# Vfd help



## WronGun (Oct 18, 2013)

I’ve been retrofitting vfd’s into lab-room exhaust systems. 

The latest 2 we installed we simply intercepted the 480 line/load with a vfd. 

These 2 vfd’s get there power from a large control cabinet. The phase A conductor goes through an amp probe that’s wired to an AHU controller which I’m not familiar with. 

However , now we have a problem since the vfd’s were introduced. Error message on vfd reads under voltage on DC power. Nothing else has changed with the wiring. The existing relays trip now after the motor has been running for 2-3 minutes. 


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## Tonedeaf (Nov 26, 2012)

Are the output conductors for the two VFD in separate conduits?

I have had problems in the pasts with weird errors due to conducts from separate drives shared conduit.

Noise effects the feedback on the controls.


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## micromind (Aug 11, 2007)

I've seen this happen when the VFD is programmed to accept a single phase input and the input is indeed single phase (either by design or by some sort of a problem) and the VFD has not been oversized enough to compensate for only 2 hots instead of 3. 

If possible, program the readout for DC Voltage and watch what happens to it when the motor is started. 

Also, see if the VFD has a DC voltage alarm level. It might be set too high.


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## WronGun (Oct 18, 2013)

I have a feeling it’s the programmer settings, which was done by the control company. 


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## splatz (May 23, 2015)

@WronGun - if you can't pass this along to the control company can you bring in someone good with drives?


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## WronGun (Oct 18, 2013)

splatz said:


> @WronGun - if you can't pass this along to the control company can you bring in someone good with drives?




I don’t have anyone that knows VFD’s very well. 

My company was hired to run power , and help with running control wires. We were hired by a national control company that specializes in energy management. I was assuming they were pro’s at this. 

I figured I was only going to be intercepting line and loads with a vfd. Changed nothing else. 


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## gpop (May 14, 2018)

WronGun said:


> I’ve been retrofitting vfd’s into lab-room exhaust systems.
> 
> The latest 2 we installed we simply intercepted the 480 line/load with a vfd.
> 
> ...


Under voltage is basically saying more power was used on the output of the vfd than was available on the input. 

Its a odd one as 480v is already 20 volts higher than required. 

To assist we really need to know the brand of vfd and what "The existing relays trip now after the motor has been running for 2-3 minutes." means.

I would start by measuring the input voltage to make sure i had all 3 legs and they are close to 480v. If they are low then i would probably program the motor/drive as a 460v. I would also see if i could monitor the dc buss voltage while the drive was running. 

Like others have said the only time i have seen this problem was when a fuse blew on the vfd input or on very old vfds where the caps are going out. I know that ABB drives will not alarm on a lost incoming leg and you would not notice until you try to pull full load on the motor.


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## WronGun (Oct 18, 2013)

These are small ABB drives.



Here is a photo of L1 running through the sensor and the relay. Again , this is all existing and was wired this way directly to the motor before we installed the vfd. 

Setting the VFD voltage to 460v was also a thought of mine. 

The first run @60hz Tripped the relay after about 1 minute.

The second run was @50Hz and it ran longer 5-7 minutes. 























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## splatz (May 23, 2015)

If I was just hired to install a pre programmed drive per the drawing I would not want to troubleshoot this, I'd just test what I was hired to do and pass it along. 

If they asked me to help troubleshoot, and it's outside my comfort zone, I'd want to agree on the price first and a waiver of liability for damage. 

Things I'd try as a dummy: 

Double check all the wiring and connections, test everything I did. 

Verify that it still works bypassing the drive. 

Seek support from manufacturer or control company's in house people - do I need separate routing, VFD cable, etc.? 

See if I can hook up a laptop screen share it with support. 

As mentioned, recruit an expert. Maybe you can bring in an HVAC company you work with, maybe someone moonlighting from their factory or plant. One of our supply houses has an in house guy who's very good with that stuff, he'd be my go to guy.


