# DC or AC



## John Melbourne (Sep 15, 2013)

I have been wondering when DC was replaced by C on ships. What were the advantages of DC over AC? 
Thanks
John


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## Frank P (Mar 13, 2005)

In 1967 my first ship the M/S Else Reith was D/C and as far as the crew were concerned there was not any advantages to having D/C, you needed a transformer to run a record player and there were only a few transformers on board..

Frank


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## Robert Hilton (Feb 13, 2011)

When on a 48volt dc vessel I told my wife we were looking for a calor gas television. Her face was a picture as she tried to decide whether I was joking or not.


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## david freeman (Jan 26, 2006)

what with a H&W two stroke opposed piston, or a H&W 4 Stroke, or a Doxford 6 Cylinder, then steam auxiliaries for feed pumps/lub oil pumps and sea water electrically driven 110v DC and boilers [SCOTCH] fans. It was another time the J/E On the 8/12 watch was a qualified electrician, and looked after the open switchboard, and gennies- Diesel driven, with their brush gear, and polishing the commutators. Then all the other gear fans in the cabin, and the steering gear motors!-fridge compressors, Not forgetting the gem, the emergency gennies was a piece of equipment 75KW ? or so driven by steam compound engine,
Dream On Macduff the ship builders dreamt up so wonderful combinations {Nickers} of machinery layouts? All to dream about?


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## John Melbourne (Sep 15, 2013)

I am trying to work out when AC replaced DC My first ships were all DC ships. The first new build I was on in 1962 was still DC and yes were all had to lug heavy transformers along with our tape recorders. But I don't think we needed them for a radio. Lloyds Register doesn't mention such detail so I wonder where I could find information like that


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## Laurie Ridyard (Apr 16, 2014)

John Melbourne said:


> I am trying to work out when AC replaced DC My first ships were all DC ships. The first new build I was on in 1962 was still DC and yes were all had to lug heavy transformers along with our tape recorders. But I don't think we needed them for a radio. Lloyds Register doesn't mention such detail so I wonder where I could find information like that


Heavy transformers ?

In 1960, I bought an AC / DC record player. @ Twas great.

ATB 


Laurie


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## Tony Morris (Oct 7, 2006)

It was not just a transformer that you needed, it was also an inverter. On my first ship, Ropners Bridgepool, the only inverter in the engine room was for the Graviner oil mist detector. There were a few lines tapped off this for private SW radios, needless to say it overloaded a few times.


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## Engine Serang (Oct 15, 2012)

John I hope no Leckys see this thread. They will spend days bombarding us with impedance, power factor and harmonics until our heads burst. And that oul carry-on with your thumb, index finger and courting finger.


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## Mad Landsman (Dec 1, 2005)

Transformers need AC. With DC it just becomes an electro magnet.
As said, you needed an inverter to make the direct current alternate. 
Some older radios would work on either, but if it had any form of transformer inside then it needed AC.


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## trotterdotpom (Apr 29, 2005)

Engine Serang said:


> John I hope no Leckys see this thread. They will spend days bombarding us with impedance, power factor and harmonics until our heads burst. And that oul carry-on with your thumb, index finger and courting finger.


I was on a Denholm's ship (DC) and recall a deck cadet asking the electrician what the difference was between AC and DC. He had a think and said: "AC's more modern."

John T


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## John Melbourne (Sep 15, 2013)

I knew I was wrong as I hit the send button. I was spooked by Frank, but that is just an excuse. I couldn't remember what it was I had to lug around from ship to ship. It was heavy.
NO I don't need to know all about impedances etc. I am past that. I just wondered when AC became standard on ships.
I had forgotten about AC/DC radios too. Just had to remember to flick the switch from 220V at home to 110V on board.
The underlying thinking behind this is that with all the devices using 24V DC about these days why don't 'modern' houses have a 24V DC circuit in the house.


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## Mad Landsman (Dec 1, 2005)

John Melbourne said:


> The underlying thinking behind this is that with all the devices using 24V DC about these days why don't 'modern' houses have a 24V DC circuit in the house.


What is becoming more common is the 5V output added to standard sockets. So called USB used to charge all one's 'devices'.


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## Baulkham Hills (Jul 11, 2008)

I remember being on an old ship in the 80's the main supply was 220DC
but also in the cabins was a socket for 110ac and another for 220ac supplied from rotary converters. Despite new joiners being warned to check the sockets some one would plug in a radio to the dc supply resulting in a flash and destruction of said radio and resultant foul language.


