Silly Power Question

[icewolf08]

Also, the other thing I wanted to point out is that it is important to meter the system anyway. The OP never mentioned what kind of 3 phases service is in the building. If they have a ∆ (delta) tap transformer they could run into issues making the adapters they want if one of the hot legs in the connector is the wild leg. In a Y tap situation they would be OK (in theory) but then it isn't a 240v system, and I think that is important to point out. Hot to neutral in 3-phase Y is 110v, phase to phase would be 208v.

I am going to pull a Derek and quote my self for the sake of the fact that I realized that there is important info I was missing.

The OP claims he is working with a 110v/240v system which to me suggests that it is a ∆ tap transformer (or he is misinformed by the venue or his electrical theory). This seems like an area for concern, and some metering. Why? Most dimmers and ML distros and the like that I have worked with are designed for 3-phase Y NOT ∆, they want every hot-to-neutral connection to be 110v.

I guess the point is that the OP and us NNED MORE INFO! Make some phone calls, and figure out what you are really working with!

 

[jonhirsh]

Now it is possible that its is a three phase set up with 3 hots and a ground no neutral. It does exist in the film world, ballast's like HMI's they do not take a neutral.

JH

 

[JD]

Now it is possible that its is a three phase set up with 3 hots and a ground no neutral. It does exist in the film world, ballast's like HMI's they do not take a neutral.
JH

Floating Deltas are out there but rare (at least on the East coast.) Most times, one leg is center tapped.

Guessing is dangerous in this business. So, I will phrase this in this fashion:
There is a good chance (for whatever reason) that this is two hot legs from a 3 phase Y source, and that you will find 120-0-120 with 208 between hots, and that the upper pin is indeed neutral, and the lower one is indeed ground as labeled. Just don't bet your life on it!!!

I have taken the plate off of many 4 blade "Range" receptacles in my life. Some have had 4 six gauge wires with proper colors, some have had 4 six gauge wires all black, BUT some have been 10/2 with the ground wire jumping between the neutral and ground pins! You can never tell.

 

[derekleffew]

Now it is possible that its is a three phase set up with 3 hots and a ground no neutral. It does exist in the film world, ballast's like HMI's they do not take a neutral.

JH

It also exists with almost every chain motor (hoist). But this service cannot be used for conventional lighting, only 208V-capable moving lights.

Always meter unknown power before tie-ing in (to save the trouble if it's the wrong type) AND at the distro before turning anything on (in case you've made a mistake). If you aren't 100% positive you know what you're doing, DON'T!
​

 

[Charc]

Perhaps I should buy a DMM?

 

[avkid]

Perhaps I should buy a DMM?

Better than that "glowy" Fluke thing you have now.

But.......
You must know how to use it correctly!!

 

[derekleffew]

Perhaps I should buy a DMM?

I have a Fluke 336A on it's way, to replace my Fluke 30. But I find this style gets the most use, as it fits in my pocket. I generally only use the voltage function, and continuity, for testing lamps and cables. I've found similar styles for under $10. Don't buy a big, expensive meter that you won't have with you in your pocket, when you need it. Just my 2¢. Once you have any meter, READ its manual, and make sure you know what you're doing before going poking around with those probes.

 

[Logos]

Can I just say that this thread scares me a little. I haven't commented at all because I simply don't understand the huge range of different power connectors you guys have to cope with in the states.
I have heaps of experience as a theatre electrician and I am qualified to test single phase appliances for electrical safety, I am not a qualified electrician within the Australian meaning of that term although I used to have a "C" class license (now called a restricted license) many years ago.
The stuff you guys are talking about here strikes me as being as dangerous and as likely to kill an inexperienced person applying the suggestions incorrectly as any of the things we don't talk about in rigging and pyro. Three phase is dangerous and so is two phase. Heck, single phase is dangerous.
Should we be giving some of this information to High School students.
Incidently some of the things that have been said on the Clamp meter thread scare me silly too.
Any thoughts?

 

[Charc]

Hey, the "glowy" Fluke thing seemed like a good idea at the time! Haha.

I know this was just discussed in another thread, but clamp style can only clamp around a single conductor, not an entire cable, right? So under what circumstance would I use that style of meter?

 

[avkid]

Hey, the "glowy" Fluke thing seemed like a good idea at the time! Haha.
I know this was just discussed in another thread, but clamp style can only clamp around a single conductor, not an entire cable, right? So under what circumstance would I use that style of meter?

Honestly, go read the other topic.

Go to your local bookstore and buy a home-owner's electrical repair book.

I'm tend to agree with Tony about this, asking too many questions can be a bad sign.

 

[David Ashton]

Never having had a delta secondary situation, how can you have a neutral?
To my logic it could have an earth and be used to drive balanced loads but I can't figure out how it could be used for dimmers, can someone please explain?

