motor failure
motor failure
(OP)
I don't hang out in this forum anywhere near enough as I should. This is great technical site. However, I do have a question that I'm hoping some of the more experienced mebers can answer. Keep in mind that I'm not a trained electrician; I'm more of general maintenace type of guy :)
I have 25 HP G.E. motor (230/460 3-phase) attached to an injection molding machine. I saw this machine running and making parts prior to me buying it. The place where it came from had it wired for 460. I brought it and rewired it for 230. The motor ran for about 5 minutes, somewhat noisy, before it started smoking and tripped the breaker. The shop that is rewiring it told me that I had the proper wire connections to the motro. I asked him what caused it to burn out? He's not sure. He says the bearings aren't in bad shape. he thinks that some of the 'varnish coating' on the windings may have worn out. It's possible that some condensation on the worn area may have caused the motor to short out. Is this possible? Thanks in advance.
I have 25 HP G.E. motor (230/460 3-phase) attached to an injection molding machine. I saw this machine running and making parts prior to me buying it. The place where it came from had it wired for 460. I brought it and rewired it for 230. The motor ran for about 5 minutes, somewhat noisy, before it started smoking and tripped the breaker. The shop that is rewiring it told me that I had the proper wire connections to the motro. I asked him what caused it to burn out? He's not sure. He says the bearings aren't in bad shape. he thinks that some of the 'varnish coating' on the windings may have worn out. It's possible that some condensation on the worn area may have caused the motor to short out. Is this possible? Thanks in advance.





RE: motor failure
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RE: motor failure
RE: motor failure
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: motor failure
Arrange the controls to turn the heater off when the motor starts.
respectfully
RE: motor failure
I would also look at whether the winding was wired right for 230 V. I would guess it would be delta connected.
* If a little knowledge is dangerous, then I am the safest person in the world *
RE: motor failure
RE: motor failure
If the rewirerer bet you to it, you can be almost certain that there was a mistake.
On the other hand, if current wasn't checked, it is very probable that the motor was overloaded. The high noise level indicates that. What setting the protection/fuses?
Gunnar Englund
www.gke.org
RE: motor failure
I agree. It could be double wye connection.
* If a little knowledge is dangerous, then I am the safest person in the world *
RE: motor failure
RE: motor failure
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Eng-tips forums: The best place on the web for engineering discussions.
RE: motor failure
If the motor start with noise this is an indication of mechanical troubles: Improper fits or bearing damage or electrical problems: improper winding connection or Single phase operation.I think due to the motor works only 5 minutes the failure was produced by single phase operation.
Check the breaker and contactors in order to find some problem with the electrical instalation.
Regards
Petronila
RE: motor failure
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RE: motor failure
RE: motor failure
RE: motor failure
how about re-sizing overload fuses, disconnect & wiring? Remember that the voltage changed from 460V to 230V.
RE: motor failure
Initially, I thought for sure that I miswired the connections. The repair shop insists that I had it wired correctly. They're also telling me that the bearings are not that bad of shape. They think that moisture caused it to short out. The noise that it made before going 'kapoot' has me baffled. Was that noise normal or not? I simply don't know because I'm not familiar with the machine when it's running. When I inspected the machine it was running but it was too noisy in the shop to really notice anything unusual. I'm stumped.
RE: motor failure
However, the noise could have developed due to unbalanced magnetic field because of initial tracking to ground of one phase.
RE: motor failure
Those would be the proper connections for a Y-connected dual voltage 9 lead NEMA motor, which constitutes what GE sells as standard. If by chance it was a dual voltage Delta-connected 9 lead motor then those would be wrong, but I haven't seen one of those in years. Is it an old machine?
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RE: motor failure
RE: motor failure
You want the currents checked.
You want to make sure the rotation is correct!
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: motor failure
1989, I doubt it would be a delta-connected motor. You can do a simple check though with a continuity tester. Disconnect the incoming leads. If it's Y connected you will have continuity between 7, 8 & 9. If Delta, you will have continuity between 7, 2 & 5.
