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optonlinene
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optonlinene

Anon

3 phase 277/480 v panel properly balanced

If I work inside one of these panels and install additional 3 phase circuits to a motor , how would you balance it if allready it's not? also the lighting is 277 v how hard would it be to locate the neutral conductor for this typical circuit?

ArthurS
Watch Those Blinking Lights
Premium Member
join:2000-10-28
Hamilton, ON

ArthurS

Premium Member

This sounds like an industrial application, not your usual home stuff that someone knowledgeable enough can tackle on their own. As such, code requires a licensed electrician to work on industrial applications (and judging from your questions, you're not), 277/480V is something to be given a great deal of respect and not played around with by DIY'ers. Should you do something wrong, don't expect your insurance company to cover you. Just sayin'!

Splitpair
Premium Member
join:2000-07-29
Cow Towne

Splitpair

Premium Member

said by ArthurS:

Should you do something wrong, don't expect your insurance company to cover you.
Screw up with 480-3 phase and one will not need the insurance company to cover one as there are guys who are paid to fill the grave after the funeral. ;-(

Wayne
TheMG
Premium Member
join:2007-09-04
Canada
MikroTik RB450G
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TheMG to optonlinene

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Not something you should be messing around with if you're not qualified or don't know what you're doing.

But anyways, there's no balancing to worry about when adding a 3-phase load (such as a 3-phase motor), since 3-phase loads will inherently draw about the same current on all 3 phases.

Balancing is a concern when it comes to single-phase circuits/loads on a 3-phase system.

Where to locate the neutral... no idea. My knowledge of 3-phase power is limited to aircraft electrical systems, so I'm not familiar with how a 3-phase commercial/industrial panel board is set up.

If it were me I'd leave this up to a qualified electrician. In addition to the obvious hazard of electric shock, commercial/industrial systems typically are powerful enough to be a severe arc flash hazard. If you don't know what an arc flash hazard is, you can find some pretty scary videos on YouTube relating to the subject. 480V/3 is not to be messed with.
nonymous (banned)
join:2003-09-08
Glendale, AZ

nonymous (banned) to optonlinene

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But haven't we heard the stories of a company not able or willing to kill production thus circuits need to be worked live. The unwilling to pay for a fully qualified person they ask someone partly qualified to work it live then boom. Part A might require some calculations and I am only an amateur. A few here can do it I bet and tell you how. May or may not though depending. Plus I am sure a few other things also.
Part B on finding the neutral I have to ask???? Need a little more info. Is it wired that badly you can not tell. A huge mess or what. Like said I am an home amateur but unless I am missing something unless it is a screwed up job that part should not be that hard. Actually simple unless I am missing something.

fireflier
Coffee. . .Need Coffee
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join:2001-05-25
Limbo

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Aircraft 3-phase power systems?

I guess I never thought about aircraft having a heavy enough load to requier 3-phase. Is it also 400hz?
srr2
join:2001-12-20
Pipersville, PA

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srr2

Member

said by fireflier:

Aircraft 3-phase power systems?

I guess I never thought about aircraft having a heavy enough load to requier 3-phase. Is it also 400hz?
Yep. Just think of all those tiny 3-ph induction motors spinning at a ridiculous synchronous speed. 3-ph is widely used for angle-position transducers, synchros, etc. You can also make really tiny "6-phase" power supplies.

leibold
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As has already been correctly answered, there is no such thing as balancing the load of a 3-phase motor because the current in all 3 phases is equal.

If you have existing 277V lighting in the same panel there will be a neutral bar in the panel or you wouldn't have 277V to begin with. Lighting loads do need to be balanced because each 277V circuit uses only one phase.

I don't know what the NEC itself says about it, but here lighting has to have separate circuit breakers, main breakers and disconnects from any other loads (which means that there are separate panels for lighting and other loads such as motors).

I also agree with the statements made that this is an area best left to professionals. You can do a lot of damage with a 3-phase motor if you can't tell the difference between left or right rotating phases (not all machines take kindly to a motor running backwards).
TheMG
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join:2007-09-04
Canada
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TheMG to fireflier

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said by fireflier:

Aircraft 3-phase power systems?

I guess I never thought about aircraft having a heavy enough load to requier 3-phase. Is it also 400hz?
Yep, large aircraft use 115V 3-phase 400Hz generators.

The main objective is to reduce weight. The higher voltage and 3-phase means you can deliver more power over the same size of wires, and the high frequency means power transformers and motors can be much smaller (thus much lighter) than their 60Hz counterparts.

Using 3-phase induction motors is also preferable compared to single-phase motors in some applications, especially ones requiring high starting torque and synchronicity. Single-phase starting mechanisms also add to the weight and size of a motor, as well as another possible point of failure, none of which are desirable characteristics.
srr2
join:2001-12-20
Pipersville, PA

srr2

Member

said by TheMG:

Yep, large aircraft use 115V 3-phase 400Hz generators.
So do small ones. Well, not light weekend-warrior types, but as small as higher-end twin engine business-class types, and many midsize helicopters. As you said, there are many good reasons to use 400Hz power.
TheMG
Premium Member
join:2007-09-04
Canada

TheMG

Premium Member

Haha, yeah, "large" is kind of open to different interpretations.

Let's just say something like a Cessna 172 will most definitely not operate on 3-phase.

John Galt6
Forward, March
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join:2004-09-30
Happy Camp

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Generally speaking, all panels are unbalanced with the exception of panels that have 3 phase only loads.

"Balancing a panel" is something that only applies "in theory" and virtually never in practice since as soon as you turn on or off any of the loads, the panel becomes unbalanced.

That said, the loads should be distributed evenly within the panel to the extent possible.

As to the neutral, it is in the panel. You open the neutral and all the connected loads will fry.

Think "fire"...

Hayward0
K A R - 1 2 0 C
Premium Member
join:2000-07-13
Key West, FL

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said by optonlinene :

If I work inside one of these panels and install additional 3 phase circuits to a motor , how would you balance it if allready it's not? also the lighting is 277 v how hard would it be to locate the neutral conductor for this typical circuit?
i WILL CONCUR.... YOU HAVE TO ASK NOT SOMETHING YOU SHOULD BE PLAYING AROUND WITH.
dipweed23
join:2009-07-21
Ypsilanti, MI

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said by nonymous:

But haven't we heard the stories of a company not able or willing to kill production thus circuits need to be worked live. The unwilling to pay for a fully qualified person they ask someone partly qualified to work it live then boom.
It is common practice in many industries to test while live. Easy to trace down problems but also dangerous. In my workplace if the ovens go wacko, the first thing we (maintinance guy or myself) do is to pop open the live panel and test the heater fuses for all 10 heating zones. Repair or replacement is done after the source is tracked down, and the machine can be taken off line and power turned off.
The one thing that really scares me is diagnosing the stupid AC servo controller which seems to get out of wack once a month.
One panel that powers both small equipment and lighting is 240 3 phase, and it's not uncommon for that one to get opened up and a breaker swapped out for different equipment, or for the "electrical engineer" who is also the president of the company, to re-phase one for a piece of equipment that is not supposed to run on the 30A breaker. I used to have to swap phases on that breaker a lot just to get a different machine back up and running after he is out there playing. If that panel is killed, all the shop lights go out and 2 machine's aux equipment is shut down, so everything is done on that one live. Not safe, but that's how it goes when small industrial companies can't afford to shut down.