View Full Version : 6.6kVA 50Hz power adaptor for someone's 'floating toy'...

8th Dec 2014, 18:36
It's a little quiet here. And I'm hoping that the somewhat ambigious title will attract JB's most esteemed experts on the 'lecky stuff... :ok:

Got a call today: "Do you know of a suitable Mediterranean shipyard...for dry-docking works on a 'big' superyacht, diesel-electric propulsion with 6 x 3600kVA diesel generators...needs a 6.6kV 50Hz shore-to-ship power supply from the yard...?". "Yes of course, I'll get back to you ASAP." I replied.

Apart from one US-built yacht about 15 years ago which required a voltage / frequency converter for a dry-docking, I've never been confronted with or needed to (rapidly) expand my knowledge on the subject. I've always been under the impression that most, if not all European shipyards capable today of accommodating 'superyachts' would be equipped with the necesary low-voltage power supplies in 50/60Hz. I've since done some googling...! Before contacting any shipyards and getting back to the client etc., I've a few questions for my esteemed colleagues so as not to appear completely ignorant:

1) Asuming that the yacht's 6 diesel generators each produce approx. 3,600kVA @6.6kV 50Hz, would a shipyard power supply of 4,000kVA approx. be adequate (on the basis that all the main ship-board systems can be run on the equivalent of 1 generator's output during dry-docking works)?

2) Why couldn't the main ship-board systems be connected to (multiple) 400V 50Hz supplies of say 750-1,000kVA each instead? Is that because the design of the main switch-board or bus is not/ cannot be easily adapted to accept this etc.?

Awaiting your input... :ok: :uhoh:

8th Dec 2014, 18:48
That seems a hell of a lot of power for even a 'super yacht'. Does it have electric propulsion?

That power supply at a PF of 1.0 would be good for 900 UK homes......Even 3600kVA seems pretty big for a yacht in dry dock.

west lakes
8th Dec 2014, 19:00
1) Asuming that the yacht's 6 diesel generators each produce approx. 3,600kVA @6.6kV 50Hz, would a shipyard power supply of 4,000kVA approx. be adequate (on the basis that all the main ship-board systems can be run on the equivalent of 1 generator's output during dry-docking works)?

That should add up OK and provide sufficient power as long as steps are taken to prevent an overload

2) Why couldn't the main ship-board systems be connected to (multiple) 400V 50Hz supplies of say 750-1,000kVA each instead? Is that because the design of the main switch-board or bus is not/ cannot be easily adapted to accept this etc.?

1000kVA is approx 1500A per phase which will require some huge cables (400mm2 two per phase) to deliver. So it would need 3 sets installed which would be quite a logistical feat. Never mind connecting them and ensuring they can safely operate in parallel.

8th Dec 2014, 19:06
be interesting if the shipyard had a 'coin in the slot' meter for electricity!

8th Dec 2014, 19:21
It only requires that much when its going through the water.

You need to find out the domestic system supply requirments.

Easy way is to go and look at the domestic services circuit breaker board and count the amps.

Then find out whats required for the ship systems which will remain on.

Then go to greko and hire the next unit up.

If you use multiple supplys they have to be in sync and phase and have a load balance feature.

It will be to keep the freezers etc going. Doubt they will need more than a 100 amp at 400v connection.

I would get back to them and speak to someone else get the full technical speks of what they need. That sounds like some clueless agent has passed on the wrong numbers

8th Dec 2014, 19:45
Thanks for the replies so far. For clarification:

1) The yacht is a diesel-electric propulsion but I don't believe that any of the main propulsion motors, thrusters etc. are required to be available when in drydock.

2) I'm not sure what the normal 'domestic' requirements of the yacht in drydock are, which is why I wished to assume it would be no more than the output supplied by just 1 generator. I'm assuming that all the 'domestic' requirements are 400V 50Hz.

3) In past experience of a 65m yacht (approx. 1600GRT), this used approx. 2 x 250A @400V 50Hz shore power supplies for 'domestic' requirements when in port (including A/C etc.). The superyacht in question is over 120m and approx. 12,000GRT... :eek:

4) Henry, I realise I'm probably way out of my depth, but that's why I'm here...?! :ok:

PS. I have no 'chums' who are billionaires. :sad:

west lakes
8th Dec 2014, 19:52
I would suggest that the 6 x 3600kVA generation at 6.6 kV is purely for propulsion.
There are probably 2 lower powered sets for domestic power

wings folded
8th Dec 2014, 20:48
Don't suppose a couple of AA batteries would do the trick, then?

8th Dec 2014, 21:17
I suspect that's all you will need for this one as well.

you need to find out what they are doing. If they are fannying around with hydraulic pumps and distillation units that won't cut it

8th Dec 2014, 21:19
All in all, you need rather more accurate information than you currently (sorry about the pun!) have available.

8th Dec 2014, 21:58
You need to consider the potential (geddit?) liability issues.

Ancient Mariner
8th Dec 2014, 22:00
If it is such a "super" yatch it will have a standard electrical shore connection able to cope with the normal requirments during dry docking.
I'd be surprised otherwise.

8th Dec 2014, 22:04
As A.M said...shore cables.

8th Dec 2014, 22:45
You might be able to use the built in diesel generators, one at a time, as an apu to support the vital services. Probably have to provide a flow of cooling water though.


Ancient Mariner
8th Dec 2014, 23:06
The 6.6 kV would be for propulsion and thrusters. Everything else is probably 240 and 400V. Why would you run the aux engines when any reputable ship yard should be able to supply shore power? A lot of extra work connecting cooling water in- and outlets.
Many ports today require the use of shore power for ships alongside to reduce pollution and noise from aux engines.

