Motor overload tripping

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Da Electrician

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We have a 3ph 460V 60hz 3hp motor.

We are having an issue with a motor tripping the Thermal overload. We have meggered the motor, tested resistance on all the windings, checked the motor bearings and the bearings of the load. Everything checks out good, the contactor in the starter had some resistance through the contacts on one of the phases. We cleaned the contacts in the contactor. The overload is a Seimes solid state thermal overload, it is rated and set correctly for the motor. This set up has been running for a couple years now with no changes other than mantainance. For some reason it just started tripping the overloads.

Any help would be appreciated !
 
Da Electrician said:
We have a 3ph 460V 60hz 3hp motor.

We are having an issue with a motor tripping the Thermal overload. We have meggered the motor, tested resistance on all the windings, checked the motor bearings and the bearings of the load. Everything checks out good, the contactor in the starter had some resistance through the contacts on one of the phases. We cleaned the contacts in the contactor. The overload is a Seimes solid state thermal overload, it is rated and set correctly for the motor. This set up has been running for a couple years now with no changes other than mantainance. For some reason it just started tripping the overloads.

Any help would be appreciated !
Click to expand...
1. Is current equal on all three phases?
2. A megger will not show you a shorted turn or turns inside a winding, so there may be significant losses from that without the leakage or series resistance of the winding changing noticeably.
3. Has the load changed in any way?
4. Does the motor itself get hot?
5. How long before the thermal trip? Does it trip only when the motor is under load?
 
If you megged the motor, then change the overload. It's not cost effective to spend much time troubleshooting everything when it's only a 3hp O/L.
 
Da Electrician said:
We have a 3ph 460V 60hz 3hp motor.

We are having an issue with a motor tripping the Thermal overload. We have meggered the motor, tested resistance on all the windings, checked the motor bearings and the bearings of the load. Everything checks out good, the contactor in the starter had some resistance through the contacts on one of the phases. We cleaned the contacts in the contactor. The overload is a Seimes solid state thermal overload, it is rated and set correctly for the motor. This set up has been running for a couple years now with no changes other than mantainance. For some reason it just started tripping the overloads.

Any help would be appreciated !
Click to expand...

Have you measured the current and compared it to the FLA of the motor and the rating of the thermal overload?
 
eric9822 said:
Have you measured the current and compared it to the FLA of the motor and the rating of the thermal overload?
Click to expand...

Ditto.
In addition, depending upon how the heaters are installed it would be also a good idea yo church for heating that may be the result of a poor connection which would cause additional heating of the thermal overload relay heaters.
 
ptonsparky said:
Those overloads do fail. We have replaced more than one set over the years.
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Seems especially prone to failure in outdoor enclosures from the Siemens brand in my experiences. I don't install new Siemens controllers any more because I have replaced too many overloads that have failed.
 
templdl said:
Ditto.
In addition, depending upon how the heaters are installed it would be also a good idea yo church for heating that may be the result of a poor connection which would cause additional heating of the thermal overload relay heaters.
Click to expand...

Pardon me for correcting you but I think you are referring to the older type thermal OL wire heaters. He mentions a Siemens solid state OL relay which I believe measures the over-current level (not heat) to determine the tripping.
 
If these are the IEC Siemens Sirius motor controllers with electronic overloads then check the pin connection between the overload block and the contactor, I have had several fail at these pins.

remove the overload on the bottom and look at the pins to see if there is any signs of heating on them, it seems that they don't make a good connection or are not properly torqued when they come from the factory already assembled together

the ones I have had a problem with is the 3RT1026-1A contactor and 3RU1126-4BBO overload

other models may also have this problem, I will try to post a photo of one.

FountainPumpControls002_zps5df2ad8a.jpg
 
To add to the above once it had started heating on the pins the OL would trip randomly, most of them that had this problem showed no signs of the heating on the front as this one did, some that didn't look like it had a problem even after I had re-torqued the pin connections would still trip which seems the heat may have damaged the current transformer coils inside of the OL or the electronics, the only fix was to replace the OL block and make sure you torqued the connections.

The one above was in a aerator pump control box next to a lake, but the box was well sealed and there were no signs of water getting into it.
 
Da Electrician said:
We have a 3ph 460V 60hz 3hp motor.

We are having an issue with a motor tripping the Thermal overload. We have meggered the motor, tested resistance on all the windings, checked the motor bearings and the bearings of the load. Everything checks out good, the contactor in the starter had some resistance through the contacts on one of the phases. We cleaned the contacts in the contactor. The overload is a Seimes solid state thermal overload, it is rated and set correctly for the motor. This set up has been running for a couple years now with no changes other than mantainance. For some reason it just started tripping the overloads.

