Canberra maiden voyage

double acting
7th January 2009, 21:01
A rumour went round at the time, that on the maiden voyage of the Canberra she lost all power entering Sydney. The story went that someone pulled in the circuit breaker of a generator which was stopped, then tried to open it using a bit of dry 4 by 4. Is this just an urban myth or is there any truth in this tale?

Pompeyfan
7th January 2009, 23:16
A rumour went round at the time, that on the maiden voyage of the Canberra she lost all power entering Sydney. The story went that someone pulled in the circuit breaker of a generator which was stopped, then tried to open it using a bit of dry 4 by 4. Is this just an urban myth or is there any truth in this tale?

Slightly true. Soon after leaving Colombo 17th June 1961, about 12 hours behind schedule condenser problems that developed earlier in the port condenser recurred with speed reduced. More engine problems bugged her meaning she stayed in Fremantle for an extra hour for engineers to repair a minor problem. She had to reduce speed crossing the Australian Bight arriving at Melbourne at 1130 on 27th June 1961 behind schedule. Engine problems meant her stopover at Melbourne was cut. She arrived at Sydney heads on 29th June 1961, 24 hours late. At a press conference the faulty condenser was explained as slowing her down coming out from Southampton had been repaired, but to make sure the engineers worked on it during her four day stay in Sydney. Hope this explains the engine trouble?. She did not lose all power entering Sydney as far as I am aware.

David

Jim S
8th January 2009, 17:23
Double Acting/Pompeyfan,
There was a very serious incident on Canberra - I don't think it was her maiden voyage though. I cannot recall the exact details but it did involve a circuit breaker being incorrectly operated on the main switchboard.
I think a 3rd Eng received serious burns from the resulting short circuit.
Canberra was out of commission for some weeks as I recall with fire damage.
I thought I had a paper on the subsequent inquiry but cannot lay my hands on it at present.
Further to above is a piece in Ships Monthly magazine of July 2006 giving an outline. " Canberra was not without her faults and incidents including a turbine and water distillation plant problem on her fourth voyage in 1962. A major explosion and fire in her main switchboard whilst off Malta on 3rd January 1963 which kept her out of service for five months".

Pompeyfan
11th January 2009, 11:57
I will look into other problems, and yes she has many. But the problems with her condenser slowing her down on her maiden voyages is true, but she did not lose power in Sydney harbour on her maiden voyage.

David

duquesa
11th January 2009, 12:24
My parents were on that voyage as full paying passengers. They subsequently went on trans pacific and left the vessel in Vancouver. I recall my father many times stating that there was a lot of "superficial" damage caused to the interior of the ship by the large number of 10 immigrant passengers. Things like the laundry machines etc. I don't believe it was one of his most memorable trips and he went on many. He had some kind of thing about maiden voyages. Southern Cross, Edinburgh Castle, Windsor Castle and Empress of Britain were among some I remember.

Pompeyfan
11th January 2009, 14:09
Maiden voyages of many ships saw problems. That is why we never advised passengers take a maiden voyage of first or last cruise the the cruising season as it then was.

I am currently researching engine problems Canberra in the years mentioned above. Will report back soon.

David

Pompeyfan
11th January 2009, 19:01
I have just spent nearly an hour explaining about her problems off Malta in early 1963, how it happened etc, but hit the wrong button and lost the bloody lot. I won't go through it all again but basically there was this brand new liner and along came the elderly Strathenden and stood by the stranded Canberra who had mustered passengers sending over fresh bread and stores.

David

gordy
11th January 2009, 23:21
Not from the horses mouth, but from my wife's cousin who was an engineer on her and did the trip to the Falklands.
He told me the trouble all started with the boiler Bailey board and there was a subsequent domino effect as all started to fall about the engineers ears.
I believe the fire on the switchboard may have started with somebody trying to hold a breaker in to avoid a blackout.
If this is a load of cobblers I'll challenge him about it when he's next home from his time on one of the Trinity House ships!

Pompeyfan
12th January 2009, 00:28
To explain better, I have decided to type it all again that I had lost earlier.

