3 phase electrics - 4 pin plug

[Roger Ford]

Silverstone Circuit, presumably in an attempt to extort extra cash from people for wiring adapters, provide 3-phase 4-pin sockets in the paddock that we're using next weekend.

I have a suitable plug, but can't figure out how to wire it. One pin is obviously the earth, and the other three are labelled L1, L2 and L3.

All I want is single-phase 240v.  I did find this diagram:

Now I suppose it makes sense that the combination of all three phases add up to 0V, which could therefore be neutral, but if you've connected all three pins together how can you possibly then connect to a single pin to get your live?

The obvious answer is "if you don't understand it don't mess with it", but that's why I'm trying to understand it.

 

 

[CharlesElliott]

Roger - it seems you can have 4 pin (3P+E) or 5 pin (3P+N+E). It clarifies but doesn't explain the 4 pin question though.

[CharlesElliott]

It seems that 240V is 'hard' if there is not a real neutral. But if the 16A sockets are 5 pin rather than 4.....then it should be easy, as per your diagram. And apparently 5 pin is the most common, not that that means anything.

[CharlesElliott]

Like here.

[Roger Ford]

Need someone to clarify whether they are 4 pin or 5 pin. The plug I have is 4 pin.  I've just been reading about "CNE - Combined Neutral and Earth". I'm guessing that's what they use, and we should just treat the earth as neutral. Don't fancy trying that without confirmation, though.

[CharlesElliott]

According to this (2008) they are all 5 pin. Or this (2015) says 5 pin as well. But it does say 32A, although I'm assuming that's a typo given Silverstone's plan says 16A.

[CharlesElliott]

Silverstone factors options. Pretty sure our section is 16A though. Those nearer the garages are 32A.

[Roger Ford]

OK - back to the electrical factors to swap my £5 four-pin for a five-pin plug then. I suppose with the time I've wasted I could have just bought a £20 adapter, but it's good to know what's what.

[Jonathan Kay]

AMENDED

Here's the wiring diagram for that family of plugs. And ABB's own version.

But what are you putting at the other end of the wire to get safe, legal 240V single-phase? 

At the explanation level: Any of the live phase pins will have 240V to neutral in single-phase working. There isn't necessarily a neutral in 3-phase working. (I don't know the right wording for this.)

Usual safety platitudes.

Jonathan

 

 

 

[CharlesElliott]

Then you still need some cable and a blue ceeform socket.....or whatever you are going to put at the other end.

[CharlesElliott]

Won't any two have 415V between them?

[Jonathan Kay]

You're right.

Amended.

Jonathan

[Paul Deslandes]

Mains electricity is transmitted using delta connections, i.e 3 wires - no neutral, and distributed as star from the local transformer, which is what you have in your diagram.  In any street the ends of the each star limb feeds a number of houses so that, more or less, each limb carries the same load and the three phases are balanced.  There have been cases of enterprising neighbours, for goodness knows what purpose, have found they are on different phases and have set up a 415 volt supply!

However I digress.  A standard connection is, at the transformer, to have the centre of the star earthed and also to provide the neutral connection, the line connection then comes from one of the phases.

line voltage = phase to phase voltage / sqrt 3

[Roger Ford]

A standard connection is, at the transformer, to have the centre of the star earthed and also to provide the neutral connection, the line connection then comes from one of the phases.

So presumably "the centre of the star" refers to the inside of the transformer coils, whereas the the three phases are taken from the outside of the coils.  That's why the diagram above is confusing - it omits the transformer coils from the diagram (edit: I guess that's what the circles represent) and makes it look like all three phases are just directly connected. I think I now understand.

Out of interest, how does the transformer get the three phases at 120 degrees steps?  Does it uses some sort of physically-rotating device, or is there an electrical method of doing this?  Or are the high voltage lines carrying separate phases?

[Paul Deslandes]

The 3-phase distribution lines around the country and to a transformer near you use three conductors, each carrying close to equal current in magnitude and at 120deg to each other in phase.  The primary of the local transformer has three windings connected effectively in a ring, i.e. delta, or triangle if you prefer, with a phase connected to each 'apex'.  Each is effectively on a separate core and the secondaries, which step the voltage down from the distribution voltage to 230/240V, are over wound on each primary and are connected as a star with neutral and earth being the star point. 

As said before, each phase is connected to a group of loads, e.g. houses, so that the load on each is close to being the same.  Balancing the loads is a major preoccupation for power companies, both for magnitude and phase, and is why reactive loads such as motors and florescent lights have power factor correction components to get the phase of the voltage and current the same, otherwise the loads can draw high currents out of phase with the voltage and not develop much power.  But that is really another topic.

Paul

[Richard Price]

"Or are the high voltage lines carrying separate phases?" - Yes.

The transformer simply reduces the voltage.

If I could be bothered to search the web, I'm sure there must be an animation to demonstrate how three phase is produced in the first instance at source  (which would stop me having to occationally scrible on paper, drawing a simple alternator, and the resultant waveforms for each phase at various points of rotation the magnetic field inside the stator windings, when trying to explain to apprentices...)

 

[Paul Deslandes]

As well as changing the voltage, the transformer converts the supply from delta to star or vice versa.

[Richard Price]

'found a simple animation here:-

http://www.ece.umn.edu/users/riaz/animations/alternator.html

 

 

[phil 01]

I'm trying to get my head around what you trrying to do, Silverstone will not be supplying a 3 phase and earth supply across a 4 pin red commando plug for the simple reason not many use just 3 phase, nearly all 3 phase installations have a neutral. So for simplification each phase  L1, L2, L3 are on a different part of the sinewave so between any phase and earth or neutral you have 230v between any pair of phases you have 400v. Hope this helps

[Roger Ford]

Yes, I think we've established (posts 6-8) that Silverstone uses 5-pin connectors, not 4. I'm just trying to understand how the four-pin connectors would work, and whether you can get single-phase 240v out of them or if they only work for 415v. I do understand how 3-phase works in general, just not how a four-wire distribution system for it would work.

[phil 01]

Roger you need to establish what size 5 pin socket outlet they are going to supply, there are 2 types generally used 16 amp and 32 amp, and then get a suitable plug to fit, I mentioned commando sockets they are MKs trade name for these sockets and plugs. Now if you require a single phase supply from your 5 pin plug connect your brown core to either L1  L2. L3 the blue to the neutral in the plug and the earth to the earth connection they will all be marked inside the plug you will then have 230v from a 5 pin socket

Regards phil

[Roger Ford]

It's 16A, and I have the correct plug, which I've wired to a standard "caravan" blue socket. I did wonder whether all Silverstone's adapters come connected to the same way - which would rather unbalance the phases. I chose L3 rather than the obvious L1 for that reason.

[Dr Slotter]

Roger - where are you guys going to be at Silverstone that needs these adaptors? In the Wing? 

[Roger Ford]

In the "support paddock", which is the area behind the "garage paddock" in the old pit area.

[nigelpugh]

Guys, as an electrical engineer I am not sure why you are making this so complicated?

The supply that Silverstone are presenting is pretty standard supply output.

Ie TP&N, ie three phase and neutral .

between each of L1, L2 and L3 you will get 415v, ie three phase.

if you want standard 230/250v AC supply, take any one of L1, L2 or L3 and Neutral, this will give you the same as a normal household supply for domestic appliances!

not sure if I have over simplified that, but in a nutshell that's all you need!

hope that helps!