# 480V Motor Pulling High Amps



## Pete H (Mar 1, 2012)

Guys, I am stumped. I need a few suggestions.

480 volt Submersible pump complete rebuild.

Stator was sent out to rewind shop. 
6 wire stator.
New bearings.
Impeller is not locked and has no resistance (free air test)
FLA on pump nametag is 7.1 amps

Line 1 pulling 8 amps
Line 2 pulling 2 amps
Line 3 pulling 14 amps

Stator wires 1 to L1, 2 to L2, 3 to L3
Stator wires 4 5 and 6 go to a thermal overload protection disk. 

We are testing the pump off of a 3 phase genset and I checked it for 480 volt output and it is right on 480 volt.

What else could be the problem? I checked for continuity from stator back through motor starter to genset lugs and all three legs have continuity.

Could the stator wires be mismarked from the rewind shop is my only guess. Any other sugestions for me to check?

Thanks for any help. :blink:


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## Big John (May 23, 2010)

Pete Holschuh said:


> ...Could the stator wires be mismarked from the rewind shop is my only guess....


 That's definitely where I'd start. Can you break apart the winding connections and check continuity between them?

-John


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## Pete H (Mar 1, 2012)

Brian, yes, I can do that but I neglected to do that yet. I should have continuity between the three motor leads, correct? So if one of the motor leads does not have continuity with the other two then I should go over and check leads 4 5 and 6 to see if they have continuity with the first three motor leads. I'm thinking aloud but that is what I will try.

Thanks for stirring my brain cells. I wil try that.


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## Big John (May 23, 2010)

If you're drawing current on each phase then you already know you have continuity between phases. What I'm thinking is that the six individual stator windings are not connected in the proper order.

If you have three of the six leads connected to a common point, I believe this is a 480 Y wound motor. 

I'd break that common point and see what the continuity was between all six of those wires. Hopefully this thing has a diagram on the nameplate and I'd check my readings against that. 

I gotta look around and see if I can find a wiring diagram for a 6 lead motor, it's been a while since I've wired one and I don't recall what windings should read continuity.

-John


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## JRaef (Mar 23, 2009)

> Stator wires 4 5 and 6 go to a thermal overload protection disk.


That doesn't make sense to me on several levels.

What is a "thermal overload protection disk". 

Why are motor leads going to it?


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## Pete H (Mar 1, 2012)

I have not seen many of them either. It is a small disc that if heated up will open up and stop the motor. Some are called Therm-O-Disc. 

I googled it and pasted a picture on this post - hopefully...

Anyway, leads 4 5 and 6 from the stator go to this "Therm O Disc". I usually work with 9 wire stators that use a different thermal setup but this is a 6 wire stator and has me confused.


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## Aussielec (Apr 1, 2012)

Pete Holschuh said:


> Stator wires 1 to L1, 2 to L2, 3 to L3
> Stator wires 4 5 and 6 go to a thermal overload protection disk.


I would disconnect this "thermal overload disk" totally before testing the motor. 

These thermal overloads might be causing you problems.


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## Pete H (Mar 1, 2012)

Aussie,

I will try that also. I did check the disc to see if it was open but it appeared to be good. But I will run the unit excluding that disc. Another good suggestion.


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## Jlarson (Jun 28, 2009)

JRaef said:


> That doesn't make sense to me on several levels.
> 
> What is a "thermal overload protection disk".
> 
> Why are motor leads going to it?


Yeah, WTF?

I have never seen embedded thermals on a 5 Hp ESP motor, and even if it did have an embedded thermal protector it shouldn't be tied into the motor leads. 

On a 6 lead ESP motor that you aren't doing wye-delta starting on the leads should be T1-T6 to L1, T2-T4 to L2 and T3-T5 to L3.


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## Pete H (Mar 1, 2012)

http://www.tsurumipump.com/prods/Submersible-Pumps/Sewage-and-Wastewater-Pumps/U-Series.aspx


Copied info from their website:

Circle Thermal Protectors (CTP) provide protection due to excessive heat build up, over current, or electrical/mechanical failure.

They are right on top of the pump. 2 bolts and out comes the Therm O Disc or Circle Thermal Protector and connected to it is leads # 4 5 & 6.


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## wdestar (Jul 19, 2008)

It seems very unlikely a motor shop would mis-mark leads, if that's the case.

Check the incoming voltage to the motor with a scope. Something's not right there.


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## Jlarson (Jun 28, 2009)

So they have it set up to run single voltage wye and use the thermal as the common point. 

That's weird. 

In that case Id start with what big john suggested break the common point and ohm 3-6, 1-4, and 5-2. The readings should be near identical. 

I'd also check the thermal's contact resistance.