It started when she was about 160 miles north east of Malta in the Ionian Sea steaming at 27 knots. In the engine room one of the officers on watch saw that one of the three turbo generators had shed its load. He tried to bring it back onto the switchboard using the standard procedure, but he was unable to do so and the generator had not only come off load, but had started to motor. Another engineer tried to get the machine back onto the switchboard. but he was also not successful as he could not trip the circuit breaker and believing mistakenly that the severe damage would result if the machine was left to motor any longer he forcibly broke the contact in conditions which were not only contrary to recognised practice but also to a warning notice posted at the spot. This caused an electric arc of great severity causing a fire which continued to be fed electrically by the other two generators. The engineer acted in good faith so I understand, but afterwards everybody wondered why he had not been incinerated. As the fire took hold of the main switchboard the ship lost all power and sounded the alarm bells. The smoke on D Deck was very thick, most of the ship was in darkness. Fire parties managed to bring the fire under control, but lifeboats were lowered, and passengers at muster stations. When the fire was out, the Captain was able to signal that he did not require help. Royal navy ships on exercising off Malta were on hand, and a rescue tug was preparing to put to sea from Grand Harbour. The RAF sent out a Shackleton of 38 Squadron based in Malta to oversee the situation. Stratheden, which had left Port Said on January 2nd 1963 heading for Naples and Marseilles diverted her course to assist. On January 4th, engineers managed to restore power to the main engines and Canberra was able to limp at four knots to Grand Harbour where more permanent repairs could be carried out. The damage to the main switchboard was so severe that the voyage could not continue with Canberra having to return to Harland & Wolff for major repairs. 2,230 passengers were on board many emigrating to Australia and other destinations. The result was a massive airlift as no other ships were available. Iberia and Orcades were in the UK but both fully booked. Others who were aboard for the world voyage took a ferry to Naples returning home by rail. The entire story can be found in many publication on Canberra.

David

stoker
6th May 2009, 15:35
I understand the breakers on the main switch board were housed in drawers like a filing cabinet, and were withdrawn by inserting a handle and screwing the breaker out. As there was power on the breaker an arc developed across the bus bars, resulting in major damage.

sidsal
7th May 2009, 20:26
We did a cruise on Canberra when she was relatively new - she was a 2 class ship and the tourist cabin had shared facilities.
I remember being told that when new they found she drew too much aft and they had to lighten the back end. Apparently there were marble topped tables around the swimming pool right aft and they were taken away. Can't rember what else ! I remember being told by the Staff Capt who was and old Conway that they had had Wilfred Pickles as a 1st class passenger - he was a radio personality - " Give er the money Barney" was his slogan. Came over as one of the lads. In reality he was an awkward so and so and he complained about the food all the time. In the end they sorted him and this is how. They said they wanted him to be satisfied and they proposed that he should approve the menus each day. He agreed enthusiasticallly. Next morning at 0500 they knocked on his door and announced they had the day's menus for him to approve of. Same next day but on the third day he said that perhaps he could let the menus be approved by the chef. Nice way to sort him I thought !

Pompeyfan
7th May 2009, 21:11
Hi Sidsal

Canberra was first and tourist throughout her 'line voyage' era changing to open-class cruising after the Christmas Cruise of 1972. That cruise was a disaster including losing my boss the Surgeon. After a 100,000 refit, she become a one class ship as she crossed to New York leaving Southampton on 24th January 1973 to begin a new life as a cruise ship. And that life began a little shaky to put it mildly?!. She also became a dollar-based ship for her cruises out of New York.

I was told the story of Wilfred Pickles, but there were a few very well known television and film stars during my time some of whom were absolute swine's, nothing like they were on the box. And then of course there was the famous politician who have I told about in other threads, but not named.

Yes, cabins of the era you speak of especially in the tourist section were not very posh. But you would have been brought a cup of tea every morning?!. Gone are the days of a Pantry on every deck!.

