Electrical consumption - single or three phase

[Squeaky]

Good evening:

Please excuse my ignorance but I have never understood the basics of electricity beyond plugging the thingy in and hoping for the best but I have recently had reason to question power/electricity consumption from single or three phase power supplies.

If I were to plug a unit into a single phase socket would it consume the same amount of power as it would in a three phase socket?

Guess what I am really asking is "does a single and three phase socket consume the same amount of power for any given appliance?"

Common sense suggests that a 1000 watt unit should use the same amount from either a single or three phase socket but is that true?

This question has arisen because I have reason to believe that Netsel Marina in Marmaris have apparently charged .44 Euros per kwh for 3 phase power for the larger yachts and when they decided to charge all yachts including those using the 16 amp sockets they simply used the same price so I am wondering if this is appropriate or should those using 16 amp sockets be charged less.

Thanks in advance

Squeaky

 

[nigelmercier]

should those using 16 amp sockets be charged less...

No.

 

[rosssavage]

For the purposes of this discussion (before all the pedants get involved...)

1kwh is 1kwh, regardless of how delivered.

 

[jerrytug]

1 kwh 3 phase is the same amount of power as 1 kwh single phase. beaten to it, the pedantry is slow tonight.
44 cents per kwh is ludicrously high, what mugs pay that? Did they see you coming? Unreal.

 

[chewi]

3 phase needs more wires. IF (big if...) the cost of the wires is significant , then single phase should be about a third of the cost of 3 phase,

However IF (still a big if) not, then there is no real excuse for overcharging the land kwh rate, but then marinas prob fall outside the scope of any regs, prob as they supply below the hw mark (or other excuse).


The truth will lie somewhere between, but will still amount to overcharging.
cynic? moi?

 

[William_H]

3 phase needs more wires. IF (big if...) the cost of the wires is significant , then single phase should be about a third of the cost of 3 phase,

However IF (still a big if) not, then there is no real excuse for overcharging the land kwh rate, but then marinas prob fall outside the scope of any regs, prob as they supply below the hw mark (or other excuse).


The truth will lie somewhere between, but will still amount to overcharging.
cynic? moi?

For the same power supply capbility a 3 phase delivery system will require much less copper total than a single phase system. Assuming as you have done that cost of wiring is significant.
A 3 phase system has in effect 3 different supplies each sharig a common return (neutral) which if the current in each phase is equal carries no current so can be omitted or very light wire. The instantaneous current in neutral wire from each of the 3 wires cancel one another out. Further the instantaniuos current in each leg partially cancels one another out so actual current in each leg is less so less voiltage drop so lighter wire required. It is all mathmatical trick that works.
So a 16 amp circuit provides about 4kw max with 2 wires. A 3 phase 16 amp circuit can provide not 12kw but about 20kw with 3 wires. (maths rusty here) hence for high powered supply 3 phase is used. For reallyb high power then higher voltage is used. All to save copper.
However for OP question 1kw is one Kw by 3 phase or one phase. Meters meter the power accordingly. olewill

 

[Daydream believer]

Surely a marina would normally run a 240V cable in a loop ( as opposed to a dead end) around a pontoon & all users would be using a single phase regardless of whether plugged to 16amp or 13 amp sockets. A loop balances the current draw on the cables. Same in a house where one has ring mains with short spurs off. With dead ends the power at the end is lower than the start- a bit like water in a hose being drawn off at intervals. the first gets most water the last gets less

If they had a supply problem or a power drop problem then they may run a 3 phase cable around the site & every so often draw the current from a different phase thus having less power demand on each phase. which as explained earlier is a cheaper way to run the cables so the cost should be less not more

This can be seen on overhead power cables in a street where supplies to each property come off different strings & a power failure on one phase does not affect every house

I can understand a super yacht possibly needing a 720 volt supply ( 3 phase)but I would be surprised if any other yachts had more than 240 volts (single phase) going into them. Super yachts would have their own dedicated generation system anyway
so when you talk about someone having a 3phase supply I suspect that the ring main is 3 phase ( which will be for all yachts) & outlets are connected to different phases but never to all 3 in one go. The safety risk would be huge ( having had a 3phase shock & being thrown 20 feet & had the skin stripped from the palm & fingers of one hand I can assure you it is VERY dangerous wrongly handled)

Or am i talking B...ks?

 

[Alex_Blackwood]

Or am i talking B...ks?[/QUOTE]

Yes, in parts.
A three phase supply, in the UK, is 415 volts BETWEEN PHASES. 230/240 between single phase and NEUTRAL. These voltage figures may vary in other parts of the globe with different frequencies i.e. 60hz is normally 440 volts betwen Phases. Note 720 volts is not mentioned!
A vessel requiring a 3 phase supply will take in the supply at the higher voltage, and have its own internal distribution system to break this down to the required voltages. Supplies may be broken down, Transformed, to 220 volts or 115 volts between phases thus negating the use of a neutral wire. This is not to say that supplies cannot be 3 phase and neutral. In which case the the "Heavy supply" can be used at 440 between phases and the lighter domestic loads supplied from a single phase and neutral at 230 volts. A 3 phase 230 volt supply with a neutral wire will give 230 volts between phases and 115 volts phase to neutral.
The marina in the original question will have either a 3 phase or 3 phase and neutral supply for large craft and a single phase and neutral for small craft.
Hope the above helps! BTW I also have suffered a 415 3phase shock, not exactly pleasant. I think that is two of us with eight lives remaining!