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## splatz (May 23, 2015)

If I have to **** around with the programming, and that is my dead last, I'd back it up first, and carefully document in my notes every change and test. 

Post all that here so the smart guys can help. 



splatz said:


> If I was just hired to install a pre programmed drive per the drawing I would not want to troubleshoot this, I'd just test what I was hired to do and pass it along.
> 
> If they asked me to help troubleshoot, and it's outside my comfort zone, I'd want to agree on the price first and a waiver of liability for damage.
> 
> ...


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## Cow (Jan 16, 2008)

So your 480v wiring is going from fuses-contactor-overload-ct donut-vfd-motor?

Is that correct?

The overload and potentially the CT donut at this point may be completely unnecessary and just more components with the potential to fail.

The way we do it in these situations, would be fuses-vfd-motor. 

The existing contactor would be used to chase the VFD's control wiring through for a 2 wire start signal.

I'm not sure what they are using the CT donut for, the diagram on the face appears to be a simple contact. So, if it's just being used to verify the motor is loaded and running, you may be able to program one of the vfd relays for "run" if it already isn't set that way by default and chase the existing CT donut control wires through it.


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## gpop (May 14, 2018)

Just guessing here
Overload relay is seeing a phase imballance as its not designed to be on the line side of a vfd.
This causes contactor to open on a running vfd. Vfd will see this as low dc buss voltage and trip.
So the question is ...... Does the contactor open before the drive trips.

I would disable the overload block then run a test.

What ever the ct to ma converter is going to may also be opening the contactor.

This really is a half arsed install


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## gpop (May 14, 2018)

Ct is probably being used as a load loss senser if the fans have drive belts


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## Jay Freeman (Aug 2, 2017)

I'd bypass that contactor and probably the CT.

It should just be breaker, VFD, Motor... 

If the DCS needs verification that the motor is running, then I'd use an output from the drive.


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## oliquir (Jan 13, 2011)

overload cant be on line side of vfd without readjusting, the overload is tripping then cutting power to the vfd that shows low dc voltage. remove the overloads or set them high enough they will never trip, vfd input current is always higher than the output at full speed


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## WronGun (Oct 18, 2013)

gpop said:


> Just guessing here
> Overload relay is seeing a phase imballance as its not designed to be on the line side of a vfd.
> This causes contactor to open on a running vfd. Vfd will see this as low dc buss voltage and trip.
> So the question is ...... Does the contactor open before the drive trips.
> ...




Good points...I’ve done many new installs in the field. The company we are working for does mostly all retrofits.... So we are back-tracking current systems..., a few hurdles but I’m learning a whole new game and meeting major clients. 


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## sparkiez (Aug 1, 2015)

This doesn't seem to have anything to do with your install. That "relay" is just an overload. The little current sensor is kind of curious. I was wondering if that is feedback for the VFD, or due to the fact it is on the load side of the overload, it could be to send a signal back that the overload has tripped. Just depends on what the wires go to, though it appears they go back to a drive.

It is perfectly acceptable if you are going to take this on to let it be known that it will take some time. Those are quite a few little devices, connected together in some sorta way to make them do things to each other and a lot of what-ifs to being trying to troubleshoot blind. Due diligence.


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## Ctsparky93 (Sep 17, 2016)

Did you get voltage reading on the line side across all phases on the vfd and control cabinet? The vfd faults without tripping the overload block right? You could bypass the line load on the starter to rule that out. What is the component above the starter a line side reactor? 


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## gpop (May 14, 2018)

WronGun said:


> Good points...I’ve done many new installs in the field. The company we are working for does mostly all retrofits.... So we are back-tracking current systems..., a few hurdles but I’m learning a whole new game and meeting major clients.
> 
> 
> Sent from my iPhone using Tapatalk


You will find this kind of work fun or frustrating depending on the engineer that sold the job (some times that engineer is in fact a sales guy that has no experience just big ideas).

