Overload issue

[edexlab]

I'm looking at a German made roller conveyor system 10 motors contactors controlled by a PLC

Issue is customer says 3 mths ago motors started stopping and overheating, and would then start again when cooled down
Overloads trip out PLC, input switches contactors off and someone presses reset
(It's a year old, the maintenance team are mechanical bias)

So as this was sold by our firm we are first to check
1st thing I notice is panel is warm, open it and hot plastic smell comes out
I felt the contactors and where they connect to Overloads it's pretty warm, and a slight melting off a small area on the top of the overloads, where the self maintaining contacts are snapped off
obvious issue here

So I turn it off check all the connections are tight, some weren't as tight as I think they should be but no loose connections

So I start turning motor circuits off to check continuity and resistance through all components , voltage at all terminals except motor as it's not safe to do this tested / inspected everything I can think of even recorded temperature of motors and the components in the board, bench tested one of the motors all good
nothing untoward found, all current readings at @ 0.6 A motor plate says 0.9 A , O/L's set at just over 1 A

So I'm checking how it's running sensors actuating contactors etc and noticed occasionally when the line builds up due to downstream conveyors being stopped by staff, that the contactors are being turned on and off very quickly with the result the motor is getting hot as fan isn't running enough air over the casing to cool it, normal running its fine
Asides from the suspect overloads and this timing issue all looks good

Yesterday I smelt a hot motor it was single phasing checked O/L and found a phase down
Removed it opened up and one of the filaments is open circuit

I report back to German Engineer he says he agrees with the timing issue but he doesn't agree with my request for new overloads to be sent even after seeing the broken one

I sent him all readings and photos etc
He's still adamant it must be a supply voltage issue or something else that I have missed as this is a small simple system
And they have built lots of these with no issues
So I'm still onsite monitoring things

So just wanted to see if others have any opinions or ideas
[automerge]1580903734[/automerge]
Burnt plastic connecting the two self maintain contacts
[automerge]1580903799[/automerge]
Open circuit filament

 

[Pete999]

I'm looking at a German made roller conveyor system 10 motors contactors controlled by a PLC

Issue is customer says 3 mths ago motors started stopping and overheating, and would then start again when cooled down
Overloads trip out PLC, input switches contactors off and someone presses reset
(It's a year old, the maintenance team are mechanical bias)

So as this was sold by our firm we are first to check
1st thing I notice is panel is warm, open it and hot plastic smell comes out
I felt the contactors and where they connect to Overloads it's pretty warm, and a slight melting off a small area on the top of the overloads, where the self maintaining contacts are snapped off
obvious issue here

So I turn it off check all the connections are tight, some weren't as tight as I think they should be but no loose connections

So I start turning motor circuits off to check continuity and resistance through all components , voltage at all terminals except motor as it's not safe to do this tested / inspected everything I can think of even recorded temperature of motors and the components in the board, bench tested one of the motors all good
nothing untoward found, all current readings at @ 0.6 A motor plate says 0.9 A , O/L's set at just over 1 A

So I'm checking how it's running sensors actuating contactors etc and noticed occasionally when the line builds up due to downstream conveyors being stopped by staff, that the contactors are being turned on and off very quickly with the result the motor is getting hot as fan isn't running enough air over the casing to cool it, normal running its fine
Asides from the suspect overloads and this timing issue all looks good

Yesterday I smelt a hot motor it was single phasing checked O/L and found a phase down
Removed it opened up and one of the filaments is open circuit

I report back to German Engineer he says he agrees with the timing issue but he doesn't agree with my request for new overloads to be sent even after seeing the broken one

I sent him all readings and photos etc
He's still adamant it must be a supply voltage issue or something else that I have missed as this is a small simple system
And they have built lots of these with no issues
So I'm still onsite monitoring things

So just wanted to see if others have any opinions or ideas
[automerge]1580903734[/automerge]
Burnt plastic connecting the two self maintain contacts
[automerge]1580903799[/automerge]
Open circuit filament

What are the voltage parameters stated on the Motors and what voltage are you supplying the machine with?
Is the conveyor system maintained properly and is it Mechanically overloaded at any stage, causing the motors to overheat due to over working?

 

[edexlab]

400v 3~
Checked gearboxes, listened to them ,temps and turned all by hand nothing except for a very slight leak of oil on one gearbox

Maintenance team not experienced electrically, they try their best I think....

As I said the contactor switching rapidly when there is a build up of boxes causes the motors to heat up, the conveyors affected most of the time are short and can only carry a couple of boxes which are well within the motors capability

 

[James]

Contactors and motors are only expected to do a certain amount of starts before they have worn out or burnt ou the contacts.
Also they are often only expected by the manufacturer to do so many starts per hour.

