Burned pump motors

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dema

Senior Member
Location
Indiana
I have been called with a question about motors. Motors are not my specialty.

I found this site with pictures:

http://globuselectric.com/motorfailure.htm

The pictures that I was sent look most like the locked rotor picture. In fact, I think you could exchange the pictures and nobody would know which is which.

The situation is that there are three separate pump stations all within a couple of miles of each other. They are three of 11 or so. They each burned up on different days when there has been no lightning. All are served by hi-leg delta. The two transformer turning single phase to three phase kind. One of the motors has been there for years. The other two have been there for months.

The overloads on the two motors that have been there for months were not sized properly, they are too big.

They are pumping from groundwater 12' or so below the surface. We are in Indiana. This happened recently in this unusual cold. Don't know if that has anything to do with it.

The two motors that have been operating for months have TVSS protection. The other one did not.

Any idea as to causes?

Thank you.
 

Besoeker

Senior Member
Location
UK
I have been called with a question about motors. Motors are not my specialty.

I found this site with pictures:

http://globuselectric.com/motorfailure.htm

The pictures that I was sent look most like the locked rotor picture. In fact, I think you could exchange the pictures and nobody would know which is which.

The situation is that there are three separate pump stations all within a couple of miles of each other. They are three of 11 or so. They each burned up on different days when there has been no lightning. All are served by hi-leg delta. The two transformer turning single phase to three phase kind. One of the motors has been there for years. The other two have been there for months.

The overloads on the two motors that have been there for months were not sized properly, they are too big.

They are pumping from groundwater 12' or so below the surface. We are in Indiana. This happened recently in this unusual cold. Don't know if that has anything to do with it.

The two motors that have been operating for months have TVSS protection. The other one did not.

Any idea as to causes?

Thank you.

A couple of thoughts.
You mention that it was very cold. Cold enough for the pumps to freeze?
Could the pumps have got silted up?
 

kwired

Electron manager
Location
NE Nebraska
I have been called with a question about motors. Motors are not my specialty.

I found this site with pictures:

http://globuselectric.com/motorfailure.htm

The pictures that I was sent look most like the locked rotor picture. In fact, I think you could exchange the pictures and nobody would know which is which.

The situation is that there are three separate pump stations all within a couple of miles of each other. They are three of 11 or so. They each burned up on different days when there has been no lightning. All are served by hi-leg delta. The two transformer turning single phase to three phase kind. One of the motors has been there for years. The other two have been there for months.

The overloads on the two motors that have been there for months were not sized properly, they are too big.

They are pumping from groundwater 12' or so below the surface. We are in Indiana. This happened recently in this unusual cold. Don't know if that has anything to do with it.

The two motors that have been operating for months have TVSS protection. The other one did not.

Any idea as to causes?

Thank you.
Make sure like Besoeker said there is no issue with driven load, and also like the information on the site you linked to says, make sure there is not too frequent starting or reversing as well.

Too frequent of starting with a high speed/high inertia load could likely do this as well, though most pumps probably are not in this category.

Is this across the line starting, VFD, or other starting method? That could change some of the questions that come next.
 

electric_cal

Member
Location
California
Have you checked the utility voltage? Phase to phase, and phase to ground?
Did you try to rotate the pump shafts by hand to verify that they are not in a frozen position?
Your description of the condition of the motor windings would indicate a possible locked pump shaft.

I would be looking for a comman problem for all 3. Utility voltage and or extreme cold.

I would also correct the problem of the overloads not being sized correctly.
Also, verify that the short circuit protection is sized correctly.
 

dema

Senior Member
Location
Indiana
Thank you

Thank you

Thank you for your input.

One thing I found elsewhere on the internet - if the ventilation opening were clogged, maybe due to snow and ice, would overheating cause overloads to function if they were sized correctly? Can heat cause damage even with protection?
 

Besoeker

Senior Member
Location
UK
Thank you for your input.

