# Motor issue



## RICHGONZO1 (Mar 5, 2012)

Yesterday I was called to a critical piece of equipment about the breaker tripping. Megged motor and checked windings, all seem good. Put my meter and measure instantaneous, 150 HP motor 177 FLA and motor is on a soft start, it's a fan. Start motor breaker immediately trips, shows only 270A? Instantaneous is set at 2000A and I looked at the analog meter on the main and didn't see a huge spike. We uncouple the motor and go for a start, tripped again with same amps, rotor is free and so is fan. Megged again and decided to change breaker because 270A does not seem right to me on a 250A breaker tripping instantly. And yes I checked both line and load sides and used 2 meters. Changed breaker and ran uncoupled at 70A pretty steady, a little high, but management decided against changing the motor. Coupled back up and what do you know it tripped again, increased instantaneous and took out the main. Decided just to go ahead and change the motor, winding readings and megger test all are the same. Started and it ran and it's been running. I hate those, makes me feel incompetent.


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## backstay (Feb 3, 2011)

RICHGONZO1 said:


> Yesterday I was called to a critical piece of equipment about the breaker tripping. Megged motor and checked windings, all seem good. Put my meter and measure instantaneous, 150 HP motor 177 FLA and motor is on a soft start, it's a fan. Start motor breaker immediately trips, shows only 270A? Instantaneous is set at 2000A and I looked at the analog meter on the main and didn't see a huge spike. We uncouple the motor and go for a start, tripped ag


What's the voltage, how did you meg it? Did you also meg the feeders? Disconnect at the load side of the soft start and try. You need to break the system into smaller parts.


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## RICHGONZO1 (Mar 5, 2012)

Sorry, sent it before I finished


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## RICHGONZO1 (Mar 5, 2012)

Also I was under the assumption that a soft start will not run with no load on it kinda like a VFD will not run without load


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## RICHGONZO1 (Mar 5, 2012)

My old job I used to have a 1hp 480v 3p with a whip on it just for that occasion. Need to get one for this shop


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## JRaef (Mar 23, 2009)

RICHGONZO1 said:


> Yesterday I was called to a critical piece of equipment about the breaker tripping. Megged motor and checked windings, all seem good. Put my meter and measure instantaneous, 150 HP motor 177 FLA and motor is on a soft start, it's a fan. Start motor breaker immediately trips, shows only 270A? Instantaneous is set at 2000A and I looked at the analog meter on the main and didn't see a huge spike. We uncouple the motor and go for a start, tripped again with same amps, rotor is free and so is fan. Megged again and decided to change breaker because 270A does not seem right to me on a 250A breaker tripping instantly. And yes I checked both line and load sides and used 2 meters. Changed breaker and ran uncoupled at 70A pretty steady, a little high, but management decided against changing the motor. Coupled back up and what do you know it tripped again, increased instantaneous and took out the main. Decided just to go ahead and change the motor, winding readings and megger test all are the same. Started and it ran and it's been running. I hate those, makes me feel incompetent.


Could just be that the inrush (magnetizing) current was very high but too fast for your meter to see it. It's very common now on energy efficient motors for that magnetizing inrush current to be 2000% of the motor FLA, but only for 1 to 1-1/2 cycles (15-25msec.) which is too fast for many meters. It varies from motor to motor, even of the same make and model, because of the random nature of the way they wind the motors to increase the efficiency. It's actually a lot more common than you might think. Changing out the motor may have worked just because the new motor was slightly different.



RICHGONZO1 said:


> Also I was under the assumption that a soft start will not run with no load on it kinda like a VFD will not run without load


No, not true. 

A) A VFD will run without a load, albeit it does no good of course. A VECTOR drive will likely trip after a few seconds because it does not see the expected motor model.

B) Most soft starters will turn on without a load, but there will not be a "soft start" because there is nothing for it to soft start, so if you read the output voltage even a second into it you will see 100%. Many, if they have Phase Loss protection, use current to detect a phase loss and will trip out in 3-5 seconds if any of the phase currents are below some threshold level, like 20%. With no load, ALL 3 phases will be below that threshold, so the condition is true and it trips.