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## Orbitaman (Oct 5, 2007)

My first ship was built in 1972 with AC Alternators, so most of the equipment onboard was AC. However, DC winch motors are easier to operate and maintain than AC, so all of the cargo winches were DC with AC/Dc converters. hope this helps?


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## R798780 (Oct 27, 2004)

Maskeliya (1954) was the first British ship with A/C winches. Just the two at No 4 hatch all the others were Clark Chapman Silent Steam. The electric winches were experimental and replaced after a couple of years with steam. Sister Maskeliya and Maturata were a/c, the next three new builds were 220 DC. Mangla and Mathura in 1960/61 were the next A/C builds with all electric deck winches, a/c as I understand.

On an earlier trip I bought a record palyer in Aden only to find it wouldn't work on Malakand's 110 DC. Then it was problematic on Maskeliya's 60 c/s A/C. a little lump of pencil eraser up the spindle and a weight on top worked though the weights had to be reduced as the eraser rubber softened til the spindle stem had to be cleaned out and start again with a new piece of rubber. I bought a 110 DC to 220/240 a/c inverter only to find that the other steamships with DC were 220 DC. 5 cargo (cluster) lamp bulbs in series and in series with the inverter cracked that problem. Things you learn as a junior deck sprog.


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## Ron Stringer (Mar 15, 2005)

All the ship's that I sailed on were British built. The first 3 had 220V dc supplies and were built in1949, 1949, 1958. The fourth built 1946 had 110V dc and then my fifth one 1953 was my first 230V AC ship. Next ship was built 1952 and back to 220V dc before going back to my last ship, built 1964, which was 230V ac again.

My Eddystone 870a cabin radio (cost me about £35) handled them all with no problems.


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## Farmer John (Feb 22, 2012)

I think the Blue Funnel "Super P"s where the first in their fleet with AC. Playing a record became a treat to be savoured on DC, lots of batteries.


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## makko (Jul 20, 2006)

Farmer John said:


> I think the Blue Funnel "Super P"s where the first in their fleet with AC. Playing a record became a treat to be savoured on DC, lots of batteries.


I confirm that Super P's were AC, built 67/68. Phrontis was my earliest ship, others were 77 onwards, all AC.
Rgds.
Dave


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## dannic (Mar 10, 2013)

Matangi, former Port St Lawrence was 350 v dc with dc/ac converters for accommodation. So in theory could have your new radio cassette running in your cabin but.....converter was serviced on Saturday morning by 2nd leccy, commutator cleaned, brushes bedded in. Great, until captains or chiefs wife plugged in hairdryer, as it was Saturday! Result of course no ac in cabins until next Saturday as 2nd leccy wouldn't do the job again!!
Dannic


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## John Melbourne (Sep 15, 2013)

Thanks all. Great to learn of the frustrations of the day!
Here in sunny but fire prone Aussie, more and more homes are having solar panels installed. Many more are waiting for Tesla batteries to come down in price so they can store the electricity rather than feed it back into the grid. Complex maths needed to work out a breakeven price! However once that becomes common I would think having a couple of DC sockets in the house might be a good investment?
John


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## spongebob (Dec 11, 2007)

This takes me back to my first trip to Suva on the Banana boat in 1957.
Many electrical goods and other non essentials were banned imports to NZ so Suva was an ideal opportunity to get myself a slide projector .
The Second engineer recommended me to a Indian owned shop keeper who gave me a good deal and I went back on board with my treasure.
We were in the second's cabin that evening having a drink or two and he asked me to bring in the projector to show a few slides. Not thinking about AC/DC matters at the time the gadget was plugged in and switched on and apart from an instant flash of light all was quiet . A look at the label told the story , AC only!
Never mind, the Second took the projector ashore the next morning and came back with a new one after convincing the dealer that the first was faulty !
It stayed in its box until berthed in Auckland when I got a relative who was a waterfront worker to take it out through the gates without a question.
That what it was like in those days

Bob


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## John Melbourne (Sep 15, 2013)

Suva was the Aden of the Pacific. You bought from Indian shopkeepers at your own risk. You were lucky to get a replacement as you were there overnight Aden merchants generally offered to wrap your purchase for you. In the back room your gift box could be filled with anything but what you bought. But of course you were at sea by the time you checked.


