# Three phase power and distribution



## beam_1973 (Aug 31, 2006)

Have searched past threads and couldn't find the exact answer ... hopefully I can describe it here (even better if someone has the answer):-

Firstly, if I have a 3 phase outlet (lets say 32 amps), a 12 x 2.4 dimmer pack and a selection of 240V fixtures that run on single phase. Some of the fixtures I want to run off dimmer channels (e.g. PARs), some I don't (e.g. intels).

Is it possible/appropriate to split the feed from the 3 phase outlet so I end up with a 3 phase outlet to run the dimmers and have a few single phase GPOs to run the intels (so its all actually running off the same 32 amp supply). To clarify, I have seen the boxes of 3 x double GPOs (single phase) that you can plug directly into a 3 phase outlet, but I want a 3 phase outlet inbetween the two, to still be able to plug the dimmer in as well (and yes, total power for dimmer and intels combined would be less than 32 amps).

Secondly, a 3 phase 32amp supply means a maximum load of 32amps on the outlet e.g. 25 x PAR56 (240V) off one 32 amp outlet, its not 3 phases x 32amps allowing for 94 amps of loading, is this correct?? Does any of this logic change if/when i convert 32amps of 3 phase down to single phase?? Do I still only have 32 amps of power available when converted to single phase.

Sorry for the long-winded question, but wanted to give as much info upfront.


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## ship (Aug 31, 2006)

That's long?

While I don't major in Euro, I do wire for it frequently. Same as US, 32A per phase no matter the voltage into it. Not a total amperage on that plug for all phases but for each phase.

You will need something within your local code applicable to distribute the power to the various components / dimmer/non-dimmer outlet safely. That component to split apart the phases I don't know what is within your code to do specifically. Might try the Blue Room http://www.blue-room.org.uk for the more localized how to or what and where you might rent if nobody else chimes in. 

I take it for granted that your dimmer pack cannot or does not have enough slots avalable to have a few non-dimming modules replacing the dimming ones to do this given it has feeding it a:
Cee 5-pin Female	Bal’s #3147 32A-9H 120/208&144/250v 32A (30A) Ceeform - blue 5-pin 3P+N+G  Female “Kupplung”

Cee 5-Pin Female	CeeForm #331509	32A-9H 120/208&144/250v	32A (30A) Ceeform - blue 5-pin 3P+N+G Female

(Leviton now also makes these plugs now.)


Given your dimmer does not have enough available slots to loose some dimmers in exchange for non-dim ones, or the modules are not feasible to rent or buy, in the US, I would do some form of portable power supply that complies with our codes to feed both such as in this case say a three phase switch panel or circuit breaker sub-panel dependant upon the amount of outlets it needs to provide for. This panel mounted to plywood that feeds the various outlets, or even a rack mount version where needed. Various definate rules about doing such things and even as under current modification by the proposed ESTA single conductor feeder requirements, how it's done is changing in as yet un-known ways. How I do stuff these days might be changing at some point.


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## jonhirsh (Aug 31, 2006)

What are your conncetions comeing out of your three phase disconnect. 

If its CamLok You can get a Distro and use the passthrough to power your dimers. 

If its not Camlok you can buy a distro that is made for what ever type of connector you have. 

Unfortuneatly when dealing with power home made is not always the best choice. 

If you were in the states or even London i would sugest you call TMB http://www.tmb.com/ they are leading experts in DIstros and such. Give there london office a call they will atlest beable to advise you on steps to take. 

JH


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## beam_1973 (Aug 31, 2006)

Ship - thanks for responding ... not sure where the UK thinking is (I'm in Sydney Aust), perhaps its the way I reference the power??? The issue is more that the work I do, the venue usually has its own dimmer pack, but not always enough single phase power to run the intels, so was hoping to put something between the house dimmer pack ad the outlet that would facilitate this. I'm trying to dig up manuals on the relevant dimmer packs that might tell me if its possible to run individual dimmer channels in a stand alone mode so that they act like a standard single phase outlet (the equivalent of turning the pre-heat up to 100% I guess). Is this likely???

Jon - yep, all good info there, and no plans to knock up something homemade, will leave the hardware and wiring up to the licensed professionals (which I am not). Excuse my lack of knowledge, but i don't think they are "camlok" connectors. I think they are "twistlock" connectors (the connectors that you plug into the outlet and then screw the orange ring on the plug onto the male thread on the outlet (is this correct??).


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## jonhirsh (Aug 31, 2006)

Thats definitly not twist lock twist is for 20amps. But if you take a photo we might be able to identify it, Could be C5 but thats usualy blue. 

There is a pic of Cam's
http://www.loudandclear.com/power/th2k1-035sm.JPG

I have no clue about what your cable is. 
Sory 
JH


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## cutlunch (Aug 31, 2006)

Beam I would talk to your local electrician as he will know the proper regulations for distribution. I know an electrician here built a portable distribution board for this sort of thing.

