Tedi, can you tell us about "DC motor withstanding water inside"?

I suspect that information may have a bearing on a valid answer.

If I design it water proof I will have an issue with overheating.That's why I desire to make it capable of withstanding some intake of water inside of the motor for the sake of cooling.

Tedi, I'm with redfred on this one. Is that what this epoxy you are looking for is... a coating for internal components of your motor, in an attempt to run this motor immersed in some liquid, using the liquid to cool these internal components by direct contact transfer?

Wow, sounds like a pretty ambitious project. Does such a thing already exist on a scale too large or small for you to use?

A google yielded 939 companies manufacturing a motor listed for use underwater. There is a selection engine available...

http://motion-controls.globalspec.com/SpecSearch/SearchForm/Motion_Controls/Motors/DC_Motors

that I used, and all I could find were motors suitable for submersion because they were sealed.

While water does not conduct electricity all that well, allowing any non compressible fluid into motor cavities does not sound like a good idea. If your motor requires more cooling than the air that you can blow around, then fabricating an air or water cooled heat sink to bolt onto the motor chassis sounds like a better idea than immersion.

Aluminum Nitride has thermal conductivity comparable to aluminum metal, is an electric insulator and way cheaper than diamond. Can you not use a solid state Peltier effect cooler? http://www.patentstorm.us/patents/6568193/description.html

You can talk to -

DR BECK & CO (india) limited

ERANDWANE DECCAN GYMKHANA, PUNE 411004, MAHARASHTRA

p: 25430902

Unless it will be under a severe load all of the time I would think any number of submersible motors would work. Sump pumps come readily to mind and they work quite well.

If it is under severe enough load to be concerned about cooling under water a finned heat sink would help alot and a bit of an impleller to direct a flow of water over the fins would greatly assist.

I can remember seeing a demo long ago by someone who had developed an insulating fluid. The demo showed him dipping a mains powered hand drill into his fluid then plunging the running drill into a tank of water whilst still holding it. Unfortunately I can't recall the details but such materials must exist.

I found this link which, whilst not the one I remember, is along the same lines.

Would Paralene coating work?

AC motors work very well IN water for instance the motors for the water jet washing pumps of the Kärcher Company. The water cooling leads to a smaller motor since the the more intensive heat transfer allows a higher current density in the stator coils.

I think you will be better served by a combination AC+variable frequency.

Is it any reason you need a DC solution?

The biggest problem is the seal for the bearings which have to be resistant to grease on one side and water on the other. In some cases where it was possible the ball or roller bearings have been replaced by plastic journal bearings using water as lubricant and cooling fluid.

I couldn't get to know details about those karcher motors.

I found some commercially sold epoxies having good thermal and good electric insulating properties.I just don't know should I add powder like aluminium nitride(bioramani would you give me some manufacturers and links?).

The motor won't be immersed, it normally wouldn't have contact with water but the safety factor has to be...let's say it has to be idiot-proof!

AC won't do.

AC with built in GFCI will protect sufficiently for hot tubs and pool operations. Remember you can make it reasonably foolproof but you can't make it damned foolproof.

Why not AC?

RPM, efficiency and power to weight ratio.

AC won't do.

Then use a brushless with a PM rotor. The supplementary friction due to water presence is small since water has a very low viscosity.

You should only protect the stator coil connections in order to avoid shorts and the zone where the rotor gives its position for the commutation of stator coils. This will be the most difficult since you can only use nonmagnetic elements.

Water will if present increase the cooling so that it has no negative influences and if in small quantities and the motor is open it will disappear as vapour!