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motor failure
2

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.

RE: motor failure

At 230 volts, the motor has to draw roughly twice as much current to provide the same output load.  That will cause increased heating of the motor which likely damaged the windings.

=====================================
Eng-tips forums: The best place on the web for engineering discussions.

RE: motor failure

(OP)
but shouldn't the windings be able to withstand the additional heating from the lower voltage since the motor is designed to run at, either, 230V or 460V?  Do you think the windings were on the verge of going bad and the lower voltage was "the straw that broke the camel's back"?

RE: motor failure

Moisture probably takes out half of all motors.  Otherwise your load it too great.  You simply MUST check the current on the three phases of your running motor.  They 'shall' be less than the name plate FLA.  If not that is most likely what killed your motor and will shortly kill your next one.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: motor failure

Condensation will kill a new motor quickly. It will kill an old motor with borderline insulation even quicker. If condensation is an ongoing problem, instal a strip heater to keep the motor frame warm when the motor is not running.
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

edison123, a standard NEMA dual voltage motor is wye connected for both voltages.  There are two windings for each phase.  In the higher voltage connection the two windings are in series while in the lower voltage connection the two windings are in parallel.  (note the 2:1 relationship between the two voltages)  Changing from 460V to 230V would double the current, but you now have two windings in parallel, so the current in each winding shouldn't change.  On the other hand, if you had one of the windings paralleled with a different phase the smoke would definitely come out.

RE: motor failure

If the rewirerers are quick to point out that it was correctly rewired, then it probably wasn't. You should examine the connections and compare to the diagram that (perhaps) is on the inside of the connection box cover.

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

davidbeach,

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

When a motor is installed, either old or new, common practice is to measure the insulation resistance before switching on the power to ensure the condition of the winding. Skogsgurra is correct that it is wrong connected to double Y.

RE: motor failure

Sorry, I misread the question. Thought you simply applied 480vac motor on reduced voltage. Please disregard my comments.

=====================================
Eng-tips forums: The best place on the web for engineering discussions.

RE: motor failure

Hello Humbleuser,

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

What seems to be missed in a number of responses here is that the motor worked fine when he observed it prior to moving the machine. That means it is not mis-sized and barring a mechanical problem that developed during the move, not overloaded. The moisture issue may have played a part, but how long was it off-line and how much moisture was it subjected to?

http:/www.jraef.com
Eng-Tips: Help for your job, not for your homework  Read FAQ731-376 pirate

RE: motor failure

If "The motor ran for about 5 minutes, somewhat noisy". It probably was wrong connected.

RE: motor failure

(OP)
The motor was working fine for the 1/2 hour that I saw it running prior to me buying the machine; it was running under 460 power.  I forgot to mention in my original post that the face plate doesn't show the lower/higher connections.  It's possible that I misconnected the leads (I had 4-5-6, 1-7-L1, 2-8-L2, 3-9-L3).  I didn't check to see how the leads were connected for the previous higher voltage (shame on me).  The motor sat for about a month before I connected it.  The only other info I have on the motor/pump is that the pump had been recently rebuilt.  I can turn the pump by hand.  I'm wondering if the motor wasn't bad to begin with which is what caused the pump to go bad.  I just don't know.

RE: motor failure

humbleuser:

how about re-sizing overload fuses, disconnect & wiring? Remember that the voltage changed from 460V to 230V.

RE: motor failure

(OP)
The breaker that is currently in the machine is 100A.  If anything, I'll need a higher rating breaker to handle the lower voltage/higher amp draw.  Keep in mind that the breaker never tripped.

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

The connection you describe is correct for 230 Volts if the motor worked on 1 wye at 460 Volts, but what if some of the terminal mark labels were improperly attached?
However, the noise could have developed due to unbalanced magnetic field because of initial tracking to ground of one phase.

RE: motor failure

Improper fuse size would not make the motor smoke!

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?

http:/www.jraef.com
Eng-Tips: Help for your job, not for your homework  Read FAQ731-376 pirate

RE: motor failure

(OP)
The machine is a 1989 model.

RE: motor failure

Get a good electrician to help you restart that bugger. Tell him you want the protection checked.
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

Oh, hey there's a thought! Reversing the motor rotation on a hydraulic pump could be nasty. Depending on the hydraulic system design you may have been trying to start or run it against a closed system, which would have been essentially locked rotor. That would have made noise!

