# ATV58 overcurrent fault



## ilikepez (Mar 24, 2011)

I would verify that the load being driven isn't changing, and that all the settings are correct. Is it happening while the motor is changing speed or anything?


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## JRaef (Mar 23, 2009)

Is the fault code displaying OLF or OCF? If it is OCF, that's an indication of some sort of intermittant locking or jamming of the load(s). It would only need to be in one of them.


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## KennyW (Aug 31, 2013)

JRaef said:


> Is the fault code displaying OLF or OCF? If it is OCF, that's an indication of some sort of intermittant locking or jamming of the load(s). It would only need to be in one of them.


Kinda disagree ther. If a single motor goes to locked rotor or even a dead short, the dedicated overload on its circuit should trip way before the over current on the drive does. If the drive is tripping on over current due to a fault on a single motor, the dedicated overload on that motor is not set correctly.


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## Handasee (Dec 18, 2009)

ilikepez said:


> I would verify that the load being driven isn't changing, and that all the settings are correct. Is it happening while the motor is changing speed or anything?


Motors are for small saw blades on an edge bander. Motors do not change speed. All motor appear to spin freely.



JRaef said:


> Is the fault code displaying OLF or OCF? If it is OCF, that's an indication of some sort of intermittant locking or jamming of the load(s). It would only need to be in one of them.


Fault code was a OCF. 



KennyW said:


> Kinda disagree ther. If a single motor goes to locked rotor or even a dead short, the dedicated overload on its circuit should trip way before the over current on the drive does. If the drive is tripping on over current due to a fault on a single motor, the dedicated overload on that motor is not set correctly.


The overloads are set correctly for the motors, but none tripped.
I only saw the fault once and it occurred with no load on the motors.


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## JRaef (Mar 23, 2009)

KennyW said:


> Kinda disagree ther. If a single motor goes to locked rotor or even a dead short, the dedicated overload on its circuit should trip way before the over current on the drive does. If the drive is tripping on over current due to a fault on a single motor, the dedicated overload on that motor is not set correctly.


Not necessarilly. An overload relay, even if set to Class 10, will take up to 10 seconds to trip on locked rotor current of 600% of the setting. Overload relays are not the Short Circuit protection for the motor.

He said that he used PKZ0s (Moeller) for the motors, but if I remember correctly, they have separate modules for Thermal OL and SC protection. If the SC module was not used, the VFD instantaneous SC trip circuit would likely trip long before the PKZ0 thermal trip would. The same might still hold true even if the SC module was there, if the VFD trip current setting is lower than the SC setting of the PKZ0.

We are not there so we can't investigate this without full details, so I'm just offering up possibilities for the OP to investigate. I don't like ASSuming that an expensive device like a VFD is defective just because you don't immediately see the potential simpler issues.


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## KennyW (Aug 31, 2013)

JRaef said:


> Not necessarilly. An overload relay, even if set to Class 10, will take up to 10 seconds to trip on locked rotor current of 600% of the setting. Overload relays are not the Short Circuit protection for the motor.
> 
> He said that he used PKZ0s (Moeller) for the motors, but if I remember correctly, they have separate modules for Thermal OL and SC protection. If the SC module was not used, the VFD instantaneous SC trip circuit would likely trip long before the PKZ0 thermal trip would. The same might still hold true even if the SC module was there, if the VFD trip current setting is lower than the SC setting of the PKZ0.
> 
> We are not there so we can't investigate this without full details, so I'm just offering up possibilities for the OP to investigate. I don't like ASSuming that an expensive device like a VFD is defective just because you don't immediately see the potential simpler issues.



I think the typical trip time for 600% on a cold Class 10 is about 4 seconds, for what it's worth. But anyways of course we don't have all the details. I'm just offering up possibilities as well. Everything is an assumption until it is confirmed/denied in the field. 

My reasoning is as follows: 

If the load is 6.4 A, and the drive rated load is 11.4, the 60 second overcurrent is what, 16amps? So they're drawing just over 1A each and we have nearly 10 Amps of head room before we trip the drive. That means a single motor is going to have to go to 1000% of whatever the running load is (unfortunately we don't know of the 6.4A is idling or with wood going through, but I'm ASSuming that is the normal running load observed before trip happens, otherwise sating that current draw is a it of a red herring) for *60 seconds* before the drive trips. Even the laziest overload is gonna trip.

Seems unlikely?


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## JRaef (Mar 23, 2009)

KennyW said:


> I think the typical trip time for 600% on a cold Class 10 is about 4 seconds, for what it's worth. But anyways of course we don't have all the details. I'm just offering up possibilities as well. Everything is an assumption until it is confirmed/denied in the field.
> 
> My reasoning is as follows:
> 
> ...


KennyW,
Well you're right, we don't know enough.

We don't know what size the motors are, we don't know exactly which drive it is, we don't know what protection modules are in the PKZ0 etc. etc. etc. 

The motor Locked Rotor Current (LRC) is independent of loading, load only determines how long it remains at LRC. So all we know is that the motors are DRAWING 6.5A total for 6 motors, so about 1.2 Running Load Amps (RLA) each. That means they are undoubtedly more than 1/4HP, because if they were, they would be running at or over FLC (1.1A). So assuming the best, that they are at least 1/3HP, that means the FLC on each one is likely about 1.4A, so the LRC would be about 8.4A and you would be correct, a single surge of 8.4A on a drive rated for 11.4A is not above the continuous rating of the VFD. But remember, there would be 5 more motors running at 1.2A each, so 6 more amps in the circuit WHEN the LRC of the 6th takes place, making it 14.4A total. Still not enough to cause the trip, but getting closer and if at the time, the other motors were at a higher RLA, it could easily happen. 

