# Conundrum: 2 motors pooped out, exact same failure



## micromind (Aug 11, 2007)

Are they NEMA or IEC?


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## Breakfasteatre (Sep 8, 2009)

micromind said:


> Are they NEMA or IEC?


They are Nord iec motors


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## micromind (Aug 11, 2007)

My luck with IEC motors and VFDs has been pretty horrible so far. 

How far from the VFD to the motor?

Is there any type of filtering on the output side of the VFD?


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## Breakfasteatre (Sep 8, 2009)

100 feet, no filters or reactors. shielded cables installed correctly


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## wiz1997 (Mar 30, 2021)

Are the motor settings in the VFD correct for the motor, primarily the frequency settings?

Are the motor internal leads connected for the proper voltage?

Overloads can be caused by the acceleration or deceleration settings. Have any of those settings been changed?

I would verify the motors are wired properly.


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## SCR (Mar 24, 2019)

Breakfasteatre said:


> We are currently commissioning a conveyor system.
> 
> the system has about 20 fractional horsepower motors at 600v.
> 
> ...


The different winding resistances are very suspicious. Are you sure these are 3-phase motors?


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## Peewee0413 (Oct 18, 2012)

wiz1997 said:


> Are the motor settings in the VFD correct for the motor, primarily the frequency settings?
> 
> Are the motor internal leads connected for the proper voltage?
> 
> ...


Joined late, but instantly what I though. I see similar current draw issues all the time when newbies get something like a SEW gear motor pre-wired for a different voltage than supplied. 

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## CMP (Oct 30, 2019)

Can you post the motor tag and a photo of the strap connections? With the current doubling, sounds as if the motors are straped for the lower voltage. Causing the motor iron into severe magnetic saturation. If both motors megged at above 20M ohm, they should run fine if connected properly. The other site motor that you connected to check the VFD output, and it ran fine, may have the connection straps not exactly the same, compare them closely, there could be a terminal differences between motors.

You could also test the two suspected bad motors, by directly connecting them across the line voltage, and checking the current draw. That could rule out the VFD and the cabling as being part of the problem or not. I would also think that if the VFD was programmed properly, that at twice the FLA current that the drive should shut itself down promptly. 600V is pretty unforgiving as to a miswired motor, so check carefully before energizing.


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## Breakfasteatre (Sep 8, 2009)

SCR said:


> The different winding resistances are very suspicious. Are you sure these are 3-phase motors?


The different resistance readings is presumably because those windings have a short in them. 

As for everyone's suggestions, all of these things have been checked. Last thing is to megger out the cable which I'm not sure how it would cause windings to short out.


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## Breakfasteatre (Sep 8, 2009)

The terminal box is strapped for 575v so that's fine.

I am finding out this morning that these motors are not inverter duty. These are motors we keep in stock. Our inventory guy didn't even know what an inverter duty motor was.....


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## Breakfasteatre (Sep 8, 2009)

New motor on, cables meggered out fine at 1000v
Ran it without the gearbox and then mounted. No problems. Bad motor batch? Who knows. we had 3 motors on another system dead too, also Nord gear motors. 
I don't ever recall issues like this when we ran sew.


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## Peewee0413 (Oct 18, 2012)

My facility rarely buys inverter duty motors for any conveyor. I do when they burn up when we are forced to run them at 20hz 19hrs a day. Not being inverter duty does not technically mean a drive can't run it.

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## Breakfasteatre (Sep 8, 2009)

Incidentally, Nord came back with the specs and they are inverter duty.

This is a conveyor system part of a complete packaging system and none of the conveyors are running at 60hz. I'm not sure what happens to voltage when you alter Hz, and in turn the amplitude of the spikes.