Any help would be appreciated !
Click to expand...
Siemens makes two different types of solid state OL relays, the ESP style that was designed by the old Furnas Co for what is now the Siemens Class 14 NEMA motor starters, and the German IEC style 3RB series. Within each of these there are sub categories, some of which will have different issues that may be in play here. Please post which type you have, I can probably help, I used to work for Siemens and know all of those products really well.

Re: field failures.
When Siemens bought Furnas, there was a serious flaw in the original ESP100 overload relay that nobody could figure out for the longest time, but it only happened on outdoor mounted starters like Pump Panels. Turned out that in the original design, condensation that might form inside of the electronics compartment had no way to drain out of it and built up. So in around 2006 they figured it out and added a weep hole in the bottom, the problem went away. But the notice to the field was really weak because they were embarrassed I think, so most people never heard it, they just quit buying Siemens...

The thing about the pins being loose on the assembled IEC starters happened when Siemens US started assembling them here in the US instead of buying them assembled from Germany. They were doing it in a facility that was slated to be shut down and moved to Mexico. Everyone in the plant knew it, none of them gave a damn about QC. But the Mexico plant got delayed, so the US facility stayed open for over a year longer than anticipated, but full of people who knew they were losing their jobs. Things like that became a big problem.
 
Jraef said:
Re: field failures.
When Siemens bought Furnas, there was a serious flaw in the original ESP100 overload relay that nobody could figure out for the longest time, but it only happened on outdoor mounted starters like Pump Panels. Turned out that in the original design, condensation that might form inside of the electronics compartment had no way to drain out of it and built up. So in around 2006 they figured it out and added a weep hole in the bottom, the problem went away. But the notice to the field was really weak because they were embarrassed I think, so most people never heard it, they just quit buying Siemens...
Click to expand...

Exactly the problem I have had with them. Quit buying them a long time ago and never knew if they solved any of their problems.


Condensation in equipment around an irrigation well in July or August in NE? Not a question of if it will happen, it will happen.
 
ATSman said:
Pardon me for correcting you but I think you are referring to the older type thermal OL wire heaters. He mentions a Siemens solid state OL relay which I believe measures the over-current level (not heat) to determine the tripping.
Click to expand...
I apologize as I was responding to the OP which stated "thermal overload relay" and I way have overlooked the reference to a Siemens SS OLR.
 
templdl said:
I apologize as I was responding to the OP which stated "thermal overload relay" and I way have overlooked the reference to a Siemens SS OLR.
Click to expand...

I get workers all the time calling electronic OL's thermal without realizing that theres no thermal in a solidstate OL, I guess its an old carryover from the days of the real thermal OL's:p actully many don't even know how they work using CT's instead of heaters.
 
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hurk27 said:
I get workers all the time calling electronic OL's thermal without realizing that theres no thermal in a solidstate OL, I guess its an old carryover from the days of the real thermal OL's:p actully many don't even know how they work using CT's instead of heaters.
Click to expand...

It is a bit disconcerting to know that there are those who are very good electricians and technicians that know the NEC inside and out but lack the understanding as to how things actually work. They are extremely good at physical installations knowing the correct way to do an install but lack the knowledge and understanding as to how a system works together. This by no means makes them poor electricians or technicians but makes it difficult for them to determine and understand the cause of a failure when troubleshooting.
 
templdl said:
It is a bit disconcerting to know that there are those who are very good electricians and technicians that know the NEC inside and out but lack the understanding as to how things actually work. They are extremely good at physical installations knowing the correct way to do an install but lack the knowledge and understanding as to how a system works together. This by no means makes them poor electricians or technicians but makes it difficult for them to determine and understand the cause of a failure when troubleshooting.
Click to expand...
I do some of my best troubleshooting unencumbered by the thought process.
 
Cow said:
Is that the guess and replace method?:)
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Yes, keep on replacing parts until you finely replace the defective one.
But, I must admit that I have been lucky enough when struggling with an issue when it just happens to start to work not knowing what in the heck I did. Just how does one respond when asked what was wrong.
 
Da Electrician said:
We have a 3ph 460V 60hz 3hp motor.

We are having an issue with a motor tripping the Thermal overload. We have meggered the motor, tested resistance on all the windings, checked the motor bearings and the bearings of the load. Everything checks out good, the contactor in the starter had some resistance through the contacts on one of the phases. We cleaned the contacts in the contactor. The overload is a Seimes solid state thermal overload, it is rated and set correctly for the motor. This set up has been running for a couple years now with no changes other than mantainance. For some reason it just started tripping the overloads.

Any help would be appreciated !
Click to expand...
Besides checking out the motor have you checked out the driven load?
 
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