It was built in a plastic distribution box of the type that is completely enclosed. It had a couple of metres of three phase cable with appropriate 3 phase plug. On the ditribution side there were two 3 phase outlets. Also there were three double socket outlets, wired one to a phase. There was also all the appropriate circuit breakers included.

It would probably cost $400 - $500 to have made as the three phase plugs, sockets are probably a $100+ each.

There are also pre-made ditribution boxes to do this. I can't think of the brand but if you go to your local electrical supply company they should put you on to them. I first saw them in the army but have seen them in civy street they are pretty generic.

You probably would be better to spread your intelligent lights supply across all phases to make it easier to balance the load on the dimmers, to avoid tripping the breakers. 

Just to give some idea of the sort of 3 phase plugs Beam is likely to be talking about I have included a couple of links.

The links below are New Zealand standard for three phase power used in lighting distribution. As New Zealand and Australia share the same standards these are probably similar to the ones Beam_1973 is talking about. If I am wrong my ANZAC buddies will be along to correct me.

http://www.pdl.co.nz/product-details.aspx?rcat=functions&catid=609&id=518

http://www.pdl.co.nz/product-details.aspx?rcat=products&catid=0&id=420

As you can see these plugs push in, then the outer ring is screwed onto the socket thread. So I am not sure how much they differ from what the US call twistlocks.


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## jonhirsh (Aug 31, 2006)

Im prety sure thats a C5 Connector. 

JH


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## beam_1973 (Aug 31, 2006)

Cutlunch - re your links to the pics, yep they are EXACTLY the ones I am talking about. And thanks heaps for your advice on costs etc. And you got ahead of my next question regarding splitting intel loads across the 3 phases, I thought that would be the case, but thanks for confirming it.

I can finally sleep easy on this issue.

Cheers
Beam


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## ship (Aug 31, 2006)

Switching dimmers to non-dim probably or at least normally would not do it properly - though it might and or at times with some gear is done. Instead a relay module that completely replaces the dimmer and is like a DMX controlled on/off switch would be preferred. That said the manual might say it's possible but you will probably have to drop a line to the manufacturer on that question given it's a ballast based fixture. If incandescent, shouldn't be a problem.

Sorry about the British thing, forget there is more than us/them (Europe) or you guys down under.

Feed thru power tapping distro would be probably the best solution. Good point about distributing and balancing the load Cutlunch.


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## Chris15 (Sep 1, 2006)

I've seen exactly what you are after. It wasn't branded, but it goes along these lines: Clipsal 32 amp 3 phase plug on ~2 metres of 3 phase cable --> 3U Rack Case -->
32 amp 3 way breaker --> 32 amp socket on rear panel &
3x 20 amp single phase breakers --> 1 double GPO front & rear per phase

With neons above each breaker to show they are on. If I were building one or getting it built, I'd be inclined to put in an RCD as well. As I understand it, since it has a flexible lead & a plug, you do not need to be a licenced electrician to build such a distro (in NSW at least... I THINK), check with a sparky.

As far as replacement with non-dims modules goes, I assume Beam is talking about the typical dimmers we have here, like these, so there are not individual modules per say, it's all together.


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## beam_1973 (Sep 3, 2006)

Chris - yeah, the spec you talk about sounds exactly like what I would need, but will probably get a sparky to build it anyway, thanks for that.

Right with the suggested dimmers too (although, more often using the HP series rather than the FP series).


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## Chris15 (Sep 4, 2006)

No Worries. Nice to see another Sydneyite. If you are after more information, just ask.

HP or FP (or GP for that matter) is simply a question of cost and need for more advanced features. The more important bit is that they aren't like the racks that seem to be the norm in North America.


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## SHARYNF (Sep 4, 2006)

I'm new here, and not directly familiar with 3 phase in AU. But here is my .02.

What is your dimmer power requirements? If it is 32 amps 3 phase, then it may not be practical or usefull to keep the 32 amp connection the service disconnect. You might need to get a box made up with say 60 amps (here in the states 3 phase boxes are usually 30 60 100) that then has a three pole 32 amp breaker with feeds the same connector people are using on the dimmer today, and then has 3 20 amp breakers that feed a set of dual outlets. Here in the US depending on budget I probably would also look at going to 100 amps, adding 6 20 amp breakers two per phase, and then wiring in a socapex connector so that it would be easy to run 6 lines for your intels, but that would be more expensive.

Just a thought

Sharyn


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## jonhirsh (Sep 4, 2006)

One last thought does the mpd1 on the bottom of this page look like what your describing. 

JH
http://www.christielites.com/rental2.php?code=4&name=Distros&linenum=0&totlines=-1


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## Chris15 (Sep 4, 2006)

OK. I think I need to clarify a couple of things.

Firstly, remember that we in essence use only half the amps as North America because of the 240 / 120 volt difference.

Secondly, camlok / powerlok I do believe are used down here, I've never seen them though, but they are only used on high current feeds. The 32amp 3 phase connector like this is the standard means of connecting 3 phase down here. In many cases, they are littered through venues. They are also what is fitted as a standard plug on most dimmer packs.

