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?

 

[westward10]

Looks like they have all been overheating.

 

[telectrix]

gorilla snot glue.

 

[Wilko]

Hmm - someone has troubled themselves to bypass the thermal overload and now terminal plate has melted. Is the motor running overloaded or am I reading too much into this?

 

[westward10]

You may expect one post to fail for some reason but to me they are all showing signs of overheating. Get a specialist to look at it and don't attempt an ad hoc repair.

 

[snowhead]

Ulimately a new block.
They're fairly standard, has the customer got an old / spare motor around?

But, you'll need a new crimp on the ends coming from the windings (or clean the existing up).

As W10 above, they all look to have damage, so clean up all the ring crimps from the windings and nuts /screws.
And the supply cables.

Then new ring crimp onto the supply cable, use a new /clean screw / nuts and washers to the damaged one.
Heat shrink over the joint if you've got any big enough (put on firts of course) tie wrap the joint away from the block so it doesn't bounce around.

 

[Silly Sausage]

Looks like they have all been overheating.

Have you noticed the fire extinguisher sitting near by?

 

[snowhead]

Hmm - someone has troubled themselves to bypass the thermal overload and now terminal plate has melted. Is the motor running overloaded or am I reading too much into this?

It's O.K they've left a Fire exstinguisher by the Motor.

 

[Silly Sausage]

It's O.K they've left a Fire exstinguisher by the Motor.

At least two of us have got good observational skills around here

 

[westward10]

I would want to know why they have ended up like that, yes a new block can be fitted but long term do you end up in the same situation or worse.

 

[westward10]

How has it been converted to 55kw.

 

[-Matt]

Hmm - someone has troubled themselves to bypass the thermal overload and now terminal plate has melted. Is the motor running overloaded or am I reading too much into this?

I suspect it was a temporary bodge that was never rectified, its been like that any least a year.

I actually measured the running currents of this motor a few weeks ago (with aim of getting onto grid supply) and it varied from around 50-100A, which FLC of 97A for a 55KW motor seemed ok.

You may expect one post to fail for some reason but to me they are all showing signs of overheating. Get a specialist to look at it and don't attempt an ad hoc repair.

Hopefully a specialist will get out tomorrow.

How has it been converted to 55kw.

That is a question I asked, but they don't know was the answer...

 

[snowhead]

How has it been converted to 55kw.

That is a question I asked, but they don't know was the answer...

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

 

[ipf]

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?

 

[Michael J]

How has it been converted to 55kw.

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

 

[-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.

 

[-Matt]

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

That looks like it! I was wondering if the base was a generic part the overload connects to, but looks like its all 1 unit.

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.

Its an ABB soft start which does not have overload protection, the L3 has been bypassed from the overload.

The motor is balanced.

So looks like the soft start is ----ed, in which case I am going to get a 110KW soft start.

Im thinking of going for one of the Schneider digital soft starts which has built in overload:

https://uk.rs-online.com/web/p/products/7106451/?cm_mmc=aff2-_-uk-_-octopart-_-7106451

Going to have a chat with my wholesaler in a bit to see how fast he can get one and for a better price than RS!

 

[Bobster]

So looks like the soft start is ****ed, in which case I am going to get a 110KW soft start.

Im thinking of going for one of the Schneider digital soft starts which has built in overload:

https://uk.rs-online.com/web/p/products/7106451/?cm_mmc=aff2-_-uk-_-octopart-_-7106451

Going to have a chat with my wholesaler in a bit to see how fast he can get one and for a better price than RS!

What is the motors duty cycle? (How many times an hour does it start and stop?).

Does it start under fully loaded in normal situations?

You may need to look at a SS the next frame size up 132KW. Either of these will not fit in the existing control panel looking at the size.

If you start installing a new control panel, you're going to take responsibility for the design and safety of the machine. Just to let you know this.

This will involve a CE declaration.

 

[-Matt]

What is the motors duty cycle? (How many times an hour does it start and stop?).

Does it start under fully loaded in normal situations?

You may need to look at a SS the next frame size up 132KW. Either of these will not fit in the existing control panel looking at the size.

If you start installing a new control panel, you're going to take responsibility for the design and safety of the machine. Just to let you know this.

This will involve a CE declaration.

Thanks, Its pretty much started once a day and then just runs all day.
Its always started empty, so the motor can spin freely.

TBH I don't think I will get any 110KWn soft start to fit in the existing enclosure, so its going to need a bigger enclosure anyway.

 

[Bobster]

The sizing of SS catches a lot of inexperienced people out, but if only starting once an hour empty you should be ok with a 110KW frame size.

You will also likely need semi conductor fuses to protect the SS to meet manufacturers installation instructions.

I haven't seen the application, so I can't offer any in depth advice.