encapsulation of winding for use on salt water

[mottt]

I want to encapsulate a electrical winding to use in salt water....but i don´t know the kind of composite or resin i´ll need, could somebody help me, cause this is not my thing... i was worried about, the diference on the thermal exparsion, about cracking...cause stator is for class F isolation, and close to the windings is posible there´s hot spots....
Then, other question is about compatibility with the isolation used on the windings, i mean, is posible to use a composite that is good electrical isolation, and good for the use in salt water.... cause the motor will work submerged onto the sea.... somebody tell me about use DER 330 (Dow Plastics) that is an liquid epoxy resin...what do you think...
thanks in advance.

 

[patprimmer]

A good free flowing high strength two pot epoxy will do just fine.

You will need to develop a technique to remove air bubbles and to keep the resin contained until it jells.

Sometimes carefully turning the object, sometimes some heat during cure, sometimes a mould and sometimes a vibrating mould can help.

It depends on complexity and shape of the part, how much excess you can tolerate how many you want to make and what facilities you have.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[btrueblood]

And, to add to Pat's advice, pulling a slight vacuum on the part after pouring the epoxy (but before it starts to gel/cure) will cause the bubbles to expand and rise to the surface more quickly, where you can deal with them (pop them, scrape away the foam, and pour in a fresh layer of epoxy).

 

[mottt]

this is a prototype motor, for this the price is not the first important factor....
maybe we could do mould where we could add the epoxy...an then vibrate it...
what do you think about the name of the epoxy i´ll use?, and about the absorption of water??

 

[patprimmer]

Whatever Ciba or Dow or Shell or whoever makes it now recommends.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[btrueblood]

...or Master-Bond, or DevCon, or Loctite.

 

[mottt]

¿what is the effect of the air bubbles on the epoxy against the water? is some negative effect??

 

[patprimmer]

It reduces cover or thickness of the resin, depending on the size and location, it might create a path for the water to the winding.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[corrosionman]

I sometimes meet transformers for the Mining industry - - the entire case is flooded with a mixture of polyester resin plus quartz sand which totally encapsulates the windings and the terminals, etc.Polyester is better than epoxy - it is thinner so runs into cavities easier also polyester resin is not so critical on the mixture proportions. The sand reduces shrinkage and also it increases the heat dissipation which is important for a transformer
Regards CM

 

[tnatale]

We used to do something similar for stators for windmills. We took a filled polyester and injected the mixture into a mold that held the stator. When it was removed from the mold we also added a thin silicone coating over the polyester to ensure that there as as good of seal as possible between the filled polyester and the stator shell. As an alternative consider looking for the epoxy systems that are often used for sump pumps, where they are constantly under water. It doesn't have the conductivity of the salt water, but it is still an aggressive envitronment.