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.

http:/www.jraef.com
Eng-Tips: Help for your job, not for your homework  Read FAQ731-376 pirate

RE: motor failure

The rewind shop should be able to tell you exactly how and why the winding failed, if they cant I wouldnt have much faith in them (sorry to be negative). They should at the very least be able to identify from the condition of the  failed winding, water and/or moisture ingress, earth faults either through insulation failure or core rubs, overload and single-phase conditions, shorts between turns and shorts between phases. I would go back to them and ask them to be more specific and which of these fault conditions applied in the hope it can shed some light on what has happened. Another thing to consider, the pump, did it rotate the wrong way when first started? Maybe it has a screw-on impeller that has loosened and screwed off while running the wrong way due to inertia. This in turn may have caused a partial siezure and overload. However my money is on an incorrect connection made when it was converted from the higher voltage to the the lower, lets be honest its the only significant change that has occured. An incorrect connection would lead to a reverse phase condition in the motor winding and a motor of that size would shake and vibrate like mad in these circumstances, this may explain the noise issue. In addition its doubtful it would reach full speed under load, it would have a reduction in power and would certainly draw unbalanced and excess phase currents leading to a burnt out winding. At the risk of sounding condescending so I say it with respect, dont ever assume that just because a motor spins everything is ok and just walk away. Full load phase currents and speed need to be checked while running as an absolute minimum and compared to the information on the nameplate. We dont see many NEMA spec`dual voltage motors of that size here in the UK, so my knowledge on this topic is limited but another consideration, again at the risk of sounding condescending. I have seen complications arise with NEMA spec motors due to the figures `6` and `9` being confused on the lead markings, if that has happened in this case it would explain everything.

RE: motor failure

jraef: "Improper fuse size would not make the motor smoke!"

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

He means putting the wrong size fuses in will not make  the motor smoke.  The wrong fuses could allow  the motor to smoke.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: motor failure

But! Having the wrong fuses could allow one fuse to fail and then the single phased motor to smoke.. Seen it many times.   So maybe the wrong fuses could  make a motor smoke.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: motor failure

Thanks for jumping in Keith, yes that's what I meant.

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.

http:/www.jraef.com
Eng-Tips: Help for your job, not for your homework  Read FAQ731-376 pirate

RE: motor failure

jraef:

fiiiuuuuf, thanks for clarifying!!glasses

RE: motor failure

I have seen a lot of hydraulic pumps that were so noisy that you could not hear the motor. Are you sure that the noise was not pump noise? The people most able to suggest the cause of burnout are the winders. Was the motor in a heated area a day or two before being started? If the motor was in an unheated area, then condensation is very possible.
respectfully

RE: motor failure

Jraef,
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

Those small dual voltage delta connected motors do exist here in NEMA land, farm crew burned up a brand new one just a few months ago.  "we connected it up just like the old one".  

RE: motor failure

ScottI2R,
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

Just a thought.Just wondering actually.Nema design letter
and the service factor designation? Were those on the name plate as well?

RE: motor failure

Hello, HUMBLEU.:  When you buy an unknown motor you should: 1) Make a  uncoupled running test; see how it sounds, see how it turns by hand ( should have very little physical resistance, it should take some time to coast to a stop), look for  cracks, loose joinery, any signs of  abuse,  for a running  UNCOUPLED load reading - You want no more than 35% of the nameplate rate  FLA at the tested voltage!; should not develop objectionable heat after several minutes.  Naturally, you want a good $$$ price!!   If  the motor doesn't pass the tests---YOU DONT WANT IT!!!  Too many pretty girls in the world;  MOTORS TOO!      When you hook up and  REWIRE in your own place,  make the same test!  Readings  should be about the same, proportionally to applied voltage.   Before you hook up your load ( making your product) know that the motor works fine!    About this 230 volt thing;  are you sure it's not 208VAC????   Even at 230 VAC you are going to have an aprox. 2X increase in current.  If your problem wasn't passable in the beginning added heat caused  by current could have been the killer.  If you have  the bad motor, get an idea with a MEGGA of just how the windings are still held together;  sure to check the center connection!   If you only have 208,  3 phase VAC and the motor nameplate isn't marked "suitable for 208 VAC" you should not have used this motor!  10 % difference in required voltage here.  why are  you changing  motors??  How is the condition of the motor starting relay and feeders??   Hope this is of some help,  MOIRA

RE: motor failure

humbleuser

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

humbleuser

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

bigbillnky

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

(OP)
The shop insisted again that I had the connection correct.  I'm thinking the bearings on visual inspection looked fine but under rotation and load they were not.  The motor was rewound and the bearings will arrive/be installed on Monday.

