# Overload tripping



## bkmichael65 (Mar 25, 2013)

Did you try changing out the overloads?


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## LATTC (Feb 12, 2012)

I would double check the wiring first. 4 sec trip is pretty fast. You gotta let that heater cool down first before resetting.


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## ponyboy (Nov 18, 2012)

if it was a solid state OL were they set correctly? if not were the heaters sized correctly?


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## wendon (Sep 27, 2010)

tfo said:


> Hi guys,
> 
> Ran into and issue at work today and hoping someone can make light of it.
> we have 2 identical motors that we were to perform a bump test and no load test (45 min run time).
> ...


You're not running a single phase motor and someone didn't install the jumper?


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## Cow (Jan 16, 2008)

Are the starters for both motors next to each other? Can you swap the T leads as a quick test?


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## ScooterMcGavin (Jan 24, 2011)

Every situtation I have had which is like the one you describe has always been an overload problem. Either not sized properly, the mechanism is weak/messed up, or the Solid state relay isn't set properly. What size motor are we talking about here? I have seen motors run with a locked rotor for more than 4 seconds before they trip before, especially with the thermal overloads.


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## JRaef (Mar 23, 2009)

If you have a Solid State overload relay of a number of brands, some have problems handling unloaded motors. They use the phase current to detect a phase loss, using a logic statement in the internal programming that says something like 

_"If any phase current is below 30% of setting, trip on Phase Loss"_

Problem is, if ALL 3 phases are below 30% of set current, the statement is still true and it trips.

No-load tests are notorious for causing this issue.


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## tfo (Jun 20, 2013)

JRaef said:


> If you have a Solid State overload relay of a number of brands, some have problems handling unloaded motors. They use the phase current to detect a phase loss, using a logic statement in the internal programming that says something like
> 
> _"If any phase current is below 30% of setting, trip on Phase Loss"_
> 
> ...


I thought this could be a possible answer but i dismissed it because everything about these 2 motors are identical.

The only difference im aware of is that one of them was pre existing and is connected to the clients devicenet system. (they can control and monitor it from their control room)

the second motor is new and the one we're having problems with. it is connected to the devicenet but a rep. for the client assures me that nothing has been programmed so it shouldnt affect running the motor from a local control station.

He did however tell me that they had a hell of a time getting the first pump to work when they commisioned it the first time around. Had to set up all kinds of bypass's is what he said.

The overload relay was supplied by the client so tomorrow im going to try and get my hands on a manual to see if there's anything im missing.


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## tfo (Jun 20, 2013)

scameron81 said:


> Every situtation I have had which is like the one you describe has always been an overload problem. Either not sized properly, the mechanism is weak/messed up, or the Solid state relay isn't set properly. What size motor are we talking about here? I have seen motors run with a locked rotor for more than 4 seconds before they trip before, especially with the thermal overloads.


They arent very big, if i recall off the top of my head, 28HP, 575v, ~36 FLA.


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## JRaef (Mar 23, 2009)

Devicenet connections or lack thereof would not necessarilly cause nuisance tripping. Even two identical motors are not going to be absolutely identical, the slightest difference in circuit resistance can mean the difference of 28% of FLC vs 31% of FLC in the above situation.

Devicenet likely means AB or CH overloads and generally does meant solid state. Post the model number(s)


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## tfo (Jun 20, 2013)

that's a good point.

I'm not right on site at the moment but the materials list im look at right now just says "overload E3+".

Does that mean anything to you?


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## SteveBayshore (Apr 7, 2013)

JRaef said:


> Devicenet connections or lack thereof would not necessarilly cause nuisance tripping. Even two identical motors are not going to be absolutely identical, the slightest difference in circuit resistance can mean the difference of 28% of FLC vs 31% of FLC in the above situation.
> 
> Devicenet likely means AB or CH overloads and generally does meant solid state. Post the model number(s)


I installed two plants with AB devicenet installed by the OEM. The OLs were factory set in the software and we had to get the OEM IT tech to set the proper ranges because of password protection.


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## tfo (Jun 20, 2013)

Ok so today the client hooked up the motor to their system and apparently it's telling them there is a ground fault somewhere.

Obviously not a dead short or it wouldnt let it run for 4 secs before tripping out.
The client says its in the power circuit but i dont see how they could know that for sure. Can these relays differentiate a ground fault in a power circuit vs. a control circuit? A megger test was done on the cable and the motor, so if there were any problems that should have picked it up.

Anyways we're going back tomorrow to take another look.


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## JRaef (Mar 23, 2009)

E3+ is an A-B SSOL.

The Ground Fault protection on the EC2 version, which is around the size you mentioned, is "residual" ground fault detection. That means that it looks at the sum of the 3 phase current vectors and they should cancel each other out. Any residual is current flowing in one phase but not the other two, ergo it must be flowing to ground. Starting transients can fool this method, that's why it has a slight time delay. So if the relay is tripping, it is either a defective relay, or there is something happening that you are not seeing with your tests. Swap the other relay with it to eliminate the first potential.


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## tfo (Jun 20, 2013)

so, everything is up an running and we dont really know why.
One of our guys rewired the bucket this morning because whoever did it the first time around did a terrible job aesthetically.

When he was finished we tried it again and it ran with no issues. Wish we could have figured out what was the exact problem. I'm guessing a loose connection somewhere.

Anyways guys, thanks for your input. You gave me some insight into potential problems i may run into later. Still have ~ 30 of them to go so im sure it's not the last problem i'll run into lol.


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## JRaef (Mar 23, 2009)

tfo said:


> so, everything is up an running and we dont really know why.
> One of our guys rewired the bucket this morning because whoever did it the first time around did a terrible job aesthetically.
> 
> When he was finished we tried it again and it ran with no issues. Wish we could have figured out what was the exact problem. I'm guessing a loose connection somewhere.
> ...


A loose connection can cause that. A loose connection means the current in 2 phases is not the same as the third, so you get a slightly different version of the problem but same result, residual current.


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