Voltage converting

Does anyone have suggestions on how to convert 120VAC to 220-400VDC all in subsea enclousures?
Is it possible to use a toroidal transformer 120VAC primary side and step up the voltage inside a bluerobotics enclousure for example? Fill it up with oil to let it be cooled down when in water.
Then go from that to another enclousure to a bridge rectifier and capacitor to get DC voltage.

Any ideas?

Hi Jorgen,
you should refer to each component datasheet if they are suited to works in oil but in general:

Can work in oil:
Transformers, bridge rectifier

Cannot work in oil:
Electrolytic capacitors

Please be note that not all components are pressure tolerant. So take also this in consideration if you’re planning to use an external oil compensator.

If everything is well dimensioned, there’s no problem to let your AC/DC converter to works in air inside an aluminum enclosure.( you can also consider a small FAN to accelerate the heat exchange with the enclosure wall)

How is it to put a external compensator to a bluerobotics enclousure? When you put oil pressure on the inside, will the flanges and end caps still be in place since this is only held in place by two o-rings?

Hi @Jhans -
The idea behind pressure-compensating an oil filled container is to allow the oil to be at the same pressure as the external fluid - that is why @SubseaLED mentioned the components needing to be pressure tolerant. The differential pressure between the inside and outside of the enclosure should be close to 0, allowing the enclosure to be used at full ocean depth (theoretically.) Typically a bladder or some other flexible container holds oil externally, so the pressures of the fluids are equivalent. If you are using components that have internal air spaces, these will fail at depth as the oil pressure will crush them!

Hey @tony-white

Yeah i know that, but i just wanted to know if you could use a external oil compensator on a bluerobotics enclousure?

@Jhans I don’t see why not!

The only thing i’m worried about is when you apply the oil pressure from the compensator into the enclousure, the endcaps may pop off, since the flanges are only held in place by the two o-rings?

Normally when using a compensator and filling up a junction box or a enclousure with oil, the lid is usally secured with bolts to the box itself.

Hi @Jhans -
I think I understand now. You’re worried that when you fill the WTE with oil on deck, the weight of the oil will cause the end caps to pop off. If you’re using our older series of enclosure tubes this may indeed be a risk, but all of our current 2, 3, & 4" enclosures use a “locking cord” that prevents the end cap from popping off. The cord would fail in shear before the tube locking channel does, and it can hold significant internal pressure. Once you’re at depth the oil pressure will be equal to the water pressure, and so the cord will not be under stress.

We’re launching some larger enclosures with this feature very very soon (less than 1 week away)- stay tuned!

Perfect! Thanks @tony-white :blush: