Submerge your power supply, and other options

Article By : Steve Taranovich

Advances in marine industry power supplies, immersion computing, and immersion cooling aim to make fully immersible power possible.

In 1975, there was a tech article regarding the extraction and access to oil resources in deep water (Reference 1). The traditional approach was to construct a massive platform in the sea hundreds of miles offshore under deep water.

An alternative method of pumping the oil out was discussed with undersea wellheads; however, a key problem mentioned was the availability of power supplies for pumping and instrumentation needs in place of using long power lines running from the mainland. In addition, stand-by power needed to be available for valve control, instrumentation, and communication needs in either a platform or a shore-based installation.

Rechargeable batteries were discussed as a possible solution, but pressures and temperatures at these depths would be challenging. Still, batteries were the best method for the 1975 power technology that was in existence at that time. Submersible power supplies were not readily available to most designers at that time.

Marine industry power supplies: The first step toward fully immersible power

Ideally, you typically do not want to see this application under water–that means the ship is sinking. However, you do want it to be good in a very high humid environment and it’s good to know that a supply employs the same components and design rules as do immersed power supplies. The PT578 by Powerbox is such a supply.

In the marine industry, power supplies must operate in a very demanding environment, requiring special attention to the components selected, the topology, and the final assembling. The requirement for marine power supplies is somewhat similar to the one for immersible power supplies. The technology platform developed for the PT578 is suitable for immersed computing systems requiring the power unit to operate safely within neutral fluid containers, but the PT578 is only designed for convection cooling and is protected against humidity and corrosion with conformal coating and can withstand high shock and vibration levels (Figure 1). Read more here.

Figure 1
The technology platform developed for the PT578 employs the same components and design rules as do immersed power supplies, but is only designed for convection cooling and not as a submersible power supply. These supplies are protected by a conformal coating so that the supply is able to work in a humid environment of up to 100%, condensing at all relevant temperatures and meet the IEC60947-2 2kV, 60s. (Image courtesy of Powerbox)

Shipping and offshore installations have a more demanding environment than a typical industrial environment. Levels of vibration can reach 4g and there can be large temperature swings from −25ºC to +70ºC with high humidity and condensation.

These types of environments need redundancy, which can be achieved through several power supplies being connected in parallel, linked to each other with ORing diodes. The PT578 has built-in circuitry in which the designer can select ‘single mode’ or ‘parallel mode with droop current sharing’.

[See more on the droop method in this EETimes article: Power Tip 27: Paralleling power supplies using the droop method]

Waterproof and used in marine applications–Yes, but how do you effectively remove the heat from that power supply when it is immersed in a fluid?

[Continue reading on EDN US: Enter immersion computing]

Steve Taranovich is a senior technical editor at EDN with 45 years of experience in the electronics industry.

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