There are limited numbers of 40 and 50 amp 3 phase connectors of the same style in use, but they are certainly in the minority, though the 40 amp variant is gaining momentum so that the dimmer can be fully loaded without overdrawing the connector.

For that reason, going to anything of higher amperage is in fact counterproductive, as in many cases, you would not be able to plug it in. In an ideal situation, yes, but since that is not what is installed in the very great majority of cases it is predominantly useless.

As for service disconnects, I don't know anything by that name, but if it in reference to a point where 3 phase is hard wired in, then as far as I know, they are only used in HIGH current connections. Certainly the most common thing is for multiple 32 amp runs before bumping up to camloks / powerloks / hard wired runs. Though this is based on my somewhat limited experience, so the really big show might be doing something entirely different.

I interpret it as beam working mostly in clubs etc. (I could be wrong though). I could almost guarantee that they will have 32 amp sockets and nothing else.

This is rapidly turning into one of those things which completely confuses people from other countries, simply because you haven't seen our venues or used our power connectors. I find the same in reverse.


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## SHARYNF (Sep 4, 2006)

I understand standards and practices are different around the world ;-)

Back to what I THOUGHT was your original question.

How much does your dimmer draw in amperage? Typically when the connect a three phase dimmer to a three phase service, they will split the dimming modules evenly across the three phases. SO for instance if you have a each dimmer rated for 2400 watts, then you are using 10 amps for each dimmer, and so your power connection would support 9 channels of dimming. IF this was the case then you could not put any other connection on that 32 amp service.

So if the dimmer you mentioned originally is actually a 12 by 2.4 it should not be able to run on the 32 amp service since it would need 40 amps per three phase leg, and at the very least you would not have any additional amperage left over to support your outlets. 

If on the other hand your dimmer was 1200 per channel, and you had a 12 channel dimmer, you would only be using 20 amps per leg (4x5) and then you could have build a box that plugged into the 32 amp three phase, and and a connector out for 32 amps for the dimmer (typically with a 20 amp breaker per leg) and an additional 10 amp breaker per leg connected to an outlet that you could use for your intels. 

I am guessing that you also could probably get or have made a box that has a 32 amp connection to the outlet you mention, and then it has a series of breakers and then outlets on it. 

In the states the typical way it is done is to just have a high amperage service disconnect that you wire in your own distro to, usually in the larger venues these are 400 amps.

Anyway hope it helps

Sharyn


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## Chris15 (Sep 4, 2006)

Sorry, it seems I was a little rude in my last post.

To answer the question, dimmer packs are 12x 10 amp. I am aware that the maths does not work out for a 32amp outlet. The trick is to not fully load each channel of	the pack and/or not have them all at 100% at the same time.

Because there is rarely a full load on the dimmer pack and circuit breakers naturally tolerate some overload before tripping, in most cases, you can get away with drawing additional power without problems. In many cases, lights and audio are run off the same 3 phase outlet, especially when it is from a generator.

l guess the bottom line is that what Beam wants can and is done, but when doing so, you need to be particularly careful not to overload your supply.


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## SHARYNF (Sep 4, 2006)

hey no problem

You just have to be more careful with three phase, since as the legs get out of balance the neutral leg starts to carry more current. and of course if you trip the breaker you will loose everything. It certainly would not be difficult to make up a simple thru box with a outlet box for each phase, and have a male on one end and female connector on the other and I guess if you trip the breaker you trip the breaker. 

Sharyn


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## cutlunch (Sep 4, 2006)

I'm downunder and we have the same system as Aussie. We don't have that much of a problem with the breakers tripping if the three phase is out of balance. 

A amatuer theatre I work at has both GFCI and circuit breakers through the distribution. Even if the balance on the load is 15amps different it won't trip the GFCI. And yes the GFCI's work. We had a faulty cable to a light bar the cable ended in a 3 pin plug at the patch bay, plug this cable into a pack and instantly the GFCI tripped. But I try to even the load where I can just to help minimise wear and tear on the dimmers.

In our venues the three phase usually terminates in 32A sockets we have as standard on our dimmer packs. The next level circuits (not outlets) up would be 60A per phase and so on until you reach the maximum you need and the building wiring is designed for. There are fuses or circuit breakers rated for each level.

If you need more power (provided the bulding can supply it ) or outlets then are hard wired in, you need to get what we call a Registered Electrician ( electrical contractor) to do the work or it is illegeal. We can only plug into approved power outlets

As Chris has said we don't run every channel on the dimmers on full load so when they design the power supply for theatres they take this into account, it's called derating. Hence the 32A instead of the 40A someone suggested. 

This post and others have made me wonder about the US electrical system. Could someone please post links to good websites on the topic.


