A new standard for dimmer 3 phase plugs

[David Ashton]

After yet another neutral burnout I have decided to do everything I can to bring in a new standard for plugs on dimmer racks.
My initial thought is for a standard which states that "a dimmer unit must have a plug with a neutral current pin capable of carrying 130% of the maximum phase current continuously"
Thus a dimmer drawing 40A/ph would have to have a neutral capacity of at least 52A
The most logical choice would be the CEEform 60A units.
These are safer and lower cost than the existing units and are standard in the 230/240V world.
Ideally it would be nice if the industry could get behind this proposal, mainly on safety grounds but if not I will pursue this alone as it is too important to let slip by.
The neutral pin on our current plugs can run at 50A+ but is the same size as the 20A plug active pin, it is totally irrational to rate a pin at 20A in one plug but 50A in another.
Thoughts please.

[rossgo]

Thory sayes if all phases are loaded equally ( in star configuration) there should be no neutral current,
I have never liked the arrangement off the 3phase plugs especially on dimmers, and distribution systems as in a perfect world you never get a equal phase load, (only if devices are connected in Delta configuation like 415v motors)
In most 3phase cables you will find the earth wire is only 2.5mm squared while the actives and neutral are 4 to 6mm squared
so my thory is swap the neutal and earth so earth is in the middle and neutral at the bottom, I'm sure that middle pin is able to handle a 10 000 Amp earth fault current for 10ms untill the CB trips off, And we have a large neutal pin that won't burn out

Of course this will have to be tested and clipsal 56 series and hpm and welco sockets and plugs will have to be redesigned and the AS3000 has to be updated

so all up your looking at 10 years before anything happens.
_________________
ROSS CARDWELL
FREELANCE LIGHT & SOUND, SYSTEM TECH
SPARKY

[Jeff morgan]

The plugs we use were never intended for the way that the lighting industry uses them. You would be hard pressed to find a manufacturer that would produce such a plug as they would wonder why the heck we would need a larger neutral and supply companies would all get a bit sus as well. Basically they would be wondering why your loads etc would be so uneven. With the constant loads we have with moving lights etc, it is much easer to get an even load on our distro's etc than running 400 par cans which could be a random supply depending on stage looks, but even then you can still even your load up.
Part of the problem is that we do not just have simple currents on supplies anymore. Switchmode supplies give off nasty Harmonics
which turn into, in simple terms end up as current back down our neutral that add onto your original current calcs. Im not sure how standards are going to feel about 130% ratting on a neutral, although supplies in buildings now are doubling the size of their neutrals becasue of these unknow currents(but thats another story.) If we started to use breakers that the neutral line goes through breaker as well as the active, 130% would be never be reached.
Yes the Clipsal/Wilco plugs maybe becoming part of a problem
but they are not all of the problem, there is a lot more to think about.

Euro plugs etc may be the answer, but there are thousands of venues that would have to change and cost the industry and awful lot, and there would be adaptors and dodgie things going on.
This could be a good idea but as said it will take many many years.

[Andy Ciddor]

All three phase theory about phase cancellation goes out the window as soon as you start chopping up the current with phase control dimming. It is quite common to find neutral currents exceeding 130% of a phase load when the dimmers are all around 30%, which happens every time we do a lamp check.
We've been having fun doing this to the neutral since phase control dimming became popular in the mid to late sixties. It is well known and actually codfied with reference to neutral size calculation in both AS/NZS 3000 (Wiring Rules) and the US NEC. However, it has only come to the general electrical public's attention since everyone else started to monkey with big harmonics in the neutral by using vast numbers of switchmode power supplies to drive electronic gear.

The film and television industries have been using decent quality three phase connectors for decades, but we're still fighting the 32A Wilco connector in every pub, club, school and community hall in the country. The phase and earth pins on this connector are comfortably rated for well over 40A (AFAIR it's actually the same pin used in Wilco's 60A connector), but the neutrals are a bit on the slender side for heavy neutral currents. Having said that, the most serious shortcoming on this connector has been that neutral pin on many versions has been difficult to terminate properly. In my experience, these neutrals are fairly frequently inadequately terminated, which leads to arcing and connection failures. This is more a function of poor connector design than inadequate electrical ratings for the components.

I'm entirely with Allthingstheatre on this issue, but it's going to take a long time to bring about any change and we'll see thousands more 3 phase connector burnouts before all the Wilco 5/32s are eventually grandfathered out of existence - long after we've left the industry.
_________________
Andy Ciddor

[David Ashton]

here is another factor which may speed up the process, cost, a 63A ceeform plug is $40 trade and the 63A socket $50 trade,[ in Europe] so it's not an expensive exercise.Sorry Rossgo but you are wrong about low neutral currents but you are no orphan there, 99.99% of electricians think the same way, and look at me like I'm a total idiot when I explain the need for a full size neutral, they learnt their theory at tech and it must be true.[I have yet to meet the electrician who does understand neutral currents but she's out there somewhere]

[Andy Ciddor]

The only problem with the cost argument is that existing venues and equipment owners have to spend Zero to keep things the way they are.