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

You are paying for the motor to be repaired and as such you are entitled to a reliable repair, as they seem unable to provide you with an accurate fault diagnosis I would be questioning there competance. A winding failure attributable to a bearing problem has 2 forms. The winding can be overloaded by a partial bearing seizure but given its 25hp the bearings will display obvious signs of damage. If a bearing collapses, the motor will suffer a core-rub, the effects of which are both catastrophic and very obvious. Ensure the repair company check and ensure the bearing housings and journals are not worn and are within the tolerances specified by the bearing maker for the relevent sise. Ask for evidence this has been done. Worn components will rapidly lead to premature bearing failure, just looking at them is not enough, they must be measured using accurate instruments and allowances made for the locked and floating ends. The shaft needs to be checked for run-out and idealy the rotor check-balanced.

RE: motor failure

With a hydraulic pump, someone may have inadvertently changed the setting on a bypass valve or a pressure relief valve. Bad valve settings can make a lot of noise
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

Check motor rotation and general operation BEFORE mating it to the pump.

RE: motor failure

humbleuser,

 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

The ability of the repair agent to provide an accurate root cause analysis is vital. High-end clients expect reliable repairs and value for money in todays market. They tend to ask 3 questions regarding motor repairs. The Accounts dept ask how much is it going to cost? The Production dept ask when will it be back? And the Engineers ask what caused it? Its accepted that if the Engineers dont get a quick and accurate answer first, accounts and production could be asking the same question again in a few days time if the motor fails again owing to the possibilty of an undiagnosed fault on the driven side or with the supply. Accounts wont like the additional repair bill and Production wont like the additional downtime. This is why customers insist on accurate root cause failure diagnosis and if a repair company cannot provide it they will find someone else who can and the buisness will go with them. We in this forum can offer advice and point you in the right direction but its my view that the full answer to your question lies with the motor and the state of the failed winding and it can only really be fully determined by careful inspection, examination and testing by competent individuals. At the very least insist with the repair co` that you are present when the final motor test is conducted. Ask for an explanation of their test procedures. As a mechanical issue is suspected ensure they conduct a locked rotor test which can highlight rotor faults, check they conduct a shaft run-out test and that vibration is within the limits for the relevent construction and manufacturing standards. Idealy they also need to check and record the G/S/E figures for each bearing and ensure they are satisfactory for the sise and speed. If the motor fails again your repair company can easily say "It was ok when it left here" and refuse to accept any warranty on their behalf but if you are present at the test it works both ways, they will ensure everything is done correctly and you will be satisfied they have done a thorough job. Reputable firms welcome witness tests for these reasons.
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

I would suggest that you ask the rewind shop for the old bearings so you ( and others ) can examine them.  As mentioned previously, if they were the problem there will  be some wear/ damage.  If there's no damage, they probably were not the problem.  And make sure you check the bearing numbers to ensure they were the correct bearing in the first place.

RE: motor failure

macmill, repair center should simply depicts or somewhat report the probable cause of the unit as to assist " root cause failure analysis" report, with these... you will have the confident to prevent the damage from happening again...
Reliable Solution as what EASA had advocated.

RE: motor failure

Hi again, Humble::   You  have said something about the  motor sitting around for about a month.  I hope that     it was protected  , if outdoor  in bad weather?  Was  the motor always together as the same pump motor set?   Should mention that it is  always good practice  to check the  insulation resistance of each winding against ground and the  internal connection continuity.   Always want to have  resistance readings towards infinity.  Should be done ,at least, with a 500 volt MEGGA.  A good MEGGA is a  MUST have tool for any  work on motors!  These checks should be  made at rewire/hook-up.   If they can be recorded; they provide some type  of motor health history.   Direction check  is CRITICAL;  should be done ( uncoupled) at site!   Should be easy change back at breaker/starter, if necessary.  RECHECK AFTER CHANGE!!!   Your comment that STRANGE  noise was present  might indicate some type of mechanical binding in the impeller housing:   corrosion build up during storage;  impeller  being loosened from wrong directon.  3 phase direction can be different at different locations.   If using a VFD for speed controll;  you must check the actual final  VFD output for proper direction.   With start up of new pump/motor set take  running load readings.   Make sure you are within and understand NEC motor running load  rateings.   Being conservative; start around 115% of FLA, increase to 140% of FLA if loading dictates.   A higher running amperage will eventually  affect the long life of your motor.  A  last thought is that you may have  a motor speed issue.    Maybe you had a 3600 RPM motor, correctly o/l protected.  You'll have to think about it!    Recheck the  o/l devices application to the starter.    Hope this is help;  at least, for the future!   MOIRA  

RE: motor failure

(OP)
The repair shop called me today and informed me that I indeed have the motor hooked up incorrectly; the motor is a delta not star.  that explains why I burnt it out.  Please keep in mind that there's no info on the face plate.  next time I will do a continuity check.  Expensive lesson on my part.