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## spongebob (Dec 11, 2007)

You are dead right John but the Second enginner , Arthur Maltby , was an older man who had been on the Pacific islands run for years and he referred a lot of business to this Trader so he had a bit of pull.
Our favourite port for trade was Apia where Burns Philip South Sea Traders traded in everything. If it wasn't in stock they would get it by next voyage .
Arrow shirts, National 8 transistors , Maxwell House instant coffee, golf balls etc , all the items longed for in NZ.

Bob


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## John Melbourne (Sep 15, 2013)

Yes Bob.
I can understand that. It was pretty much the same in Aus. I nearly got my C/E busted when I jokingly asked the Customs officer at our gangway why he didn't search his bag going ashore. The next day the Chief came up to me and ticked me off. He had a bottle of whiskey in his bag!.


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## John Melbourne (Sep 15, 2013)

Thanks Orbitaman.
Most of my ships were steamers with steam winches. Now I am trying to remember when I first saw electric winches.
Thanks also for explaining why DC motors were more efficient than alternators, but I am not sure about the changing of brushes and cleaning commutators.
John


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## spongebob (Dec 11, 2007)

Can anyone recall the maker of the electro-hydraulic winches used on all the Union co colliers and other ships in lieu of the more dependable Clarke Chapman? 

Bob


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## Engine Serang (Oct 15, 2012)

John Melbourne said:


> I would think having a couple of DC sockets in the house might be a good investment?
> John


Are you thinking of fitting Clarke Chapman winches?


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## Satanic Mechanic (Feb 23, 2009)

There are quite a few advantages to both or rather there were. AC alternators induction motors are much much simpler than DC generators and motors with basically no real maintenance such as changing brushes. The use of polyphase makes the setting up of rotating magnetic fields in the motor very easy. ac is easy to transform up and down and easy to rectify to dc. The one major advantage of DC was speed control - they are much easier to control the speed of but even that has gone by the board with the improvements in inverters. 

Lastly but not leastly Tesla was a God and Edison was a bit of a *****


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## Engine Serang (Oct 15, 2012)

They'll both kill you.


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## makko (Jul 20, 2006)

Satanic Mechanic said:


> Lastly but not leastly Tesla was a God and Edison was a bit of a *****


Hear, hear! Tesla really was an exceptional person and, as "ancient astronaut theorists" like to say, may even have had extraterrestrial help, so groundbreaking were his theories!

Edison stole other's ideas and tried to defame Tesla by holding public demonstrations to downplay AC by electrocuting animals. I hope he rotted in hell!

Then there is the 50/60Hz discussion. 50Hz generators are much cheaper than 60 Hz and so on.

While on this theme, an interesting fact: I used to go regularly to San Jose, Costa Rica and used to stay in a hotel just a few blocks from the INS for convenience. One day, having a wander around, I looked at some old photographs on the wall of the restaurant. It turns out it was the site of the first hydroelectric plant in San Jose and that San Jose was the second city "electrified" in the world! Who would have thought.........!

Rgds.
Dave


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## vickentallen (Oct 12, 2007)

Ward Leonard system, DC speed control as used on RN ships of old, for cranes and capstans etc.


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## sparks69 (Dec 18, 2005)

On my second ship (110V DC) there was a hole drilled in the deck head of the R/O's cabin with a three core wire dangling down with a three pin (AC) socket on the end. This came from the rotary converter in the chart room for the Bridge VHF.
Very handy deep sea but not much use on the coast.
If I remember rightly on a BP Birdy Boat the Radio Room and Bridge had numerous rotary converters under tables to run the Tx, Rx, VHF, and other 
equipment.
Mustn't forget a three foot long monster running the Officer's Smoke room Bush TV on the coast which we "forgot" to land when we got orders for deep sea !
Happy Daze.


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## Derek Roger (Feb 19, 2005)

Maybe a bit off topic but ! When completing dock trials on the Canadian Coast Guard Ice Breaker ; Earl Grey I being an ex Marine Engineer could not keep away from the engine room although the whole ship was my responsibility to complete .
It was of course AC in the 70;s and during alternator load tests using a steel plate on a winch which could be raised and lowered into a tank of brine to give the required loads . It came to the point when each Alternator was put on full load then the breaker tripped to check the govenor response time .
Witnessing the trial was an apprentice electrician and a very senior one .
When the alternator was tripped the apprentice asked \' I can understand that as the steel plate is lowered into the brine the load goes up But when the alternator is tripped off the switch board where does the electricity go ??? The old fellow thought for a bit and said it dissipates !
The apprentice asked what do you mean it dissipates ; the old fellow thought for a few seconds and replied " It Just Sorts of F---ks Off ;
I nearly died laughing . Happy Days Derek