David

Ian6
7th May 2009, 21:50
I was 3/O on P&O's cargo ship 'Pinjarra' in Colombo on 17th June 1961. Our normal trade was to and from Australia, but this voyage was all around the Indian sub-continent at the least desirable time awaiting the break of the monsoon. Instead of inviting the local nurses' home down for a party after loading frozen lamb etc we were perspiring gently whilst loading copra, iron ore etc with water rationing onboard. We were, however, looking forward to seeing the brand new flagship's arrival in Colombo.

'Canberra' had another small problem on her maiden voyage crossing the Indian Ocean and we were on stand-by to tow her in, if needed. We weren't but as a 'reward' the Chairman (Sir Donald Anderson) came aboard to inspect the ship whilst his illustrious passenger, Sir Robert Menzies visited Ceylon's (as it was then) finest. After a brief tour of the ship the Chairman was invited to tea in the Wardroom. After 'Canberra's air conditioned comfort the sweaty environment of a war-time built cargo ship soon palled and he was back to 'Canberra'. Our Captain then was John Wacher (his second command) who later became that rarity both Commodore of P&O and a Commodore RNR.
Ian

PRES
11th July 2009, 12:22
Another perspective of the 'sick maidens' voyage.
There are bits and pieces of rumor and fact in each of the accounts above.

Having completed a years PreApprenticeship in the Electrical Trades, I had been working for six months for an marine electrical service company in Sydney. This was a five year tenure, after which I spent four years with E & A (P&O) - as a ships electrician - er' Electrical Engineering Officer when on a passenger ship.

The electrical problems that the Canberra was experiencing, particularly in the switchboard had become well known to us in Sydney, well in advance of the ships arrival. The original plan was for the ship to stay a little longer in Melbourne and to make good the problems. This was changed and the switchboard maintaining 'jury-rig' until Sydney as a Professor of Electrical Engineering from Sweden was flying out to fault find the problem. He had been on the design team of this new system used on the Canberra.
Generically, ships up until that time were DC (Direct Current) with Generators, but the Canberra was AC (Alternating Current) with Alternators. Shoreside AC is in three phase. The Canberra used six phase. I am reasonably sure that there was very limited experience anywhere in the world with the more complex AC methods, yet alone at sea. The DC methods were already 50 years out of date compared to shoreside. The Ships electricians would have had little awareness of AC
and the Senior Engineers (Mechanical) would have been 'all at sea' totally.
A theoretical course would not have been very helpful in dealing with design problems and even slightly unusual daily routine changes.

There had been water sprayed on the live switchboard and there had been naive attempts of operations that complicated the already dangerous problems.
The Professor arrived in Sydney - the brains of the operation. My Tradesman
and I (his Apprentice) - were his arms and legs. We spent three 24 hour stints before effecting a complete solution. The Professor spoke minimal English and was erratic and highly strung. He found intense humor in what he saw on his oscilloscope screen.
Using mainly sign language, he would have us making physical design changes to the live switchboard. During this whole process, the ships 'experts' were nowhere to be seen.

I had no idea as to what the Professor was doing. I do now.

The six phase AC needed to synchronize the frequency on all six phases perfectly between the existing Switchboard power and the Alternator
(no not Generator) before the "circuit breaker" was closed on-line.
This operation was partially automatic ie, if you got one phase synchronized, then it should be safe to assume that all are synchronized.
The error in manufacture or connection of the switchboard made this a gamble with the odds against at about 3:1 of getting it right.

The Professor resolved this particular problem. For several years after this, due to our involvement with this fix, our company was the 'go to' company for Canberras' unusual ills.

Within ten years, container ships were all AC and none had electricians on board. When designed and installed correctly, AC needs very little maintenance and has many power and flexibility advantages.

My exposure to these experiences did me no harm. After a year at sea as a 'second lecky', I become E & As youngest first lecky ever. Some short time after leaving the sea, I was training computer engineers how to fault find and repair large mainframe computers - yes I even had the odd laugh at what I saw on my oscilloscope screen.

They were the days.

gordy
11th July 2009, 17:04
Thanks PRES, that was fascinating.
Gordy

Ron Stringer
11th July 2009, 18:31
Generically, ships up until that time were DC (Direct Current) with Generators, but the Canberra was AC (Alternating Current) with Alternators. Shoreside AC is in three phase. The Canberra used six phase. I am reasonably sure that there was very limited experience anywhere in the world with the more complex AC methods, yet alone at sea. The DC methods were already 50 years out of date compared to shoreside. The Ships electricians would have had little awareness of AC
and the Senior Engineers (Mechanical) would have been 'all at sea' totally.