I have a lot of freedom so i would have jumped out the starter just to see if the drive did the same thing but you may not have that freedom. 

I noticed on the picture now i can see it that the ct is in fact a amp switch. Depending on the settings it should be easy to work out what it is used for. 

I have a passion for reverse engineering control panel and retrofitting them so i kinda envy your job.


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## gpop (May 14, 2018)

If you have no control wiring to the vfd to start and stop the drive my suggestion would be to wire the drive directly to the fuses then following the manual control wiring diagram(tell us the drive model and we can tell you wiring numbers and programming).
Run the control wires and use one leg on the starter that was used for the 3 phase wire you removed. 

Now the drive will stay up and start and stop when the original starter opens and closes. If this works i would just swap the starter for a relay, use a vfd digital output to show running (same wire that are landed on the starter aux) and delete the overloads.


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## Ctsparky93 (Sep 17, 2016)

After rereading the post you said the relay trips. I think you mean the adjustable overload. The dial on the left side is to adjust amps. As long as the fla is set on the vfd turn up the amp on dial or bypass. When it trips vfd will fault on under voltage. 


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## gpop (May 14, 2018)

Ctsparky93 said:


> After rereading the post you said the relay trips. I think you mean the adjustable overload. The dial on the left side is to adjust amps. As long as the fla is set on the vfd turn up the amp on dial or bypass. When it trips vfd will fault on under voltage.
> 
> 
> Sent from my iPhone using Tapatalk


Some of the overloads will trip on phase imbalance (cheap insurance against phase loss and single phasing). No idea if the input to a vfd is balanced.


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## WronGun (Oct 18, 2013)

I will be making some adjustments this weekend and I will separate line and loads. This was an oversight on my part but ABB does recommend separate raceways. 

I may run it breaker - fuses - disco - vfd - motor 

I’m unfamiliar with the control modules that are connected with the sensors. Not sure what they do or why they would be needed anymore. 

Theses VFD’s are used for bio lab exhausts and will be wired with wall mounted control screens located at each lab. 

Im a complete novice at technical control scenarios I would assume that this Would be removed from the existing controls/sensors and will now be controlled or adjusted at each lab station. 




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## Jay Freeman (Aug 2, 2017)

You don't need fuses with a VFD.

For control, I just assumed that the only thing being changed was the replacement of contactors with VFD's. Were the lab control screens already there or are they new?

If all the control screen did was send a command to energize the contactor then all that would need to be changed now is to move the contact closure from the old contactor to the terminal strip of the VFD and set the VFD to remote operation.

If those control screens are new and include speed control then that is something altogether different and a bit more complicated.


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## WronGun (Oct 18, 2013)

Jay Freeman said:


> You don't need fuses with a VFD.
> 
> For control, I just assumed that the only thing being changed was the replacement of contactors with VFD's. Were the lab control screens already there or are they new?
> 
> ...




Yes it’s all new, we already ran low voltage cables for the screens down into lab stations. 

There is also another new control box that controls newly installed dampers within the ducts also from the screen. 

The cabinet in the picture is all existing. 


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## varmit (Apr 19, 2009)

The overload on the VFD input is not needed and could be a problem. The best plan would be to take the existing starter out of the power circuit completely and run the input power directly to the VFD from the fuses. It is a really bad thing to power up a VFD on every start cycle.

The "run" command to the VFD can use a contact on the old starter. Leave the starter coil wired as it is now and use it as a relay to start the VFD. If there is a "motor running" indication or interlock, you can use a VFD relay output. Usually one of the outputs is factory set for this purpose.


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## WronGun (Oct 18, 2013)

varmit said:


> The overload on the VFD input is not needed and could be a problem. The best plan would be to take the existing starter out of the power circuit completely and run the input power directly to the VFD from the fuses. It is a really bad thing to power up a VFD on every start cycle.
> 
> The "run" command to the VFD can use a contact on the old starter. Leave the starter coil wired as it is now and use it as a relay to start the VFD. If there is a "motor running" indication or interlock, you can use a VFD relay output. Usually one of the outputs is factory set for this purpose.