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## henry1 (Mar 25, 2015)

My first ship had been a steam turbine tanker built in 59 converted to a bulker in 67. It was 220V DC, I later sailed on a sister ship built in 57 that was 220V DC in the ER and 110V DC in the accommodation, this was achieved with two large MG sets with a sub switchboard, the rules changed in 58 so tankers could have 220V in the accommodation. 
One night on the sister ship the lights went out, mad rush to the ER but on the way down no lights but everything running ok, it was only the MG set that had tripped, the leckies always moaned that the company paid them more for an AC ship than a DC when the DC was more work.
Sometime in the mid 70's I met an old friend who had been at sea as an engineer for a couple of years, he wanted to ask me were some ships AC, I said of course why ask, he told me he had been for a job as maintainence fitter and it was a local government job so he had to have an interview with a board of people one of them was an ex C/E who asked him about his sea time, when he said his ship was AC this guy said that was impossible as all ships wer DC and he did not get the job.


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## Ron Stringer (Mar 15, 2005)

The ex-C/E obviously led a sheltered life at sea or was from square-riggers. The USA-built T2 tankers from WW2 were ac and a 1953 Cammell Laird-built ship I sailed on was also ac.


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## makko (Jul 20, 2006)

Derek Roger said:


> Witnessing the trial was an apprentice electrician and a very senior one .
> When the alternator was tripped the apprentice asked \' I can understand that as the steel plate is lowered into the brine the load goes up But when the alternator is tripped off the switch board where does the electricity go ??? The old fellow thought for a bit and said it dissipates !
> The apprentice asked what do you mean it dissipates ; the old fellow thought for a few seconds and replied " It Just Sorts of F---ks Off ;
> I nearly died laughing . Happy Days Derek


Yes, unfortunately, they walk amongst us and, more disappointingly, breed.

I had a case involving a 340kW gas turbine which had liberated a low stage compressor blade, wrecking the entire compressor section. The subsequent vibration and misalignment gave the jibber jabbers to the turbine section and it was also wrecked. Several blades exited the turbine, severing lub oil lines, causing a fire in the turbine compartment. As the turbine corkscrewed, it ripped the excitation equipment apart too. All well and good.

Quite a straightforward claim. I passed the report onto a new, youngish, degreed "engineer" to proofread and maybe pick up some pointers if he were to attend a similar event in the future. On the second day, still no response, so I went around to his hidey hole to ask when I could have his comments.

He was rapt, watching You Tube videos. Then looked up and said,"Your report is wrong! Surely, when the blade broke off it caused upstream damage to the subsequent stages!". He argued that the air was going "up" into the compressor, like "upload" not "down".

I just shook my head in desperation,"No, the air enters at the knob end and, just like a river, following the flow direction, the subsequent damage is therefore downstream."

He was having nothing of it and told me that he was researching the question of upstream/downstream on Wiki/Youtube and he would get back to me later!

I wandered off, gave a quick reread to my report and sent it out immediately. I managed to avoid using the youngish engineer ever again. He eventually left, one of his reasons being that inspections were dirty, hot and physically demanding! 

He did, however, show up about a week after I had sent the report out. He was clutching several sheets of paper with diagrams. When he started explaining the results of his research, namely that depending where the observer was situated, the damage could be either upstream or downstream, I gave him an assorted bag of anglo saxon oaths and reminded him which stop to get off the bus at!

Rgds.
Dave


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## barry john macauley (Sep 5, 2012)

*Stay grounded*



makko said:


> Hear, hear! Tesla really was an exceptional person and, as "ancient astronaut theorists" like to say, may even have had extraterrestrial help, so groundbreaking were his theories!
> 
> Edison stole other's ideas and tried to defame Tesla by holding public demonstrations to downplay AC by electrocuting animals. I hope he rotted in hell!
> 
> ...


Kimberley was second, Philadelphia first in the world. Kimberley was first in the southern hemisphere. All according to the book of words.
'Course things were different in those days.
Das Elektron maschinen is nicht fur gerfingerpoken und mittengrabben. Das sightseeren dumkophen,keepen das hands in das pockets, und watchen das blinkenlights.B\)


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## henry1 (Mar 25, 2015)

First house lit by hydroelectric power was Lord Armstrongs place in Northumberland using Swans light bulbs (patented before Edison).
First street to be lit with electric light was Mosley street in Newcastle upon Tyne, Swan was a Sunderland man but we don't hold that against him.