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## Almost Retired (Sep 14, 2021)

Breakfasteatre said:


> Incidentally, Nord came back with the specs and they are inverter duty.
> 
> This is a conveyor system part of a complete packaging system and none of the conveyors are running at 60hz. I'm not sure what happens to voltage when you alter Hz, and in turn the amplitude of the spikes.


lower hz also means lower volts, by how much is determined by how the drive is built and controlled


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## Peewee0413 (Oct 18, 2012)

Almost Retired said:


> lower hz also means lower volts, by how much is determined by how the drive is built and controlled


Lower hertz can also means lower fan cooling. Then you Fukushima a motor.[emoji91]

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## Peewee0413 (Oct 18, 2012)

Peewee0413 said:


> Lower hertz can also means lower fan cooling. Then you Fukushima a motor.[emoji91]
> 
> Sent from my SM-S908U using Tapatalk


When I used to take service calls I'd open up a peckerchead and dramatically waft my hand towards my face. Look at my apprentice and say
"Smells like money." 

He didn't last long, but never did he ask what I meant. I still to this day use that line sometimes when I open a smoked motor. Without the dramatic waft gig of course. 

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## Jlarson (Jun 28, 2009)

Small random wound motors are pretty susceptible to punch thru on the windings with drives on longer runs. It often happens quick too. 

I'd think it be real easy to be push IEC motors over their peak withstand limits on a 600 volt drive.


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## Slay301 (Apr 23, 2018)

3rd times the charm try it again


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## Peewee0413 (Oct 18, 2012)

Slay301 said:


> 3rd times the charm try it again


Probably not getting the full story...lol. In my whole career I've seen double failures once.. Allen Bradley servos sequentially made...

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## Southeast Power (Jan 18, 2009)

Breakfasteatre said:


> We are currently commissioning a conveyor system.
> 
> the system has about 20 fractional horsepower motors at 600v.
> 
> ...


Spinning free and went overspeed? What were you expecting, connect it to a load.


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## paulengr (Oct 8, 2017)

Breakfasteatre said:


> Incidentally, Nord came back with the specs and they are inverter duty.
> 
> This is a conveyor system part of a complete packaging system and none of the conveyors are running at 60hz. I'm not sure what happens to voltage when you alter Hz, and in turn the amplitude of the spikes.


Technically at the DC level it’s meaningless. The DC bus voltage is 145% of input voltage, end of story. But if we treat it as sine waves or approximations of that, then two formulas to think about. First is

Power = Torque x Speed

Conveyors are roughly speaking constant torque. If we cut speed in half then power must also be half. Now another one:

Power = Volts x Amps x 1.732 x power factor

Note that Amps is proportional to torque so we can’t change this. So clearly voltage must change. That’s why one operating mode for VFDs is “Volts per Hertz”. So if we go to 30 Hz, voltage is cut in half. In a Volts/Hertz drive it just does this (ignoring boost). In vector mode it ends up close to the same result even though it operates a little different.


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## paulengr (Oct 8, 2017)

Is the VFD cable shielded?

Have you taken the failed motor apart? I would not be surprised if you find 6 equally spaced spots near the end rings where the first couple windings are burned.


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## Almost Retired (Sep 14, 2021)

what speed/Hz are they running at ?
if these motors are expected to run continuously and well below 60Hz, the engineer made a boo boo
now if they arent running that far from 60, then never mind


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## Breakfasteatre (Sep 8, 2009)

It runs at 54hz

Cable is shielded vfd tray cable run in a wiremesh cable tray. Shield is bonded at both ends.

The 3rd motor died this morning. They had production going over the weekend so it lasted 2 days-ish. 

Can a faulty vfd cause this? I would think it would be able to know if it was outputting something that would damage the motor. 

Ab powerflex 525


We have not taken the motors apart yet. Waiting to hear from Nord regarding warranty


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## Almost Retired (Sep 14, 2021)

Breakfasteatre said:


> It runs at 54hz
> 
> Cable is shielded vfd tray cable run in a wiremesh cable tray. Shield is bonded at both ends.
> 
> ...


so it is not the speed
regarding the cable shield bonding
for instrumentation, it is usually recommended to bond one end only of the shield/ground to avoid circulating leakage currents with a parallel loop
is this a possibility here ? maybe try an amp clamp at one end of the shield while connected and running ?

there is also the two separate ground points in the drive, one for supply side common ground and one for motor ground only
(that is , if they still do that . or ever did it on your drive)


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## Breakfasteatre (Sep 8, 2009)

Vfd cable shield is supposed to be bonded at both ends unlike instrumentation cable shields. 

The bond wire at the motor is connected to the ground screw on the terminal box. There is no other ground screw

Nord is sending a tech today or tomorrow. 

On another recent project we had 3 conveyor motors die, also nord. Shorts in the windings. 


I had the millwrights also take apart the belt and look for any mechanical issues that we might have missed. Nothing obvious.


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## just the cowboy (Sep 4, 2013)

Did you take resistance readings on the new motors, before they were powered up?
Since you are running them in high voltage mode the windings are in series, half reading says shorted windings, really need you to post more information on nameplate. When you say one winding do you mean with all jumper off or with connections made up?
I have seen this on low voltage connections where it had say 40 instead of 20 ohms, varnish on lugs to connection block caused opens.


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## Breakfasteatre (Sep 8, 2009)

Meggered both spare motors with jumpers off.

I have 1 motor left. I'm going to replace the disconnect switch too Incase the contacts are faulty... Hubbell md30, not a total turd


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## Peewee0413 (Oct 18, 2012)

Breakfasteatre said:


> It runs at 54hz
> 
> Cable is shielded vfd tray cable run in a wiremesh cable tray. Shield is bonded at both ends.
> 
> ...


Did you test the FLA uncoupled then connected? If the 525 is set up correctly you would not OC to smoke the windings. How big is the conveyor/load...

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## Breakfasteatre (Sep 8, 2009)

Yes, ran uncoupled then connected to the gearbox l

load is clear plastic tubs that weigh a couple grams.

Length of conveyor is like 10 feet


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## JRaef (Mar 23, 2009)

The Nord 575V motors are wound as 332/575V, so when you connect them, *you must connect it in Wye for 575V*. If you connected them in Delta, you are connecting them as 332V and although they will run at the correct speed and create torque, you are saturating the windings and will over heat the motor. I know this because I have seen it done on a machine I built the controls for once that was sent to Canada. We had tested everything at our shop in Seattle first, but the machine was disassembled for shipment and the guy at the receiving end thought he knew better and connected it in delta.


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## Peewee0413 (Oct 18, 2012)

Breakfasteatre said:


> Yes, ran uncoupled then connected to the gearbox l
> 
> load is clear plastic tubs that weigh a couple grams.
> 
> Length of conveyor is like 10 feet


What was the current readings of each test?

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## Breakfasteatre (Sep 8, 2009)

JRaef said:


> The Nord 575V motors are wound as 332/575V, so when you connect them, *you must connect it in Wye for 575V*. If you connected them in Delta, you are connecting them as 332V and although they will run at the correct speed and create torque, you are saturating the windings and will over heat the motor. I know this because I have seen it done on a machine I built the controls for once that was sent to Canada. We had tested everything at our shop in Seattle first, but the machine was disassembled for shipment and the guy at the receiving end thought he knew better and connected it in delta.


Yes, they come pre-set 575 and I did confirm they were jumpered for wye orientation 

Once upon a time we tested a system at the shop on 240v 3 phase, low voltage on the motors. On site, the control panel furnished by another contractor was 480v. Most of the motors were set back to 480v high voltage but a couple were missed and when they guys wired them on site, they did not notice.

We now have a 480v test panel...


