) The output section is called an "inverter" as it inverts the DC back to AC 
3) The 800-11 is a line regenerative drive, so instead of diodes or scr's, the input section also has IGBT's, subsequently it requires two control boards(RMIO Boards) which is what you are switching between with your CDP312R (keypad) 
4) The boards in the output stages of an R2-R6 frame drive are the RASI which communicates to the control bd(RMIO) does a/d conversion and GF detection. The RINT(main circuit interface)which houses the power supply , does gate isolation, and measurement. Then the IGBT's(which will also have the gate drive cards soldered to them). 
5)Below is a basic block diagram of an 800, the 800-11 will have an additional RMIO and an IGBT front end. I would show you more diagrams, but they would be proprietary. 


Hmmm... Nowhere do I see a "motor side converter card"


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