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## loco (Dec 10, 2010)

Two ships that I was on, one built circa 1959, the other 1962, had, IIRC, dc for the ship's equipment, but at some time had had a low amperage 220v ac circuit made for use in cabins and crew spaces. I'm pretty sure that the plugs were not normal three pin type, and you had to ask one of the leckies to change the plug for you on your gear, and change it back again before paying off.

martyn


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## Duncan112 (Dec 28, 2006)

loco said:


> Two ships that I was on, one built circa 1959, the other 1962, had, IIRC, dc for the ship's equipment, but at some time had had a low amperage 220v ac circuit made for use in cabins and crew spaces. I'm pretty sure that the plugs were not normal three pin type, and you had to ask one of the leckies to change the plug for you on your gear, and change it back again before paying off.
> 
> martyn


Even into the '70's Bank Line had 5A roundpin sockets in the cabins. IIRC the Electricians stores had 2 plugs per round trip, cue the screwdriver in the earth hole to lift the shutters and bear wires shoved in!!


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## mrcruisine (Oct 10, 2010)

John Melbourne said:


> I have been wondering when DC was replaced by C on ships. What were the advantages of DC over AC?
> Thanks
> John


As a a Lecky trained on AC went to sea with Bankline and then all DC. Many electrical reasons which is why when electricity first started that AC was preferred over DC in transmission etc, AC far more efficient, but on ships, its the bloody maintenance for one that kept me occupied. Endless cleaning of commutators, brushgear and so on. Was so great when went with reefer company on banana boats with all AC including having AC for that matter.


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## marek sarba (Nov 27, 2008)

Speed adjustment and start of larger systems was easy in old days by DC systems despite more expensive motors (commutators) now AC is the way to go and stay this way.


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## Derek Roger (Feb 19, 2005)

Satanic Mechanic said:


> There are quite a few advantages to both or rather there were. AC alternators induction motors are much much simpler than DC generators and motors with basically no real maintenance such as changing brushes. The use of polyphase makes the setting up of rotating magnetic fields in the motor very easy. ac is easy to transform up and down and easy to rectify to dc. The one major advantage of DC was speed control - they are much easier to control the speed of but even that has gone by the board with the improvements in inverters.
> 
> Lastly but not leastly Tesla was a God and Edison was a bit of a *****


Hi there Ma Man ; I was wondering if any systems of a/c speed control using thyristors are still in use ?? I had them on a couple of ships with ASEA deck cranes . The crane were very new at the time and as such they were not watertight . Rain ( as often happens ) would run down the hoisting wire and soak the panel which housed the controls / thyristors causing havoc .
Pretty soon learned a bit about thyristors ; DO NOT use a Megger it would blow the ars e out of them .
We had a number of hoist A/C motors burned out due to the rain / water problem and when in Japan had them sent ashore for rewind with the explicit order that these were special motors with D/C dynamic braking and had to have a special winding . The Japanese who I always found very good said Hi San they fully understood . ( It was not until later I realised the Japanese would always say yes so as not to lose face .
Unknown to us they just rewound as a standard squirrel cage motor .
The motors worked fine except unknown to us there was no dynamic breaking resulting in heavy wear on the disc brakes .
The mates were complaining that the brakes did not seem to work very well ; which the engineers myself included seemed to think a notion rather than a fact.
In Kobe discharging into barges when while the C/E and myself were having an early dram we saw one of the cranes lifting a forklift out of an empty barge and as the crane swung over the bulwark the driver stopped hoisting ( as he would ) and the forklift lowered itself onto the bulwark ; tottered ; became unhooked and fell back into the barge . Chief and I went up to the bridge wing were we could the forklift with its forks stuck into the barge bottom and water flooding in 
All the Japanese dockers were looking over the side watching this and the Tug with the barge left the site .
Chief called the Old Man in to his cabin and explained what had happened as we expected a big claim against the ship .
Time passed and not a word ; they (the dockers ) thought it was their fault .
We spent a lot of time fixing up the disc brakes until we could get some properly wound motors .

I am not sure if the thyrisor control was only for speed control or also an important part of the dynamic breaking .

Be happy SM if you could shed some recent light . 

Keep Well Derek


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## searover (Sep 8, 2007)

Prior to 1961, the ss "Canberra" was designated for potential hospital service in its future, so had to conform with NATO (U.S.) requirements, i.e. power of 115 volts AC at 60 cycles. So a lot of our personal entertainment units had to be scrapped or provided with upgrades. i.e. my turntable had to have a device to control the speed of the platter. Mostly going AC was an advantage, providing more voltage versatility.