This I don’t understand. I have 3 terminals for input and 3 for output on the vfd. That is all. 


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## gpop (May 14, 2018)

WronGun said:


> This I don’t understand. I have 3 terminals for input and 3 for output on the vfd. That is all.
> 
> 
> Sent from my iPhone using Tapatalk


If you have never done this type of work before get a picture of the drive label which has the model number so we can give you real world advice rather than generic.


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## gpop (May 14, 2018)

Jay Freeman said:


> *You don't need fuses with a VFD*.
> 
> For control, I just assumed that the only thing being changed was the replacement of contactors with VFD's. Were the lab control screens already there or are they new?
> 
> ...


sorry but i disagree with not needing fuses. If you have ever seen a drive blow you would probably agree that fuses are a good idea.


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## WronGun (Oct 18, 2013)

gpop said:


> If you have never done this type of work before get a picture of the drive label which has the model number so we can give you real world advice rather than generic.




Here are the 2 vfd’s running from the the 2 contacts from the lower left of the cabinet pictured











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## gpop (May 14, 2018)

Thats a 355 which is the upgrade to the 350.

Once the wire cover is removed you will see a lot of little terminals above where the 3 phase lands. (may be covered with a yellow and red sticker that has torque spec on them).

Remove the labels and thats the control wiring. 

ABB did sell some drives that were then modified by others. Does the front panel say ABB or a different name?

If you download the manual thats free online it shows how to use the control wiring. 

Now leaving for work but i will try to get you some pictures of a 355 that is using a relay for start and stop once i get there.


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## gpop (May 14, 2018)

I can not get my phone to behave and send pictures.

Roughly go by page 112 in the manual.

Remove 3 phase from starter and overloads so you are going straight from the fuses to the drive input.

Next run 2 16g wires from the drive to the starter. Connect one to top and one to bottom so when the starter closes the. Wires will be joined

On the drive hook one wire to terminal 9 hook the other to terminal 11

Make a jumper and add that between terminals 10 and 11

Program application macro to abb standard macro
9902 standard macro
1103 should be AI1
1104 ref 1 min set to 60
1105 ref 1 max set to 60

Now the drive should start and stop when the original starter opens and closes

Any problems go to menu- changed parameters and list what you have there


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## oliquir (Jan 13, 2011)

Jay Freeman said:


> You don't need fuses with a VFD.


Fuses or breaker are required for any vfd. You must uses the ones listed in their manual (often semiconductros fuses). If the vfd blow and it was not protected by the right fuses, it may exploded, start a fire,(have seen a lot completely busted that were using standard fuses)... and will not be cover by manufacturer warranty. It is a part of their UL listing to use the right protection.


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## WronGun (Oct 18, 2013)

gpop said:


> I can not get my phone to behave and send pictures.
> 
> Roughly go by page 112 in the manual.
> 
> ...




Is this even necessary ? 

I’m confused about what starter your referring to ? 

Also is your application macro (constant speeds)

My manual reads 1202, 1203, 1204


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## gpop (May 14, 2018)

WronGun said:


> Is this even necessary ?
> 
> I’m confused about what starter your referring to ?
> 
> ...


*Is this even necessary ? *

Does it run correctly the way you have it. 

*I’m confused about what starter your referring to ? *

The one that is supplying power to the vfd

*Also is your application macro (constant speeds)?*

No which is why we are going to bull**** the drive by telling it that analog input A1 is min 60 max 60. SO it will run at 60 hertz (you can also do it in limits but limits can not be changed while the drive is running so it easier to do it here)

*My manual reads 1202, 1203, 1204?*

Probably means theres a jumper already installed and you are use a digital input to set a constant speed. That works but it can not be used as a start/stop unless you also jumped another digital input. 

