# VFD manual bypass, gf breaker trip



## tates1882 (Sep 3, 2010)

So you have a vfd connected to the motor and a wye/delta motor starter connected to the same motor? 

If both the vfd and mms are connected to the same gfi breaker, look into the control circuit for the mms. Particularly the control transformer/bonding. 

Also i assume you have the grounded conductor for the wye connection on the gfi breaker and the pigtail from breaker to busbar? 


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## JRaef (Mar 23, 2009)

Sandman1110 said:


> Hi all, I have a vfd and pump motor that functions normally until it is in bypass mode where it trips the ground fault on the upstream breaker when the motor is started. The client has replaced the breaker with the same results, so it's unlikely that is where the problem lies. the motor and connections are all correct. The motor also meggers out fine with no apparent grounds. we've gone through and checked all the mechanical connections to the pump, bearings, shaft alignment, etc.....no problems there. The motor is wye connected. inrush current is high (approx. 9.3x fla), but within trip tolerances when modeled in Easy Power. The vfd is supposed to be completely isolated when in bypass mode. Two questions....could this in fact be tripping because of a phase imbalance issue when the motor shifts from a wye start to a delta run? or more likely a nick in the feeder insulation that bleeds to ground with an across the line start?


There are some inconsistencies in your statements. You mention that it is Wye-Delta started, then say "across the line". It can't be both. Then if your Starting current is 930% of FLA and you are starting Wye-Delta, something is SERIOUSLY wrong here. Get your story straight.


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## Sandman1110 (Nov 20, 2013)

JRaef said:


> There are some inconsistencies in your statements. You mention that it is Wye-Delta started, then say "across the line". It can't be both. Then if your Starting current is 930% of FLA and you are starting Wye-Delta, something is SERIOUSLY wrong here. Get your story straight.


Already figured that most folks would realize that it would be across the line starting without holding their hand....and not to belabor the issue....really not a helpful comment and frankly abrasive. I'm looking for other opinions to why I would have a gf tripping problem on a breaker when the vfd is bypassed. If you don't have any useful input or ideas, then, please don't respond.


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## Sandman1110 (Nov 20, 2013)

tates1882 said:


> So you have a vfd connected to the motor and a wye/delta motor starter connected to the same motor?
> 
> If both the vfd and mms are connected to the same gfi breaker, look into the control circuit for the mms. Particularly the control transformer/bonding.
> 
> ...


Thanks Tates.....yes we double checked all connections. this is what's making this a head scratcher for me. We've even raised the gf trip and delay settings on the breaker to see if that would help. The breaker still trips on gf. We just finished meggering the feeders and everything checks out ok and not even any hint of any insulation break down.


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## tates1882 (Sep 3, 2010)

You could swap the motor feeder from the dol to the vfd and run it for a few. Normally vfds can detect a ground fault. Just another way to check to be double sure. My other concern is maybe the vfd being powered up when the dol is used causing enough imbalance between the phases and the neutral. Have you powered down the vfd and tried running the dol?


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## John Valdes (May 17, 2007)

Starting across the line puts every inrush amp on that breaker.
When starting using the VFD, you must have some ramp time programmed? Right?

High starting current (across the line) vs limited starting current (VFD) is what it sounds like the problem is to me.
That is, if it starts and runs with the VFD without issue.

Note: Jareaf is one of our most knowledgeable guys on this site. Especially in this discipline. Drives, soft starts and control.
I would suggest you try and work with him and get rid of the abrasive responses on your end. I bet it would be beneficial to you.

ps.....you did say wye start and DOL. So what is it.


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## Sandman1110 (Nov 20, 2013)

phase imbalance is ringing a bell....or a false gf reading? maybe rotating phase conductors over one phase? or maybe changing I^2 out setting to in? rotating the phase conductors might reduce imbalance currents on start up...I^2 in setting might allow more time for the gf to read correctly. I suppose they would be worth a try.


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## Sandman1110 (Nov 20, 2013)

John Valdes said:


> Starting across the line puts every inrush amp on that breaker.
> When starting using the VFD, you must have some ramp time programmed? Right?
> 
> High starting current (across the line) vs limited starting current (VFD) is what it sounds like the problem is to me.
> ...


I don't mind working with anybody if they are constructive....his response did not, in my opinion, appear to be constructive. So perhaps we could start over....what say you JRaef? What specific information are you needing?


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## Sandman1110 (Nov 20, 2013)

by the way.....the motor does start and run normally when on the vfd. the motor is a wye start.


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## frenchelectrican (Mar 15, 2007)

There is couple tibbits I am looking for .,,

What size the motor you are talking about ?

what voltage system it is on ? ( 480 or whatelse it is on ? ) 

but please clearify one item you say VSD and DOL ( bypassed the VSD ) and please make sure it is in correct sequnice .,,

and the motor itself it can be connected in Delta or WYE depending on what the nameplate say. make sure you double check the connections to it match up on the supply line. 

If you mention Wye delta motor starting system., if so get the VSD to run in delta mode do not run in wye connection.

Did the bypass working ok once the motor is up to the speed ? 


By the way .,, JRaef is well respected member in the fourm and he is a good motor guru.,

Myself and couple other are well versed on them. 

Try rotate the phases one turn sometime it will clear up the voltage imbalance.

but once a while I will heard the supply transfomer ( typically POCO transfomer ) can get weak with hard starting load.


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## Peewee0413 (Oct 18, 2012)

John Valdes said:


> Starting across the line puts every inrush amp on that breaker.
> When starting using the VFD, you must have some ramp time programmed? Right?
> 
> High starting current (across the line) vs limited starting current (VFD) is what it sounds like the problem is to me.
> ...


I find it funny he blasted Jareaf, who has probably forgot more about drives than this guy knows. 

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## Sandman1110 (Nov 20, 2013)

Peewee0413 said:


> I find it funny he blasted Jareaf, who has probably forgot more about drives than this guy knows.
> 
> Sent from my VS995 using Tapatalk


nice my friend....


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## frenchelectrican (Mar 15, 2007)

Peewee0413 said:


> I find it funny he blasted Jareaf, who has probably forgot more about drives than this guy knows.
> 
> Sent from my VS995 using Tapatalk


Guys .,, just keep it civil ok.,,


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## Sandman1110 (Nov 20, 2013)

frenchelectrican said:


> Guys .,, just keep it civil ok.,,


agreed. Please close this thread.


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## frenchelectrican (Mar 15, 2007)

Sandman1110 said:


> agreed. Please close this thread.


I will close this thread per OP request.,, 

but it will be nice once you find out the situation and what the results so other can learn from that.


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