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## mrcruisine (Oct 10, 2010)

*Now Big AC*

Whilst my first Bankline ships were all DC and then onto reefer ships with AC, up until my recent retirement as a Lecky, things of course have gone a lot further. Ending up in the offshore oil drilling industry with diesel electric propulsion systems with power generation being 11kV and 13.2 kV and so on, a long way from standard 3 phase systems. For a Lecky now its Disneyland for electrics


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## makko (Jul 20, 2006)

mrcruisine said:


> For a Lecky now its Disneyland for electrics


And controls! PLC's, plug and play so on and etc.!

While I was back in the UK working, we were asked to look at refurbishing some old kit, travelling scrapers/skimmers at Cotton Valley waste water works just outside Milton Keynes. THe main feature of CV was the ex incinerator which caught fire and, as it was full of asbestos, ended up "isolated", wrapped in cling film!

Anyway, the kit consisted of 30m wide "bridges" mounted on fenicular track "bogies" which, with scrapers/skimmers retracted would travel up the sedimentation tanks to the entry end. They would then lower scrapers/skimmers and travel back down to the discharge end.

The control systems were hard wired and a call to the OEM revealed that the designer had retired some twenty years previously. The traction system was by one centrally mounted motor which, via a reduction gearbox and chain/sprocket drove a single drive shaft coupled to both lateral bogies. Synchronous movement from both sides depended solely on the funicular tracks - Wear and jamming were the main problems which led to "crabbing" of the bridge. One had even become disrailed and ended up in the sh1T tank! The distance travelled depended on very intricate "clock" microswitches which would mechanically count the shaft revs and therein the distance travelled. Needless to say, one had run off the rails after a bad distance sum! Hence, all four tanks were out of action and "obsolete" to all intents and purposes.


Cost to replace one bridge control and drive "as built" GBP100,000 (microswitches were 40% of the cost.

Cost with independent master/slave drive motors and plc controls/enhanced instrumentation, GBP7,000!

We didn't get the job but it was a very interesting work up to see just how "solutions" off the shelf had developed!

Rgds.
"Not a Lecky" Dave.


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## Vindi Phil (Feb 12, 2006)

Hi, I left deep-sea in 1964 and had to take a converter / inverter with me to use my radio and tape recorder so I guess it was after that.
Phil Hughes. (Vindi Phil)


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## PeterY (Jun 24, 2008)

From what I can recall my early ships (1965s) were DC. Some were war build (Iron Monarch I) and into the 1950's. I think the first AC ship I sail on was the BP Endeavour in 1966, From then on all AC.
The biggest problem was commutator RF noise (pollution) to radio reception that required regular cleaning of the commutators and a good capacitor by-pass on at the brush holders. Ahh the good old days.


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## TonyReynolds (Oct 29, 2009)

*AC or DC*

I know that UK shipyards (at least one of them) were still building DC ships as late as 1964. I had the privilege (irony) of sailing on one such ship. It was a pity that some shipyards were stuck in this era since i also sailed on an AC ship that was built before the first one I mentioned - and it was much cleaner, brighter and provided an altogether more pleasant environment. Looking back, whilst being aware of the political groundswell (Thatcher et al) I wonder if this adherence to past (and out dated) practices was one of the nails in the coffin of British Shipbuilding(?).
Tony


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## Derek Roger (Feb 19, 2005)

Is there anyone who has experience with thristor controled ac systems ( ie speed control )

Derek


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## henry1 (Mar 25, 2015)

In 1992 I returned to sea after being ashore for three years as a surveyor, dropped a rank to 2/E. First ship was a double hull product tanker, no handover and a new C/E who had never been on that type of ship. It had Framo pumps, three way IG and a central FW cooling system. The SW pumps had Thyrister speed control in a separate room in the ER with it's own AC, the M/E had a shaft generator the control unit in it's own room with A/C and the engine control room had two A/C units.
The last ship before I left the sea in 1989 was a 27 year old cargo ship with no contol room. Bit of a culture shock.


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## Derek Roger (Feb 19, 2005)

It seems that thristor control of AC equipment is not very well known . I thought SM would be able to enlighten us ; but he has not replied to his quote ; must be on a trip somewhere rather than locked down on Glasgow Green .


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## Satanic Mechanic (Feb 23, 2009)

Derek Roger said:


> It seems that thristor control of AC equipment is not very well known . I thought SM would be able to enlighten us ; but he has not replied to his quote ; must be on a trip somewhere rather than locked down on Glasgow Green .


