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Current Affairs :: RE: A new standard for dimmer 3 phase plugs

GL — Wed, 10 Mar 2010 10:15:07 GMT

Author: GL
Posted: Wed Mar 10, 2010 9:15 pm (GMT 11)

both plugs are actually inadequate as mentioned before

any comments on the other points made (10:17, March 9)?
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Current Affairs :: RE: A new standard for dimmer 3 phase plugs

allthingstheatre — Wed, 10 Mar 2010 08:25:50 GMT

Author: allthingstheatre
Posted: Wed Mar 10, 2010 7:25 pm (GMT 11)

A quote from one of your articles
"As can be seen from this the depth at 50Hz is 9.3mm, therefore a conductor of up to �20mm diameter will effectively have no skin effect issue. However, harmonics can be a problem. If we simply take the 3rd (150Hz, a strong component with hi-tech equipment) we'll see the depth reduces to 5.4mm. This makes any conductor larger than 11mm diameter susceptible to this harmonic. The 5th harmonic (usually the one associated most with SMPS units) starts affecting conductors of a mere 8.5mm diameter and more. "
I think that eliminates 40A plugs from the problem.
However the thrust of my argument is that any pin on a plug should be rated for the maximum current it is likely to draw in it's application, so a 63 amp plug is an appropriate size for a 40A loaded dimmer and the use of a smaller pin for the neutral is stupid.
very good link.

Current Affairs :: RE: A new standard for dimmer 3 phase plugs

GL — Wed, 10 Mar 2010 01:58:16 GMT

Author: GL
Posted: Wed Mar 10, 2010 12:58 pm (GMT 11)

http://ecmweb.com/mag/electric_fundamentals_harmonics/index.html

http://www.marcspages.co.uk/pq/3250.htm

systems running 120mm powerlock?

any comment on the other points made above?
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"No matter what age we are, some have never quite left the schoolyard"

Current Affairs :: RE: A new standard for dimmer 3 phase plugs

allthingstheatre — Tue, 09 Mar 2010 13:48:06 GMT

Author: allthingstheatre
Posted: Wed Mar 10, 2010 12:48 am (GMT 11)

the power in the higher hrmonics drops off rapidly, there are any number of marginal effects, temperature humidity height above sea level, but it is of no practical use to consider them, so we don't, if you care to give a worked example of the relevence of skin effect I would be fascinated to see it.

Current Affairs :: RE: A new standard for dimmer 3 phase plugs

GL — Tue, 09 Mar 2010 12:17:16 GMT

Author: GL
Posted: Tue Mar 09, 2010 11:17 pm (GMT 11)

allthingstheatre wrote:

A typical fully loaded 12 way dimmer draws 40 amps/ phase.
When running at 35% each leg draws 15 amps and the neutral 52 amps so well within a 63 amp CEEFORM rating.When the unit is running at 35% the total load in the cable is 97 amps over 4 wires so the cable will not over heat.
Skin effect is negligable, low enough to be barely measurable, but of course it does exist, but is irrelevent to this discussion, neutral currents are not at high frequencies where it could come into play.

That's if you are allowing only for the third Harmonic (150Hz?) ? There are some above that which could come into play, yes?

by the fact you now mention skin effect does apply, even negligibly it still must be considered and taken into account and there is relevancy in the ratings

~ so back to the plug and sockets ratings... Amperage, Voltage and Hertz? Compliancy = what? The equipment cabling, venue cabling and (mains?) supply transformer are rated to what values??

the 12ch dimmers are capable of outputting 40A/ phs, true... mostly though they would be outputting just under 33A/phse, if all outlets had a maximum of fairly normal loading.

Thanks for links...
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Current Affairs :: RE: A new standard for dimmer 3 phase plugs

Don Allen — Tue, 09 Mar 2010 10:41:28 GMT

Author: Don Allen
Subject: Low Frequency Skin Effect ?
Posted: Tue Mar 09, 2010 9:41 pm (GMT 11)

Skin effect is not relevant at ac mains frequencies, it is relevant for high frequencies and most relevant at microwave frequencies of Ghz. This link will provide a guide http://techdoc.kvindesland.no/radio/feed_lines/20060919164711506.pdf

Did you mean circulating currents ?

This article is about skin effect in buss bars so is more relevant but the resistance units in the first table are Micro Ohms. http://www.copperinfo.co.uk/busbars/pub22-copper-for-busbars/sec4.htm
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Current Affairs :: RE: A new standard for dimmer 3 phase plugs

allthingstheatre — Tue, 09 Mar 2010 10:35:12 GMT

Author: allthingstheatre
Posted: Tue Mar 09, 2010 9:35 pm (GMT 11)

A typical fully loaded 12 way dimmer draws 40 amps/ phase.
When running at 35% each leg draws 15 amps and the neutral 52 amps so well within a 63 amp CEEFORM rating.When the unit is running at 35% the total load in the cable is 97 amps over 4 wires so the cable will not over heat.
Skin effect is negligable, low enough to be barely measurable, but of course it does exist, but is irrelevent to this discussion, neutral currents are not at high frequencies where it could come into play.

Current Affairs :: RE: A new standard for dimmer 3 phase plugs

GL — Tue, 09 Mar 2010 09:30:10 GMT

Author: GL
Posted: Tue Mar 09, 2010 8:30 pm (GMT 11)

allthingstheatre wrote:

skin effect is irrelent at 50 or 150Hz.just using 63a CEE for dimmers instead of 40a Wikco would be perfectly satisfactory.

not if it isn't adequate to carry the values as discussed earlier.... and that leaves the elephant in the room still ignored, that being venue wiring and supply transformer.

How can skin effect be "irrelevant", when the higher the frequency, the less copper is seen, thereby reducing the effective core size of the cable? (take the frequency high enough and ferrites become an insulator)
At 50Hz, the conductor core size is rated for that value, is it not?
Both Wilco and CEEform are rated for Amperage, Voltage and Hertz, are they not?
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Current Affairs :: RE: new seller on ebay??

s30866 — Tue, 09 Mar 2010 06:55:12 GMT

Author: s30866
Posted: Tue Mar 09, 2010 5:55 pm (GMT 11)

jeez. a 50" Plasma..

I'm sure many Cables and Leads go missing every year but any one else got any stories of major pieces of gear disappearing?

Current Affairs :: RE: new seller on ebay??

hdmcc — Mon, 08 Mar 2010 13:11:06 GMT

Author: hdmcc
Posted: Tue Mar 09, 2010 12:11 am (GMT 11)

i dont no about lighting gear specifically, but i work in Parliament House in Canberra and a few years ago we had a 50inch plasma stolen from our store room, the weird thing being the plasma had no base (being designed to go on a stand) and they left the case.

so if that can happen i imagine plenty of gear "goes missing"