Use a high voltage tether without adding weight

Allowing an underwater ROV to perform remote inspection activities at greater depths required the tether from the ship-based power source be extended. Distributing the original design’s low voltage over the longer tether was not practical due to voltage drops. Moving to a high-voltage 700V low-loss tether, however, required conversion to a lower SELV voltage onboard the ROV. This typically requires a custom converter that takes up space and adds weight, not feasible in an ROV that needs to be able to carry increased payloads. The key goals were:

• Extending the tether, required for deep or remote inspection, without loss of performance
• Avoid the high cost of a custom discrete power solution while saving space and weight
• Retain clear transmission of data via the tether for onboard sensors

Compact, lightweight 48V conversion in the ROV

The extremely small, low weight BCM® Bus Converter, acting as a DC-DC transformer, converted the high voltage from the tether down to the 48V distribution architecture on board the ROV. It provided a simple, easy to implement, off-the-shelf solution. Key benefits were:

• High-voltage tether reduced the supply current, and thus losses for a given cross-section of copper conductor, allowing for a thinner, longer tether
• Reduced footprint of 1.5kW solution to just 41cm²
• Low noise conversion topology prevented interference with communications over the tether