Comments by "SeanBZA" (@SeanBZA) on "Why Did Dali Lose Power in Baltimore? | NTSB Releases Preliminary Report" video.

  1. Small correction the oil pumps and cooling water systems will all be run off the 440VAC bus, as they are low power loads, under 20kVA per motor, so easily run off a 440VAC power link, which is a lot cheaper motor wise, as you use standard insulation on the motor, and standard insulation on the wires, which is a lot cheaper than 6600VAC insulation and control gear. Same for hydraulic oil pumps, all running off the low voltage bus. Bow thruster high voltage because they need the power delivery, and the long cables for them also make high voltage advantageous, despite the need for much more robust and thicker insulation, and much more expensive control gear. The high voltage on a motor means a much larger motor frame, as now you have so much more volume in the windings being occupied by insulation, instead of copper or aluminium wire. As well with high voltage insulation cooling is harder, you need to either have air channels down the windings for cooling, and run the windings at a much lower current so they generate less heat, or have much lower power density in the motor, making it much bigger for the power. Expensive below roughly 50kVA, and the 6600VAC control gear is a lot more expensive over your common low cost 440VAC control gear, that is cheap, and common world wide in industry.
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