In your situation though, the soft starter SHOULD have prevented the high inrush. So you might want to check to see if someone has turned on a feature called "Kick Start" (also called "Pedestal Start" or "Boost Start", something like that). This feature is kind of dumb because it defeats the PURPOSE of a soft starter to some extent. It allows the user to goose the initial voltage, up to 100%, for the first 2 seconds after a Start command. In theory this can be useful if you have a lot of friction or icing, or if you want a very low level boost to begin with so that you pull up chain slack or something. But 99% of the time you do NOT want to use it if set high, yet people sometimes turn it on anyway, not knowing why or even what it is. If it's on, it probably should not be, or it is set way too high.


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## RICHGONZO1 (Mar 5, 2012)

JRaef said:


> Could just be that the inrush (magnetizing) current was very high but too fast for your meter to see it. It's very common now on energy efficient motors for that magnetizing inrush current to be 2000% of the motor FLA, but only for 1 to 1-1/2 cycles (15-25msec.) which is too fast for many meters. It varies from motor to motor, even of the same make and model, because of the random nature of the way they wind the motors to increase the efficiency. It's actually a lot more common than you might think. Changing out the motor may have worked just because the new motor was slightly different.
> 
> No, not true.
> 
> ...



I had a feeling that my meter wasn't picking it up fast enough. usually it does pretty good on catching it, it's a fluke 376. What about a recording amp meter, wonder if they could capture that? I'm looking for one now and have had the aemc ones that seemed to work well, I'm curious of what else is on the market. Maybe when I do more research I'll post.

I didn't see the use of dropping the leads off the soft start, it ran uncoupled! That's what really didn't make any sense!

I could see it ramping up while it was uncoupled so I kinda ruled out the soft start not going through its sequence. I will have to look for that parameter, i was thinking that the soft start was bypassed before it ran uncoupled. Also on a side note, there was no ol class specified. I just went ahead and threw a 30 in there seeing as it has a high inertia load and takes roughly 30 seconds to fully ramp.

But in the end, it was the stupid motor failing under load and reading clear on static. I think the PDMA would have caught that.


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## lefleuron (May 22, 2010)

Here is something I have come to learn after many years of doing this.

You and I try our best to diagnose a motor using 500-2000 dollars or so of equipment. We use our knowledge and tools at hand.

Sometimes a good motor shop with $60,000 to $200,000 dollars worth of equipment cannot pin-point exactly what is wrong with a motor- they just recommend a complete rebuild.

I believe that the equipment you and I use is great for "ball-park" figures 
that we use, combined with what we have learned over the years to make our best guess.

But sometimes many small things add up in a motor, none that you or I could point to and say "thats the problem", but combined they cause these types of odd problems.

Certainly nothing to feel bad about, this stuff happens in factories across the globe every day. Happened to me 5 months ago, same kind of thing.


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## varmit (Apr 19, 2009)

I would tend to blame the soft start. That is about the only thing that could trip the breaker instantly if there is no ground fault down stream of the soft start.

I have seen control boards with intermittent failures that would create a phase to phase short in the power section a few times before the drive failing completely.

YOU DO NOT WANT TO MEG MOTOR LEADS IF CONNECTED TO A VFD OR SOFT START.


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## RICHGONZO1 (Mar 5, 2012)

varmit said:


> I would tend to blame the soft start. That is about the only thing that could trip the breaker instantly if there is no ground fault down stream of the soft start.
> 
> I have seen control boards with intermittent failures that would create a phase to phase short in the power section a few times before the drive failing completely.
> 
> YOU DO NOT WANT TO MEG MOTOR LEADS IF CONNECTED TO A VFD OR SOFT START.


Not the soft start, ran uncoupled. Changed the motor and ran. If you meg connected to a VFD or soft start, you have no business working in industrial alone.


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## Big John (May 23, 2010)

It's very strange to me that changing the breaker made _some_ difference but didn't completely solve the problem. It's also very strange to me that you have a soft-start in place that in theory should reduce the exact problem you're seeing, it makes me believe the issue is with the soft-start, but yet changing the motor solved the problem.

What type of of soft-start? Were the breaker settings identical, and did you get any trip flags? Were the models of motor the same? I don't use PDMA so I'm not familiar, what tests does that run on it?

What Lefleuron says is true, though: I've seen a five guys with 150 years of combined experience and about $150,000 worth of test equipment get stumped by a motor for days.


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## varmit (Apr 19, 2009)

Intermittent problems are the worst.

