3 Phase Theory - Balanced Star and Delta loads

Thread Starter


Joined May 21, 2007
Hi. Firstly id like to say hi. Im new to this forum :)

Secondly I would like to ask for your help regarding an assessment I have to do for my MCA Officer of the watch certificate at college. Im not an electrically minded person, never have been, mechanics is more of my thing. Im into the last 3 weeks of my course before it finishes and im starting to panic to get this assessment done. I really havent the foggiest. I can get the definitions of how a star and delta load are connected in a balanced system but the rest is jibberish to me. lol.

Anyone who could guide me in the right direction with this outcome will be forever in my debt. lol. I have uploaded the assessment.

Thanks all, Bryan



Joined Apr 2, 2007
try this link
before we can help u ,we wud like u to try to at least understand the concept
yourself,some of the answers are on this link also try some googling,

most of the question asked can be easily found in any book touching the subject of electricity distribution .

for the first question if i m getting the question right, all you need to do is connect a load in star formation(as shown in the subsequent question.) to a star configuration supply(which is similar in configuration to load) generally given thru a 3 phase transformer with windings connected in star.
similarly for delta.
if for the next question you want the derivation then you shud look for it in a book in case u r unable to find one then i might try to help.
in case of star connected load
line current = phase current.
line voltage=sqrt(3)*phase voltage.
the angle between current and voltage phasor will depend upon load which in this case must be 0 degrees electrical.
draw the graph using any phase voltage as reference and rest of phase voltages will lag this voltage by 120 degree electrical increasingly hence plot each phase voltage at an angle of 120 degree from previous one taken in order.
the line voltage vector will be difference of the vector for any two phase voltage.fraw line current in phase with phase voltage taking suitable scale.
for delta connected load:
line voltage= phase voltage.
line current=sqrt(3)*phase currrent
draw phasor in similar way as described above.
in this case line current vector will be sum of two phase current vector(simply invert a vector in direction keeping magnitude same and join the arrow tips to get the difference).

with the third one either u will have to buy me aticket to your location or start praying or just start doing some self study(its very easy once u get the hang of it)