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

Next time use an ammeter to check the running motor currents.

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

(OP)
I assume these leads are connected to thermocouple.  Where would the thermocouple be mounted?

RE: motor failure

(OP)
Could you please post a link to where I may be able to get a thermocouple for a motor applaication?  Thank you.

RE: motor failure

Hi, HUMBLEU: The two small wires in your  motor  originally were most probably the high heat/thermal protector.  They are normally closed switches that are  calibrated to go open when an abnormally high temperature is sensed in the motor. They are inbedded in one of the motor windings. You will have to check w/ GE, etc. to know what  their set temperature is.   There is quite a variety. They could be wired into your controll circuit to provide a motor stop/alarm.  Their intent is some degree of fire protection.  Although not to be an  actual motor control device; they can in an emergency supply a world of good.  They do not  reset until  normal temperature ( what that is?) is obtained.  A lot of damage can be done to a motor relying on a high heat device to open in controlling a motor!   No matter what exact type of motor control circuit you have, your first concern should be to STOP that motor before any harm  is done.  Where they originally wired  to your PLC system?   I'm believing them to be this, as described, normally closed switch.   This could have been used ,if wired, to provide a digital input to your PLC signifing that motor temperature was OK.  I think it to be unlikely that they are the ends of a thermocouple or even an RTD.  Did your original 25HP, 230 volt  motor have a certain two small wires wired to your (its) PLC?    When you rewired this purchased 25 HP, 460 volt motor for 230 volts; I'm understanding  that it had a certain two wires,  did you connect them to any two wires you may have originally disconnected?   Basically, if you had them in the beginning , you need them now!  If the original motor had these two wires connected to the PLC; then you  possibly  need them.  You must  understand  your motor controll circuit!!!!  Again!!! If these certain two wires were originally connected , to the PLC, you need them.   Let me ask you another way; the first time you saw these wires, what were they connected too?      MOIRA

RE: motor failure

(OP)
I haven't traced the wires yet, but one of the wires coming out of the motor was labeled "PC".  The two wires from the control panel are labeled but I'm having a hell of a time finding their reference in the machine schematics.  If it is a connection for a thermocouple then I can do with out it.  If it's an overload protection device that is normally closed then, and correct me if I'm wrong, I'll tie the two wires together to close the circuit.  I know, I know this is jury rigging but I need to get this machine back up and running.  If anyone knows definetavely what those leads are for please let me know.  A link to a replacement part would be truly appreciated.

Thanks everyone for your help!

RE: motor failure

Thewires most likely were from some type of temperature monitoring device. There are several types. Some connect to a dedicated module that monitors the temperature and opens the motor control circuit if/when the motor temperature is too high.
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

Hi, again, HUMBLE.:      I'm not positive  that they are thermal  o/l switch.   I'm pretty sure they are (were).  If they were  just a straight digital open/close verify for  OK temp. of the motor then you can  temp. get away with a  jumper to keep this part of the  PLC as seeing  a good, closed  issue.   I pretty sure  that they weren't  a thermocouple (to create an analogue voltage input) ,or an RTD ( to create an analogue current  input) to  Your  PLC  Does your PLC have  analogue current or  voltage inputs?? Can you see the digital input rack when you jumper ( splice together the two wires?? Hopefully you have led indicators for each input???     Check and find the  ACTUAL motor  starting relay for your  25HP motor.   I think you will find thermal/mechanical  o/ls.  One for each phase.    Each heater element should be able to operate a common , normally  closed overload switch.  This is what you want!   This is your motor running overload;    which will stop your motor if their is a problem!   You probably have some assortment of switches; hand or automatic to turm the motor on/off under normal r un conditions.  Should be a size 2 starter.   I'm hoping again that you can find all this in  one  box/ compartment.  Then again the   motor starter is probably   in the MCC.  Ask G.E., give them all your motor  name plate, serial # , data  Getting holp of your PLC's  ladder logic print and the elemental electrical schematic will be big help.  Do you have colligues  in an IT department; contact them!         MOIRA