I have not forgotten that it was Allthingstheatre a couple of decades ago, who convinced a then somewhat skeptical Andy Ciddor, to take a close look at the real (rather than theoretical) sum of currents in the neutral of a dimmed system
_________________
Andy Ciddor

[Jeff morgan]

Im with Andy, The neutral alot of the time seems to come loose, the use of ferrules make a better connection and hold much better than bare copper. This can curve the heating up of the neutral area.
Still you have to know your loads. They are getting much trickier to deal with.
It would be rather interesting to find out how responsive manufacturers would be to the idea of production industry plug and socket. but then again there is Standards to deal with ...OH! the Standards .

[JBoer]

[Jeff morgan]

My God how have us 99.99% of electricians survived the last 80 years.
98% of electrician's do not work in this industry, and it is very different
So that comment was not really fair.

[rossgo]

OK Lets set the record straight
I only said that is the thory of electricity and it doesn't really work in the real world, electrical enginieers and sparkies have to compinsate for things like power factor , harmonic destortion and fault conditions when designing items and wiring installations inacordence to AS3000 so if something happens no one is killed or injured and property is not dammaged.
Electrical items have to be tested and have to meet Austalian Standards

Also test and tag qualified people are not electricians

DID YOU KNOW: More plumbers get electricuted than electricians,
why you ask?
well it's due to the earth currents traveling back to the substation along the main water pipes in the street and when a plumber cuts the pipe and grabs it "futt"
_________________
ROSS CARDWELL
FREELANCE LIGHT & SOUND, SYSTEM TECH
SPARKY

[David Ashton]

Well Jeff my comment may not be fair but it is accurate, and Rossgo there is a great amount of theory available on neutral currents in dimmer circuits and the problems are going to get much worse with the proliferation of switch mode power supplies and it is time to deal with it.
And no-one has yet explained how a pin is rated at 20A in one plug and 50A in another is safe?
This is a safety issue, it has to be addressed.
Further common scenario- neutral pin burns out -dimmer blows up and takes out lamps and ruins show, how cheap is that?

[rossgo]

so what exactly have you got running off your supply?
Is it a clipsal 56series 50A or 32A plug n socket?
It's going to get even worse as some of the new clubs and pubs only have a single 20Amp 3phase socket, which to me is about as useful as tits on a bull, I had to use 6 GPO's


I Know i couldn't strike my mac 500's and mac600's up at once cause of the peak currents.

If Frank or PC or anyone who uses more than 30 movers on large rig are looking at this string I have a question
Do you strike your intelligent fixtures individually,in groups or all at once?

also speaking of burnouts my mate had 4 multipars pluged into the one patch and of course over one night we managed to melt the 10amp plug n socket and the pins fused together so we had to cut whole thing off and replace.

I think the power plugs n sockets need to be doubled in capacity for the entertainment industry but this will add to the cost of things
_________________
ROSS CARDWELL
FREELANCE LIGHT & SOUND, SYSTEM TECH
SPARKY

[David Ashton]

The "more or less standard plug" is the 40a this will power a12 way rack at full load, at 50% the neutral current is 50ish amps.This applies only to dimmer circuits, movers with magnetic ballasts will neutral cancel and not be a problem and I have no idea about switch mode ballasts as I can't afford them, but I imagine they would have neutral problems but not to the same extent.If anyone would like to lend me a dozen electronic ballast movers for a couple of weeks I would be happy to run some tests.

[GY]

Heres an idea.....
Why dont we just work within the constraints of the gear that is out there in the world that we use every day??
What I am saying is we know that a 32amp three phase plug will melt down if fully loaded or have neutral issues etc. We know that a 4 way weiland cable gets real hot if it has a all lines loaded at close to 10 amps.
And so on.
What we need to do is think harder before and during setting up lights what we are doing and why with what gear.
Examples of this are rossgo and his 4 multi pars. If they were only used occasionally the cabling would have survived. The same with plugging a 4 way mole into a 10amp cable. The mole draws 2600 watts- 10.8 amps. But we know that its only used for the flashy bits, so its only on a few seconds at a time. The cable copes with that and has time to cool down (the current inrush for breakers is another thread, but a lot of dimmers have 13amp breakers for this reason).
So the thing to do is think about what your doing as you prep and set up. The cable cases and racks of all of us are full of cables with various connectors on them already. We just need to pick the right one for a use. Dont use that thin weedy 7.5amp cable to run your MAC 2k, maybe grab the fatter 15amp cable off the rack. I know there is cable on the racks of the hire companies with cable size ranging from 1mm to 2.5mm. Just dont assume all cable is the same- a weiland is not just a weiland.
For all the sparky types we are now getting into current capacity and voltage drop matters. Think about it.
Maybe we need to go and read AS3000 and brush up on the info on voltage drop and current capacities and if a cable is run in air or conduit or direct buried etc and apply and extrapolate that info into our entertainment use.
Thats it for now
_________________
GY

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[David Ashton]

Nice theory, but it is dependent on lighting guys understanding the problems, the dimmer neutral problem is simply not understood in general even among lighting technicians, even students coming out of academic institutions have not understood or been taught about it.
Further with a fully loaded dimmer there is no way around these problems, the designer/director want these lights, at this time and at this level.