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RE: motor failure
RE: motor failure
Can you explain what you meant by this? Is your statement for this specific "humbleuser" situation. I'm so confused now, all this time I tought using OL fuses helps protect motor from damages.
RE: motor failure
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: motor failure
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: motor failure
But in this case, had he failed to change fuses when he went from 480 to 240V they would have been 1/2 the required size and would have blown almost immediately, which would have prevented the motor from smoking. Your point about the single phasing causing the motor to burn out is valid, but in this case 30 seconds is far too short of a time for it to start smoking from that cause IMHO.
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RE: motor failure
fiiiuuuuf, thanks for clarifying!!
RE: motor failure
respectfully
RE: motor failure
Correct me if I'm wrong, but shouldn't the fuse rating INCREASE?
Scott
In a hundred years, it isn't going to matter anyway.
RE: motor failure
RE: motor failure
Yes, it SHOULD have. I was pointing out that IF he did not increase the fuse size when changing from 480 to 240, his 480V rated fuses would be too small and blow immediately.
RE: motor failure
and the service factor designation? Were those on the name plate as well?
RE: motor failure
RE: motor failure
I have to ask what exactly did the noise sound like? I think it would help trouble shoot the cause or at least give everyone a better idea, A hum or sizzle to me is electrical and chatter or clank = mechanical. Smoke is the end result.
Chuck
Getting older is inevitable
Acting your age is optional
RE: motor failure
The windings of a correctly-connected motor that failed from single-phasing will be easy to spot. If it was wye connected(most likely), two of the three stator windings will be charred. If it was delta connected, only one will be charred. If the motor failed due to an overloaded condition OR a mechanical problem, all three windings will be charred.
I would suspect that the motor or load was either damaged in transit or improperly reassembled/aligned, or a faulty connection existed and caused the failure. A poorly made connection or a high-resistance grounded fault will allow a motor to start, but will create a noise similar to true single-phasing. The motor will perform poorly and fail in short order if the control does not trip the motor off line.
Have a qualified electrician examine ALL the control components for proper size, rating, and OPERATION before reconnecting the motor. Also, thoroughly check the mechanical components of the machine. Keep in mind a bad bearing when cool can seem fine, turning effortlessly and having little or no play. Once it reaches load and speed it will soon start to heat up and lock down. A non-contact infrared temp gun is a great tool for finding this type of bearing problem.
Bigbillnky,C.E.F.....(Chief Electrical Flunky)
RE: motor failure
I have to question your description of potential bearing problem as this is very unique in my experience. The bearings I have had heat up and lock down self destruct very soon and cool down/recovery not likely. We use self aligning, precision thrust, and standard roller.
My questions - What type of bearing have you experienced this condition with ? And how often ?
Chuck
Getting older is inevitable
Acting your age is optional
RE: motor failure
I believe I mentioned that the pump had been rebuilt a few months ago. I don't know exactly what was wrong with the pump; I'll find out on Monday. For those not familiar, the pump is bolted onto a mounting frame that is bolted onto the motor face. It's pretty difficult for the motor/pump to be misaligned. A sleeve coupling is used; and the hubs were snug on their respective shafts.
I think it's the bearings that caused it. Just my $0.02 worth.
RE: motor failure
RE: motor failure
I think the two most important issues to check are;
1> Voltage. Make sure you are on a 240 volt three phase system.
2> Pump settings. Make sure that none of the pressure switches or pressure relief valves are out of adjustment. You may have a solenoid controlled unloader valve or dump valve that is not opening properly.
Either a voltage problem or a pump loading problem will show up as excess current so check your motor currents.
respectfully
RE: motor failure
RE: motor failure
With such incident, im pretty sure you never did wrong upon wiring it on 230V (it's simple).
The issue here is the "reliable solution" of the culprit that was the repair center ambigiuos diagnose of failure, as i agree to stardelta.