RE: motor failure

H  Humble:::: If you have other similar machines, check them!   Check with operating personnel, sometimes these folks can be a tremendous asset.   Your pump supplier may be able to help.      MOIRA

RE: motor failure

I concurr with Waross and will elaborate. The leads will have been Thermistors which are temperature sensetive resistors. Usualy there are 3 of them in series with one buried in a coil from each phase during manufacture/rewind. The `PC` means they have a positive temeperature coefficient, i.e the resistance increases as temperature increases. They connect to a control module that monitors any increase in resistance then flags an alarm or shuts down the supply as the temperature of the winding increases. By burying them in a coil from each phase circuit the whole winding is monitored. The operating temperatures for the Thermistor are indicated by the colour of its leads. Its all in the link.
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

startdelta,
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.

http:/www.jraef.com
Eng-Tips: Help for your job, not for your homework  Read FAQ731-376 pirate

RE: motor failure

(OP)
Thank you everyone.  A technician from the repair shop is installing one right now as I type.  They admitted that it was their fault for not installing one.  I hope to have this motor back in the machine and connected by the end of the day.  Again, thanks everybody.

RE: motor failure

(OP)
I installed the motor back in the machine and connected the power to motor...correctly!!!  After pump ran for a few minutes and all of the air was bled from the hydraulic system the motor/pump combo run nice and smooth.  The thermistor (165C rating) is connected to the PLC and that should take care of that.

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

I am pleased to hear you have finally sorted out the issue and the machine is now earning money!. I must add that I think this thread has been particularly informative and would be surprized if all the the contributors have not learned something from the comments of the others. I for one have (TQ Jraef)

RE: motor failure

To me this problem was a classic mess created by the limited knoledge on electric motors of both, the user and repair shop. However that seems to be the normal way that lot of bussines run nowdays.

RE: motor failure

(OP)
Hey, I'm a molder not a motor repair man :)

RE: motor failure

I apologize for being sarcastic, but if a motor expert should be hired on time shouldn’t you avoid all problems and money expenses?

RE: motor failure

aolalde:

"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

Hi, Humbleuser:  I think, you are a credit to yourself and who ever you work for!   You had your problems, but stuck it out and accomplished what you were intrusted to do!  You did a GOOD JOB!  Hopefully for all of  us,  our work can be one continuing  educational process.   Only a few years  back,  none of us would  even had the pleasure   our recent conversations.  Keep up th good work!   MOIRA

RE: motor failure

(OP)
Thank you moira.  I'm the owner of a modest injection molding company.  So basically, I'm the maintenance man, purchasing agent, set up man, salesman, tooling engineer, expert troubleshooter...you get the picture.  I do have a few people working for me such as operators and foreman.  But the delicate stuff like changing motors, insert changes, quoting jobs, etc. I do myself for peace of mind.  This forum has been extremely helpful.

RE: motor failure

Thanks humbleuser, glad we could help. Don't mind aolalde's grumpiness, he isn't usually like that and has been offering a wealth of knowledge here for quite a while. But we all get a little tired of people who attempt to use the Internet in lieu of hiring the right person, while some of us "right persons" are sitting idle or getting laid off. It's not your fault, it's just the way things are now. In actuality you did do this correctly for someone who had to do most of it themselves, you just got hooked up with a rewind shop that appears to be in want of some additional expertise.

Post their info so we can all send them an invoice wink (just kidding)!

http:/www.jraef.com
Eng-Tips: Help for your job, not for your homework  Read FAQ731-376 pirate

RE: motor failure

I sympathise with Humbleuser, he has had an avoidable issue that has cost him money both in repair costs and in downtime. I do think it true to say if proffesional advice had been sought from the outset the bill would have been much lower. However if these situations never arise people like myself and the many others employed in the repair industry would be out of work.

RE: motor failure

GE motors seldom have thermisters.  Most often, they utilize Klixons, which are sealed thermal switches manufactured by Texas instruments.  I would be concerned with an internal thermal set for 165C unless the winding and leads were Class H

RE: motor failure

Humble,

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

(OP)
The lead read "PC".  The repair shop said that there was a thermistor installed but they had forgotten to install it initially.  They sent a guy out he installed it here at my shop.  The motor seems to be running just fine now.

RE: motor failure

humbleuser,
 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.





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