You just might be a little harsh on ship's engineers and electricians. AC ships were at sea in WW1 and a mainstay of fuel transport in WW2 were the T2 tankers - not just AC but turbo-electric propulsion. Somebody kept them going through the trials and tribulations of wartime and for a long time afterwards. All this was well before the 1961 ''Canberra''. You are right though that 6-phase AC was not common at sea in the 1960s.

K urgess
11th July 2009, 18:56
This page lists the main motors as three phase.
http://www.sscanberra.com/appfftechnical.htm
Balancing the loads on 6 wire 3 phase systems can be a very tricky operation especially if the phase wires have been muddled up.

Jim S
11th July 2009, 19:54
The Shipbuilder and Marine Engine-Builder of the day states that each propulsion turbo-alternator set is rated 32,000 kVA, 6000 volts, 3 phase, 51.5cycles, 3100 amps at 3,087 rpm equivelant to 85,000 shp on two sets.
Certainly the propulsion motors were in effect two half motors within a common frame and on a common shaft. Interestingly it is stated that the two turbo-alternators cannot be paralleled. The normal full power arrangement would be port turbo-alternator supplying both port motor units. The starboard turbo-alternator supplying both starboard motor units.
For cruising at powers up to 40,000 shp one turbo-alternator set can supply both propulsion motors. Just to make things even more interesting both propellors can be synchronised this is done by the port turbo-alternator providing power to both port and starboard forward propulsion motors and the starboard turbo-alternator supplying power to both port and starboard after propulsion motors.
I hope that makes some sense in the reading as I was getting dizzy just typing it.
There is no mention of 6 phase.
Needless to say it obvious that the control system switchgear was complex.

Boseley
11th July 2009, 20:32
I did the maiden voyage, all these stories, this is all news to me, but then I was a mere Tourist Winger working my Bs off, to keep the 10 migrants happy and the arrogant so & sos that came on for the Pacific cruise. Ah yes happy days!!

K urgess
11th July 2009, 21:31
That's definitely complicated, Jim.
Not being able to parallel the two alternator sets implies some phase variance between the two. Could be taken as 6 phase but the mix you suggest seems to indicate that at least the phases were in the same order or not all the motors would turn in the right direction when connected to a different alernator set.. (EEK)
Now I've given myself a headache.
I used to hate three phase and trying to balance them within small units. It was alright when you had megawatt motors, the control useage didn't make much difference to the balance. (Thumb)

voyagerx1
11th July 2009, 22:01
I was A/S on The Northern Star back in early 1973, one trip out of Sydney for one of the two weeks cruises and we had engine trouble just off Lord Howe island, too deep to deploy the anchor we drifted slowly onto the island, it was said that if they couldn't get the engine trouble repaired we would all be sitting in lifeboats, luckily our engineers did a good job and we continued our cruise a few hours late but all safe and sound onboard, anyone remember that? Jan-Feb-Mar 1973 PS I was officr steward on the outward bound trip and 3 cruises. homeward bound I got a full 2 sittings of passengers with childrens meals, two sittings of 10 plus children, my idea of fun but then the officers were now being served by Ann Lake in early pregnancy, officers a light job.. if any of my officers remember Bernie then please write back. My birthday in Suva plus taking the cute little dancer out for dinner then a drink in the deck cadet officers cabin afterwards, boy did he get a ticking off from the first officer for having me in his cabin.... PPS oh we had boiler trouble and the hull needed scraping so instead of entering ;Melbourne we sailed to Sydney where they had the facilities to do the repairs, friday morning loading supplies for all male stewards then free untill monday morning 8 am, a great time in Sydney, lol the stewardesses having to serve officer meals while laid up......