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## beam_1973 (Sep 4, 2006)

To clarify ... yes most of my work is in pubs/clubs that run 3 phase 32 amp outlets, or on some ocassions only 3 phase 20 amp outlet  which is very limiting. Most of the time, we are lucky enough to be able to run lighting off a different circuit to the PA which obviously increases lighting capacity as well as minimises potential for battles with the sound engineer about hums in their PA allegedly caused by lighting  

As was mentioned in my initial email, it was always my intention to NOT run more than a 32 amp load when dimmers and intel's were combined with a thru-box or the like. Again it comes down to just being smart with programming and setting scenes that don't call on all fixtures at once to avoid the trip.

Unfortunately, when the power is already established in the venue, its not so easy to ask them to just run another 32 amp circuit etc etc.

All very valuable discussion.


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## SHARYNF (Sep 4, 2006)

It is interesting to see the different implimentations.

I am assuming that the outlets you have are the 5 pin versions with the central neutral?

Every country has different code practices. In most places when ever you take a higher rated service like 32 amps and then you want to provide outlets that are rated at a lower rate say 10 amps you are required to put a breaker in the line, so as to protect the usually lower gauge wire and connectors that are down stream. I see clipsel makes a box that can plug into a 32 three phase and split out to lower rated boxes, but of course it does not pass on a 32 three phase connection. 


US power is quite complicated with different systems

Our residential outlets are 120 volt, with hot, neutral and ground, typically the outlet is rated for 15 amps via the standard 3 prong plug, and multiple outlets can be all wired to the same breaker which is typically 25 amps. In a lot of other countries there is a requirement for a breaker or switch per outlet, this is not the case in the US. Our plugs are not fused either.

We have in homes 220-240 volt appliances such as stove/ air conditioner etc these are wired with two hots, neutral and the ground. Here is where things get complicated. in the typical home, the main service to the house is two 120 volt hot leads, and a common, and ground. The two 120 volt leads are in Phase with one another, and as such if you measure the voltage between the two hot leads, you get the 240 volts. This makes it easy to get multiple 120 volt outlets by simply taking one hot, the neutral and the ground, and our electircal home panels support this with alternating connection to one leg and the other side to the other leg, so when you plug in a dual breaker you get access to the two legs. 

Where it gets complicated is the next step up to three phase

There are basically two types of three phase in the US one is called wye and the other delta

In the wye system you have three hots, and a center tap which is the neutral, each phase is 120 degrees from the other, SO if you connect one phase and a neutral, you get 120 volts, but if you connect the two phases and the neutral you get 208 volts due to the phases not being 180 degrees from one another. So wye works fine for deriving 120 volt type service, but you need to be careful that motors etc that need 240 and are not three phase can run on 208 or for instance it is possible to connect a dimmer pack as single phase, BUT it is really dual phase if it is connected to two legs of the wye and it only gets 208 volts, SO for dimmers we can have problems when you go into a small venue and have a portable dimmer pack which is a step up from the back pack type. IF the service is the home 240 service with two 120 and a neutral, ground 4 wire system you can hook it up fine no problems, but if you are on a three phase system, and for instance you don't have the dimmer set up for three phase (5 wires) you could wind up with only 208 volts

In larger venues it is not a problem and if you only work larger venues it is not a problem since you then just have the right cable and connect it in standard 3 phase. 

There is another 3 phase system in the US called delta, here there IS no center tap, instead you have power just between the 3 legs, each leg has the full 120 and you do get a full 240 system, BUT it can get dangerous to connect a single phase load to this type of power since you don't have a neutral, and the whole thing gets complicated and you can wind up with what is called a wild leg that has about 190 volts instead of the 120 volts.

Usually when you go above 30 amps in the States in a non professional venue you don't have any plug access, and you need to wire into the main supply.Typically you will have an electrician at the venue if it is small who will 
wire you into an appropriate breaker in the main panel, and you will run your own distro system from there. For instance we have a few distro's one for smaller gigs is a 100 amp three phase system, the electrician wires it into the 100 amp breaker in the panel, then we have 150 feet of 5 conductor cable that goes to a roll around rack, inthe rack is a 100 amp three phase panel, and then a series of 20 amp breakers all feeding outlet boxes or socapex 6 circuit connectors. If we wanted we could have done 30 or 60 amp bates connectors for more lights etc.

For carrying high amp loads to a distro we use camlok connectors, there are single wire push on and lock connectors that are made for large gauge wires.

In venues where they do regular performances and people bring in their own equipment, they typically have a disconnect box there. The disconnect is wired permanently into the house system and since it can be switched off it is ok for someone who knows what they are doing and is not an electrician to connect into it . Typically there are 100 amp in small places but are more typically 400 amps.

when you get to professional distro's what you do is have the cables run from the disconnect to the first distro with camlocks (5 three hots red black blue, neutral white and ground green) and plugs into the distro, then there are camlock OUTS on the distro to allow you to then feed the next distro with camlocks also, so you can hook up a string of distro's