 

[derekleffew]

You are correct, allthingstheatre, IN THE U.S.A., services without a neutral cannot be used with dimmers, but can be used with chain motors and 208V moving lights that don't use a neutral anyway. Dimmers use the 3 hot legs of 3ø power as independent legs, and never output more than 120V. Delta service should never be used in the entertainment industry ever. Delta has a high (wild or stinger) leg that outputs 277 volts, instead of 208. My venue has 2x 600amp, 8x 400amp, 12x 200amp services: all Wye-connected, 5wire, HHHN+G 3ø 120/208VAC.

Logos, you too are correct. This thread scares me too. It should scare everyone or at least alert them to the dangers of working with electricity. Another Senior Team member and I discussed hiding or closing the thread, but we agreed we were not offering advice, only pointing out the dangers, and therefore it was a valuable thread.

How many different ways can we say:

"If you do not know what you are doing,
DO NOT attempt it, call a licensed electrician!"?​

 

[David Ashton]

So to summarize, the socket in the original question, which has a neutral an earth and two phases would be a working, star, 2 phase socket, but is the wrong type of socket for the job, as it is designed for 3 phases and earth in a balanced system.
Is that correct?

 

[tgates]

I was just looking at the picture that you posted of the plug. Tio me, it looks like has three Hs and one G, which would be more in line with the type of plug it is. 3 phase with a ground where the neutral is supposed to be for that plug. Does anyone else see that as an H?
Sadly, I've seen these sorts of plugs used as hotels to feed distro boxes, bridging the neutral and ground in the distro. Not to code, and a terrible idea.

 

[derekleffew]

allthingstheatre--yes, you are correct to my understanding of the situation, other than the fact that I don't know what "star" means in your description. Two hot legs. 110-120V between H & N, 220-240V between the two hots if it's truly single phase, or 208V between H & H if it's two legs of a Wye-connected 3ø service, which is doubtful, I hope. Any voltage higher than 240V: run away and don't touch it.

JD--I'm pretty sure the "277V" for the plug was a misprint on Leviton's part, as they DO list the mating receptacle as 3ø 120/208V. NEMA 18 says HHHN.

 

[David Ashton]

Sorry star = Y

 

[tgates]

I think a Delta secondary with a nutral puts out over 120 volts between the stinger and nutral, but still put out 208 between all of the hots, including the stinger.

 

[derekleffew]

I was just looking at the picture that you posted of the plug. Tio me, it looks like has three Hs and one G, which would be more in line with the type of plug it is. 3 phase with a ground where the neutral is supposed to be for that plug. Does anyone else see that as an H?
Sadly, I've seen these sorts of plugs used as hotels to feed distro boxes, bridging the neutral and ground in the distro. Not to code, and a terrible idea.

tgates, liteman posted a picture of a receptacle, not a plug. Plugs are always male, receptacles are always female. Connectors can be either, but are usually female if talking plug and connector. In audio terms the plug always goes into the jack.
It's hard to read the top pencil designation, jonhirsh thought it was an "H," but liteman, who took the picture, says it's an "N". We'll not know until someone goes to the venue with a meter. And I wouldn't trust pencil labels anyway.

 

[icewolf08]

I think a Delta secondary with a nutral puts out over 120 volts between the stinger and nutral, but still put out 208 between all of the hots, including the stinger.

I am going to refer you back to this image:

A ∆ (delta) tap transformer is 220-240v from phase to phase. It is 110-120v from two phases to the center tapped neutral, and 208v from the third phase to neutral. It actually works out a perfect triangle math if you draw the triangle with sides that are 240 units long all of your measurements will add up to the above listed voltages. You don't get to say "I think..." when working with electricity. It is when people don't know that they get into trouble. If you think you know what you are doing, you shouldn't be doing it when it comes to electricity.

allthingstheatre--yes, you are correct to my understanding of the situation, other than the fact that I don't know what "star" means in your description. Two hot legs. 110-120V between H & N, 220-240V between the two hots if it's truly single phase, or 208V between H & H if it's two legs of a 3ø service, which is doubtful, I hope. Any voltage higher than 240V: run away and don't touch it.

Derek, you mention above (in the blue highlight) "110-120V between H & N, 220-240V between the two hots if it's truly single phase." This would NOT be a single phase system. If it were a single phase system you would have 0 voltage between the hot legs. Why? Because voltage is a differential and two hots from a single phase would be at the same point in the AC waveform at the same time, thus there would be no differential between them.

You then went on to say: "or 208V between H & H if it's two legs of a 3ø service." Which is not always true. You only get 208v between hot legs on 3-phase Y (wye) service. On a 3-phase ∆ (delta) service you get 220v/240v between phases and 208v from wild leg to neutral.


This thread should serve as an extreme caution to all who don't understand and have not been taught about electricity. Even when you are trained you need to exercise extreme caution, you can't just say "oh this plug fits in this receptacle so it should work."

 

[David Ashton]

So are there different recomended plugs for star{Y} and delta systems?