Will the all DC electric grid of my young and tender days be back on ships in the future?:
PS> I know that DC grid for propulsion motors and other major equipment has been around, especially for various OSV, for some time. (Still with AC for hotel service etc.)
It makes adding a battery bank and putting generators on and offline a lot easier for sure. I worked on a 120 volt DC setup once and that was pretty unusual to still see in the 1990s. My family had a boat set up with 120 DC back in about 1912 or so.
The technology swings from ac to dc every decade as converting technology changes as to which way is more efficient
Siemens, Warsila, Kongsberg etc all got products
Its all about the gen sets and propulsion, you wont be having 120v dc bilge pumps
Higher frequency high voltage is better for secondary power
EU and green will put solar panels on boats…lol
If it all uses less fuel then the ships will be built that way.
Just think after all the green crap in the EU, Germanys reduction has only been because their industry is dying.
I sailed on a cruiser built 1944 with a ring main DC power supply. During a exercise simulating battle damage at Pearl Harbour the invigilators would shut down a turbo generator in one compartment then another diesel generator somewhere else and the lights stayed on.
Yes they do, as has ABB:
https://new.abb.com/marine/systems-and-solutions/power-generation-and-distribution/onboard-dc-grid
So far DC Grid has mainly been used on various offshore vessels and dregers etc.
The Electric ferries that are now becoming the standard in Norway obviously has all DC Grid. The conversion from the HV AC grid is done at the onshore charging station:
https://ntnuopen.ntnu.no › bitstream › handle › I…
PS> AC power (220/440V) is available where required for ship’s systems and pax. facilities.
Latest MODUs / Drill ships now use DC grid instead of AC Generators and SCRs, or VFC electric motors.
There have been dc gen sets and propulsion around for decades.
DC in primary grid is one thing
Going secondary is scary stuff as thats back to the deadly dc pumps in the engine room
That is what I said in the OP, although not for propulsion on the ships I was on.
Ships built in the 1950s-60s mostly had DC generators and DC grid for everything, incl. hotel services.
The earliest ships with electric propulsion had DC generators, mostly driven by steam turbines, with DC propulsion motors. (See T-2 tankers of WWII fame)
This did not catch on, however, but ac generators became the norm from the 1970s or so. DC converters were used to supply DC power where needed. (instruments etc.)
PS> On MODUS SCRs were used to supply DC to drilling motors and propulsion (where fitted) until VFC became the norm.
A very, very long time ago I sailed briefly on the Louisiana Brimstone which was originally the T2 tanker Camp Charlotte built in 1942. The propulsion motor was a 2,300 volt 3 phase synchronous/induction unit.
T2 tankers were steam turbine electric because during WWII the manufacturing of geared turbines was prioritised for naval vessels.
Coming from an old crude oil tanker to a clean oil T2 was a revelation. Just a switch to turn on a cargo pump. She had an entire new hull forward of the pump room, with a new funnel and the midship accomodation moved on top of the after house.
I take it the 120 volt bilge pumps were shocking people back in the day?
dc at higher voltage makes sparks jump further…
Insulation needs to be bigger
breakers etc
Did the whole accommodation vibrate like the Texaco Saigon? The bridge vibrated so badly that the Mates has to keep a rough log and then make a fair copy elsewhere.
No it didn’t. I was on my way home with the missus from Singapore to NZ from the Texaco Plymouth when they had to fly the 2nd Mate off the Bombay. HO said they would pay the missus air fare home if I took the Bombay from Darwin to Newcastle NSW. She was quite a revelation after dealing with the Plymouth but I only spent just over a week onboard.
The old man was a bit of a cabinet maker and the bar had been turned into a replica of an old English pub complete with horse brasses.
DC? T2? Better do so better research. T2 Tanks were 2300 Volts AC- the only DC was Emergency Power feeds and Nav junk. The only DC generators aboard T2’s were the Rotortrol exciters for the SSTG’s and the Propulsion Generator and Motor- I know I sailed on one for about 6 months…
It makes sense. I knew they were used as temporary power stations supplying some small settlements after the war. It would have been a lot more difficult if they had been DC.
Ahh yes, now I remember. When I had just joined my first ship, a tanker, we did a trip from UK to Drammen in Norway with a load of bunker fuel for 2 (or 3?) T2 tankers that was used to supply power for new industry in the area. This was In 1959.
I stand corrected re:T2 tankers, but stand by the rest of my post #7.