Alistair Macnab
11th July 2009, 23:13
Another rumour I heard about "Canberra" in her early days after launching, was that she was noticed as dangerously weak longitudinally and that when she was afloat in Belfast in early 1961, the shipyard further strengthened the forward section where distortion had formed.
I was adjacent to her in Harland's on the "Carronbank" with turboblower and scavange fire problems of our own.

Jim S
11th July 2009, 23:20
Sorry - I misread Pompeyfan's explanation of the switchboard fire. The chain of events had nothing to do with propulsion power generation but with general ship's power generation.
Canberra had four AEI turbo alternators rated at 1,500 kW, 440 volts three phase, 60 cycles plus two Paxman diesel driven alternators rated at 200 kW, 440 volts, three phase, 60 cycles. These of course would be capable of being paralleled up to the main switchboard. If as seemed to happen one of the turbo alternators had load shed and started to motor it should have automatically tripped off the switchboard by a reverse power relay. It seems that did not happen and the engineers tried to manually trip the breaker by an unorthodox means. In hind sight it is easy to criticise the action of the engineers but events would be taking place very quickly as with best intentions they tried to avoid a black-out.
Such 440 volt a.c power generation was by Canberra's completion in 1961 not uncommon.

Philthechill
13th July 2009, 13:09
Another perspective of the 'sick maidens' voyage.
There are bits and pieces of rumor and fact in each of the accounts above.

Having completed a years PreApprenticeship in the Electrical Trades, I had been working for six months for an marine electrical service company in Sydney. This was a five year tenure, after which I spent four years with E & A (P&O) - as a ships electrician - er' Electrical Engineering Officer when on a passenger ship.

The electrical problems that the Canberra was experiencing, particularly in the switchboard had become well known to us in Sydney, well in advance of the ships arrival. The original plan was for the ship to stay a little longer in Melbourne and to make good the problems. This was changed and the switchboard maintaining 'jury-rig' until Sydney as a Professor of Electrical Engineering from Sweden was flying out to fault find the problem. He had been on the design team of this new system used on the Canberra.
Generically, ships up until that time were DC (Direct Current) with Generators, but the Canberra was AC (Alternating Current) with Alternators. Shoreside AC is in three phase. The Canberra used six phase. I am reasonably sure that there was very limited experience anywhere in the world with the more complex AC methods, yet alone at sea. The DC methods were already 50 years out of date compared to shoreside. The Ships electricians would have had little awareness of AC
and the Senior Engineers (Mechanical) would have been 'all at sea' totally.
A theoretical course would not have been very helpful in dealing with design problems and even slightly unusual daily routine changes.

There had been water sprayed on the live switchboard and there had been naive attempts of operations that complicated the already dangerous problems.
The Professor arrived in Sydney - the brains of the operation. My Tradesman
and I (his Apprentice) - were his arms and legs. We spent three 24 hour stints before effecting a complete solution. The Professor spoke minimal English and was erratic and highly strung. He found intense humor in what he saw on his oscilloscope screen.
Using mainly sign language, he would have us making physical design changes to the live switchboard. During this whole process, the ships 'experts' were nowhere to be seen.

I had no idea as to what the Professor was doing. I do now.

The six phase AC needed to synchronize the frequency on all six phases perfectly between the existing Switchboard power and the Alternator
(no not Generator) before the "circuit breaker" was closed on-line.
This operation was partially automatic ie, if you got one phase synchronized, then it should be safe to assume that all are synchronized.
The error in manufacture or connection of the switchboard made this a gamble with the odds against at about 3:1 of getting it right.

The Professor resolved this particular problem. For several years after this, due to our involvement with this fix, our company was the 'go to' company for Canberras' unusual ills.

Within ten years, container ships were all AC and none had electricians on board. When designed and installed correctly, AC needs very little maintenance and has many power and flexibility advantages.

My exposure to these experiences did me no harm. After a year at sea as a 'second lecky', I become E & As youngest first lecky ever. Some short time after leaving the sea, I was training computer engineers how to fault find and repair large mainframe computers - yes I even had the odd laugh at what I saw on my oscilloscope screen.

They were the days.Pres! I'm not electrically-minded so you'll have to bear with me please!