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## Breakfasteatre (Sep 8, 2009)

Peewee0413 said:


> What was the current readings of each test?
> 
> Sent from my SM-S908U using Tapatalk


~0.6 amps in both instances, below nameplate Fla, for the 2nd replacement (3rd motor ) that lasted the weekend

The first replacement motor ( the second motor installed) drew 1.6 amps immediately and let the stank out


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## gpop (May 14, 2018)

If i was evil how could i cause a problem like this to torment my trainee.

I could miss-wire the motor a number of different ways and even add a jumper over one coil pack but he would probably figure that out after the fist one popped.
If it has a heater i could wire that to the wrong voltage or wire voltage to a built in thermal sensor i don't think he would notice that straight away.
I could set the vfd to hold the motor instead of stopping it over long periods but that should be easy to spot.
Vfd cable makes being evil harder unless someone terminated the ground at a common bar rather than at the drive or left a huge piece rolled up on the back of the cabinet.

Maybe im not evil enough or you simply have a bad batch of motors especially if all the failures are the same HP.


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## Peewee0413 (Oct 18, 2012)

Is the gearbox turning a chain or just a driving sprockets or a roller? 

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## Breakfasteatre (Sep 8, 2009)

Peewee0413 said:


> Is the gearbox turning a chain or just a driving sprockets or a roller?
> 
> Sent from my SM-S908U using Tapatalk


Gearbox is driving a shaft with a sprocket.

With the motor off, you can easily turn the shaft by turning the input spline inside the gearbox with your hand


I think I might have figured out what the issue was. I've alluded to it earlier in the thread. I'll be sure to update it tomorrow


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## JRaef (Mar 23, 2009)

gpop said:


> If i was evil how could i cause a problem like this to torment my trainee.
> 
> I could miss-wire the motor a number of different ways and even add a jumper over one coil pack but he would probably figure that out after the fist one popped.
> If it has a heater i could wire that to the wrong voltage or wire voltage to a built in thermal sensor i don't think he would notice that straight away.
> ...


I did a project once with 144 small (3/4HP) Baldor motors on evaporative coolers, all run by VFDs. Within the first 6 weeks, we lost 80 motors! I went through every trick in my book trying to figure it out, but Baldor kept blaming the VFDs, saying that these motors were "inverter ready" (note, they didn't say inverter DUTY...).We went so far as to hook up scopes to the motors while running to look for voltage spikes etc. and the highest we saw was 900V, which would have been WELL within the acceptable range for a motor even if it WASN'T "inverter ready". Finally after another month of hair pulling, Baldor admitted they had some sort of design flaw on these small frames and replaced them all with 1HP motors for free.


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## paulengr (Oct 8, 2017)

Breakfasteatre said:


> It runs at 54hz
> 
> Cable is shielded vfd tray cable run in a wiremesh cable tray. Shield is bonded at both ends.
> 
> ...


Yes VFDs can fail motors in hours. Lots of ways.

They can shred bearings from bearing fluting…basically lack of filtering.

They can destroy windings from reflective waves from locating a drive too far away without proper filters.

If you have a bad analog input on the drive many can do bad things. Motors with current imbalances of 5% need to be derated by 30% so a 10 HP motor is now 7 HP. If a VFD sensor goes out of calibration it can eat motors.

If there are harmonics issues (likely in your case) you can induce crazy variable voltage DC bus and tear up the VFD or motors.

Sometimes especially on small VFDs or light loads you can have a single bad diode or transistor destroying motors.

Often customers put in load reactors “just because” and these or other output filters go bad, wiping out motors in hours.

Output contactors in bypasses can do this too.

I’ve seen all of the above and more. Sometimes you get fault codes, sometimes not. In your case this is particularly difficult with multiple motors per drive because the good ones disguise the one going bad.

Nobody is going to rebuild those motors. I’d just take it apart and do a full evaluation anyway. It is pretty rare to see a “bad batch” of motors but once in a while we catch something.


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## paulengr (Oct 8, 2017)

Do you have an actual ground between frame and VFD, not just a foil shield? That’s important for bearing fluting.


