Dehumidifier inside azipod (pod propulsion system) 2

[Mr_Curious]

Hello.
I am seeking information about does pod propulsion system (azipod) have dryer inside in order to reduce humidity so that the insulation of electric motor does not deteriorate.

If it is installed there where dryers (heaters) are usually attached ?

 

[Gr8blu]

Azipods come in two basic configurations. Type "A" has the motor external to the pod, with a complicated gear train running from the motor (in the hull) to the prop (at the end of the pod), which eliminated the whole "humidity in the pod" discussion. Type "B" has the motor mounted within the pod nacelle, with a more-or-less direct drive to the prop. Here, the electrical connections have to come from within the hull through the connecting assembly to the motor.

In both cases, the motor is (likely) going to be a totally-enclosed construction - typically with a water-to-air cooler assembly. In this construction the primary coolant is air, which is kept internal to the motor and is never exchanged with the surroundings. The secondary coolant is some form of liquid (water-glycol solution, sea water, or "pure" water), which may be a once-through design (typical of sea water) or a recirculating design (glycol or "pure" water loop).

Motors are - generally - manufactured with anti-condensation heaters installed within the motor frame. These heaters are never powered when the motor is in operation, as current through the windings is sufficient to keep everything above the dew point. Their only use is when the system is shut down or idled.

Converting energy to motion for more than half a century

 

[cranky108]

One might think, and I might be wrong, that the motor might be in a oxygen deficient atmosphere such as Nitrogen, or if high speed even hydrogen. Or have some kind of system to chemically remove moisture.
But what would I know, I have worked mostly with generators on land.

 

[Heaviside1925]

No heaters. If they are like ESPs, then the motor will be oil encapsulated. Gases as a general rule are much less conductive of heat are not as good at cooling than liquids. The dielectric oil will prevent water ingress but also provide the required dissipation of heat through conduction to the motor housing and in turn, to the ambient water that it is submerged in.

Edit per Compositepro comments, they are 100% correct.

 

[cranky108]

Interesting. While the oil is a lubricate, and coolant, it also offers more friction to movement than a gas would.
But that is likely optimized in the design.

 

[Compositepro]

Just to clarify a minor issue with the comments above, organic liquids do not have good thermal conductivity. Heat transfer is mostly due to convection, either natural or forced. It is the flow or movement of the fluid the carries the heat, not the conduction.

 

[FacEngrPE]

https://www.linkedin.com/pulse/abb-azipod-mock-up-kari-kääriäinen

https://www.navylookout.com/aab-compact-azipod-2/

 

[jraef]

These are now AC motors driven by the equivalent of a VFD (more specialized), which makes it easy to keep the motors warm from the inside by energizing the stator windings with low voltage DC.


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[jpts]

Some corrections, Azipods (which is a trademark of ABB) don't have any kind of gear, the electric motor is always inside the pod and drives the propeller directly. In so-called L-drive there is one angle-gear and the electric motor is outside the pod, but this has nothing to do with Azipod.

Azipods are not encapsulated in oil. In compact Azipods (generally below 5MW) cooling is carried out by sea water only. In larger Azipods, most of the cooling is done with external fans outside the pod (they circulate the air inside the pod), but part of the heat dissipates into sea water surrounding the pod. To avoid condensation when the motors are not running, there are most likely normal space heaters in the motor winding. Alternative would be to run the fan motors, since their power turns into friction (=heat) when the air flows through the motor, keeping the temperature above dew point

 

[edison123]

Thanks for the info.

Muthu

http://www.edison.co.in