# Interesting Troubleshoot.



## micromind (Aug 11, 2007)

About 4 months ago, I replaced a soft-start with a VFD at one of the cities wells. It's a 300 HP hollowshaft vertical motor and the bowls are about 400' down. 

FLA of the motor is 340 amps, SF is 1.15. It usually ran at about 350 amps or so. They would cook a motor every 2 years or so and had a spare on site. 

Got a call that the existing motor had failed and the rewound one was installed. It would not go past 9HZ, then it's trip on O/L. 

The VFD is an A/B 753, 361 amp. I had the current limit set at 450 amps, it ran the old motor just fine. 

When I got there, everything looked ok, the well co. had meggered the new motor and said it was ok. Parameter 7 is output current (I think......lol) so I set that in the display and lit it off. 450 amps or so.........9HZ. 

DC bus voltage was about 685 no-load and 660 @ 450 amps. 

Motor is 6 lead and is connected correctly, 2 leads are T1, 2 more are T2, and the other 2 are T3. 

The rewind shop sent a tech out, we disconnected the motor from the VFD and surge tested it. It looked good. 

At this point, it's either the motor or the VFD. 

They had a 250HP spare at another well, so they brought it over. While it was still strapped to the truck bed, I connected it to the VFD with 3 - #2s and a #6 ground. 

I set the ramp to 10 seconds and 30HZ. 

It ran just fine. Peak current was about 180 and it went to 24 amps once it stabilized. 

Obviously, a bad rewind. But why would it surge test ok? If one of the coils were reverse polarity, would a surge test pick it up? 

I'd really like to know but I'm not sure if the motor shop will admit that they screwed up.


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## backstay (Feb 3, 2011)

What's a surge test? Is that a bump of the motor like we would do for rotation?


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## joebanana (Dec 21, 2010)

If the spare ran on the truck, then the original motor needed a trip back to the rewinder They'll never admit if they screwed up. But, if it comes back and runs, they won't have any choice but to admit it.


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## telsa (May 22, 2015)

ALL substantial gear needs to be properly tested before being sent into the field.

What a screw-up !


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## frenchelectrican (Mar 15, 2007)

micromind said:


> Got a call that the existing motor had failed and the rewound one was installed. It would not go past 9HZ, then it's trip on O/L.
> 
> The VFD is an A/B 753, 361 amp. I had the current limit set at 450 amps, it ran the old motor just fine.
> 
> ...



There is very specfic reason why it kicked out due one set of coils maybe two is reversed of normal portalrty connection just like a multi cylinder engine with crossed sparkplug wires ( connected wrong location ) it may turn over but will not take full load at all. 

basically the same way with DC motors too just remember that when if you ever get one of the field and armutre on backward connection it the same thing.,, it will turn over a little but once you crank up the voltage it will just grunts hard inside.

Hupmm most motor shop will not really spill the beans too much on their mistake espcally with reversed coils sets which I have see it once a while but not very often.


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## John Valdes (May 17, 2007)

backstay said:


> What's a surge test? Is that a bump of the motor like we would do for rotation?


Its an expensive piece of electronic equipment designed to test motor winding's and all related to motor winding.
Google "Baker Surge Tester" and see for yourself.



micromind said:


> About 4 months ago, I replaced a soft-start with a VFD at one of the cities wells. It's a 300 HP hollowshaft vertical motor and the bowls are about 400' down.
> 
> FLA of the motor is 340 amps, SF is 1.15. It usually ran at about 350 amps or so. They would cook a motor every 2 years or so and had a spare on site.
> 
> ...


Its not unusual to for a VFD to be a better judge of motor integrity than any test equipment including the equipment motor shops use.

I personally have seen shop testing show no issues, while the VFD does see it. Its usually a ground fault that the VFD is pretty darn good at recognizing.
We had to send motors back to the manufacturer to get an answer.
Not exactly sure what they do different than a motor shop, but in two cases like this, Baldor verified the ground fault and replaced the motor under warranty.

