# i need help regarding Altivar 58 VFD



## Mr Riz (Jul 4, 2012)

I need answers regarding Altivar 58 VFD. I shall be very thankfull to you for this.

I want to know that what are the possible reasons for SCF fault code?
What will happen if its potentio meter is disconnected while running and connected after it comes to zero?
What will happen if its potentio meter is short?
What will happen if potmeters common wire is grounded?

I need this info because this vfd goes to SCF fault with just
potmeter,s common wire is disconnected and then reconnected after it
comes to zero. Vfd is more than 2 years old.


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## John Valdes (May 17, 2007)

Mr Riz said:


> I need answers regarding Altivar 58 VFD. I shall be very thankfull to you for this.
> 
> I want to know that what are the possible reasons for SCF fault code?
> What will happen if its potentio meter is disconnected while running and connected after it comes to zero?
> ...


Drives trip for many different reasons and that's why we have given them a name.
"Nuisance" trips. 
Nuisance trips rarely are a major issue other than they occur for no apparent reason and you have no idea why.
If you know why the drive trips, it is no longer a nuisance trip.

Now. Why are you trying to run a control with any wires disconnected?
If the drive is programmed to use a 0-10 vdc potentiometer for speed reference, it needs a potentiometer connected.
Would this cause a trip? I say it very well could. Yes. So, reconnect it and leave it alone.
You also must use the correct pot and connect it exactly as shown in the diagram. The drive manual will tell you what type and the specs it requires. Check the specs on the pot.

Once you have reconnected all the wires correctly and verified you indeed have the correct pot, you can do some troubleshooting to see if you can locate the origin of these trips.

The trip you mention indicates an issue with the motor.
So, disconnect the motor and run the drive without any load at all. (most inverters will allow this).
If it runs and does not trip, it is the motor or the wiring to the motor.
From here its just a matter of checking the wires and the motor to see which one is the culprit.
Does it run without a motor connected?

Do you have a line reactor on this drive? Anything new happen around the plant lately. POCO fix anything?
Does your nuisance tripping occur at a certain time very day?

Let us know the answers to all these questions. Using a megger like described above may be required to locate the short if one is present.
Make sure the drive is isolated when megging the conductors or the motor.


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## John Valdes (May 17, 2007)

Drives trip for many different reasons and that's why we have given them a name.
"Nuisance" trips. 
Nuisance trips rarely are a major issue other than they occur for no apparent reason and you have no idea why.
If you know why the drive trips, it is no longer a nuisance trip.

Now. Why are you trying to run a control with any wires disconnected?
If the drive is programmed to use a 0-10 vdc potentiometer for speed reference, it needs a potentiometer connected.
Would this cause a trip? I say it very well could. Yes. So, reconnect it and leave it alone.
You also must use the correct pot and connect it exactly as shown in the diagram. The drive manual will tell you what type and the specs it requires. Check the specs on the pot.

Once you have reconnected all the wires correctly and verified you indeed have the correct pot, you can do some troubleshooting to see if you can locate the origin of these trips.

The trip you mention indicates an issue with the motor.
So, disconnect the motor and run the drive without any load at all. (most inverters will allow this).
If it runs and does not trip, it is the motor or the wiring to the motor.
From here its just a matter of checking the wires and the motor to see which one is the culprit.
Does it run without a motor connected?

Do you have a line reactor on this drive? Anything new happen around the plant lately. POCO fix anything?
Does your nuisance tripping occur at a certain time very day?

Let us know the answers to all these questions. Using a megger like described above may be required to locate the short if one is present.
Make sure the drive is isolated when megging the conductors or the motor.


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## JRaef (Mar 23, 2009)

SCF means it is detecting a Short Circuit on the output, the motor side of the transistors. A VFD detects short circuits by watching yhe rate of rise in current. You either really have a short circuit, or your constantly playing around with the speed command is making the drive turn on and off rapidly, which is causing spikes in motor side because of residual voltage, which the drive is interpreting as a short circuit.


