# Powerflex 70 SW 36 fault



## Macool (Mar 11, 2019)

We have a cooling tower that is recently faulting 36 sw. only at night. It’s for a cooling tower fan. 
Increased accel time to 30 sec. 
verified flying start enabled
Checked fan belts 

Anyone run into this fault?


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## just the cowboy (Sep 4, 2013)

Even though it is a overcurrent trip, check the line voltage at night. If the plant is not running the same as day work the line voltage may be rising at night with low load.


Can it be freezing at night?


Also please fill out your about me profile so we know where you are and what is your skill level.


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## Macool (Mar 11, 2019)

That’s kind of the direction I was thinking. May have to hook up a recorder to monitor voltage fluctuations at night. We have a bad power grid here. Voltage can drop out and fluctuate. 

I’m on mobile. Does not show options to update profile. I’ll try later at a desktop. Already used the admin and email links. Fields don’t show up.


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## JRaef (Mar 23, 2009)

Software Over _*Current *_(fault 36) means the _current _jumped to over 200% of the drive rating for more than 1 millisecond. This will have nothing to do with voltage.


A common issue when using Flying Restart is if the Run command is intermittent and the Off time is of short enough duration that the Flying Restart is not triggered. The drive command is cycling off and back on really fast, causing the motor to regen from residual magnetism so the drive re-connects a little out of phase, causing a current spike. Flying Restart requires that the drive be off for I think about 2 seconds.


Another possibility is that the Gain on the Flying Restart is sett too high (and the system is requiring it at some time during the night). The Gain setting (parameter 170) is the sensitivity of the sweep detection, the system that detects the rotation speed of the motor so that the drive can match it. If set too high, the drive is possibly acting too quickly, causing the out-of-phase connection mentioned above. The factor default setting is 4000 (decimal value, out of 32,767). If it is left at that value, try setting it lower. If someone set it higher, put it back to 4000.


If not either of thise, then this is likely the result of a problem in the wiring or the motor. VFDs are better at finding circuit problems than regular starters...

If it only happens occasionally, the usual suspect is moisture related; something gets wet, causes current to flow where it shouldn't then in doing so, evaporates the moisture so when you test the circuit later, everything looks good. This would typically show up as a Ground Fault on the VFD, but if it happens too fast, it can show up as SW OC. On more than one occasion I've seen this where there is water in a conduit and, somewhere, a tiny nick in the cable insulation. it could also be the early signs of a turn-to-turn short taking place inside of the motor as a result of standing waves due to long term VFD use without the proper precautions. Turn-to-turn faults don't show up on standard megger tests to ground, because it is not shorting to ground.


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## Macool (Mar 11, 2019)

Thank you. I’ll check the settings. Being an evaporative fan. Moisture can be an issue at any time. 



JRaef said:


> Software Over _*Current *_(fault 36) means the _current _jumped to over 200% of the drive rating for more than 1 millisecond. This will have nothing to do with voltage.
> 
> 
> A common issue when using Flying Restart is if the Run command is intermittent and the Off time is of short enough duration that the Flying Restart is not triggered. The drive command is cycling off and back on really fast, causing the motor to regen from residual magnetism so the drive re-connects a little out of phase, causing a current spike. Flying Restart requires that the drive be off for I think about 2 seconds.
> ...


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