Motor selection

[Guardiano]

Hi,

We are in the process of selecting a 750 kW 50 Hz 400 V for a conveyor.The motor will be located in the outside environment but sheltered with corrugated iron sheets.The plan of a particular motor is herewith attached.We don't have any particular problem with this motor but the air inlet is on the drive end side and the air is most likely more polluted on the drive end than on the non drive end side!I don't know if this argument is really true. I'm looking for the expert opinion as I don't want to select the wrong motor.
Thanks

Guardiano

 

[electricpete]

It appears to be an Open Drip Proof motor, in which case the cooling air comes in direct contact with the stator / winding.

Most people probably don’t pay a lot of attention to the location of the air inlet, but probably should.

I don’t know if there are any firm guidelines for this situation. It seems like a judgement based on cost/risk assessment.

To get more opinions:
1 – what type of pollutant are you talking about and how concentrated (if that can be quantified).
2 – is machine fed from vfd? voltage spikes might exacerbate polluted winidngs.
3 – what is cost to buy a new motor with air intake in more favorable location? I would guess $20,000 ?
4 – how painful is motor failure?


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(2B)+(2B)' ?

 

[DickDV]

One other thought: how about specifying the same motor but with epoxy VPI varnish system. I've seen these motors run ok under water! Not recommending that, understand.

 

[edison123]

Open type motors in an outdoor environment (even the corrugated sheet cover) is a bad idea. I suggest closed type motor to prevent operational headaches.

Muthu

http://www.edison.co.in

 

[starkopete]

Hi,
Depending on what this motor is coupled to, I might be concerned about whether the air flow to the inlet will be sufficient.

Thanks

 

[rhatcher]

edison123's suggestion for an enclosed motor is a good one.

My concerns for this design would be; moisture (rain or condensation), contamination from driven load (grease, oil, debris, etc.), and (per starkopete) reduced air flow due to proximity of load or related equipment at the air inlet.

Also, I would say that for any motor this large (expensive) that heaters should be installed regardless of whether it is open or enclosed.

 

[Guardiano]

Hi all,

Many thanks for all your replies.This is not an open drip proof motor but a totally enclosed motor with a degree of protection IP55.The method of cooling is IC511.My only concern is the air intake from the drive end rather from the NDE side.There is no marginal difference in cost compared to a standard motor but this motor is available right now and we urgently need a replacement motor NOW.

Guardiano

 

[ScottyUK]

IC511 is a TEAAC design - closed internal air circuit with an air/air heat exchanger.

What is the contaminant - material off the conveyor? If it is something which is likely to adhere to the heat exchanger fins then you will probably need to have a good maintenance regime in place.

A motor this size is probably a semi-custom design: can the manufacturer modify the flow direction of the outer air circuit? I'm slightly suprised that the flow direction is as you indicate - this is contrary to to virtually every motor with a centrifugal fan on the NDE of the shaft, which exhaust toward the DE of the shaft.


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If we learn from our mistakes I'm getting a great education!

 

[Kiribanda]

Guardiano,
While agreeing with ScottyUK,this IEC motor should have its air flow from NDE to DE irrespective of the direction of rotation.It is clearly stated in IEC 34-6.It is interesting to know how the air flow is made reversed unless ordered like that.Also since it is a TEFC motor,in my opinion you should not worry about contamination of windings.Contamination will be only outside frame which you may need to clean regulary.

 

[Kiribanda]

Guardiano,
Just an additional note.It looks like this is an induction motor with rotor slip rings.Is it correct?In that case,the air flow blowing from DE to NDE may be used to cool the slip rings too so that you may have to think of contaminants.Does the rotor terminal box has got its own ventilation louvres?Appreciate your input.

 

[ScottyUK]

Kiribanda - IC511 has a closed internal air circuit with a heat exchanger. Listed in IEC 60034-6.


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If we learn from our mistakes I'm getting a great education!

 

[macmckim]

Based on the drawing the motor is a TEAAC (IC511) - here in North America, we call it a TETC (totally enclosed tube cooled) with the cooling tubes that are 360 degrees around the stator versus IC611 that has heat exchanger on top of motor frame.

Motor looks to be Wound Rotor MOtor with the external fan on the
DE side of the motor. Have seen this on many WRM over the years.
Basically have the fan on the DE, reduces the motor's over-all length - plus allows easy access to the slip rings /brushes that
are on the non-drive end. Its a good design for a WRM.

 

[edison123]

Many slipring motors have the cooling fan on the DE due to space constraints on the slipring end, which is usually the NDE for easy brush maintenance and inspection.

All in all, I would say, go for this totally enclosed motor, especially since it is readily available.

Muthu

http://www.edison.co.in