3 phase motor intermittantly tripping

[tosh999]

I have got a 3 phase motor running a conveyor belt, every couple of days it will trip the overload. I have tested the motor, windings are ok, not drawing excessive current, good insulation resistance. It has a brake mounted on it but this seems to be releasing ok.
Motor does get a bit hotter than the 2 conveyor motors next to it.
any ideas

 

[Pete999]

What is the flc of the motor?
What are the overloads set at?
How it it wired DOL or SD
How is the motor configured Star or Delta?

 

[westward10]

If it is running hotter than the other two and the motors are under similar loadings could be a bearing problem.

 

[Barry White]

Intermittent problems are the hardest to find. could be as said above.
Do the basic things first
Check the belt runs freely no stiff bearings or badly tracked belts.
Clean the fan, cowl, and motor casing so it can cool correctly.
Check condition of any remote isolator and the actual contactor loose, dirty or pitted contacts can cause intermittent phasing and overload. Also check and test cable condition.
Use a clamp meter to check the current draw each phase.
Do you know if its tripping on start up or after its been running for a while?

 

[ams3521]

If it is running hotter than the other two and the motors are under similar loadings could be a bearing problem.

Exactly what came to my mind if all the motors are of the same spec.

 

[Marvo]

More info required. As per Pete's questions, how's it wired, YD, DOL or is there a drive?

 

[Corona]

What material are you conveying? If the environment is dusty or damp, or the faulting conveyor is used more than the others, you may have to up the PPM on that asset. Overloads generally set at 5/8 FLC or 65% ish, if its already been cranked up there may be much knee work and head scratching.

 

[koldwater]

If the current, load, load frequency, and environmental are same as other two motors. You confirmed all wiring. you could be seeing the results of a past problem. Like a previous load issue over heated motor and caused insulation failure, or contractors worn from past problem. Basically I am reminding you to consider, past abuse may have have caused degradation which now presents itself to appear as intermittent problem when it is really an accumulative issue. Ringing it and use a scope may help verify.

 

[netblindpaul]

...
Ringing it and use a scope may help verify.

Not quite sure how the motor can answer a phone for you to ring it!

 

[Bobster]

What material are you conveying? If the environment is dusty or damp, or the faulting conveyor is used more than the others, you may have to up the PPM on that asset. Overloads generally set at 5/8 FLC or 65% ish, if its already been cranked up there may be much knee work and head scratching.

Only if the motor is YD and the overload is in the delta leg.

 

[Pete999]

You mean insulation resistance testing then.
Which is the correct term, not ringing, or megging, or meggering.

Stupid Septics Meg a motor, what next?

 

[LeeH]

I had to change the rotation of 2 motors on a US machine yesterday.

Some of you will like the termination.

The whole machine was a mess, panel and everything.

View attachment 35872

 

[Bobster]

Common practice in the states, and when the cores get too big for fire nuts:

View attachment 35874

View attachment 35875

 

[mickfred]

Are all the conveyor s the same ,if not the heat can be a red fishy , most likely bearing or damaged fan (if not swap overloads over)

 

[koldwater]

Stupid Septics

Cheers. My stupidity could be all my own, nothing to do with what country I am from. Enjoy your retirement.