Damp In 3 Phase Motor

[binky]

Is there a chance that since the alterations that the motor is just not getting up to speed?

pretty sure it is running fine, certainly sounds healthy enough

 

[Marvo]

Many years ago I had a conversation witth a senior electrical inspector with

an insurance company about TEFC (Totally Enclosed Fan Cooled) motors.

It was thought that the "damp" problem would be solved by this design.

Not so.  Seems that when opened up, damp had been present at some time

in the past.  Corrosion pools in the end covers etc.  At the time, no-one could

explain it.

If the fan motor is mounted in the duct with the blade directly on its shaft it's most likely a pad mounted TEAO motor. If the fan is bifurcated design or has a pulley driven shaft it would most likely be TEFC. I'm not sure which type of fan or motor Binky is referring to.An IR reading of 0.25Mohm would certainly warrant investigation. I don't blame them for removing it but surely the drive itself would have picked up such a low IR as an error or fault condition.

 

[Technician]

Could you tell us what TEAO is Marvo?

Found it; but I'll wait for Marvo. :Blushing

 

[Marvo]

TEAO is totally enclosed air over, I'm not sure but this might be a NEMA term and could be called something else in your local regs. The motor is sealed and has no cooling fan on the back of it so it's better suited to applications where there's dust or grease in the airstream that would block the cooling fan. They rely on the extracted airstream going through the main fan housing for their cooling.

 

[Technician]

That is a great table Canoe;  could some of those classifications 

be applied to motors in Ex or flameproof in ATEX locations.  I

frame this question carefully because open type motors (IC01)

would never be found there.

Or is there a different table?

 

[binky]

'An IR reading of 0.25Mohm would certainly warrant investigation. I don't blame them for removing it but surely the drive itself would have picked up such a low IR as an error or fault condition.'

inverter did pick up issues and refused to start-up. 

picture of motor and fan below - you can make out gaps around cable entries. Sorry for not posting before, I forgot I had this in dropbox

 

[binky]

Fortunately drying the motor out is not my problem, the damp being historical in nature, and I think its failure is something to do with all the extra lovelly weather we've been having getting into gaps around cables entry points (I did seal these up, but damage was already done??). The place has a nice warm foundry to sort it out! The inverter has been tweaked in my abscence and without consultation (due to lower performance) so all warranty would be invalid anyway. What I was really interested in is possible causes of lower performance, and whether damp was the cause. I did consult the in-house maintenance guys with technical questions like 'is it spinning the right way?' and ' how do you know it's working properly' at the time of installation, but to no avail :shakehead Might still take you up on the motor though - all i need then is a propeller and I can build my own wind turbine :^O

Have you changed your phone number paddler? - would have run back if you had come up on screen, I was probably driving around south-hams at the time and this seems to affect how the phone screen works sometimes.

 

[Marvo]

Just out of interest what's that 3rd gray cable going to the left of the terminal box? It's not very clear on my 8 year old screen

Edit, Also what's the smaller gland for on the back of the terminal box?

 

[binky]

being a tidy place (not) that's a bit of plastic pipe and nothing to do with motor. The small TRS gland serves no purpose except as another water entry point ( or vent )

 

[Technician]

Only an observation Canoe;  by Class F would you mean insulation

class F?  IIRC this is only one step above one of the most common,

class E, and would this limit the temperature to which the windings

could be taken while drying out?

Would agree totally with you that heaters in the windings should have

been fitted considering the possibility of intermittent duty outside.

 

[Marvo]

We usually just fit a roof type cover to prevent corrosion and water ingress, it's low-tech but it's cheaper and quicker than trace heaters etc. Then again our lowest temperatures are around 5 Celsius in mid winter so maybe heaters are a preferred option in the UK with the lower ambient temps.

being a tidy place (not) that's a bit of plastic pipe and nothing to do with motor. The small TRS gland serves no purpose except as another water entry point ( or vent )

Thanks, wouldn't have guessed it was a pipe, it looked like an add on cable. Can I ask another 'can't see very well' type question? In the bottom right hand corner of the photo, what is that circular blue steel thing that looks like it might be part of the motor or fan unit?

 

[binky]

its the bit that fell off Marvo :slap

think thats the lid for the barrell that sits under filter cleaning-out valve - the place most definetly needs a touch of '5S', thats's cleaning tidying and organising for those not familiar with Japanese manufacturing philosophy. The site makes Steptoes' yard look tidy

 

[steptoe]

who's the bird in the background?

thats what I want to know.

 

[Technician]

Presspahn;  one of the higher rated insulating materials...still made

in a little place not too far from me.

 

[binky]

 Update on motor-

new motor fitted, and all is well again, so can only assume something about inverter control method reveals dying motors, (that or fiddling with motor speed finished it off :innocent )

 

[Technician]

Presspahn turns up as insulation material in many of the

books I have.

From my memory of the building, the company name is

Presspahn limited.