So then if the motors are just one size up at 1/2HP rated 2.5A FLC, the LRC for one motor could be 15A, which is right at the likely hardware trip limit of the drive (the only version I found that appears close to the specs quoted is a 3HP 208V single phase input, which is rated for transient loads of 15A max.). 

So one 1/2HP motor going into LRC of 15A while the other 5 motors are running at 6A collective RLA would be 21A and DEFINITELY cause the drive to trip and likely long before the PKZ0 would react to it.

Other factors: If someone turns OFF one of those drives with the PKZ0 while running, no problem. But if they then turn it back ON while the drive is already running, you would get EXACTLY the same condition: 1 x LRC + 5 x RLA, exceeding the hardware trip limit of that (assumed) drive.

Bottom line (again), we don't know enough, but in my mind it is highly likely to be something in the way it is being used rather than the drive being defective. Eliminate all the other issues first.

And by the way just FYI, the "Class" designation of Over Load Relays is based _specifically _on the maximum trip time at 600% current. So Class 10 is defined as tripping in 10 seconds, Class 20 is 20 seconds, Class 30 is 30 seconds. So a Class 10 CAN trip in 4 seconds and still be valid, but it would also pass if it took 10 seconds.

Great discussion though. I like how you think despite our disagreement. :thumbsup:

Handasee, 
Please take from this the info on what you need to look for.


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## just the cowboy (Sep 4, 2013)

I would agree with JRaef first make sure no one is turning off/on one of the manual motor starters. Operators may not know they shouldn’t due it or are taking a shortcut. Most drives don't like power cut while running or load opened/closed while running. There are exceptions of coarse.

Have a good weekend


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## KennyW (Aug 31, 2013)

JRaef said:


> KennyW,
> Well you're right, we don't know enough.
> 
> We don't know what size the motors are, we don't know exactly which drive it is, we don't know what protection modules are in the PKZ0 etc. etc. etc.
> ...


Yeah fair point about the trip class. Our reasoning is actually pretty similar except on the scenario that they are 1/2hp motors though, because if they each have an FLA of 2.5A, 2.5 * 6 = 15A, which means the continuous full load rating of the connected load is equal to the 60 second rating of the drive. (That 15A transient means for 60 seconds). In this scenario the drive is simply undersized.  So that said, maybe it runs for 1 minute at a time then trips in which case we found the problem! Haha!

Good discussion.


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## Handasee (Dec 18, 2009)

JRaef said:


> KennyW,
> 
> 
> We don't know what size the motors are, we don't know exactly which drive it is, we don't know what protection modules are in the PKZ0 etc. etc. etc.
> ...


Operator does not have access to the PKZM 


just the cowboy said:


> I would agree with JRaef first make sure no one is turning off/on one of the manual motor starters. Operators may not know they shouldn’t due it or are taking a shortcut. Most drives don't like power cut while running or load opened/closed while running. There are exceptions of coarse.


The drive model no. is ATV58HU41M2.
4 motors have the following nameplate data:3 ph, 200Hz, 220V delta, 2.5amps, 12000rpm. The other 2 motors are smaller but the nameplate is not visible,so I can't tell you the exact specs. The operator turns on the motors with one button, so no one is turning the manual motor starters on/off.
Today the machine worked for 30 minutes before it tripped out.
Observing the drives display, the input voltage varied from 211 volts to 216 volts. The motor draw under load varied from 6.5 volts to 7.1 volts. 
These motors are basicly running no load.
Owner called in the machine service tech to look at it. First thing he said it must be one of the cables going to the motors. He pulled and twisted each cable but was unable to cause a fault on the drive. He left, telling the owner to disconnect one motor at a time until he finds the problem.
Looks like I will be there next week.


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## Jabberwoky (Sep 2, 2012)

Have you tried attaching digital clamp-ons with the peak reading enabled? Is the peak current draw the same on all the motors after it trips the drive?


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## KennyW (Aug 31, 2013)

Yeah even just a clamp meter on one of the phases, with the peak-hold enabled would be a good idea. At least you'll know if the current actually spiked and how high. 

4x2.5A fla motors is already 10A. Drive continuous rating is only 11, and there's 2 more smaller motors, too. So really it's like JRaef says, any small issue could trip it, it's sized really tight. 

Is it a homag machine? Those trimmer motors always die. If so I'd consider putting OC protection on each motor to save hassles in the future.


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## Handasee (Dec 18, 2009)

Jabberwoky said:


> Have you tried attaching digital clamp-ons with the peak reading enabled? Is the peak current draw the same on all the motors after it trips the drive?


I put a clamp-on at the output of the load reactor-measured 7.5 amps on peak.



KennyW said:


> Yeah even just a clamp meter on one of the phases, with the peak-hold enabled would be a good idea. At least you'll know if the current actually spiked and how high.
> 
> 4x2.5A fla motors is already 10A. Drive continuous rating is only 11, and there's 2 more smaller motors, too. So really it's like JRaef says, any small issue could trip it, it's sized really tight.
> 
> Is it a homag machine? Those trimmer motors always die. If so I'd consider putting OC protection on each motor to save hassles in the future.


Machines a SCM, manufactured in 2000. Motors mfg by "Coees"


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## Jabberwoky (Sep 2, 2012)

If you are using a digital clamp-on with a fast enough update speed with peak hold on then I'd say its likely a drive issue. If it is the drive probably the current sensing section. Probably not worth the time/cost to try and repair such a small drive. 

I haven't had a chance to look at the drive specs you could try to run the drive with nothing on the outputs. If it trips over current with no load it is a problem in the drive. In this configuration it is still possible not to trip even if there is something wrong with the drive.


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