# Hot Motor



## ace24wright (Jul 10, 2012)

I have a 200hp DC Baldour motor here at work, due to a plc I/O problem in the main drive (which people who get paid much more than I are dragging thier feet to replace) themotor doesn't always stop when turned off at the controls, operator must take an extra minute to make sure the RPM's come down and stop's. this did not happen the other nite when I got to work and that baby was running and smoking and hot to touch. After checking the fields, brushes, and commutator ( all looked good). Short of megging it is there anything else I could check and what would the life of this motor be after such an incident?


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## Zog (Apr 15, 2009)

What do you mean short of megging it? Have you already checked that?


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## ace24wright (Jul 10, 2012)

no I did not It's been running fine since sat.


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## Big John (May 23, 2010)

If it's smoking it means you're either baking out the bearing lubrication and/or baking off the winding insulation. I would've meggered it, but that's only helpful if you have a plan to repair it or trend it if megs poorly.

Otherwise, check the brushes, maybe give a squirt to any grease points, and put it back on line.

What application is this thing in that normal operation allows it to overheat without tripping any protection?

-John


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## ace24wright (Jul 10, 2012)

a sheet plastic extruder. we don't do any motor repairs, shipped out for that. As crazy as it is I have never megged a motor her at work(a mock 480 in a class)after this I've been reading up on it.


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## ace24wright (Jul 10, 2012)

thanks Big John, I'm all over checking the thermal overload as soon as it goes down, thinking the PLC issue might have something to with that.


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## John Valdes (May 17, 2007)

I would have a motor ready to go in to take its place while you have this one checked out. Unless you have 3-5 days for repairs. I know sometimes it is cost prohibited to have a spare of this size.
I really do not get your question as you state the motor does not stop? What does this mean?

"the motor doesn't always stop when turned off at the controls" ?????


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## nolabama (Oct 3, 2007)

John Valdes said:


> I really do not get your question as you state the motor does not stop? What does this mean?
> 
> "the motor doesn't always stop when turned off at the controls" ?????


Me X2 on this too. Switch off motor does not turn off= big problem. Does it have a time relay that causes it to run a few more seconds or so?


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## ace24wright (Jul 10, 2012)

It's an I/O issue with the PLC in the main drive Engineer and head electech already troubleshot this, it is weird. you stop it at the control panel and you can watch the rpm's slow down than it kicks right back up to tha last rpm setting. no time relay. not the stop relay either. Thanks John but we do keep a spare for all our extruders


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## ace24wright (Jul 10, 2012)

talked to head elctech this morning, thermal overload protcts the armature, field weaking alarm in PLC did not trip out so fields must have stayed full voltage


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## Big John (May 23, 2010)

ace24wright said:


> ...Thermal overload protects the armature....


 I would double check the wiring or setting on that thing. A thermal OL that allows the creation of Magic Smoke ain't doing it's job.

-John


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## ace24wright (Jul 10, 2012)

roger that!


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## Motorwinder (Dec 30, 2010)

Check the ohms of the shunt fields. Sometimes the ohm value will be on the name plate. If not, divide the field voltage with the field amps. (ohms law) to get a ballpark of where your ohms should be. If the ohms are too low, then your shunts are cooked. This is a very common failure when the fields are left on at full voltage.

You can also do a voltage drop test if you have 4 lead field circuit. Simply energy F1 and F4 with 120 volts AC. Then check between the two sides for even voltage. IE: F1 to F3 = 60 VAC and F2 to F4 =60 VAC. If you have more than 10% difference in voltage, then your fields are bad.


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## ace24wright (Jul 10, 2012)

fields ohmed out right on, f1 to f2 to f3 to f4 - f1 to f4 with 2 and 3 tied together


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## Motorwinder (Dec 30, 2010)

ace24wright said:


> fields ohmed out right on, f1 to f2 to f3 to f4 - f1 to f4 with 2 and 3 tied together


If your speed is holding steady, your motor is ok.

You might talk to your boss about a economizer circuit for your shunts. Or leave the blower running all the time. (if it has one)..


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## ace24wright (Jul 10, 2012)

Yeah, the blower is tied in to the drive


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## John Valdes (May 17, 2007)

ace24wright said:


> Yeah, the blower is tied in to the drive


You mean the blower only comes on when the motor is running?
I would have the blower run until the disconnect is pulled to off.


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## MDShunk (Jan 7, 2007)

Whatever the cause, if the motor was visibly smoking before, but it still runs, it's safe to say that years and years of life were taken out of the motor. As John rightly says, have your spare ready to go, unless you can tolerate the downtime for rebuild. I'd also talk with your maintenance manager to get some planned downtime to replace this, rather than to have to take reactive unplanned downtime at the worst possible time in production. Purchase the new motor, plan downtime and replace it, then send out your old one to have a rebuilt spare in stores.


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## ace24wright (Jul 10, 2012)

Sorry, I should have been more clear,the blower is tied into the drive cabinet, it's always on


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