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## paulengr (Oct 8, 2017)

Almost Retired said:


> so it is not the speed
> regarding the cable shield bonding
> for instrumentation, it is usually recommended to bond one end only of the shield/ground to avoid circulating leakage currents with a parallel loop
> is this a possibility here ? maybe try an amp clamp at one end of the shield while connected and running ?
> ...


Instrumentation grounding rules do not apply to power. And VFD cable has a drain which is different as well. Bond away. It can’t hurt unlike communications.

Drives never really separated grounds. They both connect to the DC bus.


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## 460 Delta (May 9, 2018)

JRaef said:


> I did a project once with 144 small (3/4HP) Baldor motors on evaporative coolers, all run by VFDs. Within the first 6 weeks, we lost 80 motors! I went through every trick in my book trying to figure it out, but Baldor kept blaming the VFDs, saying that these motors were "inverter ready" (note, they didn't say inverter DUTY...).We went so far as to hook up scopes to the motors while running to look for voltage spikes etc. and the highest we saw was 900V, which would have been WELL within the acceptable range for a motor even if it WASN'T "inverter ready". Finally after another month of hair pulling, Baldor admitted they had some sort of design flaw on these small frames and replaced them all with 1HP motors for free.


How pray tell were you able to get them to fess up to a design flaw? 

OEM’s are loath to ever admit fault. 

Maybe you sent Rocko and Vinny down for a “friendly” meeting?


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## sullmitw7 (5 mo ago)

Breakfasteatre said:


> We are currently commissioning a conveyor system. the system has about 20 fractional horsepower motors at 600v. the first conveyor is the shortest, and so far, has several days worth of run time on site, and several days of run time at the shop. This morning, the VFD faulted, overload. the motor was running at double the name plate amps. There was no obvious mechanical problem with the conveyor. motor was isolated from the gearbox and still drew twice fla motor was wired to a different VFD and still drew twice fla a known good motor was wired to original VFD that had the bad motor and it ran at nameplate fla no problem New spare motor was brought in from the shop. It was installed, turned on and within seconds it was up at double nameplate amps, exactly the same as the first. Isolated from gearbox, run on a different vfd, same result. both motors fla were 0.8 amps and both motors drew 1.8amps pulled the motors and isolated the wiring. Meggered out the windings and they were fine, but 1 set of windings on both motors (the same winding on both) was showing half the resistance as the other two windings. 20ohms vs 40 for the other two. I have 2 more motors coming in tomorrow interestingly, the motors were within 20 digits on their serial numbers. I am going to bring the megger to site and check the cable, which is about 100 feet of 14/4 + aux VFD tray cable run in a enclosed wire mesh cable tray but i dont see how the cable could be damaged and allow the motor to run motor was not single phasing any thoughts/suggestions?


 This can be an issue with extra long motor feeders. I’ve had the same thing happening on larger 3ph, 480vac motors on vfd. You will need to install a sized line filter for each motor. The basic is this, vfd’s are great for short run feeders, but at 100 + ft you will see this more often. If you could capture with a scope meter a segment of a motor running, and blow up the image , also check peak to peak voltage, you’ll find a lead spike that can go as high as 50+ volts. Without special testing equipment it’s in the grey area. It’s that lead spike that causes a burnout in a winding. And it’s usually very close to a cluster inside the motor windings.


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## sullmitw7 (5 mo ago)

Breakfasteatre said:


> We are currently commissioning a conveyor system.
> 
> the system has about 20 fractional horsepower motors at 600v.
> 
> ...


The issue is the distance. You will need to install a line filter for each motor. Why? It softens the blow. VFD have a tendency to have a lead end spike on the block wave form. This starts to happen at or near 100’. If you could acquire a scope meter and capture a run segment, blow it up, also check the peak to peak voltage. You will find a small spike at 50+ volts on the lead edge of the wave form. It’s that spike that cause the burnout in a winding, and inspection of the windings would show the burnout pretty close to the internal wind clusters. 
Sound really dumb, but the line reactor/filter will solve the problem. In the future, watch the distances, after 4-5 motors you’ll see the patterns. Knowing this can help you become a better electrician. The cost of a scope meter is 1k+, I just happen to have one. And I needed to know why.


