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  • Thread starter reedsinthewater
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Discuss Balanced three phase install. in the Commercial Electrical Advice area at ElectriciansForums.net

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reedsinthewater

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Hi all,

Would i be correct in thinking the term 'balanced' three phase install refers to the balancing of all three phase currents, and if so could someone expand a little for me please.

Thanks.
 
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scotsparky

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Arms
yes your right a ballanced 3 phase sysytem is when the Phases have equal current such as a motor circuit. In a truelly ballanced circuit such as a motor they is no neutral as (TP&E motors). A quick check to see if a sysytem is ballanced is to clamp the Neutral. If it is imballanced the neutral will be carrying the imballanced current.

Sorry dont know the maths but i am sure that someone else could help with that.
 
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Guest123

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Hey.

It is also very difficult to have a purely balanced 3P system if you have any single phase loads on any of your DB's i.e lighting and power etc. With a 3P load the current is balanced out on each of the phases as they are at a different point of the sine wave at any point of the cycle where as a single phase load only has 1 phase and a neutral so the current can only return down the neutral conductor thus creating the imbalance between the phases.

Hope this helps.:)
 
D

DHES-LTD

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  • #4
Hey.

It is also very difficult to have a purely balanced 3P system if you have any single phase loads on any of your DB's i.e lighting and power etc. With a 3P load the current is balanced out on each of the phases as they are at a different point of the sine wave at any point of the cycle where as a single phase load only has 1 phase and a neutral so the current can only return down the neutral conductor thus creating the imbalance between the phases.

Hope this helps.:)
Well said!
 
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baldsparkies

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  • #5
Surprising how often you find add on's over the years that end up causing unbalanced load problems. poor old neutral is often the victim with overheat. As said good old clamp meter tells the story.
 
G

Guest123

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  • #6
True.

Whats more surprising is the guys that dont bother checking on old Mr neutral before adding and altering to see how overworked he is. Clampmeter????????? unbalnced load????????
 
i came accross an unbalaced load in a window factory from memory L1 20a L2 20a L3 80a
the factory was vacant we were just making safe
the plant was pulling 20a a phase the extra 60a on L3 was all the low bay lights:eek:
 
G

Guest123

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  • #8
i came accross an unbalaced load in a window factory from memory L1 20a L2 20a L3 80a
the factory was vacant we were just making safe
the plant was pulling 20a a phase the extra 60a on L3 was all the low bay lights:eek:
I rest my case your honour.:)
 
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baldsparkies

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  • #9
worst case I came across was when the neutral detached due to overloading was in a composite panel way down in the basement. Lots of single phase appliances to replace they don't like 400 volts up um Mr mannering.:eek:
 
a similar story a couple times when testing i removed incoming neutral from 3ph cu to test accross n-e bars and
(yep you got it) put the lid back on and turned on only to find flickering lights etc and had forgot to put neutral back
 
G

Guest123

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  • #11


Theres a smiley for everything these days.:)
 

sparks1234

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Arms
worst case I came across was when the neutral detached due to overloading was in a composite panel way down in the basement. Lots of single phase appliances to replace they don't like 400 volts up um Mr mannering.:eek:

Yep the lights I saw with no neutral suddenly took up smoking
 
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baldsparkies

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  • #14
Sad thing was a sparky had been to the place I was called to only the week before. The receptionist said she had noticed the lights flickering every time someone used the lift. He told her he had checked it out, but he only checked a couple of boards on the ground floor riser.Left saying it was an intermittent fault probably a bad connection somewhere, (Naa you don't say) Anyway we were called the following week but to late elvis had left the building. Fried hand driers electronic light fittings fire alarm panel computers and a couple of vending machines,what a mess.
On the plus side, the recepcionist was a babe:D
 
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