Re the comments on ground fault and unbalanced loads

It is not a ground fault that occurs with the unbalancing, it is that since you have three phases of power, 120 degrees out of phase and a common neutral in a balanced system all the current returned is balanced out and you basically have 0 on your neutral BUT if it gets out of balance you can wind up with some voltage on the neutral not the ground.It depends onthe type of load you have on the system. This in sensitive concert pa type stuff can cause some noise problems that can drive you crazy. 

http://www.allaboutcircuits.com/vol_2/chpt_10/2.html
http://en.wikipedia.org/wiki/Three-phase_electric_power

Sharyn


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## Chris15 (Sep 5, 2006)

Yes, we use the 5 pin version. The 4 pin version does get used but only for things which don't need a neutral, stoves or motors or the like. Interestingly enough, many buildings particularly specify when installing the outlets that they are to have a full sized neutral to handle only 1 phase being on. On the outlets, Neutral is the centre pin, Earth at 6 O'Clock, Phase A at 9 O'Clock, Phase B at 12 O'Clock and Phase C at 3 O'Clock. That is the Clipsal style plug. I saw a HPM one the other week which had 5 pins around the circumference, no central pin and certainly incompatible with Clipsal style outlets. The pins were much smaller than the Clipsal one, something I find a slight concern. I am thinking that they may be a european or US plug.

The Australian electrical system is 240 volts RMS Phase - neutral and 415 volts phase - phase. You can tap from any phase to neutral for a single phase connection. Standard power as delivered to homes as well as other places is 3 phase, with loads being balanced as much as possible across all 3 phases. Some homes only have 1 or 2 of the phases connected, with load balancing done at street level by connecting different houses to different phases. The number of phases depends on the amount of power drawn by the customer. One can also get 3 phase put on upon request for things such as ducted air conditioning, but it comes at a price and with a waiting list.

Standard circuits in homes / offices would be a 16 or 20 amp breaker to say 8x 10 amp GPOs. Another form of derating. Standard plugs and outlets are rated to 10 amps. 15 and 20 amp connections are not uncommon, but are almost always individually wired back to the nearest switchboard and individually breakered.

Not to be picky, but I would think that your double hots would in fact be 180 degrees out of phase, if there were in phase, there would be no voltage difference between them.

As far as breakering a downstream lower amperage supply, I don't know the rules here, but even if it is not mandated, it would be a very sensible move.

As for a 3 phase 20 amp connector, WHAT was the idiot who installed it thinking? Not only is there not enough power to do, well almost anything, but it is incompatible with the STANDARD connector in use. That and the fact that it is not even the same size as a 32 amp connector. (You can't even put a 20 amp plug on the dimmer and cable it with 32 amp cable and plug it into either outlet, I know it wouldn't be a great move, but it might be the sort of thing that gets you out of a problem. Or you can't use 20 amp dimmers with 20 amp plugs and plug them into a 32 amp socket.)

Why is it that the world can't be anything like standardised in electrical systems? (Voltage, Plugs, not to mention frequency...)


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## SHARYNF (Sep 5, 2006)

Hi Chris
Couple of .comments

The reason that some appliances and motors can just have the 3 hots and ground and no neutral is that in this case the load is equal on all legs and they balance out to zero.

Once you have different loads on different legs you need to have the neutral.

the reason for the full size or in some cases over sized neutral is that it is possible if the load is unbalanced significantly that you can be returning more amps than any individual leg. This is typically where in an overloaded situation the neutral wire is the one that overheats and gets damaged.


Re the in phase or 180 degrees

If the two legs are 180 degress out of phase. then the leg to leg measurment is infact zero, since when one leg is high at say 120, the other leg is low at minus 120, so the leg to leg is zero, But the leg to neutral is still 120

Power and connections and plugs are great fun, here in the US we tease the members of the EU where they cannot even agree on the same power connector Or TELEPHONE connector. Then again in Japan there are areas running 60hz and others running 50hz. 

Sharyn


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## Chris15 (Sep 5, 2006)

Sharyn,

If I may have the right of reply,

Commercial cooking appliances are normally balanced across all phases and so don't need the neutral, but as far as I can see, anything which does not have a single control over all 3 phases needs a neutral connection. Stoves etc. only when they have 3 elements of equal wattage connected such that they are all controlled as one. You are right, only if the load is PERFECTLY balanced, can the neutral be omitted.

If one looks at the maths, then at no point on say a 40 amp 3 phase supply, can the neutral current exceed 40 amps. (Assuming no active is drawing more than 40 amps.) With 1 active pulling 40 amps and the other actives pulling nothing, you get 40 amps on the neutral. As you start to pull current on any other active, then the neutral current will decrease. (If you want to go into the maths, add up the sine of the angles at any point, it is never greater than 1, hence in this instance, you never get more than 40 amps.)

I am still yet to be convinced about the actives being in phase, but I'm open to explanation. I'll try doing the maths and see what I get. At present, I would think that when 180 degrees out of phase, there would be 240 volts between actives, and if evenly loaded, there need not be a neutral, using the same principle as the currents cancelling out in a 3 phase system.

Now, about you yanks and the what 3 different mains connectors in common use... But I guess if it were all the same, life would not be very interesting now, would it?

