Melted motor terminal post?

[-Matt]

Customer has this 110KW (converted to 55KW) motor powered via a generator.

They had a problem with the generator cutting out on startup showing overload fault.

Having investigated this issue, along with the motor overload having been bypassed!! (will be rectifying this!)

when I took the cover off the motor I noticed the nylock nut had melted its plastic with signs of overheating.

whilst removing the link bar to test the coils, I found the whole terminal post had melted out of the insulating section. and pretty corroded terminals.

My assessment is a poor connection on the terminal posts .

The coils seem ok.

Im trying to get a motor expert to come out and give his opinion and repair option. however having trouble getting someone out quickly, and customer needs this running ASAP.

Can anyone think of a temporary or permanent, safe fix?
I guess it really needs new terminal block and posts?

What do you guys think?

 

[-Matt]

There isn't a Variable speed drive somewhere is there?

Nope, from soft starter (55KW) direct to motor.

However im not overly familiar with soft starters and did note the motor was wired in star, I would have expected delta?

If they were solid connections, I find it difficult to understand why a terminal would burn out like that before a winding going down.
Looks like a complete rewind and terminal block, who knows the internal damage done. How do the windings read?

I did wonder if it was a loose connection on the star link connection?

However now wondering if it should have been in delta?

The readings were pretty low, all around 0.5ohm, which did seem low for a motor this size?

Good question the only way I can think of is that they sent it to get rewound to 55kW. Bit expensive though.

Yes I couldn't work this out, im sure it would have been cheaper to just get a 55KW motor!

But its apparently been in this configuration for several years...

 

[westward10]

Interesting it is running in star as that could cause issues if it is not running up to full speed and is not cooling. Would need to see the rating plate.

 

[PEG]

Continuing the miss marple theme...has any water been running off that truss section?

 

[ruston]

And is it getting any cooling through the vent , or is it all gunged up with the crud we can see on the outside.

 

[timbobelfast]

And while you are there tie the stator down to earth as well

Is it a DOL starter? Bit of a beast, a nice Soft Start should prolong life.

 

[TJ Anderson]

Interesting it is running in star as that could cause issues if it is not running up to full speed and is not cooling. Would need to see the rating plate.

I was thinking the same.

Also, That's been wired for Delta at some point due to six wires brought upto motor terminals.
I reckon that's what they mean when they are (incorrectly) saying it has been de-rated to 55kw as they have bridged it into star permanently back at the starter.

 

[TJ Anderson]

Ignore my last. I've looked at photo again. He removed the star links at the motor.

 

[Michael J]

I think it could have been started when it was 110kW using a LRS (liquid resistance starter) that would explain the Star configuration.It was then probably upgraded to the soft starter but motor was not changed to Delta.

 

[Michael J]

Please ignore my last post as it would have had to be a wound rotor

 

[-Matt]

Thanks, motor expert came out this morning and confirmed the motor should only be in Delta! And that it is a 110KW motor!

However he tested the coils again himself and confirmed the motor was ok. When I left him he was going to look for a new terminal block and replace that.

Now my problem is....

Its running off a 105KVA generator.

The soft starter is only rated to 55KW.

25mm SWA running to the motor.

Along with the bypassed overload.


I think to get this rectified correctly the customer is going to need to dip his hand into his wallet.....

 

[westward10]

Thanks for getting back, did sound odd running in star.

 

[-Matt]

As a further curve ball, I had the motor briefly running earlier, after initial start up, and no material in the mill the motor was pulling 20A in L1 and L3, but 200A in L2!!

This would explain the generator going into overload.

Im thinking possibly the soft starter is buggered from overload?

I also need to sort the lack of overload, does anyone know what this overload system is called? The L3 has melted, so someone has just bypassed it! (it also needs a tidy up!!)

 

[westward10]

It is just an overload relay.

 

[snowhead]

I also need to sort the lack of overload, does anyone know what this overload system is called?

Similar to this;
LOVATO 11RF180 THERMAL OVERLOAD RELAY 120-200A RANGE (600427) | eBay - https://www.ebay.co.uk/itm/292991963327

 

[Bobster]

It doesn't even look like the O/L is used. Dependent on the type of soft start, the O/L protection may well be built into that.

Have you measured that all of the windings are balanced, through the cable to the motor?

If they are, then yes the SS is likely kaput.