Motor winders know how to do one thing very well. Wind motors.
Sometimes when a motor comes into the shop, its late at night or on weekends.
The driver that picks up the motor is usually trained to count the winding turns and fill out a form for the winder.
He cuts out one the stator end, counts turns and puts it in a burn out oven. Then it gets removed 8 hours or so later and is sand blasted and the core is tested.
It is only then that the motor goes to the winder.

In the 6 years I worked in a motor shop I have never seen a winding connected wrong as far as polarity.
Now there are many other problems that could present themselves. But polarity is hard to screw up on a rewind.
I'm not even sure how it could have left the shop like this as they do run test motors before allowing it to be returned to the customer.
They don't always do a load test. But they do surge test or Hi-Pot test, then run the motor.

A good motor shop wants to know whats up as much as you do Rob.
A motor this size and style would get the luxury treatment at a good shop.


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## Big John (May 23, 2010)

I don't know the answer to your problem except to say a surge test is first-and-foremost an insulation integrity test. You could have a very wonky motor, but as long as there were no turn-to-turn failures or ground faults, it would pass a peak-to-peak surge test.

Where it would likely show up is the difference in line-to-line surge tests because you're comparing impedance on the windings for each phase, instead of comparing each winding to itself. The problem is, your rotor is in a different position relative to each phase winding and affects the impedance of each phase winding differently. So if you do a L-L test without rolling the rotor by hand, it will fail every time because there will be too much difference between windings. 

This is why most places don't do L-L tests on large motors (me included). But you miss out on that very important winding impedance data which may have indicated your fault.


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## Mike_kilroy (Sep 2, 2016)

Being johny on the spot, did you try swapping each set of windings? Wouldn't take long, only 3 to try. You might be a hero.

Sent from my SM-G900V using Tapatalk


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## John Valdes (May 17, 2007)

Mike_kilroy said:


> Being johny on the spot, did you try swapping each set of windings? Wouldn't take long, only 3 to try. You might be a hero.
> 
> Sent from my SM-G900V using Tapatalk


The connections he needs to reverse* could* very well be tied down to the stator and dipped/VPI and baked.


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## Mike_kilroy (Sep 2, 2016)

John Valdes said:


> The connections he needs to reverse* could* very well be tied down to the stator and dipped/VPI and baked.


Yep could be, but not in his case. 

He said it had 6 wires, two each marked T1, T2, T3. So all 3 "coils" were brought out to his connection point.

I have watched motor rpr shop techs use clip leads to tie the wires together for final testing, then unclip it all and maybe LABEL it later - easy to swap a T2 & T3 label on each end of a coil.

I have also clearly instructed rpr shops how to reconfig H windings in each phase and have them mess it up so the resulting motor is now configured for 4x higher voltage instead of double.


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## John Valdes (May 17, 2007)

Mike_kilroy said:


> I have also clearly instructed rpr shops how to reconfig H windings in each phase and have them mess it up so the resulting motor is now configured for 4x higher voltage instead of double.



Not sure I understand your statement.
"H" winding? Are you talking wire temp?
Mess it up?

Thanks in Advance.


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## JRaef (Mar 23, 2009)

John Valdes said:


> ...
> Its not unusual to for a VFD to be a better judge of motor integrity than any test equipment including the equipment motor shops use.
> ...


Alternate definition of "VFD":
"Veritable Fault Detector"

Because modern VFDs are now having to look at very tiny little details about the "motor equivalent circuit" in order to do some of the advanced magic they do, they now see things that other testing procedures might miss.


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## Bird dog (Oct 27, 2015)

JRaef said:


> Alternate definition of "VFD":
> "Veritable Fault Detector"
> 
> Because modern VFDs are now having to look at very tiny little details about the "motor equivalent circuit" in order to do some of the advanced magic they do, they now see things that other testing procedures might miss.


So, would it be overkill or best practice to hook a motor up to the VFD for testing before you drop it down the well?


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## Mike_kilroy (Sep 2, 2016)

John Valdes said:


> Not sure I understand your statement.
> "H" winding? Are you talking wire temp?
> Mess it up?
> 
> Thanks in Advance.