Regards,

Chris


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## SHARYNF (Sep 5, 2006)

makes for a good discussion ;-)

when ac is 180 degrees out of phase on let is at 120 volts and the other leg is at minus 120 volts, remember this is a ac circut not dc, 

This is why for instance with what we call wye three phase the ac of each leg is 120 as referenced to the neutral as it goes from 120 + to 120e but since the phases are not 180 degress but 120 degrees out of phase you get hot leg to hot leg 208 volts not 240. 

If you remember from the maths and electrical design, the current in the hot needs to be returned on the neutral, if all the three phases are being used, then all three balance each other out, BUT if you have two of the phases being used, then since they are never 180 degrees out of phase, on the return side neutral you can have greater then the amperage on a single leg, but less that the total amperage of the two legs. 

Out of interest, if you measure on your 32 amp 5 pin connector, from the hots to the neutral what voltage do you get, and if you measure from hot to hot what voltage do you get?

We do have a service here called delta here you can get the full voltage, but that service cannot be split into a set of single phase services easily and uses what is called a corner neutral. 


Sharyn


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## Chris15 (Sep 5, 2006)

Remembering that when comparing two voltages, you are looking at the difference between them, so you subtract. 120 - (-120) = 240? We could completely complicate this by actually using peak - peak voltage rather than RMS values...

The US electrical system seems like something which would need a tonne of in depth study for me to understand. I think I'll just be content in knowing that it is complex and not try too hard to understand it. 

If you only have 2 phases, an equal current being drawn on each, then there is no "neutral" current.

In 3 phase, you can't get a neutral current higher than the highest neutral current, because the phases are always 120 degrees out of phase. Say when phase A is at 0 volts, phase B will be at root 3 on 2 x 240 volts and phase C is negative that. When all equally drawn, the current balances out as A+B+C=0. With zero load on phase C. A+B= 120x root 3. I think I did a graph at one point, I'll dig it up.

Meter a 3 phase outlet here and you get 240v phase - neutral and 415v between phases, so a split is dead easy, since it is exactly the same as the service used to feed single phase.

Clear as mud?


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## koncept (Sep 5, 2006)

clear as mud...kinda...i've been following this and havent worked with alot of 3phase distros yet so im currious what is a corner neutral...


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## Chris15 (Sep 5, 2006)

I am also intrigued by the concept of "corner" neutrals. Do they bear any resemblance to a fake neutral? Not something I've ever encountered down here...


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## beam_1973 (Sep 5, 2006)

Chris15 said:


> As for a 3 phase 20 amp connector, WHAT was the idiot who installed it thinking? Not only is there not enough power to do, well almost anything, but it is incompatible with the STANDARD connector in use. That and the fact that it is not even the same size as a 32 amp connector. (You can't even put a 20 amp plug on the dimmer and cable it with 32 amp cable and plug it into either outlet, I know it wouldn't be a great move, but it might be the sort of thing that gets you out of a problem. Or you can't use 20 amp dimmers with 20 amp plugs and plug them into a 32 amp socket.)



Good question grasshopper ... this particular venue has gone to the trouble of installing two seperate 3 phase circuits (one for lighting and one for PA), yet has only bothered to run a 20 amp circuit for lighting, not sure what the PA circuit is, its tucked in behind the amp/FX racks and too difficult to get at without dismantling everything (another display of high intelligence!!).

The whole install is a bit dodgy ... the inhouse patching on the lighting bars isn't labelled (well, some of the piggy back plugs at the rack are but the outelts on the bars aren't) and the bars themselves are 2" pipe that is only clamped in which means the pipes can rotate if you hang heavier fixtures horizontally rather than straight down. But that is all a bit off topic so will stop that one there.


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## SHARYNF (Sep 5, 2006)

Probably the best thing is to just refer you to a site that does a better job of explaining this.

http://www.tpub.com/content/doe/h1011v4/css/h1011v4_135.htm

http://www.kilowattclassroom.com/Archive/DELTAWYEPhasors.pdf#search="three phase delta"

all you have to do is to just page next thru the pages for a more indepth explanation. It will also cover wye and delta setups and will hopefully explain a corner system better.

It is a lot more complicated that you may think ;-0

the reason for a delta system is with a center tap on the supply transformer supplying the ground and neutral. This allows for 240V 3 phase as well as three different single phase voltages (120V between two of the phases and the neutral, 208V between the third phase (sometimes known as a wild leg) and neutral and 240V between any two phases) to be made available from the same supply. This is PRETTY common in the US based on the variety of voltages all able to be supplied from the single transformer. It can be tricky to connect in to unless you know what you are doing. 

Chris15, your coment re the two phases is incorrect because the two phases are not in phase with one another but 120 degrees out

the math is a bit more complex
http://www.3phasepower.org/3phasepowercalculation.htm

our two hot wire systems do have a neutral, 

Again if you research the literature you will see that in a three phase system with a neutral in a severely unbalanced situation or a fault the neutral wire needs to be rated to support aprox 1.8 times the amp rating of a single leg.