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## Mr Riz (Jul 4, 2012)

as this VFD is installed without any reactor in the output and input line. 
magger of the motor cable from vfd side is maggerd when it is connected with motor it was clear.
and when the vfd was run without output conection it still gives the same fault of SCF.
This vfd drived 45 KW Boiler FD fan motor.
it uses 0 10 volt for pot meter. as there are thre points for potmeter in this VFD >> *+10 AI1 com * in my scenario common wire denote the wire connected at *AI1*
while running its pot meters common wire was disconnected and after that when the vfd came to zero rpm it was reconnected but the VFD dosnt take the refrence signal and be there with the *SCF FAULT.*
IS that due to potmeter's common wire.


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## Speedy Petey (Jan 10, 2007)

I merged the two threads you have going on this topic.


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## JRaef (Mar 23, 2009)

Mr Riz said:


> as this VFD is installed without any reactor in the output and input line.
> magger of the motor cable from vfd side is maggerd when it is connected with motor it was clear.
> and *when the vfd was run without output conection it still gives the same fault of SCF*.
> This vfd drived 45 KW Boiler FD fan motor.
> ...


The SCF fault should have _*ZERO *_to do with the placement of the potentiometer wiring, unless as I said, you were doing this with the motor running and the constant on-off command is causing current spikes on the motor side. But from your description now of it happening with the motor disconnected, that means there is some serious interference coming into the control board from that potentiometer circuit. The circuit should be completely isolated against that, so if this is happening, that is indicative of a faulty board and it should be replaced ASAP.


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## Mr Riz (Jul 4, 2012)

The potentio is disconected once and then reconected once after that. If the turning off and on command of potentio cause the rise in current then y that dont give the overload fault. If the motor side connections hav losing .. What are there effects on this scf fault.


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## JRaef (Mar 23, 2009)

Mr Riz said:


> The potentio is disconected once and then reconected once after that. If the turning off and on command of potentio cause the rise in current then y that dont give the overload fault. If the motor side connections hav losing .. What are there effects on this scf fault.


Sry, i hav trbl rdng ur trunctd text styl typng. We dnt chrg $ by the ltr here, its OK 2 us whle wrdz. :wallbash:

Seriously though, I'm not looking for an argument with you, I was trying to help. You seem to be bent on parceling out information in minuscule chunks and then complaining that I don't seem to understand.

You never said how many times you can connected and disconnected the pot wires. But anyway, I said in my last post that if this is happening with the motor disconnected, it has nothing to do with motor current issues, time to move on now. 

Look, I've been troubleshooting VFDs for 20+ years now, I can tell you that there are no "magical" failures, there is always an explanation. But in most cases, you can drive yourself nuts and exhaust your budget trying to get down to the EXACT cause. My advice is to eliminate the most likely possibilities of recreating it after fixing it, then fix it. You likely have a bad control board and possibly deficient wiring to your potentiometer. The pot wiring is likely picking up some noise from surrounding power wiring. That noise is SUPPOSED to be prevented from causing issues on the control board by proper shielding, but what gets through also SHOULD have been filtered out in the interface circuit of the control board. If it was not properly shielded, it may have worked for a while but the constant barrage of noise and spikes may have damaged the isolation method, whatever it was. The empirical evidence is that it apparently is no longer filtering because you are seeing nuisance trips that can have no direct relation to that pot circuit. 

Re-do the pot wiring with _properly_ shielded control cable and replace the control board. If you are confident now that the pot circuit was wired and shielded correctly, then just replace the board. If you are absolutely sure it isn't the control board either, then it could be that you have a cracked transistor module that is leaking to the heat sink. But that usually shows up immediately, not after a while. Sometimes (rarely), it can be something that only happens when it gets hot enough, but not likely. Besides, that would have nothing to do with pot wiring, it would have to be strictly coincidental.

Good luck.


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## MechanicalDVR (Dec 29, 2007)

Have you tried Tech Support? 1-888-SQUARED


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## Mr Riz (Jul 4, 2012)

Thanks mr jraef for such detail information. I want to ask that why the direct connection of motor with vfd output is not recommended?
In the above mentioned scenario the the same pot meter wiring works pretty good with another vfd from invert brand. what is the normal life time for a vfd?
The above mentioned vfd was more than6 years old. What are your recommendations which we must take into account so that we can minimize such type of fault.


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