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## sullmitw7 (5 mo ago)

460 Delta said:


> How pray tell were you able to get them to fess up to a design flaw?
> 
> OEM’s are loath to ever admit fault.
> 
> Maybe you sent Rocko and Vinny down for a “friendly” meeting?


Look at line reactor/filters for each motor. And yes, the higher voltage you can’t see with most meters, a good scope meter, or one that can give you a true peak voltage. The filter/reactor softens the spike, save the motor.


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## paulengr (Oct 8, 2017)

460 Delta said:


> How pray tell were you able to get them to fess up to a design flaw?
> 
> OEM’s are loath to ever admit fault.
> 
> Maybe you sent Rocko and Vinny down for a “friendly” meeting?


Funny. I’ve had to do just that, more than once. Have you ever heard of a factory acceptance inspection? It’s very common with large, expensive custom equipment. How about site inspections for quality control?

But the most ridiculous situation was when Howard Industries held up a half dozen transformers. I had one or two for Nutrien, largest fertilizer company in the world. Consol, a major coal company had several too. All going into custom built substations. So it was 16 week delivery. We were told engineering done, steel ordered, winding started, all the usual things. Suddenly at 16 weeks things didn’t sound right, like when Howard said they just preferred steel!?!! That’s when the builder sent “Rocko”. He shows up at the door promptly at 8 AM. Where is the owner? Out for the week. How about the plant manager? Called in sick. That’s when “Rocko” said that’s funny I just talked to him on the cell phone when I pulled in the drive. That’s when it got ugly. Turns out nothing was done. 80% of their employees were in jail because of an ICE raid. The transformers were shifted to other manufacturers and Howard got scratched off everyone’s Christmas list.

That’s not the only time I had to either send someone or show up at a vendors office to get to the bottom of an issue. When OEMs screw up they usually try to hide it, hoping the problem will get better on its own instead of just owning up and taking steps to clean it up.


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## Wardenclyffe (Jan 11, 2019)

Check number of poles in the drive setting,...


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## Peewee0413 (Oct 18, 2012)

Wardenclyffe said:


> Check number of poles in the drive setting,...


I thought that was typically used for RPM feedback?

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## Wardenclyffe (Jan 11, 2019)

Peewee0413 said:


> I thought that was typically used for RPM feedback?
> 
> Sent from my SM-S908U using Tapatalk



Number of poles determines speed, he said it was running twice the speed?


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## Almost Retired (Sep 14, 2021)

Wardenclyffe said:


> Number of poles determines speed, he said it was running twice the speed?




twice the *amps*


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## Wardenclyffe (Jan 11, 2019)

Don't check the setting then,...


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## paulengr (Oct 8, 2017)

Peewee0413 said:


> I thought that was typically used for RPM feedback?
> 
> Sent from my SM-S908U using Tapatalk


In V/Hz mode it’s just used for calculations in pretty much all other modes it’s important. For instance in sensorless vector the VFD effectively calculates the 6 parameter motor model. During operation it measures current and phase angle to estimate torque and speed. If you feed in incorrect name plate data the tuning might work or might not. Tuning in vector mode can be so touchy that simply swapping motors requires redoing the tuning (autotune again).


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## gpop (May 14, 2018)

Wardenclyffe said:


> Don't check the setting then,...


That got me thinking which is odd as im only on my first cup of coffee. 

Maybe someone maxed the pulse frequency to quieten down the motors. 