Three-phase I can understand but how the 'kin 'ell does SIX phase work, how is it generated and what are the advantages? Obviously the advantages must have been considerable for P&O to adopt such a system!

Like I said I'm NOT electrical so can you keep your explanation as simple as possible please so's I can follow it!!! Ta, Phil(Hippy)

francophile
21st December 2012, 21:57
Good evening. My first post so please be gentle with me! Lying in bed sulking with a bad back when I came across this excellent forum. However as an ex-Canberra Engineer I felt the need to sign up and correct a few falsehoods: so please forgive my resurrecting such an old thread.

Firstly SIX phases?..not sure what planet PRES is on.
Canberra, when launched was down at the stern. I heard two stories and not sure which if either is true. One story goes the calculations didn't allow for water in the boilers and the second that the boilers had been fitted 6" too far aft. This was rectified by filling the Forepeak and 1 DB's (P&S) with concrete and also the fitting of a marble staircase up fwd.
The Canberra was extremely versatile and could be set up as Jim S says. Indeed during the 80's when the Starboard alternator windings shorted and was being repaired we sailed on the Port alternator supplying two half motors, one on each shaft at 18 knots.
The four T/A.'s, of which 3 would running at any one time, supplied the hotels load and also DC excitation to the main alternators. So one would supply the port alt and another the stbd. If this concept is understood then it can be seen there is no need for the main alternators to be synched?
The main swithchboard fire: exactly as stated, T/A started motoring and didn't reverse current trip. A first trip lecky crowbarred off the breaker, getting thrown across the genny flat and burnt for his troubles. The arcing also caused a severe fire..one thing PRES did get correct is that sea water was sprayed on the main board at one point. Harland & Wolff admitted liability and paid for the repairs.
As a footnote, the Bogey's versatility came to the fore next morning. With the fire extinguished and the bus-bar linking the port & starboard halves of the switchboard removed, the port half being undamaged she set off for Malta on 1 alternator and 2 half motors..at 18 knots..the Stratheden standing by sent a memorable message to the effect that..."we are supposed to be standing by you..would you mind slowing down as we cannot keep up"
Apologies for the length of my post.

Varley
22nd December 2012, 01:43
Francophile,

I assume Canberra had synchronous motors started on the damping bars.

Was second motor winding for reduced voltage starting in that mode or simply redundancy? (assume PRES mistaking six terminal with withsix phases instead of two three phase windings separately switched and in parallel)

francophile
22nd December 2012, 14:29
The propulsion motors were started as induction motors, then excitation increased until "synched" and then run as synchronous motors. D.C excitation being supplied to the alternator rotor (directly coupled to the turbine) from the T/A's.

Don't what you mean by damping bars?"

Now I think about it it is rather frightening how much I have forgotten in the 25 years since I sailed on there.

I am friends with a chap who was one of her last C.E.T.O.'s, who has a far better memory than myself and also a far better style of writing. If needs be I will ask him to explain things far better than I can!

The main motors were in fact two "half" motors (21 pairs of poles each) mounted on one shaft in a for and aft arrangement. This gave flexibility and I suppose redundancy.

Considering the age of the Canberra I do question whether modern diesel electric "advancements" on newer vessels are in fact that at all!

P&O's M.V. Aurora's cancelled world cruise last year being a point in case. Her half motors rather than being a separate "for and aft" arrangement are integrated, so if you like double the amount of poles. The "pulsing" being done by means of (rather large!) thyristors. The idea being each motor segment now has to turn the shaft half as far. Resulting in less vibration and smoother running? Or cancelling trips because an engine needs replacing as opposed to re-configuring it as the Canberra would have.

Varley
22nd December 2012, 18:44
The propulsion motors were started as induction motors, then excitation increased until "synched" and then run as synchronous motors. D.C excitation being supplied to the alternator rotor (directly coupled to the turbine) from the T/A's.

Don't what you mean by damping bars?"

Now I think about it it is rather frightening how much I have forgotten in the 25 years since I sailed on there.

I am friends with a chap who was one of her last C.E.T.O.'s, who has a far better memory than myself and also a far better style of writing. If needs be I will ask him to explain things far better than I can!