When we repair such machine, before we strip out the winding or dismatle it, we conduct a pre-diagnostic survey or query as why is the unit needs for repair? Consequenlty, we conduct diagnotic testing, visual inspection and check up. Thereby, we acquire our own assestment of " root cause failure analysis " and reported to our client, since we offer a repair warranty.
in your case, The best thing you'll have to undertake is to run the machine without load to ensure the unit is good. Eventually, try to investigate your load if it really fits your motor capability.
RE: motor failure
There is a worldwide repair trade organsisation known as EASA and members operate within a code of practise. The EASA website offers a PDF download in the `Industry Info` section that explains minimum requirements relating to repairs and testing which I am sure you will find useful.
http://www.easa.com/
RE: motor failure
RE: motor failure
Reliable Solution as what EASA had advocated.
RE: motor failure
RE: motor failure
Now I have another question. I just noticed that the motor did not come back with two small wires that it had before. One of the wires was marked "PC". I'm guessing that it's for the PLC control on the injection moldinvg machine. What signal it provides is beyond me. Can someone confirm that these 2 leads are for the PLC and do I really need them? Thanks.
RE: motor failure
Those are/were temperature leads. Sad if you don't have them and need them..
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: motor failure
RE: motor failure
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: motor failure
RE: motor failure
RE: motor failure
Thanks everyone for your help!
RE: motor failure
If it was working when you aquired the machine it would have most likely saved the motor. If you had a good quality motor overload relay, it would have likely saved the motor.
The temperature detector is usually imbedded in the motor windings as the motor is being wound or rewound.
Do what most people do with older motors with inoperative thermal sensing. Forget it. It's too late now in any event.
This is an added level of protection which most motors don't have, and was apparently out of service on your motor anyway.
BUT DO use a good quality motor overload relay (often a part of a magnetic motor starter).
respectfully
RE: motor failure
RE: motor failure
RE: motor failure
http://www.aev.co.uk/
Here in Europe larger motors usualy have 2 sets of thermistors, a lower value set to flag a warning, usualy about 120 deg, then a higher value set to trip usualy about 160 deg. I have never seen Klixon type cut-outs or thermal trips fitted in a standard motor of this size. Most machines are fitted with thermistors as standard but they are not always employed by the end-user which may explain why you cant find any reference in the machine schematic.
Your rewind company should have replaced them as a matter of course, they cost nothing and the fact they didnt means I have even less confidence in them now. I would be demanding to know why they were not, at the very least they should have checked with you if they were vital.
RE: motor failure
Just FYI, here in the US thermistors are not as automatic as they are elsewhere in the world, you pretty much have to special order them. In fact a lot of people here have no idea what they are or what to do with them when they see them in IEC motors. Many rewind shops frequently leave them out because they are used to customers having no clue or even putting power on them thinking they are Klixons and causing problems when they reconnect the motor. I'm not saying that's the right thing to do, it just happens a lot. I still agree that the rewinder should have asked.
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RE: motor failure
RE: motor failure
Thanks a million to everyone that made suggestions. This is the most useful/helpful forum that I belong to. Keep up the good work, forum members.
RE: motor failure
RE: motor failure
RE: motor failure
RE: motor failure
RE: motor failure
"humbleuser" is not an electrical expert (neither do us, we are humans) he said that in the begining, thanks for the apologize (2-tumbs up for you) We are here to try and answer/help for different situations, as in "humbleuser's" situation for example.
regards
RE: motor failure
RE: motor failure
RE: motor failure
Post their info so we can all send them an invoice
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RE: motor failure
RE: motor failure
RE: motor failure
Are you sure that the wires were marked "PC"? That does not make much sense - no one uses PC for a PLC. I think the marking was "PTC", which means Positive Temperature Coefficient and is used to distinguish PTC from NTC. PTC is the type used in motors because they have a well defined switching temperature. NTC is more of a measuring component with a smooth resistance curve.
Gunnar Englund
www.gke.org
RE: motor failure
RE: motor failure
I also read such leads before as PC - a two lead wire temperature sensor. But i wonder why GE used this marking to specify its purpose.
Anyway, skogsgurra is on the right track. PC is somewhat used to be as PTC.