If they have been starting and stopping very fast for some time, they may well have reached there end of life.

Check manufacturer data sheet for the info.

 

[edexlab]

I'm thinking it's a straightforward thing
Replace hot and heat damaged overloads as one has already failed
Change PLC program to give a longer delay to ensure there aren't too many boxes on conveyor at any time and then monitor temperature in the panel and motors to see if the heat is a symptom or the cause

But the German guy is saying there must be another issue and won't accept that the Overloads could be the cause, ie whether caused by connections/ bad batch , says its impossible....

 

[Pete999]

400v 3~
Checked gearboxes, listened to them ,temps and turned all by hand nothing except for a very slight leak of oil on one gearbox

Maintenance team not experienced electrically, they try their best I think....

As I said the contactor switching rapidly when there is a build up of boxes causes the motors to heat up, the conveyors affected most of the time are short and can only carry a couple of boxes which are well within the motors capability

Understand you saying the Mechanical engineers aren't biased to the Electrical side of things, but not maintaining something that is relying on an Electrically driven Mover can and does sometimes cause stress to the Mover in this case the Motor and it's associated control gear.

 

[edexlab]

Yes checked switching ratings of contactors
These are standard components for this firm
As said before this company builds big and complex systems usually longer than this a

 

[Pete999]

I'm thinking it's a straightforward thing
Replace hot and heat damaged overloads as one has already failed
Change PLC program to give a longer delay to ensure there aren't too many boxes on conveyor at any time and then monitor temperature in the panel and motors to see if the heat is a symptom or the cause

But the German guy is saying there must be another issue and won't accept that the Overloads could be the cause, ie whether caused by connections/ bad batch , says its impossible....

No good changing the overloads just because they are getting warm, first step is to find out why They are getting warm, otherwise the same may happen to the replacements.

 

[edexlab]

No good changing the overloads just because they are getting warm, first step is to find out why They are getting warm, otherwise the same may happen to the replacements.

Agree 100% and have been constantly checking things for 2 days , not seen anything unusual at all

As I said before after all checks the Overloads that have tripped have done so when it's set at just over 1 A,
I've had clampmeters on and watched and it's never gone above the running current approx 0.6A

Admittedly I only have two clampmeters available so I've checked two phases and alternated between them to try and catch a higher reading, requested a third one ....

 

[edexlab]

Also when the overload failed there were no spares, so as a test ran it directly off the relay for a few hours until got a replacement, monitored the current / voltage to see if the motor was behaving and not seen anything strange, so to me it points back to the overloads again,

 

[Pete999]

Agree 100% and have been constantly checking things for 2 days , not seen anything unusual at all

As I said before after all checks the Overloads that have tripped have done so when it's set at just over 1 A,
I've had clampmeters on and watched and it's never gone above the running current approx 0.6A

Admittedly I only have two clampmeters available so I've checked two phases and alternated between them to try and catch a higher reading, requested a third one ....

Rather than do that hire a supply monitor and leave connected for a period of time

 

[edexlab]

It was just to keep them going but also I think its shown that the motor may be ok
I have 2 new overloads fitted spaced all of them so there is an air gap , set it slightly below rated current, and in manual reset

Part of the problem is the overloads were set to auto reset and when they first had problems here they just pressed the master reset and carried on until it happened again, no investigation into why it was stopping .
[automerge]1580912439[/automerge]
I've asked them to get supply monitored also

 

[Pete999]

It was just to keep them going but also I think its shown that the motor may be ok
I have 2 new overloads fitted spaced all of them so there is an air gap , set it slightly below rated current, and in manual reset

Part of the problem is the overloads were set to auto reset and when they first had problems here they just pressed the master reset and carried on until it happened again, no investigation into why it was stopping .
[automerge]1580912439[/automerge]
I've asked them to get supply monitored also

Nothing much more you can do at present other than keep an eye on things and await the delivery and installation of the monitor is there.

 

[ipf]

You say the machine's a year old...….surely it's still under some warranty with the suppliers, from your point of view. I would have thought they'd have maintenance engineers at the ready if it's that new.
How much did it cost? If there are 10 motors involved, it must decent sized.
Your firm must have come across problems before.

 

[edexlab]

This is third party equipment sold as a package for complete system,

My company (Dutch) builds the main machine, that feeds product to the conveyor I work for UK service dept, this conveyor is built in Germany
I'm here as first response to the warranty, as the OEM is abroad its easier for us to attend first

They're sending a Senior Engineer today
However it's been running fine today no stops for 6 hrs so far which they haven't had for several weeks usually runs for between 30mins and 2 hrs before its stopping