At this point im not sure what good advice is verses advise that may confuse you a point where you make a mistake. After installing 100+ drives i forget that it was once complicated. You may need to call for ABB tech support for your first drive and they will send someone like jreff who can take there time and explain how things work and the correct way to install a drive. (they also know lots of smart things that avoid problems before you even realize there will be a problem)

Like a said earlier it sounds like you was given a half arsed plan to start with and a abb355 would not have been my first choose of drives as it will fault on high dc buss voltage every time the power flickers. (it has no internal drive reactor) A 550 would have been a better drive and we haven't even got to the fun part where you ask about the motor noise that's driving every one nuts or how to set up a automatic reset as they are tired of resetting it after every flicker.


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## Jay Freeman (Aug 2, 2017)

oliquir said:


> Fuses or breaker are required for any vfd. You must uses the ones listed in their manual (often semiconductros fuses). If the vfd blow and it was not protected by the right fuses, it may exploded, start a fire,(have seen a lot completely busted that were using standard fuses)... and will not be cover by manufacturer warranty. It is a part of their UL listing to use the right protection.


Fuse or Breaker? I agree... breakers seem to get the job done for short circuit protection. 

Using fuses plus breakers with a VFD is just overkill.


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## WronGun (Oct 18, 2013)

gpop said:


> *Is this even necessary ? *
> 
> 
> 
> ...




It doesn’t run correctly because of the sensor it’s triggering. I’m wondering if should have it run through it to begin with. 

At the end of the day I’m not responsible for programming but I’d like to make sure my part was done right.

Learning the basics of programming is a plus though as it seems I’ll be doing lots of these. 


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## WronGun (Oct 18, 2013)

I’m Wondering if it’s necessary after adding the vfd. 


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## gpop (May 14, 2018)

Jay Freeman said:


> Fuse or Breaker? I agree... breakers seem to get the job done for short circuit protection.
> 
> Using fuses plus breakers with a VFD is just overkill.


Ive seen drives that were not fused blow so hard that parts are all over the mcc. Ive also seen a breaker catch on fire and a 10hp drive trip out not only its own breaker but the 800 amp behind it. 

I would not even consider installing one with out fusses which is why i have gone back and put fuses on drives that original were installed with out them.


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## gpop (May 14, 2018)

WronGun said:


> It doesn’t run correctly because of the sensor it’s triggering. I’m wondering if should have it run through it to begin with.
> 
> At the end of the day I’m not responsible for programming but I’d like to make sure my part was done right.
> 
> ...


No disrespect but you are out of your depth and you need help from some one with drive/controls experience. 

The sensor is a CT switch its not affecting the drive but it probably opening the starter that's on the line side that shouldn't be there in the first place. If its not the CT opening the starter then its probably the overload relay that should be there either.


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## glen1971 (Oct 10, 2012)

gpop said:


> No disrespect but you are out of your depth and you need help from some one with drive/controls experience.
> 
> The sensor is a CT switch its not affecting the drive but it probably opening the starter that's on the line side that shouldn't be there in the first place. If its not the CT opening the starter then its probably the overload relay that should be there either.


I believe you mean "...the overload relay that shouldn't be there either."?


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## WronGun (Oct 18, 2013)

gpop said:


> No disrespect but you are out of your depth and you need help from some one with drive/controls experience.
> 
> 
> 
> The sensor is a CT switch its not affecting the drive but it probably opening the starter that's on the line side that shouldn't be there in the first place. If its not the CT opening the starter then its probably the overload relay that should be there either.




No disrespect taken, I am certainly out of my depths. I started out doing small things for this company but somehow got dragged into doing all their vfd work. I figured here is my chance to learn. 

I was up front and told them no control, no programming. I don’t have that knowledge. 

I’m learning now that I I will need some basic fundamentals especially when retrofitting these into existing systems. 