Sorry for confusing description... Reliance had a habit for years on some high performance spindle motors to make each phase out of 4 separate windings, then hook them together inside the endbell of the motor. The old drives were 230v 3ph. They used high tech high voltage wire (insulation) so the motors could handle 460v easy.

So for retrofitting the old obsolete drives we have a local motor shop "reconfig" the 4 windings so we can run with a 460v VFD - thus 1/2 the size and space. So the original vs new specs become:

*MOTOR DATA*
Reliance 15 HP spindle motor with nameplate date:

*ORIGINAL MOTOR DATA BEFORE RECONFIG*
15 HP, 1500/4500 rpm
46 amps, 180 Volt
210tdz FRAME, Model P21G9401A, run with VC-90 before now

*RECONFIGURED IN ENDBELL FOR 460V OPERATION *
15 HP, 1500/4500 rpm
23 amps, 360 Volt
210tdz FRAME, Model P21G9401A, run with new Refu drive

Motor shops, seeing 180v on nametag, figure they have to put all 4 windings in SERIES! When we go to startup that machine, the current is thru the roof until we send it back and have them change it...


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## Mike_kilroy (Sep 2, 2016)

Another similar model, also called H for some reason is as shown. in attachment. Anyway, point was motor shops typically do not have engineers, and so can mess stuff up if non standard like this.

*ORIGINAL MOTOR DATA BEFORE REWIND
*30 HP, 1500/4500 rpm
110 amps, 51.4Hz 
PF=0.90 (we believe)
145 Volt, calculated magnetizing current Isd=34.7amp
This motor increases to approx. 215Vac at around 74Hz or 2220rpm

Reliance spec update: they now say 145V, .804pf, 30.2a no load, 121a rated

*RECONFIG for use on 460V MOTOR DATA 
*30 HP, 1500/4500 rpm
60.5 amps, 51.4Hz 
PF=0.80
290 Volt, magnetizing current Isd=30amp
This motor increases to approx. 430Vac at around 74Hz or 2220rpm


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## Mike_kilroy (Sep 2, 2016)

Bird dog said:


> So, would it be overkill or best practice to hook a motor up to the VFD for testing before you drop it down the well?


i THINK IT would be overkill.

Do we see our sophisticated drives saying ground fault and all the local motor shop guys tests saying no? Yep. Then the rewind shops getting involved and seeing the issue. The good VFDs will detect this much better than all the surge, hi-pot, etc local tests. But that does not mean if makes sense to hook up to a cheap VFD first.


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## JRaef (Mar 23, 2009)

Bird dog said:


> So, would it be overkill or best practice to hook a motor up to the VFD for testing before you drop it down the well?


How do you check rotation? I do it by hooking up the drive to the motor before dropping it. Pulling a motor is an expensive proposition. 

I once was involved in one where the 200HP deep well submersible pump was not tested above ground. After being connected to the VFD and bypass soft starter, the drive would run the motor, but not at full speed so no water to the top of the well (1500ft). The soft starter just tripped on OL after a few minutes. After a $10k biil to pull the pump back out, turned out someone had over tightened an access plug over the pump/motor coupling and the plug was rubbing against the coupling. The rubbing caused a nearly locked rotor in the motor, so it couldn't get to full speed. The VFD would just go into current limit without tripping, but the reduced speed meant the water column couldn't rise. The soft starter would finish ramping and then tripped. Had they tested it above ground, they would have seen it, saved themselves $10k+ the delays.


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## micromind (Aug 11, 2007)

Update........I wasn't there but was told over the phone by the head of Public Works. 

The motor came back from the shop today, it was installed and connected by the well guys. It ran perfectly. 

The shop said there were 'issues' with it but didn't elaborate so I don't know exactly what was wrong with it. 

It could have been something as simple as 2 of the 6 leads mislabeled or it could have been something internal. Wish I knew. 

Main thing is it's been pumping 2600 GMP for about 6 hours and looks like it's ok now.


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## Jlarson (Jun 28, 2009)

'issues'

That's motor shop code for we ****ed up it up super bad.


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