OT: These motors are getting HOT! Why?!?

sparkie

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So I've attached a couple images of one of the three motors. They are ~1 HP motors. I have included the name plate images, and images of the gear box. Here is a bit about the setup:

They are fed from an electronic phase converter/power supply. The input is 240V single phase. The converter outputs ~240V delta. I am feeding each motor with a forward-reversing motor starter and overload. I have confirmed motor operation in forward and reverse direction. They operate just fine from a controls point of view.

The conveyor was purchased used, for a cheap price. When I checked out the motors, all motors were wired up for 460V. Given that we were on 240V delta, I changed them over to 230V. I've wired up many three phase motors, I'm sure they are correct, but I have included a picture here as well. I also 100% confirmed this matches the wiring diagram provided on the motors yesterday.

The problem is that these motors are getting HOT. I mean, hot enough that I can smell the windings. This is happening FAST too. Even if you run them for just a little bit and turn them off, the heat transfers to the outside and after a couple minutes the motor gets hot to the touch. It isn't normal.

Here is what I've done:

Confirm that the motors are wired for 230V

Take an amp draw. On two of the motors I'm reading 0. On one I'm ready .25. This is worrisome, but not the end-all. These motors are supposed to draw ~2A FLA, however they were drawing ~3A.

Take voltage reading at the peckerhead while running. I get an even ~240V across. I don't remember exact numbers, but it was nothing to cause any concern. I usually look for more than a couple volts difference, and the difference was inconsequential enough that I dismissed it.

Here are my additional thoughts:
The amp draw being high doesn't make sense. I would expect to see about 1.6-1.8 given that the voltage is higher than nominal. For some reason these motors are using more power than they should be. I'm really leaning toward this being a mechanical issue.

These motors are 72% efficient, so I would expect that they run hotter than other motors, but I wouldn't expect to smell windings on any motor.

I have not yet megged and/or checked the resistance of the windings. I do, however, suspect that these motors may have been ran at the wrong voltage and that the windings have shorted out, causing the increased voltage draw.

One motor tripped the overload. Despite being set at 2.8A and drawing over 3A, two of the motors did not trip the overloads. I'm wondering if these overloads are bad.

What are you guy's thoughts?


Also: there are two images of the inside of the peckerhead. One is original 460V, the other is where I moved it over to 230V (where the wires are crossing the terminal block).

 
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The conveyor was purchased used, for a cheap price. When I checked out the motors, all motors were wired up for 460V. Given that we were on 240V delta, I changed them over to 230V. I've wired up many three phase motors, I'm sure they are correct, but I have included a picture here as well. I also 100% confirmed this matches the wiring diagram provided on the motors yesterday.

Not that im going to be a lot help on this one but.... were they running hot when wired for 480?

And I agree with Paul, any chance its a transfer heat coming from the boxes?
 
It could be. I won't know for sure until later today. I'm not sure if they were running hot when on 460. The person they bought it from said they "only used it a couple times." Those are SEW sealed motor/gearbox systems. We can remove them and separate. I didn't see any way to add / check oil or grease in the gear box. I didn't look that closely either. If I'm not mistaken, those units are supposed to be sealed.

I can do a couple checks on motor winding resistance and update, but the only reason I can think of to get a higher current draw at a higher voltage is an increased load.
 
I’m not convinced these are wired correctly for low voltage. Usually 4,5,6 are tied together for a Y connection. I don’t see that in a pic.
 
Googling "SEW SA47/T" returns some images where it looks like there is a plug/breather on the gearbox. It also looks like the motor and gearbox can be separated from each other.

When measuring currents, are you sure that your meter measures True RMS ?
Measuring with a regular meter on a motor driven via a VFD will give false values.
 
I’m not convinced these are wired correctly for low voltage. Usually 4,5,6 are tied together for a Y connection. I don’t see that in a pic.

I didn't think to get one, but I'll have to get a pic of the inside of the peckerhead cover. There is a very clear wiring diagram on 230V wiring vs 460. I'm with you on this, but they are wired per manufacturer specification from the sticker inside.

The other thing is that I've always seen jumper bars with a low voltage configuration, however the terminal block also had three rows of terminals on it, where this one has only two.

These motors aren't driven via a VFD. Yes, this is an RMS clamp meter.

And good to know they can be separated. I've never really had to do it much. Perhaps I can find a manual on opening up the assembly and verifying lubrication.
 
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Might be missing something, but I can't see the jumper between the brown white and yellow to form the star point on the left hand side of the 230V winding.
http://acim.nidec.com/motors/usmotors/TechDocs/ProFacts/Starting-Methods/Part-Winding.aspx

You might be trying to power it from just one of the windings.

Motor overload will not trip until it gets to 125% of its setting, and even at 126% it will take a while to trip.

I'll get a confirmation on this, as well as a picture of the diagram inside the peckerhead. Now I can say that the diagram specifies that in order to go from 460V to 230V and back you only have to move the three leads: blue red and black from the terminals marked W1V1U1 to W2V2U2 and that line is to go to them. It doesn't show or mention there being a jumper anywhere between the terminals.
 
Some phase converters don't really generate the full 3rd leg. They just develop a voltage on the 3rd leg but no real power. So the motor is actually running single phased. I have seen other motors run hot when running on phase converters.
if it were me I would run them on a VFD single phase in 3 phase out it also gives you the FOR - REV and overload in one unit
 
Be careful if you do separate the motor and gearbox, they can make quite a mess. There should be a hex plug near the top and near the bottom of the gearbox to facilitate an oil change. The few times we have had to separate the motor and gearbox, we had to make sure to have sealant on hand. We used RTV to re-seal them.

I cannot be entirely sure about this, but do the red, blue, and black wires attached to U1, V1, and W1 go to the brake on the back? All of our SEW Eurodrive motors have brakes on them, and each one requires a brake rectifier to control them. Ours have red, blue, and white wires, but they are run in exactly the same way that the ones in your last picture are, through a tube that runs out to the brake through the end of the motor.

Here is a link to the diagrams: https://download.sew-eurodrive.com/download/pdf/9PD0049.pdf
 

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