I’m going to take down all the notes from this thread and some recommendations from ABB and try to figure this out tomorrow morning. 

I will separate line and loads

Keep fuses 

Reconfigure CT settings or bypass (will check with control company) 

Recheck VFD settings 


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## gpop (May 14, 2018)

Me talking to my self. 

Why would they add a expensive CT to the panel in the first place when a cheap aux would work.

There has to be something special that a aux can not do. Why would they want to monitor a fan

If the fan stops but the compressor stays running the unit will freezes up so it could possibly damage the coil or the compressor. 

So you need to prove the fan is running but that still doesn't explain a CT

The fan has a belt so the CT switch is set to close only when the amps are higher than a motor running with no load.

So what happens if you bypass it. 

Compressor probably will not run. 

So the CT probably has nothing to do with the fan but is part of the control circuit for the compressor

Can i prove that before stripping the panel 

Yep just lift the switch wire when its running and see what happens


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## WronGun (Oct 18, 2013)

gpop said:


> Me talking to my self.
> 
> Why would they add a expensive CT to the panel in the first place when a cheap aux would work.
> 
> ...




This was existing. 

It originally went breaker -> CT/Starter -> Motor 

Now we’ve added a vfd and used the same line that was in the control cabinet and kept L1 running through the CT. 

The new VFD has its own set of controls and monitor in the lab area. 


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## Wardenclyffe (Jan 11, 2019)

This may or may not be something to check on, If the drives are added to the system where the motors are not "Inverter Duty" they might have an issue with anything that is away from 60Hz. Especially lower Hz and heat doing the motors in.


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## WronGun (Oct 18, 2013)

Everything turned out good today. 

Separated line/load 

Bypassed the starter, kept load side L1 running through the CT but this required installing a jumper between the 2 CT terminals which showed the system as “active” on the existing Bactalk controller. 

After this was up and running.. I landed the control lines and installed Jumper on 9&11, jumper on 10&12 start/stop.

Programmed basic parameters on the VFD’s

Done...

Never thought I’d be getting into this work , but I like it. I have 6 more on next weeks schedule. 



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## gpop (May 14, 2018)

The ct should have a adjustment screw if you start the drive and turn the screw down until the switch closes that should work better than a jumper.


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## gpop (May 14, 2018)

Ask your boss to buy you a drive and a motor that is rated for what ever voltage you have at the shop. Grab some toggle switches and some light bulbs then play on a bench learning how the inputs/outputs and program works. 

Ive always trained the guys that are new to drives on the bench. As a added bonus our ABB rep promised to replace any drive that we programmed in a way that damaged the drive.


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## Wiresmith (Feb 9, 2013)

WronGun said:


> Everything turned out good today.
> 
> Separated line/load
> 
> ...


so what do you think the problem was?

thanks


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## WronGun (Oct 18, 2013)

Wiresmith said:


> so what do you think the problem was?
> 
> 
> 
> thanks




I think the issue was the line side passing through the CT, it is now the wired with Load-side.



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## WronGun (Oct 18, 2013)

So we now have another issue with the larger drive, in the last couple weeks it’s gone through 2 sets of fuses (17.5amp).

Is there a reason to upsize the fuses now that we’ve added a vfd. These are the same size fuses that have been pushing this motor for years. 


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## gpop (May 14, 2018)

WronGun said:


> So we now have another issue with the larger drive, in the last couple weeks it’s gone through 2 sets of fuses (17.5amp).
> 
> Is there a reason to upsize the fuses now that we’ve added a vfd. These are the same size fuses that have been pushing this motor for years.
> 
> ...


When stuff doesn't work its time to read the manual.

page 378 tells you the size/type of fuses for the drive


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## WronGun (Oct 18, 2013)

gpop said:


> When stuff doesn't work its time to read the manual.
> 
> 
> 
> page 378 tells you the size/type of fuses for the drive




I changed Fuses to 25A which I called ABB about, problem solved.


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