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Topic Title: phasing in/out/ladder method.
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Created On: 24 February 2010 06:21 PM
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 24 February 2010 06:21 PM
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Posts: 34
Joined: 10 July 2009

hi guys

what are your thoughts on this,can you confirm i am correct please?

i have two seperate 3 phase supplies i need to "join" them correctly.

so to establish correct phasing i use the ladder method.

so voltages between cables as follows

N TO N 0 volts
N to any other phase 240v
phase to phase 415v
like phase to like phase 0 volts

so i can identify which phases can be connected together and also the neutral, the only thing i cant identify is the actual phase colours but that is irrevalant as i have correctly connected things up!

what are your thoughts on this i would like to confirm the colours and rotation . i have been told getting correct phase rotation on a phase rotation meter does mean the way the rotation meter is connected indicates the rotation colour wise!

thanks for any help.
 24 February 2010 07:27 PM
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Joined: 25 July 2008

Sounds like you are on the right track. There is a big difference between phasing and phase rotation and I find it scary how many sparks dont appreciate the difference.
A phase rotation meter indicates whether the rotation is positive or negative. RYB = YBR = BRY or YRB = RBY = BYR.
One supply that is RYB will give the same rotation as one that is BRY but they will not phase.
As you say test lamps will show you which cores can be connected but will not give any indication of the colours or rotation.
When you refer to the ladder method, I assume you mean moving alternate ends of the lamps up one connection similar to climbing a ladder? If you are I can confirm that it works well with one or two riders, however most DNO's frown on it and advocate a slightly longer winded method.
Remember to watch out for non standard connected transformers a Dy11 and a Yy0 transformer will show almost no voltage between phases, but dont try and connect them.
 24 February 2010 08:20 PM
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Joined: 10 July 2009

yes thats exactly what i want to do, indentify the phasing and connect like to like, can you describe the ladder method for me please,using the test lamp or do i have it already
 24 February 2010 09:12 PM
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Joined: 28 July 2005

Ladder method with test lamps (Showing half light and full light)

N to all phases - half light (prove your lamps)
R to R - No Light
R to Y - Full light
Y to Y - No Light
Y to B - Full Light
B to B - No Light
B to N - Half light (Prove your lamps)


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