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## JRaef (Mar 23, 2009)

Jlarson said:


> So they have it set up to run single voltage wye and use the thermal as the common point.
> 
> That's weird.
> 
> ...


Yep, I think that's right, but I've never seen that done before either and it's fraught with all kinds of dangers if you ask me.

Single voltage Wye connected motor, L1,L2,L3 go to 1,2,3, then 4,5,6 are tied together. So likev he said the three sets of valid windings (when separated from that disc thing) are 1 and 4, 2 and 5, 3 and 6. A continuity reading across any other pair will mean mismarked or shorted windings and your rewind shop needs to answer for it.


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## Jlarson (Jun 28, 2009)

JRaef said:


> Yep, I think that's right, but I've never seen that done before either and it's fraught with all kinds of dangers if you ask me.


I've never heard of this Tsurumi Pump before today. None of our pump reps handle them as far as I know. 

That be kinda of pain to t shoot on an emergency call if when you're going in blind and don't know that thermal is in there. Plus now you have another place for the pump to start leaking cause you have that access cover for it. 

Don't like it one bit. :no:


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## micromind (Aug 11, 2007)

As I see it, there are 3 windings, each 277 volt. They should be labelled as such; winding #1 is 1&4, winding #2 is 2 and 5 and winding #3 is 3 and 6. 

Obviously, this motor is designed to be connected wye, and the thermal overload breaks the center of the wye. The O/L is just a snap-disc that breaks all 3 leads when it gets too hot from excessive motor current. 

The vast majority of 3ø A/C compressors are connected this way, and the O/L is sealed inside the frame.

The first thing I'd do is megger the motor with the O/L connected. Next, I'd disconnect the O/L and megger 1 to 2, 3 to 1, then 2 to 3. 

If that's Ok, I'd check resistance of all 3 windings with the O/L connected. You'll need a meter that has a low Ω scale as the readings will likely be less than 1Ω. All 3 should be very close to the same. If not, disconnect the O/L and splice 4,5 and 6 together. Repeat the Ω test. 

Next, I'd keep 4,5 and 6 spliced and apply power to 1,2 and 3. I'd check current on 1 and 4. They should be very close to the same. Do the same for 2 and 5, then 3 and 6. If 1 is different from 4, or 2 is different from 5, or 3 is different from 6, there is a problem with the windings. The coils are not wound the same. It'll need to be re-wound. 

Don't keep more than about 10 amps on any leg for more than about 10 seconds; this type of motor will not tolerate excessive current for very long. 

Also, check voltage A to B, C to A, and B to C while it's running. With this type of motor at 480, 6 or 8 volts imbalance is about the limit.


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## micromind (Aug 11, 2007)

Pete Holschuh said:


> I have not seen many of them either. It is a small disc that if heated up will open up and stop the motor. Some are called Therm-O-Disc.
> 
> I googled it and pasted a picture on this post - hopefully...
> 
> Anyway, leads 4 5 and 6 from the stator go to this "Therm O Disc". I usually work with 9 wire stators that use a different thermal setup but this is a 6 wire stator and has me confused.


Klixon makes these too. I've seen them factory installed in the terminal box of small 3ø motors.


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## Jlarson (Jun 28, 2009)

micromind said:


> The vast majority of 3ø A/C compressors are connected this way, and the O/L is sealed inside the frame.


In the HVAC case it's pretty much the rule though not the rare exception. 

Maybe I'm just old school but I think any type of temp switch on a submersible pump should be brought to the surface and part of the control circuit for easier t-shooting.


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## micromind (Aug 11, 2007)

Jlarson said:


> In the HVAC case it's pretty much the rule though not the rare exception.
> 
> Maybe I'm just old school but I think any type of temp switch on a submersible pump should be brought to the surface and part of the control circuit for easier t-shooting.


Same here.

Considering the hassle of pulling the pump just for a failed O/L, it's not worth it.

On 3ø submersible pump motors, I usually use class 10 heaters. Those motors won't handle as much abuse an a normal NEMA frame one will. 

If possible, I also use some sort of phase failure relay as well.


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## Jlarson (Jun 28, 2009)

> Those motors won't handle as much abuse


Setting the level so the stop float is above the top of the pumps helps too, that way you always have liquid around the motors while they're running for some extra cooling.


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## JRaef (Mar 23, 2009)

From the looks of it, these people seem to be as cheap as cheap can be. Check out their "control panel"!

http://www.tsurumipump.com/prods/control-panels.aspx


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## Big John (May 23, 2010)

JRaef said:


> From the looks of it, these people seem to be as cheap as cheap can be. Check out their "control panel"!


