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Old 01-15-2019, 10:46 AM   #1
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Default These motors are getting HOT! Why?!?

I've posted this on another forum too, but I know there are a lot of motor experts here, so here it is:

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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Old 01-15-2019, 10:57 AM   #2
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Check the phase converter output. A-B, B-C and A-C See if the readings are all good. Phase converters can jack you on the derived phase pretty easy. Derived to ground is useless to read by the way most of the time with Converters.
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Old 01-15-2019, 10:59 AM   #3
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Quote:
Originally Posted by macmikeman View Post
Check the phase converter output. A-B, B-C and A-C See if the readings are all good. Phase converters can jack you on the derived phase pretty easy. Derived to ground is useless to read by the way most of the time with Converters.
My voltage readings are phase to phase, not phase to ground.
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Old 01-15-2019, 11:06 AM   #4
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you haven't given any information about the mechanical operation. did you check rotation, binding, etc on the output side ? (I'm assuming you did, but . . . . it wouldn't be the first time two motors were fighting each other)
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Old 01-15-2019, 11:31 AM   #5
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Electronic phase convertors may be the issue. Not everything runs good on them. They do not produce a true third leg .


Also do you have a picture of the hook up diagram for the motors, most use some type of jumper to do that change. If a wye wye motor don't use jumpers the horsepower usually changes, and your nameplate don't show that.


Do you have a small VFD around with single phase in three phase out, If so try running one motor off of that. Here is one for $136.00 https://www.automationdirect.com/adc..._vac)/gs1-21p0
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Old 01-15-2019, 12:01 PM   #6
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Quote:
Originally Posted by sparkiez View Post
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.

How long did they run on 460 before you realized the voltage was wrong?
O current with the motor running sounds to me like a high resistance connection somewhere.
Could even be inside the motor. Or motors.

Have you tried a new motor in place of the motors that show zero current draw?
Since you measured voltage at full load at the motor, I'm kinda leaning to the motor itself. And the only reason I say that is you say the motors were on 460. Or did you mean they were wired for 460 and you caught that before they were powered up?
Did you run these motors at 460 then change them to 230?
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Old 01-15-2019, 12:05 PM   #7
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Note. The two connections box diagrams look to be wired for 460 not 230. Delta.
I see no jumper to make the motor connection a star or wye. Star for high and delta for low voltage on IEC motors.
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Old 01-15-2019, 12:11 PM   #8
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Default wye/ wye wye

Quote:
Originally Posted by John Valdes View Post
Note. The two connections box diagrams look to be wired for 460 not 230. Delta.
I see no jumper to make the motor connection a star or wye. Star for high and delta for low voltage on IEC motors.

I said same thing about jumpers. But if you look at nameplate it is a wye /wye wye motor.
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Old 01-15-2019, 12:15 PM   #9
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Wiring looks wrong.

One y connection is inside the motor. When you made it a yy there should be one external y connection where all 3 leads are joined
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Old 01-15-2019, 12:24 PM   #10
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If you understand that the bolts on the ceramic block are not connected to anything underneath then you have to ask yourself why 3 wires go no where on the left side of the picture
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Old 01-15-2019, 01:13 PM   #11
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That is what I'm seeing also. To clarify:
The motors were at 460. I changed the wiring to 230V. I used the schematic provided with the motor. That schematic does not show there being a jumper for a 230V connection. I'm showing the wiring before I changed it and after.

Now in the past, I've wired these things for 480 and removed those jumpers. I suspect that this has happened here, or that the motors were originally shipped for 460V. I'm going to confirm, and then add the jumper in, as I suspect I'm only running on one set of windings. I'm also going to double check the wiring diagram on the peckerhead to see if that jumper is in fact shown there.
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Old 01-15-2019, 01:22 PM   #12
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If they are to be joined skip the jumper and just put all 3 on one bolt
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Old 01-15-2019, 01:45 PM   #13
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I don't think you have it connected correctly.


Look at the diagram on pdf page 8 of this document. There is supposed to be a jumper across the terminals on the left side of your photo of the terminal block

https://download.sew-eurodrive.com/d...ms_9PD0058.pdf


Also, there is a brake on your motor, the brown and yellow wires that come off of the right side of your photo of the terminal block. It's possible that because they are feeding an internal rectifier to make DC for the brake, the fact that you are on a phase converter is making that rectifier not produce enough DC and the brake is not fully releasing.
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Old 01-15-2019, 03:46 PM   #14
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Easier image to look at...


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Old 01-15-2019, 06:46 PM   #15
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I didn't know about the brake on the motor. However, the issue was that U2-V2-W2 were not connected. Glad it was something simple. I would much rather miss something simple than something complicated.
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Old 01-15-2019, 07:48 PM   #16
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Working on this style motor always makes me glad most of the ones I work with are NEMA.

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Old 01-15-2019, 09:10 PM   #17
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Quote:
Originally Posted by Forge Boyz View Post
Working on this style motor always makes me glad most of the ones I work with are NEMA.

Sent from my Moto Z (2) using Tapatalk

I agree.


We come across these a few times a year. I always have to stare at them a bit longer than the usual Baldor, etc. I can almost wire those with my eyes closed.
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Old 01-15-2019, 09:29 PM   #18
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Quote:
Originally Posted by Forge Boyz View Post
Working on this style motor always makes me glad most of the ones I work with are NEMA.

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If you remove the ceramic block you can wire nut like a normal motor (most rewinds come back with out the block as they tend to crack easily) you just have to get use to the u-v-w markings.
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Old 01-15-2019, 09:56 PM   #19
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This reminds me of a panel saw I ran a circuit to. It had one of those motors on it, and was bought as a 230v 50hz saw, which obviously doesn't work. We asked about switching the motor to 480v so it could run on 60hz (and so we didn't have to set a transformer) and were told that one of their people had to do the conversion or no warranty.
I was there the same time the tech was doing the voltage conversion, and he seemed to be taking his good old time changing the motor starter. When he got to the motor, he took the peckerhead apart, and after a while when I walked past, he said "Hey can you make sure I'm doing this right. I've never changed the voltage on one of these before."

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Old 01-16-2019, 12:06 AM   #20
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With U2, V2 and W2 disconnected, 3 of the 6 coils were not energized, leaving the other 3 to carry the entire load.

Even though they were grossly overloaded, the line current would be somewhat normal but instead of being split among 2 sets of windings, only one set was carrying the total current.

This would cause fairly rapid heating..........lol.
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