Cast iron vs Aluminium 3

[radug]

Hello,

I would like to know which are the differences between cast iron and aluminium squirrel cage motors in terms of performance, environment withstand,...

When should be a cast iron motor used and not an aluminium motor?



Thanks.

 

[electricpete]

Personally I don't recall seeing any aluminum frame motors at our plant but I hear they have a reputation for being flimsy. Also they are prohibited by IEEE 841. I'd be inclined to stick with traditional cast iron frame. Perhaps more important for belt load which may tend to distort frane and cause misalignment internal to the machine

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(2B)+(2B)' ?

 

[ScottyUK]

On aluminium motors you will find that screws and bolts tend to oxidise in place with a strength of bond that exceeds that of the fastener. I too prefer iron frame motors.

 

[BigBill53]

My father was a motor rewinder, and working with him I have had quite a bit to do with both types.

You will find aluminium motors are generally only in smaller frame sizes. I haven't seen one much larger than 3kW. They are usually a bit cheaper and easier to install (because they are lighter). However, they will corrode like crazy if left outdoors (they are made out of the cheapest scrap aluminium you can get - it tends to oxidise and then flake and go brittle). Seem to last pretty long if indoors. Don't expect to repair them - in fact, it's really not worth repairing anything small (under 30kW) anymore anyway (unless you are in a developing country where labour is cheaper).

Cast iron motors don't have any of these problems. Their frames are much stronger, but they are heavier and harder to install. They will last a lot longer if exposed to the elements, which is the main thing really.

Check the fan cowl on the motor - a lot of cast iron motors will have a tin or aluminium fan cowl and these only last about 5 years outdoors (well, longer in dryer areas). Here in Australia we can get what we call a "mine spec" motor, which has a cast iron fan cowl (amongst other things).

Oh, and don't put aluminum motors in a salty environment. Very small lifespan.

 

[itsmoked]

Nice info Big. Thanks.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[radug]

Thank you. I saw aluminium motors indoors but not outdoors. I wanted to know which was the reason for this. Now it is clear to me.

 

[ozmosis]

If you have aluminium motors in a food or beverage environment that are not coated with special lacquers, then the cleaning agents used in wash down (strong alkalis like caustic soda) will destroy them very quickly. Caustic soda and Al will generate a lot of heat and visibly eat in.
Acids in the Beverage industry, not just in the cleaning but in the drinks (e.g. Coca cola) will not only have a damaging result but also for the hygiene level (if important) due to the rough surface created on the motor.
And these applications are indoors usually.

However, this would also be true for cast iron, so the use of motors with the necessary coating is important.