 They didn't lie, it is _technically _a panel.... :laughing:

-John


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## Jlarson (Jun 28, 2009)

All the labels make it look good. :laughing:


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## Big John (May 23, 2010)

Jlarson said:


> All the labels make it look good.


 Makes you wonder what it all says, how hard is it to write "On/Off"? 

-John


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## JRaef (Mar 23, 2009)

Big John said:


> Makes you wonder what it all says, how hard is it to write "On/Off"?
> 
> -John


For a Japanese label maker? It may be the crowning achievement of his/her career!
:thumbup:


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## Pete H (Mar 1, 2012)

Today I conducted all of your suggestions. Thanks again for all who replied.

I came to the conclusion that it has to be the Therm-O-Disc as the problem but I was not really sure about that either since the disc had continuity through all of 6 of the points of contact on it. I couldn't see how a new one would make any difference but I had ruled out everything else - so I thought. The owner walks in and asked if I megged the (new) winding. I said no, but I would. The @!?%!Z thing did not megg out. . So the brand new stator from the rewind shop was faulty this whole time. Not happy. I sent it back to the rewind shop, rewind it again and told THEM to sweat it back into the pump motor shell and test it before sending it back to us. 

What a revolting development as my mom used to say :no:.

Have a good weekend. Supposed to be HOT and sunny this weekend in the Green Bay area.


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## Big John (May 23, 2010)

Pete Holschuh said:


> ...The @!?%!Z thing did not megg out. . So the brand new stator from the rewind shop was faulty this whole time....


 Not really surprised because I've had a lot of bad experiences with rewind guys. I'm assuming it was a ground fault? If it was open, I don't understand how you were drawing current on that phase.

-John


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## JRaef (Mar 23, 2009)

Big John said:


> ...I don't understand how you were drawing current on that phase.
> 
> -John


Induction from the other phases, just like a rotary phase converter.

A lot of motor shops around here won't even bother with 5HP motors any more and if they do, they send them out, sometimes to Mexico. Maybe that's what happened here. 

The only guy that still winds small motors locally is a guy who also has a store front for fixing vacuum cleaners and sewing machines, an "Old Technology" store if you will. He reminds me of the guy Emmet on the old Andy Griffith show who had the Fix It Shop where they brought things to even if they worked just to keep him busy. He fixed everything with a hammer if I recall.


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## Big John (May 23, 2010)

JRaef said:


> Induction from the other phases, just like a rotary phase converter....


 Well, I guess that's also a good question: Would I expect to see current on the derived phase of an RPC if there was no load present? 

I can't see how you'd have current flow in an open winding. Voltage, sure, but where's the current flowing to?

-John


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## JRaef (Mar 23, 2009)

Big John said:


> Well, I guess that's also a good question: Would I expect to see current on the derived phase of an RPC if there was no load present?
> 
> I can't see how you'd have current flow in an open winding. Voltage, sure, but where's the current flowing to?
> 
> -John


Good popint. Honestly? I didn't think that through that far, too much effort today. :whistling2: I'm in the middle of about $2 million in projects that are in various stages of incompletion, some bordering on meltdown, because of factories not being able to keep up with a huge spike in demand. What is this "recession" thing everyone keeps speaking of?

I miss my old life as a 'lectrician and I come here for stress relief, the problems here are usually so much more solvable... 
:drink:


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## Big John (May 23, 2010)

No worries, just had to double-check. Maybe _Pete_ will tell us what the megger results were.

-John


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## RIVETER (Sep 26, 2009)

Pete Holschuh said:


> Guys, I am stumped. I need a few suggestions.
> 
> 480 volt Submersible pump complete rebuild.
> 
> ...


Check the rpm on the shaft.


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## Pete H (Mar 1, 2012)

Results from megger were:

L1 went to OL
L2 slowly crept up to OL 
L3 stayed at zero
L4 went to OL
L5 went to OL
L6 stayed at zero

Thanks for all of the input guys. Much appreciated.


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## Pete H (Mar 1, 2012)

Riveter:

what would checking the RPM of shaft indicate? Please explain.

Pete


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## RIVETER (Sep 26, 2009)

Pete Holschuh said:


> Riveter:
> 
> what would checking the RPM of shaft indicate? Please explain.
> 
> Pete


If the shaft was not rotating in the range of the designed rpm, the CEMF would be excessive and the current would be higher. Or maybe I did not fully understand the question.


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## Pete H (Mar 1, 2012)

Riveter:

As it turned out, the newly rewound stator was bad which I failed to megg out early on in the rebuild. 

Question to you is WHY would the rotor be turning at incorrect RPM? If it had no drag on it, new bearings and seal it should turn at the correct RPM if the correct amps / voltage was applied in my opinion.


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