One thing I found elsewhere on the internet - if the ventilation opening were clogged, maybe due to snow and ice, would overheating cause overloads to function if they were sized correctly? Can heat cause damage even with protection?
I'm inclined to think the snow or ice would melt if the motor got that hot. Even in normal operation on load, a motor gets quite hot to the touch.

Simple overload protection is operated by overcurrent. They don't, as a rule, detect motor overheating.
Correctly sized overloads should have prevented the damage but they would not have prevented the overload occurring in the first place. The cause of that needs to be sought.

I assume that the damaged motors will be replaced? When they are, can you measure the current being drawn?
 

dema

Senior Member
Location
Indiana
Motor current

Motor current

Yes, we can measure the current being drawn. The peculiar thing is that there were 11 motors in the area and three went out, all at different times. Three motors were recent - two of these went out. And one of the others. They all are quite charred. Definitely not lightning as that would have had an entry and an exit wound - not the whole windings. And not likely single phasing, because that would have had striped burns on the windings. (I looked at the pictures on the site I posted - lovely site.)

So it seems rather mysterious.
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
You mentioned two transformers to convert single phase to three phase. It does not work that way.
Possibly you have a three phase primary feed and the two transformers are configured as an open delta to supply the same three phase at the service voltage.

One thing that can burn out a three phase motor very quickly is single phasing, where one of the phase voltages goes away because of a primary or secondary fault condition.
It it happens while the motor is running, excess current will be drawn that could cause damage before oversized overload protection activates. And if the motor overload is sensing sum of the three phase/line currents rather than each one individually it might also not operate fast enough.
If the pumps are submersible, then running dry or running without water flow past the motor can burn the pump out.

If single phasing is happening periodically for a short period of time, then a pump which was running might survive but a pump which tried to start during the single phase condition could be quickly toasted, as it would not be turning at all.

Finally, a brownout on one phase rather than a complete loss could also cause problems.

Can you put a recording meter on all three phases and leave it there for awhile?
 

dema

Senior Member
Location
Indiana
Open delta

Open delta

It is single phase overhead with two transformers connected in open delta to provide a three phase service for motors. Perhaps I said it wrong. They do that a lot around here for pump stations.

I think monitoring is a great idea. I'll work on making it happen. Thank you.
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
It is single phase overhead with two transformers connected in open delta to provide a three phase service for motors. Perhaps I said it wrong. They do that a lot around here for pump stations.

I think monitoring is a great idea. I'll work on making it happen. Thank you.

It cannot really be a single phase overhead, since a transformer can only change the phase of a single phase input by zero or 180 degrees.
It may be only two phases of a three phase wye on the overhead (possibly referred to as an open wye??), in which case you could have two phases from line to neutral or a single phase from line to line depending on how you connect to it.
That is enough to get a full three phase secondary set in the form of an open delta.
And once you have that open delta, you can also construct a complete wye if needed using additional transformers.
 

kwired

Electron manager
Location
NE Nebraska
It is single phase overhead with two transformers connected in open delta to provide a three phase service for motors. Perhaps I said it wrong. They do that a lot around here for pump stations.

I think monitoring is a great idea. I'll work on making it happen. Thank you.

Look carefully, to have an open delta you must have two phase conductors and a neutral on the primary, or three phase conductors and no neutral can be done but is generally only done if the primary is delta connected, most of the time they are using line to ground single bushing transformers and then you have to go with two phases and a neutral.

The tricky part is when it looks like it is only single phase supply, if you look carefully the ungrounded conductors on the very top of the pole are not connected to one another - because one phase comes from one direction and the other phase comes from the other direction, the neutrals are same potential and is bonded on through. There are a lot of them like that in the rural areas around here.
 

dema

Senior Member
Location
Indiana
I hope I get to know the outcome

I hope I get to know the outcome

Sometimes they want an answer to their question and then they vanish. I have asked for the outcome and been told to wait a bit.
 
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