I have seem many things work fine several times repeatedly, then fail the next try.


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## RICHGONZO1 (Mar 5, 2012)

Big John said:


> It's very strange to me that changing the breaker made some difference but didn't completely solve the problem. It's also very strange to me that you have a soft-start in place that in theory should reduce the exact problem you're seeing, it makes me believe the issue is with the soft-start, but yet changing the motor solved the problem.
> 
> What type of of soft-start? Were the breaker settings identical, and did you get any trip flags? Were the models of motor the same? I don't use PDMA so I'm not familiar, what tests does that run on it?
> 
> What Lefleuron says is true, though: I've seen a five guys with 150 years of combined experience and about $150,000 worth of test equipment get stumped by a motor for days.


Maybe the breaker was weak? Not sure, this thing kicked my a** until 2am last night. They really didn't give me too much time to tshoot the soft start, mechanical was changing it out and it was locked out almost the entire time. I maybe had 30 min alone, but it did start uncoupled with the new breaker and not the old. There could be many reasons why it chose to start that time. Just one of those things that bug the crap out of me, especially when everyone is breathing down your neck forcing you to make a decision and the whole plant is on its a**. This definitely was not the first, nor the last. I'll probably order another soft start and have it on hand just in case and I can justify it because it is extremely critical.

Thank you guys for reassuring me that these things happen and there is a reason why, but to have everything in place to catch it is impossible with just a simple meter.


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## JRaef (Mar 23, 2009)

What brand of soft starter?


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## RICHGONZO1 (Mar 5, 2012)

JRaef said:


> What brand of soft starter?


Allen Bradley SMC


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## RICHGONZO1 (Mar 5, 2012)

Big John said:


> It's very strange to me that changing the breaker made some difference but didn't completely solve the problem. It's also very strange to me that you have a soft-start in place that in theory should reduce the exact problem you're seeing, it makes me believe the issue is with the soft-start, but yet changing the motor solved the problem.
> 
> What type of of soft-start? Were the breaker settings identical, and did you get any trip flags? Were the models of motor the same? I don't use PDMA so I'm not familiar, what tests does that run on it?
> 
> What Lefleuron says is true, though: I've seen a five guys with 150 years of combined experience and about $150,000 worth of test equipment get stumped by a motor for days.


That's what made me think soft start as well and the breaker should not trip instantaneous like that. But when it was uncoupled it wouldn't start and when we put a new breaker in it started and ramped! So I kind of eliminated all that and when it was coupled it tripped! Breaker was exactly the same and when I did crank up the instantaneous up 1 click it took the main out with no trip indication. I believe the main is a 800A GE AKD breaker with a versa trip unit on it, recently calibrated.

PDMA can do a lot on the dynamic part, static it really only checks all three phases for resist imbalance, inductive imbalance, Meg's it, does a polarization index on it and a dialectic absorption test and a voltage step test. I think it may have caught it and I could have tested the new motor and did a comparison. it's really a nice preventative maintenance tool on high HP and critical motors, but helps in these situations. They are quite pricey I think 60k is the base model, but at my last company, we sent a motor out for bearing failure and they sent it back with a complete rewind and a 60k bill. The guy in charge of the PDMA called them out on it and they had to reduce the bill. They might have smoked it on the bench. Payed for itself that time, might be able to justify it on this one, we were down for 12 hours on break down and 12 hours on warm up.


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## JRaef (Mar 23, 2009)

RICHGONZO1 said:


> Allen Bradley SMC


The SMC definitely has a Kick Start feature. It also has an optional setting to use it as a solid state contactor, basically an across-the-line starter, no ramp. If someone enabled that, it would also allow that high inrush to be seen by the breaker. If it's an SMC-Flex is could have welded bypass contacts, although that should show up as a fault on the display.

So one more question: Was/is there a Shunt Trip in the circuit breaker? On the SMCs, the Shorted SCR trip function is often used to shunt trip the line circuit breaker to avoid the possibility of having multiple shorted SCRs that can fry the motor. But because the SMC does not have multiple Fault relays, if they want to do that, the Fault relay output is wired to the Shunt Trip, so if there is ANY other kind of fault on the starter, the breaker is tripped. If you have an SMC Dialog or Flex, you can look at the fault history to see what caused the trip. But on the original SMC that programmed with DIP switches, there was no history record.