The main motors were in fact two "half" motors (21 pairs of poles each) mounted on one shaft in a for and aft arrangement. This gave flexibility and I suppose redundancy.

Considering the age of the Canberra I do question whether modern diesel electric "advancements" on newer vessels are in fact that at all!

P&O's M.V. Aurora's cancelled world cruise last year being a point in case. Her half motors rather than being a separate "for and aft" arrangement are integrated, so if you like double the amount of poles. The "pulsing" being done by means of (rather large!) thyristors. The idea being each motor segment now has to turn the shaft half as far. Resulting in less vibration and smoother running? Or cancelling trips because an engine needs replacing as opposed to re-configuring it as the Canberra would have.

Francophile,

Regret I do not think you can start one like that. Horrendous things would happen to the exciter winding conditions spinning in an unsynchronised rotating field.

Damping bars?

I have to fudge this as all I understand is that the ability of a synchronous machine to cater for unbalance phase currents depends on its damping. In construction damping can be a cage (as in asynchronous motor) superimposed on the rotor or separate short circuited rotor windings (consequence of unbalanced phase currents is heating of rotor surface).

On the Bulker forum I have had an interesting conversation with some T2 guys. I think we had come to the conclusion that the main rotor winding(s) would be shortcircuited until motor as close to synch as slip would allow and then the excitation applied. Perhaps there were no damping bars (currents must be the same if the bus powers nothing else) and the short circuited winding(s) acts as 'cage' winding while short circuit.

Guessing the propulsion bus to be separate from other electrical uses the voltage drop during starting seems unproblematic but the two "half motor" concept is used (mainly in the US) to provide "reduced voltage" starting (actually, of course, reduced current so as to minimise voltage drop on the network). Starting current DOL is betgween 5 and 8 times the MCT figure for the individual winding and so if you start one first (the motor can deliver half the commbined KW load quite happily) the starting current will be between 2.5 and 4 times what the combination would take. The second winding will take some kick when it is energised but nothing like the same.

francophile
22nd December 2012, 20:16
You know, it's rather annoying after spending six years working somewhere to be told by someone who has not been anywhere near the ship that you are talking rubbish!
I can assure you, your theorising notwithstanding, that Canberra's main motors spent 37 years starting as induction motors and switched to synchronous motors.

francophile
22nd December 2012, 22:17
A copy of an email I've received from my ex-SETO mate..said he had a good memory!
Hi! Further to our recent chat, here’s an account of the Start/Synch/Run sequence used to start up Canberra’s propulsion motors.
1. Move Console lever to the “Start” position. This applies 3-phase (NOT six-phase!) current from the main 6 kV alternator sets to the stators of the propulsion motors, initiating a rotating magnetic field in the stators. This rotating field induces currents in the rotor windings, “dragging” the rotor around with it and thus functioning as an induction motor. The current taken at this time is massive, with the ammeter needles hammering the end-stops.
2. When the rotor has reached a speed of 30 rpm, its inertia has been reduced sufficiently to allow synchronization to take place. The Console lever is now moved to the “Synch” position. A high-level DC excitation current, derived from the DC excitation sets in the TA flat, is applied to the rotor windings via a series of slip-rings at the NDE of the rotor. This excitation current initiates a magnetic field in the rotor, which then “locks” firmly with the rotating field in the stator. Physically, the rotor will actually “jerk” slightly forward or back at this time, as the fields lock.
3. The synchronization process is quick and, almost immediately after it takes place, the Console lever is moved to the “Run” position with very little delay between the two movements. This now reduces the rotor excitation current to its much lower, nominal, level sufficient to maintain the rotor field and hold synchronization.
4. The ship’s speed may now be altered, simply by varying the amount of steam fed to the turbine, thus varying its speed, the speed of the alternator and, hence, its output frequency. Varying the frequency will vary the speed of rotation of the stator fields and, finally, the speed of the rotors and the propellers.
As a further point of interest, there was a so-called “Propeller Synchronization” facility, supposedly used for fine adjustment of the propeller speeds to match them exactly. This involved switching in/out banks of resistors in the stator field circuits, weakening the field in one stator and enhancing it in the other, thus effecting a slight difference in the torque developed between the two motors, allowing the propeller speeds to level. I never saw this used in practice, so have no idea whether it worked or not!