I have another idea. OP can you ask the drive what settings are not at default and post the list (it should be short and is easy to do especially if you have a laptop)


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## frankendodge (Oct 25, 2019)

So I'm out of my element here.. not a motors guy, though I love reading this stuff.
The original post said 2 identical motors with serial numbers within 20 digits of each other both had low resistance on the SAME winding, and wouldnt work on a second known good vfd. A different brand similar motor ran fine.
Wouldn't this point to a bad batch of motors, with windings internally connected in parallel instead of series on one phase? The way QC seems to be going across every end of manufacturing I wouldn't be surprised..


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## CMP (Oct 30, 2019)

Breakfasteatre said:


> Gearbox is driving a shaft with a sprocket.
> 
> With the motor off, you can easily turn the shaft by turning the input spline inside the gearbox with your hand
> 
> ...


Do you have some updates? We would be interested in hearing about the trouble shooting.


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## JRaef (Mar 23, 2009)

460 Delta said:


> How pray tell were you able to get them to fess up to a design flaw?
> 
> OEM’s are loath to ever admit fault.
> 
> Maybe you sent Rocko and Vinny down for a “friendly” meeting?


As it happened, the mechanical contractor on the job had just done a similar project down the road and had the EXACT same issue but in their case, even though they were using a different brand of VFD. Baldor had blamed the VFD mfr on that one too, but the problems never got resolved even when he changed the VFDs. I showed him our findings on the VFDs and convinced him that this was not a VFD issue, so he pulled the local Baldor rep in and threatened him with NEVER allowing Baldor motors on any of his projects again. He probably was putting in 5,000 motors per year all over the West Coast, so it was significant enough to garner some attention. So yeah, his version of "Rocko and Vinny" I suppose...


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## Breakfasteatre (Sep 8, 2009)

so, fortunately for me because I was busy finishing up another production line installation, I didn't do any of the final troubleshooting. 

I suspected an issue with the disconnect causing an intermittent single phasing condition. I was able to replicate it by hitting the disconnect with the butt of a screw driver. I would momentarily lose the contact. maybe. I was doing it by myself and could have easily jiggled the lead on my meter causing the loss of contact


someone else changed out the motor, vfd and disconnect over the weekend and its been running all week. I can't say for certain what the issue actually ended up being. They also upped the size to 1hp.

it just so happens that this motor was the furthest one from the panel, at about 100'

I will mention the recommendation to add reactors and/or filters to the integrator we work with

i appreciate all of the suggestions


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## MikeFL (Apr 16, 2016)

*Thanks* for the update!


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## micromind (Aug 11, 2007)

Thanks for letting us know how it turned out. Very much appreciated!


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## FisherElectricAutomation (Jan 5, 2021)

I would have also been inclined to investigate your difference in winding resistance. I presume its a dual voltage, 9 or 12 lead (no photo of name plate or connections attached), but none the less I'm leaning towards miswired from the factory. If it is one leg might be connected parallel. Problem with too many theories, changing drives, disconnects and testing cables I think you were on the right track in the first place. I know the rush to fix with production deadlines pulling 24hr shifts. It's fixed now and thats great, but what was the issue? The motor current reading on the 525 will not show you a-b a-c and b-c separately which could have reinforced this, should have rented a three phase scope at the minimum on site. Fluke makes a drive analyzer for this purpose mda-550 is on my christmas list  DO NOT SEND THE FAULTY MOTORS BACK YET. Take them to a reputable motor shop for a written report

We had a number of 5hp baldors, also in chillers probably 5 years back, **** the bed in a slaughterhouse week after week. One by one replacing them over conveyor lines for double time sometimes twice in a row. Local motor shop checking and rewinding them was the ultimate fix. Baldor blamed us and Rockwell. Refrig contractor's vendor had same issues with different controls, ECs. Prestart QC and records are extremely important if anyone ever gets sued


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## Peewee0413 (Oct 18, 2012)

The only drive I ever had blow in my face on power up was a Baldor. I do like thier washdown motors though. 

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