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## RICHGONZO1 (Mar 5, 2012)

JRaef said:


> The SMC definitely has a Kick Start feature. It also has an optional setting to use it as a solid state contactor, basically an across-the-line starter, no ramp. If someone enabled that, it would also allow that high inrush to be seen by the breaker. If it's an SMC-Flex is could have welded bypass contacts, although that should show up as a fault on the display.
> 
> So one more question: Was/is there a Shunt Trip in the circuit breaker? On the SMCs, the Shorted SCR trip function is often used to shunt trip the line circuit breaker to avoid the possibility of having multiple shorted SCRs that can fry the motor. But because the SMC does not have multiple Fault relays, if they want to do that, the Fault relay output is wired to the Shunt Trip, so if there is ANY other kind of fault on the starter, the breaker is tripped. If you have an SMC Dialog or Flex, you can look at the fault history to see what caused the trip. But on the original SMC that programmed with DIP switches, there was no history record.


No shunt, still haven't gotten back to the starter. I saw it ramp up and it was hanging in there at like 1200 amps for awhile and it just took off. They start it once and it runs forever, even when they take down the production, it's used for cooling and ventilation for entry along with its primary function of introducing super heated air into the combustion chamber. It's also on the emergency generator circuit, literally never stops.


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## lefleuron (May 22, 2010)

RICHGONZO1 said:


> It's also on the emergency generator circuit, literally never stops.


 Those are the best calls of all. The TRUE PLANT EMERGENCY calls.:no:

Machines are down, materials are cooling off inside said machines, 200 people standing around with thumbs inserted in rectal areas, all waiting on YOU.

Throw in a plant manager, 2 chemical engineers pretending they know about electricity, one "maintenance" manager who smells like toilet water and has paint stains on his cover-alls, and its a real party.


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## Big John (May 23, 2010)

lefleuron said:


> ...Throw in a plant manager, 2 chemical engineers pretending they know about electricity, one "maintenance" manager who smells like toilet water and has paint stains on his cover-alls, and its a real party.


 :lol: Also they are all absolutely sure of how everything should work, except that when you ask each guy he gives a completely different answer than the last guy. 

Also, here are the only prints we could find. We were using them as a place-mat under the coffee machine so they may be _a little _stained and hard to read....


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## RICHGONZO1 (Mar 5, 2012)

On top of all that, since the plant was down, they wanted me to change the rpm on a 4160 liquid cooled VFD and run some fiber in the main sub! Not exactly easy jobs nor jobs I would want to rush on!


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## tates1882 (Sep 3, 2010)

What was the instant breaker set to? Depending on the setting that may give you a hint on wether the kick start feature was being used.


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## RICHGONZO1 (Mar 5, 2012)

It's running now and started up fine, bad motor


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## hardworkingstiff (Jan 22, 2007)

RICHGONZO1 said:


> It's running now and started up fine, bad motor


Thanks for sharing all the info you did, it helps us all learn. :thumbsup:

I'm curious though, have you figured out why you didn't find the motor fault when megging? How did you know it was the motor, changed it and everything worked OK? Did anyone tear into the motor yet? Do we know what was wrong with the motor? 

Thanks again for all the info.


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## John Valdes (May 17, 2007)

hardworkingstiff said:


> Thanks for sharing all the info you did, it helps us all learn. :thumbsup:
> 
> I'm curious though, have you figured out why you didn't find the motor fault when megging? How did you know it was the motor, changed it and everything worked OK? Did anyone tear into the motor yet? Do we know what was wrong with the motor?
> 
> Thanks again for all the info.


Lou. VFD's are extremely sensitive and usually much more sensitive than anything you can test with in his environment.
When I worked in a motor shop, we sometimes had trouble pinning down the exact issue.
There were times we had to send the motor back to the manufacturer (provided it was still under warranty) to get a report as to what the problem was. Ground fault was most always the initial report. We could recreate the ground fault in house with another drive, but were not successful with the test equipment.

We had hi-pot, Baker surge tester, electronic resistance measuring, and meggers and sometimes we could not pin down the problem.
Now we could have forced the problem to show itself, but sending it back to the manufacturer was a better idea as long as they had a spare or we could sell them a spare until the manufacturer could report back.

This why I always told my customers to keep spares if at all possible. Spares for critical equipment.
I understand you cannot always have a spare due to cost. But always know where your replacement is, in case you need it.