8th Dec 2014, 23:14
Well if it fluctuates between dry dock and water: do it need up and down sea shore cables?

8th Dec 2014, 23:43
Google Cold Ironing
From an Ex Merchant Navy bod

Loose rivets
8th Dec 2014, 23:54

The Flying Pram
9th Dec 2014, 12:43
It's possible that there are no "domestic" generators, and all such loads are supplied by transformer(s) from the 6.6kV Bus. When there are already 6 (identical?) gensets to provide propulsion power, there is more than enough redundancy. The fact that the request is for 6.6kV, rather than 400/230volts does tend to suggest that is how things are configured. If nothing else, it drastically reduces the physical size of cabling required. It might have a smaller "standby" set or sets, but these would probably be only for very basic loads. If the dry dock work involves testing of the propulsion system then the higher voltage would obviously be needed, and as pointed out above, organising cooling water for one or more engine is not going to be easy...

Ancient Mariner
9th Dec 2014, 13:04
It has been number of years since I last set foot on a merchant vessel, but using 6.6 kV for anything but propulsion and thrusters is new to me.
I really can't see what you save on running large power consumers like AC and compressors on 6.6. kV instead of 400 V.
I am just grateful that I don't have to crawl around a confined space filled with 6.6 kV motors and cabling.
Hairy stuff. :eek:

9th Dec 2014, 13:27
You might want to call Roses harbour. They have some pretty large equipment available and can bring in even larger equipment when needed. They service some small superyachts, and of course a large fleet of trawlers.

Port Roses S.A.
Avinguda de Rhode, s/n
17480 ROSES (Girona)
Tel. 34- 972 154 412
Fax 34- 972 153 768
VHF canal 9

[email protected]

9th Dec 2014, 18:50
800kw-2400kw Power Set Diesel Generator 6 Kv - Buy Generators 6 Kv,Generators 6kv,6kv Diesel Generator Product on Alibaba.com (http://www.alibaba.com/product-detail/800kW-2400kW-Power-set-Diesel-Generator_1870980256.html?s=p)

Looks like you can even get portable jobs as well.

west lakes
9th Dec 2014, 19:06
Looks like you can even get portable jobs as well.

Lots of good kit out there, we've had 2 x 1650kVA sets running in parallel feeding an LV to 11kV transformer with the whole lot in parallel with our system. That worked great after one of the sets was reparied after a "problem" on the first day on site. (4 cylinders of a V16 quad Turbo diesel do not like being hydrauliced!)
At present we've a similar sized one feeding a divorced part of the 6.6kV network owing to a cable fault under the M61 in Lancashire

9th Dec 2014, 19:23
Aye I have seen the container jobs and heard the tortured torment of them when the load sync unit gets confused.

A lot of Africa survives on them

10th Dec 2014, 17:50
Once again, many thanks to you all for the various input.

Which allowed me to pose all "the right questions" of the 'prospective client' and obtain their swift responses. All without coming across as a complete idiot apparently... :ok:

I've been able to clarify that during this (first ever) dry-docking of the yacht, their "shore-to-ship" power supply requirements will be: 6.6kV 3 phase 50Hz with a capacity of 1600kW (or about 140A @ 6,600V). I'm not going to bother with 'power factor' or any losses due to cable lengths etc., leaving that to the shipyard/s unless it becomes important. Apparently, under "normal cruising conditions" the yacht would use between 25-40% more than 1600kW when berthed in port, with a full complement of guests and (85 crew) aboard. :eek:

More about the yacht (sorry, I have to be somewhat discrete concerning the real name):

- All on-board power is produced by 6 x 3600kVA diesel gensets supplying a total of approx. 17,000kW + 'emergency' generator.

- The main propulsion is through 2 x 6,000kW electric motors driving 'conventional shafts and propellors' with rudders. There are also a supplementary 2,100kW azimuthing drive (690V) and 2 x 700kW bow thrusters.

- Apart from the main and manoeuvering drives, all the other major services aboard are 400V 3 phase 50Hz supplied though transformers and various switchboards.

- The "shore-power" connection aboard is situated in the steering gear compartment, consisting of a single socket (YES - it takes a single big plug...!) rated @ 6,6kV max. 298A.

However, there remains a major hurdle to overcome before '(cold)-ironing out' properly. The yacht still has to be fitted with a 'key-component' of the system before taking-on any 6.6kV shore-to-ship power supply: a dedicated 'control & monitoring' system on-board to interface with the existing switchboard and external shore power supply. Without which, it would be dangerous. And why the 'shore-to-ship' electrical cable (http://www.nexans.fr/eservice/France-en/pdf-family_26074/BUFLEX_PLUG_6_10_12_kV.pdf) (eg. BUFLEX PLUG 6/10kV 3x185+2x50 +(5x2,5)C+12FO) needs all those extra fibre optic and pilot cores in addition to the main current carrying ones apparently...

For anyone interested in simply retrofitting existing ships to be able to accept a 'shore-to-ship' power supply when in port, see here (http://www.sam-electronics.de/fileadmin/user_upload/Broschueren_PDF_Dateien_Energie___Antriebe/DS_1.090.08_2014.pdf) for a 20'/40' containerised solution.

I'll post some photos of me sipping vintage champagne if (when) I get invited aboard... ;)

10th Dec 2014, 18:00
Make sure you roll-out the cable - too much current through a coiled-up cable will generate serious heat!

10th Dec 2014, 18:40
With the cable weighing in the region of 8-9kg per metre, there had better be some mechanical assistance (or a high density of Filipino seamen) aboard... ;)

10th Dec 2014, 20:23
have you found anywhere that can plug you into the national grid though?

Or is it going to be a gen set next to it?