I probably should not have brought it up but is makes for endless discussion with electricians

Typically what people fail to consider is that the current flowing from
one leg to another leg of a three-phase system is not
three-phase current. A single coil of a delta system and a load
connected to the two terminals of that single coil form a
single-phase current loop. Three such loops constitute a
three-phase system. We are dealing with only one of those
loops, a single-phase system. The same can be said of a Y
configured three-phase system although each of the three loops
involve current flowing through two coils instead of just one in
the delta system, jsut to make things even more confusing.

People assume that in a three phase system that 120 times a second there is a non-zero voltage between
the center point of the load and ground. 

BUT it does not work that way. What you have is precisely the
same thing as in a normal 240/120 volt single phase service
which is derived from one loop of a three-phase system. The
neutral conductor, the neutral buss and the grounding electrode
system are all at ground potential. If you connect the neutral
to the center of the load it is also at ground potential. Such
a connection is possible in a balanced phase to phase load with
a junction at the center point of the load. No current will
flow through the neutral in such a case because the center of
the load is at ground or neutral potential and the only EMF
potential present is strictly from leg to leg so long as the
loads on either side of neutral are in all respects equal and
balanced. It may seem counter intuitive to have the center point
of an electrical load at ground potential while at the same
time, the end terminals of that load are at 120 volts above
ground potential, but that is the common and ordinary case.

Keep thinking in terms of three-phase current flow and it will
never work for you. It wont work because what you are dealing
with is not three-phase current. ;-)

Again probably beyond what this forum is really interested in 

While the voltages are different, and the plugs used are different, the three phase theory is the same around the world, it ws actually originally developed in Germany

For trivial grins, Edison in the states was in favor of dc voltage, it was Westinghouse that pushed for ac voltage, mainly due to the ability to use smaller wires for transmission and transformers.

At one time Niagara falls had a two phase generator, something that today does not exist, all was changed over to three phase.
http://www.3phasepower.org/2phasesystems.htm

three phase is common in generators, and also the alternators in your cars, which are ac devices and convert to dc

All interesting stuff, most people get confused with three phase ;-) but I will shut up and not get carried away any more

Sharyn


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## Chris15 (Sep 6, 2006)

OK. This is getting far too complex. Please can you explain this to me: 'normal' US power - domestic supplies etc. - are 2 phases off a 3 phase supply? That would explain why they are only 120 degrees out of phase rather than 180 degrees which would be the case if there were only 2 phases.

I'll look at all the referenced materials when I get a chance, and then I shall look at replying.


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## SHARYNF (Sep 6, 2006)

I agree it is getting complex but a fun discussion anyway
In the US and the UK when a home is delivered its power service it is via a transformer that is connected across one phase, with a center tap. This is where the confusion comes about 

The power distribution to the city street is 3 phase, and depending on the location can be a a variety of high voltages. IF you are a commercial customer then you can get the delivery of all three phases, again via a transformer, and there are two ways to hook up to the transformer, the wye and the delta as talked about in the previous, and you have the various options mentioned before

BUT if you are a residence, then you get a transformer connection that is only on one phase, as I said has a neutral tap. So we can have 120 volt appliances, and 240 volt appliances depending on if you connect to a single hot and neutral or two hots and a neutral. Technically it is not single phase or two phase but split phase. 


http://en.wikipedia.org/wiki/Split_phase

What you are saying is that in Australia, three phase is distributed to every home, and that explaines some of the differences, since you don't have our split phase. 

Sharyn


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## SHARYNF (Sep 6, 2006)

so is it all UBI (Useless bits of information)

Well answereing my own question, I guess it varies

Basically as far as the US goes, most people are familiar with the power in their homes how it works and how things are hooked up.

Where you really have to be careful even if someone else supposedly an electrician is involved is to make sure they know and understand what they are doing.

A lot of more industrial sites for instance if you were doing a rave in an old warehouse or factory, are likely to be wired up with delta three phase. Delta three phase is the most problematic for us lights and sound folks. It is great for the factory, but many pro audio/lighting people will totally stear away from it unless the person doing the hookup can really prove that they are doing it correctly, This all stems from the odd situation from most peoples experiences that they are not familiar with a system where depending on what wires you connect to you get a whole range of voltages not just two.

This means that if they connect you to the "wild' leg you will have a serious over voltage and probably damage your equipment


If the facility on the other hand has a wye service, then the hook up is a bit easier, but you need to be aware that you are not going to get 240 volts, that you will only get 208 volts and that some equipment may not operate at its full power level. For instance I have seen this with dimmers, where if you have a three phase dimmer you have no problem but if you have a dimmer that has the option for single or really split phase, that if you hook it up to the service derived from a three phase service that has been split you will not get the full performance, and can wind up tripping breakers on the dimmer. 
In that case you would be better to rewire the dimmer back to three phase but you may not have the cable available to do that.