Varley
23rd December 2012, 02:26
You know, it's rather annoying after spending six years working somewhere to be told by someone who has not been anywhere near the ship that you are talking rubbish!
I can assure you, your theorising notwithstanding, that Canberra's main motors spent 37 years starting as induction motors and switched to synchronous motors.

Sorry to step on your toes. It was not my intention. An asynchronous motor is a more precise name for an induction motor.

Your correspondent omits (for me, the ignorant) of how the torque is applied to the rotor (as an induction motor). Is the excitation winding short circuited (across the sliprings) until DC is applied?

Forget it, I'll not bother engaging with you again but merry Christmas anyway.

richardwakeley
23rd December 2012, 05:23
Merry Christmas Dave,

As an ex-Blue Funnel R/O-Purser who later pretended to be an electrician on gantry crane bulkers, I have no idea what all this stuff is about! I could find faults and clean the motors & brakes, but don't ask me about electrical theory.

I watched Canberra depart Southampton on her maiden voyage, 2nd June 1961. My father took me there for a day out to see it - I was 9. I still have the notebook I kept (wasn't wearing an anorak, honest) and see that Ivernia was in port on the same day. Also Lord Astor's Yacht "Natalie".

Best regards,

Richard

Varley
23rd December 2012, 11:45
Richard,

A merry one to you too (just off to buy the last ton of sprouts, pick up the bird and get in the cats' food).

As I said before, the odd stores and engine room cranes were my only practical acquaintance with this difficult and off-hire-critical tribe (for our tribe's sake I tried to steer new builds towards hydraulics!).

You might be surprised how little more there is to book learn (Mr. Innes's lectures that allowed me to absorb it were few but by far the most useful of the AMEC course at Saudi Shields). You might also be surprised at how much clearer everything becomes when you have these tools as well as the screwdriver. I emphasise, it is only a little more knowledge, else how could my lonely little grey cell have managed.

David V

Peter Eccleson
29th December 2012, 23:50
Dave, you always were a technical brain box! :-)

Varley
30th December 2012, 02:48
Peter,

I assume you mean sad!! But if you thought that then, you should have seen me after drilling by Mr. Innes!

This thread is more relevant than is obvious. Some of the 'get you home' auxiliary propulsion systems utilise a synchronous shaft alternator as a motor but using brushless machines. Before redundancy was inflicted we had such creatures.

These are supposed to be started asynchronously on the damper bars with a 'black box' that 'handled' the exciter winding conditions safely when spinning in an AC field (from the main stator) and then decided when to switch on the excitation according to dropping frequency in the exciter winding and detection of a zero (the field stator was necessarily energised at the outset).

This arangement by one of the less expensive makers.

Prunes of same device often blown to bits, disabling SG and emergency propulsion.

I note that the 'quality' makers have similar offerings but using a pony motor and synchroscope (actually unfortunately not exactly but automatic variation of same). Text book but obviously more expensive than a bit of silicon stuck on the rotor shaft but I suspect overall more reliable by a mile.

Commiserate with Francophile, rather than me, as I fear I was unfair and did not treat him as gently as he requested. If I say that a passed chief plumber of our marine administration is just as hazy on the operation of the T2s (basically the same as Canberra in principle) on which he sailed (and, as he trumpets, "without any need of and E/O") you will see I am not being in anyway critical. Only continuing in my surprise!

Graham Wallace
4th January 2013, 18:39
One of my closest buddies was an Engineer on the Canberra during her maiden voyage, but like most of us has done many more things over the last 52 years and his memory is not what it once was
.
He is not a member of SN but I have enticed him to have a visitors look at this thread and he may be able to enlighten us.

I have the feeling his mind was on very different 'things' on those voyages, he could never understand why I sailed on tankers with only an all male crew.

Graham

Varley
4th January 2013, 22:23
Graham, Very good of you to humour one who anoraks in electricity. David V