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## 8V71 (Dec 23, 2011)

Good to see you around JV. :thumbup:


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## hardworkingstiff (Jan 22, 2007)

John Valdes said:


> Lou. VFD's are extremely sensitive and usually much more sensitive than anything you can test with in his environment.


If I understand the thread correctly, the breaker tripped and the VFD did not ID the motor fault. Megging didn't ID the motor fault. 

The OP finally got management to change out the motor and everything is fine, and that's how they determined it was the motor.

Did I understand the thread correctly, if not, what did I mess up?


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## John Valdes (May 17, 2007)

hardworkingstiff said:


> If I understand the thread correctly, the breaker tripped and the VFD did not ID the motor fault. Megging didn't ID the motor fault.
> 
> The OP finally got management to change out the motor and everything is fine, and that's how they determined it was the motor.
> 
> Did I understand the thread correctly, if not, what did I mess up?


No Lou. Its my fault for not reading the complete thread.
It was the breaker not the SS. I called it a VFD :no:

Sorry about making it even more of a mystery.


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## RICHGONZO1 (Mar 5, 2012)

Yea the strange thing was I did a resistance check on the windings from the bucket and got .04 on each phase to phase. Then I went to the motor and got .0, I assumed a short, but when I did a resistance check on the new one, read the same? I chopped it up to a motor failing under full load because it ran uncoupled. Just one of those...


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## John Valdes (May 17, 2007)

RICHGONZO1 said:


> Yea the strange thing was I did a resistance check on the windings from the bucket and got .04 on each phase to phase. Then I went to the motor and got .0, I assumed a short, but when I did a resistance check on the new one, read the same? I chopped it up to a motor failing under full load because it ran uncoupled. Just one of those...


Resistance readings on a motor this size are not very helpful, unless you have the correct instrument to measure with. With a motor this size, resistance readings will look like dead shorts and are not reliable. 

Check a small motor and see that you can read these windings as they have more resistance. With large motors you cannot get an accurate reading with a multimeter.


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## JRaef (Mar 23, 2009)

It still bothers me that the breaker tripped and not the soft starter. Like I said, the soft starter would have tripped before the instantaneous trip of the breaker unless someone set it up as an Across-the-Line starter or set the Kick Start at 100%, neither of which is a good idea and you don't want to leave it that way.


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## Big John (May 23, 2010)

And it still bothers me that a new breaker changed the trip events. Those MVT trip units I believe have a 10% tolerance, and maybe the original happened to be tighter than the replacement, but if there was a solid ground fault, that shouldn't have mattered.

OP, what megger did you use? I have seen small meggers respond the way _Valdes_ suggested where there wasn't enough test current to charge the capacitance of the windings, and they would initially appear as hard shorts.


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## RICHGONZO1 (Mar 5, 2012)

Big John said:


> And it still bothers me that a new breaker changed the trip events. Those MVT trip units I believe have a 10% tolerance, and maybe the original happened to be tighter than the replacement, but if there was a solid ground fault, that shouldn't have mattered.
> 
> OP, what megger did you use? I have seen small meggers respond the way Valdes suggested where there wasn't enough test current to charge the capacitance of the windings, and they would initially appear as hard shorts.


I used a biddle hand crank several times, tried a 5kv fluke only at 500v for 30+ seconds. I Megged the service at 1000v because I was leaning towards the feeders at the time because of when that much current is delivered through the wires it would "flex" the wires in the conduit and make a pinging sound and could flex up to a fitting or sharp pull point such as an LB. I been off for a few days and have been busy so I haven't made my way back to the SS. Other electricians looked at the SS and have not reported anything out of the ordinary. 

The breaker I changed was a HMCP Cutler with instantaneous set low in my opinion, 2000 amps with a 177 FLA on a fan to me is sized correctly, but conservative seeing as the fan has a high inertia load. I plan on having an easy day tomorrow or this weekend and will dig into those parameters. 

I'm with you guys, something is not right and the motor was barely a year old. But that could be mis alignment or something mechanical. Still shouldn't let this one go too soon. I'll post when I go through the SS hopefully tomorrow.


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## HARRY304E (Sep 15, 2010)

8V71 said:


> Good to see you around JV. :thumbup:


X2....:thumbup:


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