I’m in China actually, where everything is more or less back to normal!

Just been offline for a bit.

Ok thyristor control of ac motors is pretty big stuff these days, they are much cheaper and compact than ever before - I’m mainly dealing with danfoss aquamasters at the moment - look them up , good bits of kit.

Now there are a few motors that these really come into play. Totally ignoring propulsion motors as they are a separate case, Seawater cooling pumps and engine room fans are the big ones. Big motors that by nature are vastly oversized for almost all running conditions. So you can slowly ramp them up - so no big starting current , and have them control their speed to match a particular set point (cooling fresh water temperature / engine room pressure) - very good fuel savings. When you want to stop them, ramp them down again, so no big sudden load reduction.


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## Derek Roger (Feb 19, 2005)

Satanic Mechanic said:


> I’m in China actually, where everything is more or less back to normal!
> 
> Just been offline for a bit.
> 
> ...


Thanks for that my first experience with thyristors was 52 years ago 
and our Lekys knew little to nothing about them and how the system worked . 
Derek


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## makko (Jul 20, 2006)

Derek Roger said:


> Thanks for that my first experience with thyristors was 52 years ago
> and our Lekys knew little to nothing about them and how the system worked .
> Derek


Derek,

There are lots of products here ( https://iseinc.com/SCR_Power_Contro...MIhqaO18ma6QIV3x-tBh1BTgNCEAAYASAAEgI7pPD_BwE ), Zero Fired (lower harmonics for surrounding equipment and Phase Fired, single and 3 Phase from 25 to 1200A. The nice thing is that they are accompanied by their Installation Guides and Manuals.

Good stuff to get your teeth into in "confinement"!

Rgds.
Dave


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## Ron Stringer (Mar 15, 2005)

In 1965 when I sailed on the maiden voyage of ss Regent Pembroke we had endless problems with the thyristor-controlled excitation of the main alternators. Several blackouts and much drifting about. All the spares available on board were used to keep one alternator in service until we arrived at our loading port in Saudi Arabia. 

GEC Stafford flew an engineer, Alex Sutherland, out to Ras Tanurah to fix the problem - apparently the technology was new to them and he was one of the design team. Having worked all day in Stafford and at a moment's notice been driven to Heathow to catch a BOAC VC-10 flight to Dahran, he staggered off the plane in the early hours of the morning, to be 'snatched' by a large black gentleman in Arab dress who was holding a card bearing Alex's name. The man spoke no English and, grabbing the bags that Alex had brought, hurried him to a large American car parked outside, pushed him into the back, jumped in the driver's seat and drove them away into the night. He later told us he was terrified he was being hijacked because the man didn't speak and all Alex could see out of the window was glimpses of desert. He arrived at the berth in Ras Tanurah just before dawn after a hair-raising drive and came aboard.

Warmly-greeted by the Old Man and the Chief, it was suggested that after such a traumatic trip, he shouldn't start work until he had rested and was shown to a cabin where he could dump his bags and sleep.

What they didn't tell him was that we were just finishing loading and soon after he turned in, we sailed for Pointe-a-Pierre in Trinidad - 28 days away around the Cape of Good Hope. When he came down for breakfast to see what Ras Tanurah looked like in the daylight, all he could see was the sea. He was a little upset about that because he had expected to be flying home that day since he was moving house the following day and his wife was on her own and would have to deal with it. He was given promises that he would be dropped off at the first convenient port and would be flown home from there. Again, what he wasn't told was that with our laden draft, there was no port that could take us in between Ras Tanurah and Pointe-a-Pierre!

He set to with the spare thyristors and other parts that he had brought with him and got the second alternator running again. Only for a day or so when something failed again. More spares were air-freighted from England to Muscat, where we anchored off the port for a day or so, waiting for them to arrive. This time there were lots of spare thyristors and although we had several more failures Alex was able to keep fixing things until we arrived and he could leave the ship and fly home from Port of Spain, a month later. Design modifications that arrived in Pointe-a-Pierre seemed to fix the problem and I don't remember any more blackouts caused by thyristor failures in the following voyages in the 15 months that I stayed with her after that.


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## KEITHMAR (Oct 8, 2012)

Yes Derek , I spent three years working in Abu Dhabi on some of the largest cutter/ suction dredgers in the world (at that time?) as Electrical Maintenance Eng. The big A:C: driven cutter motors were all Thyristor controlled,I do not remember many control problems , and these were BIG Barstuards that sometimes when cutting very hard material would shake the Dredger to "bits for a second or two until the system cut the voltage and slowed the cutter motor, picking up again as the material softened A few bits and bobs , of course but if memory serves ??? I only replaced a couple of thyristors in 3 years, Never understood why They were not more popular in Shipping?