Again, all fun, good discussion, 

Sharyn


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## Chris15 (Sep 6, 2006)

The stuff on split phase means things now make a whole lot more sense.

Slight clarification on Australian power distribution.
Across the country, power is distributed at a couple of hundred kilovolts. Down the streets, the normal thing is that there is a set of 4 wires, running 3 phase + neutral and then above that is a 3 wire 3 phase supply of about 11kV that feeds transformers that drop it down to 240 / 415. Individual houses and small businesses etc. may just have their connection between a phase and neutral. Which phase they get connected to is chosen to balance the load best by the electricity company. In some cases, a customer may get a connection to 2 phases, normally when they have more demand than the electricity company is happy to feed off single phase. This is falling out of favour these days, but can still be found in older houses. Then you get to the three phase connections. This is becoming increasingly prevalent in homes. This is because of the load new houses draw and / or the connection of things like ducted air conditioning with 3 phase motors.

In commercial situations, with proper distribution boards etc. the bus bars will run A, B, C down or across and repeating. That way you can put in a single pole / phase breaker, a double pole or a triple pole breaker depending on the load being connected. Some homes do have what might be termed a proper switchboard/ distribution board (mostly newer homes) but the vast majority have an assortment of fuses, circuit breakers and the like mounted almost randomly. Would a picture help?

I am still planning to read up on all the stuff about 3 phase, but haven't gotten a chance yet. Then perhaps it might make sense (oversizing neutrals etc.)

What do we all think about perhaps asking a mod to split this topic so that the original thread stays as being about the distribution and creating a new thread for the discussion of international electrical systems, the physics of three phase etc.?


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## koncept (Sep 6, 2006)

that sounds good... i wouldnt mind a picture of these random connection things it sounds interesting but very stupid....it kinda makes you wonder how something like that could have ever passed code...


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## SHARYNF (Sep 6, 2006)

Splitting this out make sense.

I probably got a bit carried away on the details but I have see some instances where people were almost killed and a lot of expensive gear was destroyed do to a mis connection.

Sharyn


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## SHARYNF (Sep 6, 2006)

HI Chris

Here in the states to save money they only run three wires for power distro,(zillions of miles of copper wire saved) on the poles they then create the neutral at the transformer. Interesting that AU does it differently, unless they have a larger street transfomer and they are then sub distrituting it.
Also interesting that they would connect to two phases vs the split phase. Again usually the problem with that is that you don't get the full voltage if you do that vs a split phase transformer setup

Balancing loads on the phases is pretty typical, back at the power generation stations they typically are doing that all the time over the grid.

Good discussioin 

Sharyn


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## Peter (Sep 7, 2006)

Kinda to jump in here with more random information...

As Sharyn said, transformers are used at the pole level to balance the three phases, however on an even larger scale, large institutions (like my college) balance the phases and loads across entire networks. I forget how many grids my college is pluged into, but it is in the 3-4 range, and we dynamically load ballance and phase balance for the power companies in the area (and get a nice discount on our electricty bill).

This works nicely for the power companies, however really bad things happen when stuff goes wrong in a situation like ours... (I have been told stories of a bus parking on an older run of cam years ago, arcing it, and it taking out about half the city's power... oops!)


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## Chris15 (Sep 7, 2006)

Next time a mod is passing through, would they mind terribly splitting the topic please?

I'll get a photo of the main switchboard at Church. That'll give you an idea of what I'm talking about switchboard randomness (its basically domestic style).

Yep, we use a street transformer every dozen or two houses. Before such transformers, everything is 3 wire (or multiples of 3). Shall get a photo of such a transformer if that is of any use.

I think the lack of split phase makes it a lot easier to connect mixed single and 3 phase load.

I'm probably also getting a bit wordy in this thread, but it is all in the name of electrical safety. (Much of the time, Information leads to understanding which then leads to doing it safely.)

I know that some of the universities here run with ring mains and substations every couple of buildings. I saw a video that said that the University of Western Australia (other side of the country but hey) was an annual power bill of AU$ 3 million. Not small amounts of power...


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## SHARYNF (Sep 7, 2006)

If you know any electricians in AU, ask them if the transformers used for large buildings are all wye or are they delta, be interested to see if you folks just have one transformer setup. If you see one of these transformers you can see from the hook up picture which they are, one looks like a wye three points, with a center in a star, or delta looks like a triangle. 

Figured there would only be three wires. This is why the power companies and the large users are balancing loads, Same as here, if you can get the load balanced then on the main grid don't need the neutral. 

I agree the more people know about a topic they the more aware they are and it does increase the likelyhood of safe practice.

Sharyn


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## Chris15 (Sep 7, 2006)

Haven't quite understood the difference between transformers.

Shall do some research. One of our woodwork teachers was a sparky and has kept up his electrical licence.


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## SHARYNF (Sep 7, 2006)

HERE is a link you can print out and use to talk with him
http://www.elec-toolbox.com/usefulinfo/xfmr-3ph.htm

Sharyn


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