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## R904444 (Jun 24, 2006)

TonyReynolds said:


> I know that UK shipyards (at least one of them) were still building DC ships as late as 1964. I had the privilege (irony) of sailing on one such ship. It was a pity that some shipyards were stuck in this era since i also sailed on an AC ship that was built before the first one I mentioned - and it was much cleaner, brighter and provided an altogether more pleasant environment. Looking back, whilst being aware of the political groundswell (Thatcher et al) I wonder if this adherence to past (and out dated) practices was one of the nails in the coffin of British Shipbuilding(?).
> Tony


Hi Tony,

I sailed on the MV Vancouver Trader ex Essex Trader that was built by Ausin & Pickersgill in 1968 and was DC. it was built for the St Lawrence Seaway and had tension winches for use in the locks - maybe this was the reason it was DC. I was 4th Engineer on it in 1976 and it had lots of earthing problems. This was maybe the last DC ship built in Britain?

Andy McArthur


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## dannic (Mar 10, 2013)

Pando Bulk bought secondhand a capsize bulker built in Hyundai, 6 cylinder main engine and shaft generator, variable input/constant output. Understandably thyristor controlled and separate aircon room next to control room. No one really knew how it did what it did. This was 1995, ship was 5 years old.Just before sailing from somewhere, had an alarm on shaft gen system, leccy sweated but thought he had found which pcb was faulty, no spares.
Sent it couriered back to Hyundai, who said they didn't make them any more so would need to repair it! Eventually got card back and inserted it …..much to leccy's satisfaction all back to normal.


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## makko (Jul 20, 2006)

dannic said:


> This was 1995, ship was 5 years old.......Sent it couriered back to Hyundai, who said they didn't make them any more so would need to repair it! Eventually got card back and inserted it …..much to leccy's satisfaction all back to normal.


This is the thing with modern electronics - The moment it leaves the factory, it is obsolecent! It behooves the person responsible to understand the kit, what does what and maybe improvise (or have means to) in an emergency: PC, external measurement/improvised feedback signal etc.
Rgds.
Dave


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## makko (Jul 20, 2006)

As an example, Auxy No.5 on Barber Priam threw a piston. Ok, thought 4th. who had just taken the watch from me, get another genny on the board. Correct. The entire ship became aware of the situation because the ME stopped - The CW tank was MT! I was the first down, because I hadn't got my boiler suit off when it happened.

Listening to what happened from the 4th., I got the control drawings out. It turned out that there was a fault in the control system - No.5 WAS the emergency genny, hence, any attempt to start a genny went directly to No.5 - Lub press., fuel press, and CW on engine - With a broken entablature, the CW (18" diameter?? memory playing up) just dumped the water, at pressure, into the bilge.

When the Lecky showed up, we managed to overrride the system by connecting another genny (with welding cables!!) to make it "think" that it was starting No.5 when it was N E other! This also involved welding a floor plate over the CW inlet to "get" pressure on No.5. All in all, it took about 50 minutes, rolling ever more alarmingly, in mid Pacific (We got to 40 degrees at some points).

The cable to India Buildings and humourless reply were things of legend! However, it just went to show, familiarity, not just with the plant, is the name of the game.

Rgds.
Dave


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## kewl dude (Jun 1, 2008)

*Just a reminder re: T2 auxiliary generators*

Despite T2's being A/C that did not mean there were no DC generators. 

Attached:
Westinghouse-Port-Side1.jpg (147.8 KB) 
GE-port-side.jpg (130.5 KB) 
GE-stbd-side.jpg (170.1 KB)


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## rogd (Jul 2, 2018)

Avanewman said:


> AC and DC generators serve different primary purposes. This is especially evident in the type of devices they each power. Typically, AC generators power home electrical appliances and small motors such as juicers, vacuum cleaners, and food mixers. However, DC generators are used to power large electric motors such as those used in subway systems. On the website Aircon is Not Cold - Contact Us Now to Check & Fix, I found that batteries used for off-grids are also charged using direct current generators because they provide efficient and reliable energy supply. In an AC generator, the coil through which current flows is fixed, and the magnet usually moves. In contrast, the ring in a DC generator is not set; instead, it rotates in a fixed field.


I think you need to catch up a little.


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